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Marshall Orem J. Skimming stones. SLEEP ADVANCES : A JOURNAL OF THE SLEEP RESEARCH SOCIETY 2023; 4:zpad026. [PMID: 37650120 PMCID: PMC10465270 DOI: 10.1093/sleepadvances/zpad026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 04/19/2023] [Indexed: 09/01/2023]
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2
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Haouzi P, Tubbs N. Effects of fentanyl overdose-induced muscle rigidity and dexmedetomidine on respiratory mechanics and pulmonary gas exchange in sedated rats. J Appl Physiol (1985) 2022; 132:1407-1422. [PMID: 35421320 DOI: 10.1152/japplphysiol.00819.2021] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The objective of our study was to establish in sedated rats the consequences of high-dose fentanyl-induced acute muscle rigidity on the mechanical properties of the respiratory system and on the metabolic rate. Doses of fentanyl that we have previously shown to produce persistent rigidity of the muscles of the limbs and trunk in the rat (150 -300 microg/kg iv), were administered in 23 volume-controlled mechanically ventilated and sedated rats. The effects of a low dose of the FDA approved central alpha-2 agonist, dexmedetomidine (3 microg/kg iv), which has been suggested to oppose fentanyl-induced muscle rigidity, were determined after fentanyl administration. Fentanyl produced a significant decrease in Crs in the 23 rats that were studied. In 13 rats, an abrupt response occurred within 90 seconds, consisting in rapid rhythmic contractions of most skeletal muscles, that were replaced by persistent tonic/tetanic contractions leading a significant decrease of Crs (from 0.51 ± 0.11 ml/cmH2O to 0.36 ± 0.08 ml/cmH2O, 3 minutes after fentanyl injection). In the other 10 animals, a Crs progressively decreased to 0.26 ± 0.06 ml/cmH2O at 30 minutes. There was a significant rise in V̇O2 during muscle tonic contractions (from 8.48 ± 4.31 to 11.29 ± 2.57 ml/min), which contributed to a significant hypoxemia, despite ventilation being held constant. Dexmedetomidine provoked a significant and rapid increase in Crs towards baseline levels, while decreasing the metabolic rate and restoring normoxemia. We propose that the changes in respiratory mechanics and metabolism produced by opioid-induced muscle rigidity contribute to fentanyl lethality.
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Affiliation(s)
- Philippe Haouzi
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Pennsylvania State University, College of Medicine, Hershey, PA, United States
| | - Nicole Tubbs
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Pennsylvania State University, College of Medicine, Hershey, PA, United States
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3
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Homma I, Phillips AG. Critical roles for breathing in the genesis and modulation of emotional states. HANDBOOK OF CLINICAL NEUROLOGY 2022; 188:151-178. [PMID: 35965025 DOI: 10.1016/b978-0-323-91534-2.00011-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Breathing can be classified into metabolic and behavioral categories. Metabolic breathing and voluntary behavioral breathing are controlled in the brainstem and in the cerebral motor cortex, respectively. This chapter places special emphasis on the reciprocal influences between breathing and emotional processes. As is the case with neural control of breathing, emotions are generated by multiple control networks, located primarily in the forebrain. For several decades, a respiratory rhythm generator has been investigated in the limbic system. The amygdala receives respiratory-related input from the piriform cortex. Excitatory recurrent branches are located in the piriform cortex and have tight reciprocal synaptic connections, which produce periodic oscillations, similar to those recorded in the hippocampus during slow-wave sleep. The relationship between olfactory breathing rhythm and emotion is seen as the gateway to interpreting the relationship between breathing and emotion. In this chapter, we describe roles of breathing in the genesis of emotion, neural structures common to breathing and emotion, and mutual importance of breathing and emotion. We also describe the central roles of conscious awareness and voluntary control of breathing, as effective methods for stabilizing attention and the contents in the stream of consciousness. Voluntary control of breathing is seen as an essential practice for achieving emotional well-being.
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Affiliation(s)
- Ikuo Homma
- Faculty of Health Sciences, Tokyo Ariake University of Medical and Health Sciences, Tokyo, Japan.
| | - Anthony G Phillips
- Djavad Mowafaghian Centre for Brain Health and Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada
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4
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Mitchell GS, Baker TL. Respiratory neuroplasticity: Mechanisms and translational implications of phrenic motor plasticity. HANDBOOK OF CLINICAL NEUROLOGY 2022; 188:409-432. [PMID: 35965036 DOI: 10.1016/b978-0-323-91534-2.00016-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Widespread appreciation that neuroplasticity is an essential feature of the neural system controlling breathing has emerged only in recent years. In this chapter, we focus on respiratory motor plasticity, with emphasis on the phrenic motor system. First, we define related but distinct concepts: neuromodulation and neuroplasticity. We then focus on mechanisms underlying two well-studied models of phrenic motor plasticity: (1) phrenic long-term facilitation following brief exposure to acute intermittent hypoxia; and (2) phrenic motor facilitation after prolonged or recurrent bouts of diminished respiratory neural activity. Advances in our understanding of these novel and important forms of plasticity have been rapid and have already inspired translation in multiple respects: (1) development of novel therapeutic strategies to preserve/restore breathing function in humans with severe neurological disorders, such as spinal cord injury and amyotrophic lateral sclerosis; and (2) the discovery that similar plasticity also occurs in nonrespiratory motor systems. Indeed, the realization that similar plasticity occurs in respiratory and nonrespiratory motor neurons inspired clinical trials to restore leg/walking and hand/arm function in people living with chronic, incomplete spinal cord injury. Similar application may be possible to other clinical disorders that compromise respiratory and non-respiratory movements.
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Affiliation(s)
- Gordon S Mitchell
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, United States.
| | - Tracy L Baker
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI, United States
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5
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Welch JF, Perim RR, Argento PJ, Sutor TW, Vose AK, Nair J, Mitchell GS, Fox EJ. Effect of acute intermittent hypoxia on cortico-diaphragmatic conduction in healthy humans. Exp Neurol 2021; 339:113651. [PMID: 33607080 PMCID: PMC8678369 DOI: 10.1016/j.expneurol.2021.113651] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 02/11/2021] [Accepted: 02/12/2021] [Indexed: 01/06/2023]
Abstract
Acute intermittent hypoxia (AIH) is a strategy to improve motor output in humans with neuromotor impairment. A single AIH session increases the amplitude of motor evoked potentials (MEP) in a finger muscle (first dorsal interosseous), demonstrating enhanced corticospinal neurotransmission. Since AIH elicits phrenic/diaphragm long-term facilitation (LTF) in rodent models, we tested the hypothesis that AIH augments diaphragm MEPs in humans. Eleven healthy adults (7 males, age = 29 ± 6 years) were tested. Transcranial and cervical magnetic stimulation were used to induce diaphragm MEPs and compound muscle action potentials (CMAP) recorded by surface EMG, respectively. Stimulus-response curves were generated prior to and 30-60 min after AIH. Diaphragm LTF was assessed by measurement of integrated EMG burst amplitude and frequency during eupnoeic breathing before and after AIH. Following baseline measurements, AIH was delivered from an oxygen generator connected to a facemask under poikilocapnic conditions (15 one minute episodes of 9% inspired oxygen with one minute room air intervals). There were no detectable changes in MEP (-1.5 ± 12.1%, p = 0.96) or CMAP (+0.1 ± 7.8%, p = 0.97) amplitudes across the stimulus-response curve. At stimulation intensities approximating 50% of the difference between minimum and maximum baseline amplitudes, MEP and CMAP amplitudes were also unchanged (p > 0.05). Further, no AIH effect was observed on diaphragm EMG activity during eupnoea post-AIH (p > 0.05). We conclude that unlike hand muscles, poikilocapnic AIH does not enhance diaphragm MEPs or produce diaphragm LTF in healthy humans.
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Affiliation(s)
- Joseph F Welch
- Breathing Research and Therapeutics Centre, Department of Physical Therapy, University of Florida, Gainesville, FL, USA.
| | - Raphael R Perim
- Breathing Research and Therapeutics Centre, Department of Physical Therapy, University of Florida, Gainesville, FL, USA
| | - Patrick J Argento
- Herbert Wertheim College of Engineering, University of Florida, Gainesville, FL, USA
| | - Tommy W Sutor
- Breathing Research and Therapeutics Centre, Department of Physical Therapy, University of Florida, Gainesville, FL, USA
| | - Alicia K Vose
- Breathing Research and Therapeutics Centre, Department of Physical Therapy, University of Florida, Gainesville, FL, USA
| | - Jayakrishnan Nair
- Breathing Research and Therapeutics Centre, Department of Physical Therapy, University of Florida, Gainesville, FL, USA
| | - Gordon S Mitchell
- Breathing Research and Therapeutics Centre, Department of Physical Therapy, University of Florida, Gainesville, FL, USA
| | - Emily J Fox
- Breathing Research and Therapeutics Centre, Department of Physical Therapy, University of Florida, Gainesville, FL, USA; Brooks Rehabilitation, Jacksonville, FL, USA
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6
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Haouzi P, McCann M, Tubbs N. Respiratory effects of low and high doses of fentanyl in control and β-arrestin 2-deficient mice. J Neurophysiol 2021; 125:1396-1407. [PMID: 33656934 DOI: 10.1152/jn.00711.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
We have investigated the potential acute desensitizing role of the β arrestin 2 (β-arr2) pathway on the ventilatory depression produced by levels of fentanyl ranging from analgesic to life-threatening (0.1 to 60 mg/kg ip) in control and β-arr2-deficient nonsedated mice. Fentanyl at doses of 0.1, 0.5, and 1 mg/kg ip-corresponding to the doses previously used to study the role of β-arr2 pathway-decreased ventilation, but along the V̇e/V̇co2 relationship established in baseline conditions. This reduction in ventilation was therefore indistinguishable from the decrease in breathing during the periods of spontaneous immobility. Above 1.5 mg/kg, however, ventilation was depressed out of proportion of the changes in metabolic rate, suggesting a specific depression of the drive to breathe. The ventilatory responses were similar between the two groups. At high doses of fentanyl (60 mg/kg ip) 1 out of 20 control mice died by apnea versus 8 out of 20 β-arr2-deficient mice (P = 0.008). In the surviving mice, ventilation was however identical in both groups. The ventilatory effects of fentanyl in β-arr2-deficient mice, reported in the literature, are primarily mediated by the "indirect" effects of sedation/hypometabolism on breathing control. There was an excess mortality at very high doses of fentanyl in the β-arr2-deficient mice, mechanisms of which are still open to question, as the capacity of maintaining a rhythmic, although profoundly depressed, breathing activity remains similar in all of the surviving control and β-arr2-deficient mice.NEW & NOTEWORTHY When life-threatening doses of fentanyl are used in mice, the β-arrestin 2 pathway appears to play a critical role in the recovery from opioid overdose. This observation calls into question the use of G protein-biased μ-opioid receptor agonists, as a strategy for safer opioid analgesic drugs.
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Affiliation(s)
- Philippe Haouzi
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Pennsylvania State University, College of Medicine, Hershey, Pennsylvania
| | - Marissa McCann
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Pennsylvania State University, College of Medicine, Hershey, Pennsylvania
| | - Nicole Tubbs
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Pennsylvania State University, College of Medicine, Hershey, Pennsylvania
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7
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Trevizan-Baú P, Dhingra RR, Furuya WI, Stanić D, Mazzone SB, Dutschmann M. Forebrain projection neurons target functionally diverse respiratory control areas in the midbrain, pons, and medulla oblongata. J Comp Neurol 2020; 529:2243-2264. [PMID: 33340092 DOI: 10.1002/cne.25091] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 11/25/2020] [Accepted: 11/29/2020] [Indexed: 12/12/2022]
Abstract
Eupnea is generated by neural circuits located in the ponto-medullary brainstem, but can be modulated by higher brain inputs which contribute to volitional control of breathing and the expression of orofacial behaviors, such as vocalization, sniffing, coughing, and swallowing. Surprisingly, the anatomical organization of descending inputs that connect the forebrain with the brainstem respiratory network remains poorly defined. We hypothesized that descending forebrain projections target multiple distributed respiratory control nuclei across the neuroaxis. To test our hypothesis, we made discrete unilateral microinjections of the retrograde tracer cholera toxin subunit B in the midbrain periaqueductal gray (PAG), the pontine Kölliker-Fuse nucleus (KFn), the medullary Bötzinger complex (BötC), pre-BötC, or caudal midline raphé nuclei. We quantified the regional distribution of retrogradely labeled neurons in the forebrain 12-14 days postinjection. Overall, our data reveal that descending inputs from cortical areas predominantly target the PAG and KFn. Differential forebrain regions innervating the PAG (prefrontal, cingulate cortices, and lateral septum) and KFn (rhinal, piriform, and somatosensory cortices) imply that volitional motor commands for vocalization are specifically relayed via the PAG, while the KFn may receive commands to coordinate breathing with other orofacial behaviors (e.g., sniffing, swallowing). Additionally, we observed that the limbic or autonomic (interoceptive) systems are connected to broadly distributed downstream bulbar respiratory networks. Collectively, these data provide a neural substrate to explain how volitional, state-dependent, and emotional modulation of breathing is regulated by the forebrain.
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Affiliation(s)
- Pedro Trevizan-Baú
- The Florey Institute of Neuroscience and Mental Health, Discovery Neuroscience Theme, The University of Melbourne, Parkville, Victoria, Australia
| | - Rishi R Dhingra
- The Florey Institute of Neuroscience and Mental Health, Discovery Neuroscience Theme, The University of Melbourne, Parkville, Victoria, Australia
| | - Werner I Furuya
- The Florey Institute of Neuroscience and Mental Health, Discovery Neuroscience Theme, The University of Melbourne, Parkville, Victoria, Australia
| | - Davor Stanić
- The Florey Institute of Neuroscience and Mental Health, Discovery Neuroscience Theme, The University of Melbourne, Parkville, Victoria, Australia
| | - Stuart B Mazzone
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Victoria, Australia
| | - Mathias Dutschmann
- The Florey Institute of Neuroscience and Mental Health, Discovery Neuroscience Theme, The University of Melbourne, Parkville, Victoria, Australia
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8
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Welch JF, Argento PJ, Mitchell GS, Fox EJ. Reliability of diaphragmatic motor-evoked potentials induced by transcranial magnetic stimulation. J Appl Physiol (1985) 2020; 129:1393-1404. [PMID: 33031020 DOI: 10.1152/japplphysiol.00486.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The diaphragmatic motor-evoked potential (MEP) induced by transcranial magnetic stimulation (TMS) permits electrophysiological assessment of the cortico-diaphragmatic pathway. Despite the value of TMS for investigating diaphragm motor integrity in health and disease, reliability of the technique has not been established. The study aim was to determine within- and between-session reproducibility of surface electromyogram recordings of TMS-evoked diaphragm potentials. Fifteen healthy young adults participated (6 females, age = 29 ± 7 yr). Diaphragm activation was determined by gradually increasing the stimulus intensity from 60 to 100% of maximal stimulator output (MSO). A minimum of seven stimulations were performed at each intensity. A second block of stimuli was delivered 30 min later for within-day comparisons, and a third block was performed on a separate day for between-day comparisons. Reliability of diaphragm MEPs was assessed at 100% MSO using intraclass correlation coefficients (ICC) and 95% limits of agreement (LOA). MEP latency (ICC = 0.984, P < 0.001), duration (ICC = 0.958, P < 0.001), amplitude (ICC = 0.950, P < 0.001), and area (ICC = 0.956, P < 0.001) were highly reproducible within-day. Between-day reproducibility was good to excellent for all MEP characteristics (latency ICC = 0.953, P < 0.001; duration ICC = 0.879, P = 0.002; amplitude ICC = 0.789, P = 0.019; area ICC = 0.815, P = 0.012). Data revealed less precision between-day versus within-day, as evidenced by wider LOA for all MEP characteristics. Large within- and between-subject variability in MEP amplitude and area was observed. In conclusion, TMS is a reliable means of inducing diaphragm potentials in most healthy individuals.NEW & NOTEWORTHY Transcranial magnetic stimulation (TMS) is a noninvasive technique to assess neural impulse conduction along the cortico-diaphragmatic pathway. The reliability of diaphragm motor-evoked potentials (MEP) induced by TMS is unknown. Notwithstanding large variability in MEP amplitude, we found good-to-excellent reproducibility of all MEP characteristics (latency, duration, amplitude, and area) both within- and between-day in healthy adult men and women. Our findings support the use of TMS and surface EMG to assess diaphragm activation in humans.
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Affiliation(s)
- Joseph F Welch
- Breathing Research and Therapeutics Center, Department of Physical Therapy, University of Florida, Gainesville, Florida
| | - Patrick J Argento
- Herbert Wertheim College of Engineering, University of Florida, Gainesville, Florida
| | - Gordon S Mitchell
- Breathing Research and Therapeutics Center, Department of Physical Therapy, University of Florida, Gainesville, Florida
| | - Emily J Fox
- Breathing Research and Therapeutics Center, Department of Physical Therapy, University of Florida, Gainesville, Florida.,Brooks Rehabilitation, Jacksonville, Florida
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Hudson AL, Walsh LD, Gandevia SC, Butler JE. Respiratory muscle activity in voluntary breathing tracking tasks: Implications for the assessment of respiratory motor control. Respir Physiol Neurobiol 2019; 274:103353. [PMID: 31760130 DOI: 10.1016/j.resp.2019.103353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 10/24/2019] [Accepted: 11/18/2019] [Indexed: 10/25/2022]
Abstract
How the involuntary (bulbospinal) and voluntary (corticospinal) pathways interact in respiratory muscle control is not established. To determine the role of excitatory corticobulbar pathways in humans, studies typically compare electromyographic activity (EMG) or evoked responses in respiratory muscles during hypercapnic and voluntary tasks. Although ventilation is matched between tasks by having participants track signals of ventilation, these tasks may not result in matched respiratory muscle activity. The aim of this study was to describe respiratory muscle activity and ribcage and abdominal excursions during two different voluntary conditions, compared to hypercapnic hyperventilation. Ventilation was matched in the voluntary conditions via (i) a simple target of lung volume ('volume tracking') or (ii) targets of both ribcage and abdominal excursions, adjusted to end-expiratory lung volume in hypercapnic hyperventilation ('bands tracking'). Compared to hypercapnic hyperventilation, respiratory parameters such as tidal volume were similar, but the ratio of ribcage to abdominal excursion was higher for both voluntary tasks. Inspiratory scalene and parasternal intercostal muscle activity was higher in volume tracking, but diaphragm and abdominal muscle activity showed little to no change. There were no differences in muscle activity in bands tracking for any muscle, compared to hypercapnic hyperventilation. An elevated ratio of ribcage to abdominal excursion in the bands tracking task indicates that participants could not accurately match the targets in this condition. Inspiratory muscle activity is altered in some muscles in some voluntary tasks, compared to hypercapnia. Therefore, differences in muscle activity should be considered in interpretation of studies that use these protocols to investigate respiratory muscle control.
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Affiliation(s)
- Anna L Hudson
- Neuroscience Research Australia and University of New South Wales, Sydney, Australia.
| | - Lee D Walsh
- Neuroscience Research Australia and University of New South Wales, Sydney, Australia; Platypus Technical Consultants Pty Ltd, Canberra, Australia
| | - Simon C Gandevia
- Neuroscience Research Australia and University of New South Wales, Sydney, Australia
| | - Jane E Butler
- Neuroscience Research Australia and University of New South Wales, Sydney, Australia
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Luu BL, McBain RA, Taylor JL, Gandevia SC, Butler JE. Reflex response to airway occlusion in human inspiratory muscles when recruited for breathing and posture. J Appl Physiol (1985) 2019; 126:132-140. [DOI: 10.1152/japplphysiol.00841.2018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Briefly occluding the airway during inspiration produces a short-latency reflex inhibition in human inspiratory muscles. This occlusion reflex seems specific to respiratory muscles; however, it is not known whether the reflex inhibition has a uniform effect across a motoneuron pool when a muscle is recruited concurrently for breathing and posture. In this study, participants were seated and breathed through a mouthpiece that occluded inspiratory airflow for 250 ms at a volume threshold of 0.2 liters. The reflex response was measured in the scalene and sternocleidomastoid muscles during 1) a control condition with the head supported in space and the muscles recruited for breathing only, 2) a postural condition with the head unsupported and the neck flexors recruited for both breathing and to maintain head posture, and 3) a large-breath condition with the head supported and the volume threshold raised to between 0.8 and 1.0 liters to increase inspiratory muscle activity. When normalized to its preocclusion mean, the reflex response in the scalene muscles was not significantly different between the large-breath and control conditions, whereas concomitant recruitment of these muscles for posture control reduced the reflex response by half compared with the control condition. A reflex response occurred in sternocleidomastoid when it contracted phasically as an accessory muscle for inspiration during the large-breath condition. These results indicate that the occlusion reflex does not produce a uniform effect across the motoneuron pool and that afferent inputs for this reflex most likely act via intersegmental networks of premotoneurons rather than at a motoneuronal level. NEW & NOTEWORTHY In this study, we investigated the effect of nonrespiratory activity on the reflex response to brief sudden airway occlusions in human inspiratory muscles. We show that the reflex inhibition in the scalene muscles was not uniform across the motoneuron pool when the muscle was recruited concurrently for breathing and postural control. The reflex had a larger effect on respiratory-driven motoneurons than those recruited to maintain head posture.
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Affiliation(s)
- Billy L. Luu
- Neuroscience Research Australia, Randwick, New South Wales, Australia
| | - Rachel A. McBain
- Neuroscience Research Australia, Randwick, New South Wales, Australia
| | - Janet L. Taylor
- Neuroscience Research Australia, Randwick, New South Wales, Australia
- The University of New South Wales, Sydney, New South Wales, Australia
- Edith Cowan University, Joondalup, Western Australia, Australia
| | - Simon C. Gandevia
- Neuroscience Research Australia, Randwick, New South Wales, Australia
- The University of New South Wales, Sydney, New South Wales, Australia
| | - Jane E. Butler
- Neuroscience Research Australia, Randwick, New South Wales, Australia
- The University of New South Wales, Sydney, New South Wales, Australia
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Raux M, Demoule A, Redolfi S, Morelot-Panzini C, Similowski T. Reduced Phrenic Motoneuron Recruitment during Sustained Inspiratory Threshold Loading Compared to Single-Breath Loading: A Twitch Interpolation Study. Front Physiol 2016; 7:537. [PMID: 27891099 PMCID: PMC5102887 DOI: 10.3389/fphys.2016.00537] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 10/26/2016] [Indexed: 12/14/2022] Open
Abstract
In humans, inspiratory constraints engage cortical networks involving the supplementary motor area. Functional magnetic resonance imaging (fMRI) shows that the spread and intensity of the corresponding respiratory-related cortical activation dramatically decrease when a discrete load becomes sustained. This has been interpreted as reflecting motor cortical reorganization and automatisation, but could proceed from sensory and/or affective habituation. To corroborate the existence of motor reorganization between single-breath and sustained inspiratory loading (namely changes in motor neurones recruitment), we conducted a diaphragm twitch interpolation study based on the hypothesis that motor reorganization should result in changes in the twitch interpolation slope. Fourteen healthy subjects (age: 21–40 years) were studied. Bilateral phrenic stimulation was delivered at rest, upon prepared and targeted voluntary inspiratory efforts (“vol”), upon unprepared inspiratory efforts against a single-breath inspiratory threshold load (“single-breath”), and upon sustained inspiratory efforts against the same type of load (“continuous”). The slope of the relationship between diaphragm twitch transdiaphragmatic pressure and the underlying transdiaphragmatic pressure was −1.1 ± 0.2 during “vol,” −1.5 ± 0.7 during “single-breath,” and −0.6 ± 0.4 during “continuous” (all slopes expressed in percent of baseline.percent of baseline−1) all comparisons significant at the 5% level. The contribution of the diaphragm to inspiration, as assessed by the gastric pressure to transdiaphragmatic pressure ratio, was 31 ± 17% during “vol,” 22 ± 16% during “single-breath” (p = 0.13), and 19 ± 9% during “continuous” (p = 0.0015 vs. “vol”). This study shows that the relationship between the amplitude of the transdiaphragmatic pressure produced by a diaphragm twitch and its counterpart produced by the underlying diaphragm contraction is not unequivocal. If twitch interpolation is interpreted as reflecting motoneuron recruitment, this study supports motor reorganization compatible with “diaphragm sparing” when an inspiratory threshold load becomes sustained.
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Affiliation(s)
- Mathieu Raux
- Sorbonne Universités, UPMC - University Pierre and Marie Curie Univ Paris 06, Institut National de la Santé et de la Recherche Médicale, UMRS1158 Neurophysiologie Respiratoire Expérimentale et cliniqueParis, France; AP-HP, Groupe Hospitalier Pitié-Salpêtrière Charles Foix, Département d'Anesthésie-RéanimationParis, France
| | - Alexandre Demoule
- Sorbonne Universités, UPMC - University Pierre and Marie Curie Univ Paris 06, Institut National de la Santé et de la Recherche Médicale, UMRS1158 Neurophysiologie Respiratoire Expérimentale et cliniqueParis, France; AP-HP, Groupe Hospitalier Pitié-Salpêtrière Charles Foix, Service de Pneumologie et Réanimation Médicale (Département"R3S")Paris, France
| | - Stefania Redolfi
- Sorbonne Universités, UPMC - University Pierre and Marie Curie Univ Paris 06, Institut National de la Santé et de la Recherche Médicale, UMRS1158 Neurophysiologie Respiratoire Expérimentale et cliniqueParis, France; AP-HP, Groupe Hospitalier Pitié-Salpêtrière Charles Foix, Service des Pathologies du Sommeil (Département "R3S")Paris, France
| | - Capucine Morelot-Panzini
- Sorbonne Universités, UPMC - University Pierre and Marie Curie Univ Paris 06, Institut National de la Santé et de la Recherche Médicale, UMRS1158 Neurophysiologie Respiratoire Expérimentale et cliniqueParis, France; AP-HP, Groupe Hospitalier Pitié-Salpêtrière Charles Foix, Service de Pneumologie et Réanimation Médicale (Département"R3S")Paris, France
| | - Thomas Similowski
- Sorbonne Universités, UPMC - University Pierre and Marie Curie Univ Paris 06, Institut National de la Santé et de la Recherche Médicale, UMRS1158 Neurophysiologie Respiratoire Expérimentale et cliniqueParis, France; AP-HP, Groupe Hospitalier Pitié-Salpêtrière Charles Foix, Service de Pneumologie et Réanimation Médicale (Département"R3S")Paris, France
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12
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Jaiswal PB, Davenport PW. Intercostal muscle motor behavior during tracheal occlusion conditioning in conscious rats. J Appl Physiol (1985) 2016; 120:792-800. [PMID: 26823339 DOI: 10.1152/japplphysiol.00436.2015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 01/22/2016] [Indexed: 11/22/2022] Open
Abstract
A respiratory load compensation response is characterized by increases in activation of primary respiratory muscles and/or recruitment of accessory respiratory muscles. The contribution of the external intercostal (EI) muscles, which are a primary respiratory muscle group, during normal and loaded breathing remains poorly understood in conscious animals. Consciousness has a significant role on modulation of respiratory activity, as it is required for the integration of behavioral respiratory responses and voluntary control of breathing. Studies of respiratory load compensation have been predominantly focused in anesthetized animals, which make their comparison to conscious load compensation responses challenging. Using our established model of intrinsic transient tracheal occlusions (ITTO), our aim was to evaluate the motor behavior of EI muscles during normal and loaded breathing in conscious rats. We hypothesized that 1) conscious rats exposed to ITTO will recruit the EI muscles with an increased electromyogram (EMG) activation and 2) repeated ITTO for 10 days would potentiate the baseline EMG activity of this muscle in conscious rats. Our results demonstrate that conscious rats exposed to ITTO respond by recruiting the EI muscle with a significantly increased EMG activation. This response to occlusion remained consistent over the 10-day experimental period with little or no effect of repeated ITTO exposure on the baseline ∫EI EMG amplitude activity. The pattern of activation of the EI muscle in response to an ITTO is discussed in detail. The results from the present study demonstrate the importance of EI muscles during unloaded breathing and respiratory load compensation in conscious rats.
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Affiliation(s)
- Poonam B Jaiswal
- Department of Physiological Sciences, University of Florida, Gainesville, Florida
| | - Paul W Davenport
- Department of Physiological Sciences, University of Florida, Gainesville, Florida
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Luu BL, Saboisky JP, Taylor JL, Gandevia SC, Butler JE. TMS-evoked silent periods in scalene and parasternal intercostal muscles during voluntary breathing. Respir Physiol Neurobiol 2015; 216:15-22. [DOI: 10.1016/j.resp.2015.05.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 05/13/2015] [Accepted: 05/18/2015] [Indexed: 10/23/2022]
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14
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Narula M, McGovern AE, Yang SK, Farrell MJ, Mazzone SB. Afferent neural pathways mediating cough in animals and humans. J Thorac Dis 2014; 6:S712-9. [PMID: 25383205 DOI: 10.3978/j.issn.2072-1439.2014.03.15] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Accepted: 03/04/2014] [Indexed: 12/12/2022]
Abstract
The airways and lungs are densely innervated by sensory nerves, which subserve multiple roles in both the normal physiological control of respiratory functions and in pulmonary defense. These sensory nerves are therefore not homogeneous in nature, but rather have physiological, molecular and anatomical phenotypes that reflect their purpose. All sensory neuron subtypes provide input to the central nervous system and drive reflex changes in respiratory and airway functions. But less appreciated is that ascending projections from these brainstem inputs to higher brain regions can also induce behavioural changes in respiration. In this brief review we provide an overview of the current understanding of airway sensory pathways, with specific reference to those involved in reflex and behavioural cough responses following airways irritation.
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Affiliation(s)
- Monica Narula
- 1 School of Biomedical Sciences, University of Queensland, QLD 4072, Australia ; 2 The Florey Institute of Neuroscience and Mental Health, VIC 3010, Australia
| | - Alice E McGovern
- 1 School of Biomedical Sciences, University of Queensland, QLD 4072, Australia ; 2 The Florey Institute of Neuroscience and Mental Health, VIC 3010, Australia
| | - Seung-Kwon Yang
- 1 School of Biomedical Sciences, University of Queensland, QLD 4072, Australia ; 2 The Florey Institute of Neuroscience and Mental Health, VIC 3010, Australia
| | - Michael J Farrell
- 1 School of Biomedical Sciences, University of Queensland, QLD 4072, Australia ; 2 The Florey Institute of Neuroscience and Mental Health, VIC 3010, Australia
| | - Stuart B Mazzone
- 1 School of Biomedical Sciences, University of Queensland, QLD 4072, Australia ; 2 The Florey Institute of Neuroscience and Mental Health, VIC 3010, Australia
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15
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Butler JE, Hudson AL, Gandevia SC. The Neural Control of Human Inspiratory Muscles. PROGRESS IN BRAIN RESEARCH 2014; 209:295-308. [DOI: 10.1016/b978-0-444-63274-6.00015-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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16
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Stuth EAE, Stucke AG, Zuperku EJ. Effects of anesthetics, sedatives, and opioids on ventilatory control. Compr Physiol 2013; 2:2281-367. [PMID: 23720250 DOI: 10.1002/cphy.c100061] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
This article provides a comprehensive, up to date summary of the effects of volatile, gaseous, and intravenous anesthetics and opioid agonists on ventilatory control. Emphasis is placed on data from human studies. Further mechanistic insights are provided by in vivo and in vitro data from other mammalian species. The focus is on the effects of clinically relevant agonist concentrations and studies using pharmacological, that is, supraclinical agonist concentrations are de-emphasized or excluded.
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Affiliation(s)
- Eckehard A E Stuth
- Medical College of Wisconsin, Anesthesia Research Service, Zablocki VA Medical Center, Milwaukee, Wisconsin, USA.
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17
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Abstract
Many articles in this section of Comprehensive Physiology are concerned with the development and function of a central pattern generator (CPG) for the control of breathing in vertebrate animals. The action of the respiratory CPG is extensively modified by cortical and other descending influences as well as by feedback from peripheral sensory systems. The central nervous system also incorporates other CPGs, which orchestrate a wide variety of discrete and repetitive, voluntary and involuntary movements. The coordination of breathing with these other activities requires interaction and coordination between the respiratory CPG and those governing the nonrespiratory activities. Most of these interactions are complex and poorly understood. They seem to involve both conventional synaptic crosstalk between groups of neurons and fluid identity of neurons as belonging to one CPG or another: neurons that normally participate in breathing may be temporarily borrowed or hijacked by a competing or interrupting activity. This review explores the control of breathing as it is influenced by many activities that are generally considered to be nonrespiratory. The mechanistic detail varies greatly among topics, reflecting the wide variety of pertinent experiments.
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Affiliation(s)
- Donald Bartlett
- Department of Physiology & Neurobiology, Dartmouth Medical School, Lebanon, New Hampshire, USA.
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18
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Khan HM, Ahmed B, Choi J, Gutierrez-Osuna R. Using an ambulatory stress monitoring device to identify relaxation due to untrained deep breathing. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2013; 2013:1744-7. [PMID: 24110044 DOI: 10.1109/embc.2013.6609857] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The objective of this paper is to assess the efficacy of deep breathing as a relaxation activity using a wearable stress monitor. For this purpose, we developed a protocol with different mentally stressful activities interleaved with regular sessions of deep breathing. We used three physiological sensors: a heart rate monitor, a respiration sensor, and an electrodermal activity sensor, to extract parameters that are consistent with the dominance of the sympathetic nervous system. Our results indicate that a large number of subjects were not able to perform the paced deep breathing exercise properly, which caused their stress levels to increase rather than to decrease. The study also showed that our wearable stress monitor can be used to monitor breathing technique and assess its effectiveness in relaxing individuals.
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Hudson AL, Gandevia SC, Butler JE. Control of human inspiratory motoneurones during voluntary and involuntary contractions. Respir Physiol Neurobiol 2011; 179:23-33. [DOI: 10.1016/j.resp.2011.06.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Revised: 06/14/2011] [Accepted: 06/14/2011] [Indexed: 11/17/2022]
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Moreira TS, Takakura AC. Commentaries on Viewpoint: Initiating inspiration outside the medulla does produce eupneic breathing. What is the role of brain stem neurons in eupneic breathing. J Appl Physiol (1985) 2011; 110:858; author reply 859. [PMID: 21510000 DOI: 10.1152/japplphysiol.00006.2011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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21
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Hudson AL, Gandevia SC, Butler JE. Common rostrocaudal gradient of output from human intercostal motoneurones during voluntary and automatic breathing. Respir Physiol Neurobiol 2011; 175:20-8. [DOI: 10.1016/j.resp.2010.08.023] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Revised: 08/26/2010] [Accepted: 08/30/2010] [Indexed: 10/19/2022]
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22
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Murray NPS, McKenzie DK, Gandevia SC, Butler JE. Voluntary and involuntary ventilation do not alter the human inspiratory muscle loading reflex. J Appl Physiol (1985) 2010; 109:87-94. [DOI: 10.1152/japplphysiol.01128.2009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The reflex mechanism of the short-latency inhibitory reflex to transient loading of human inspiratory muscles is unresolved. Muscle afferents mediate this reflex, but they may act via pontomedullary inspiratory centers, other bulbar networks, or spinal circuits. We hypothesized that altered chemical drive to breathe would alter the initial inhibitory reflex if the neural pathways involve inspiratory medullary centers. Inspiration was transiently loaded in 11 subjects during spontaneous hypercapnic hyperpnea and matched voluntary hyperventilation. Electromyographic activity was recorded bilaterally from scalene muscles with surface electrodes. The latencies of the initial inhibitory response (IR) onset (32 ± 0.7 and 38 ± 1 ms for spontaneous and voluntary conditions respectively, P < 0.001) and subsequent excitatory response (ER) onset (80 ± 2.9 and 78 ± 2.6 ms, respectively, P = 0.46) and the normalized sizes of IR (65 ± 2 and 67 ± 3%, respectively, P = 0.50) and ER (51 ± 8 and 69 ± 6%, respectively, P = 0.005) were measured. Mean end-tidal Pco2 was 43 ± 1.5 Torr with dead space ventilation and was 14 ± 0.6 Torr with matched voluntary hyperventilation ( P < 0.001). A mean minute volume >30 liters was achieved in both conditions. The absence of significant difference in the size of the IR suggested that the IR reflex arc does not transit the brain stem inspiratory centers and that the reflex may be integrated at a spinal level. In voluntary hyperventilation, an initial excitation occurred more frequently and, consequently, the IR onset latency was significantly longer. The size of the later ER was also greater during voluntary hyperventilation, which is consistent with it being mediated via longer, presumably cortical, pathways, which are influenced by voluntary drive.
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Affiliation(s)
- N. P. S. Murray
- Prince of Wales Medical Research Institute and University of New South Wales, and
- Department of Respiratory and Sleep Medicine, Prince of Wales Hospital, Sydney, New South Wales, Australia
| | - D. K. McKenzie
- Prince of Wales Medical Research Institute and University of New South Wales, and
- Department of Respiratory and Sleep Medicine, Prince of Wales Hospital, Sydney, New South Wales, Australia
| | - S. C. Gandevia
- Prince of Wales Medical Research Institute and University of New South Wales, and
| | - J. E. Butler
- Prince of Wales Medical Research Institute and University of New South Wales, and
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23
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Hudson AL, Butler JE, Gandevia SC, De Troyer A. Interplay Between the Inspiratory and Postural Functions of the Human Parasternal Intercostal Muscles. J Neurophysiol 2010; 103:1622-9. [DOI: 10.1152/jn.00887.2009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The parasternal intercostal muscles are obligatory inspiratory muscles. To test the hypothesis that they are also involved in trunk rotation and to assess the effect of any postural role on inspiratory drive to the muscles, intramuscular electromyographic (EMG) recordings were made from the parasternal intercostals on the right side in six healthy subjects during resting breathing in a neutral posture (“neutral breaths”), during an isometric axial rotation effort of the trunk to the right (“ipsilateral rotation”) or left (“contralateral rotation”), and during resting breathing with the trunk rotated. The parasternal intercostals were commonly active during ipsilateral rotation but were consistently silent during contralateral rotation. In addition, with ipsilateral rotation, peak parasternal inspiratory activity was 201 ± 19% (mean ± SE) of the peak inspiratory activity in neutral breaths ( P < 0.001), and activity commenced earlier relative to the onset of inspiratory flow. These changes resulted from an increase in the discharge frequency of motor units (14.3 ± 0.3 vs. 11.0 ± 0.3 Hz; P < 0.001) and the recruitment of new motor units. The majority of units that discharged during ipsilateral rotation were also active in inspiration. However, with contralateral rotation, parasternal inspiratory activity was delayed relative to the onset of inspiratory flow, and peak activity was reduced to 72 ± 4% of that in neutral breaths ( P < 0.001). This decrease resulted from a decrease in the inspiratory discharge frequency of units (10.5 ± 0.2 vs. 12.0 ± 0.2 Hz; P < 0.001) and the derecruitment of units. These observations confirm that in addition to an inspiratory function, the parasternal intercostal muscles have a postural function. Furthermore the postural and inspiratory drives depolarize the same motoneurons, and the postural contraction of the muscles alters their output during inspiration in a direction-dependent manner.
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Affiliation(s)
- Anna L. Hudson
- Prince of Wales Medical Research Institute and University of New South Wales, Sydney, New South Wales, Australia; and
| | - Jane E. Butler
- Prince of Wales Medical Research Institute and University of New South Wales, Sydney, New South Wales, Australia; and
| | - Simon C. Gandevia
- Prince of Wales Medical Research Institute and University of New South Wales, Sydney, New South Wales, Australia; and
| | - Andre De Troyer
- Laboratory of Cardiorespiratory Physiology, Brussels School of Medicine and Chest Service, Erasme University Hospital, Brussels, Belgium
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24
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Davenport PW, Reep RL, Thompson FJ. Phrenic nerve afferent activation of neurons in the cat SI cerebral cortex. J Physiol 2010; 588:873-86. [PMID: 20064855 DOI: 10.1113/jphysiol.2009.181735] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Stimulation of respiratory afferents elicits neural activity in the somatosensory region of the cerebral cortex in humans and animals. Respiratory afferents have been stimulated with mechanical loads applied to breathing and electrical stimulation of respiratory nerves and muscles. It was hypothesized that stimulation of the phrenic nerve myelinated afferents will activate neurons in the 3a and 3b region of the somatosensory cortex. This was investigated in cats with electrical stimulation of the intrathoracic phrenic nerve and C(5) root of the phrenic nerve. The somatosensory cortical response to phrenic afferent stimulation was recorded from the cortical surface, contralateral to the phrenic nerve, ispilateral to the phrenic nerve and with microelectrodes inserted into the cortical site of the surface dipole. Short-latency, primary cortical evoked potentials (1 degrees CEP) were recorded with stimulation of myelinated afferents of the intrathoracic phrenic nerve in the contralateral post-cruciate gyrus of all animals (n = 42). The mean onset and peak latencies were 8.5 +/- 5.7 ms and 21.8 +/- 9.8 ms, respectively. The rostro-caudal surface location of the 1 degrees CEP was found between the rostral edge of the post-cruciate dimple (PCD) and the rostral edge of the ansate sulcus, medio-lateral location was between 2 mm lateral to the sagittal sulcus and the lateral end of the cruciate sulcus. Histological examination revealed that the 1 degrees CEP sites were recorded over areas 3a and 3b of the SI somatosensory cortex. Intracortical activation of 16 neurons with two patterns of neural activity was recorded: (1) short-latency, short-duration activation of neurons and (2) long-latency, long-duration activation of neurons. Short-latency neurons had a mean onset latency of 10.4 +/- 3.1 ms and mean burst duration of 10.1 +/- 3.2 ms. The short-latency units were recorded at an average depth of 1.7 +/- 0.5 mm below the cortical surface. The long-latency neurons had a mean onset latency of 36.0 +/- 4.2 ms and mean burst duration of 32.2 +/- 8.4 ms. The long-latency units were recorded at an average depth of 2.4 +/- 0.2 mm below the cortical surface. The results of the study demonstrated that phrenic nerve afferents have a short-latency central projection to the SI somatosensory cortex. The phrenic afferents activated neurons in lamina III and IV of areas 3a and 3b. The cortical representation of phrenic nerve afferents is medial to the forelimb, lateral to the hindlimb, similar to thoracic loci, hence the phrenic afferent SI site in the cat homunculus is consistent with body position (thoracic region) rather than spinal segment (C(5)-C(7)). The phrenic afferent activation of the somatosensory cortex is bilateral, with the ipsilateral cortical activation occurring subsequent to the contralateral. These results support the hypothesis that phrenic afferents provide somatosensory information to the cerebral cortex which can be used for diaphragmatic proprioception and somatosensation.
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Affiliation(s)
- Paul W Davenport
- Department of Physiological Sciences, Box 100144, HSC, University of Florida, Gainesville, FL 32610, USA.
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25
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Davenport PW, Vovk A. Cortical and subcortical central neural pathways in respiratory sensations. Respir Physiol Neurobiol 2009; 167:72-86. [DOI: 10.1016/j.resp.2008.10.001] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2008] [Revised: 09/29/2008] [Accepted: 10/01/2008] [Indexed: 10/21/2022]
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26
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McKay LC, Adams L, Frackowiak RS, Corfield DR. A bilateral cortico-bulbar network associated with breath holding in humans, determined by functional magnetic resonance imaging. Neuroimage 2008; 40:1824-32. [DOI: 10.1016/j.neuroimage.2008.01.058] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2007] [Revised: 12/19/2007] [Accepted: 01/23/2008] [Indexed: 02/05/2023] Open
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27
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Butler JE. Drive to the human respiratory muscles. Respir Physiol Neurobiol 2007; 159:115-26. [PMID: 17660051 DOI: 10.1016/j.resp.2007.06.006] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Revised: 06/07/2007] [Accepted: 06/07/2007] [Indexed: 11/24/2022]
Abstract
The motor control of the respiratory muscles differs in some ways from that of the limb muscles. Effectively, the respiratory muscles are controlled by at least two descending pathways: from the medulla during normal quiet breathing and from the motor cortex during behavioural or voluntary breathing. Neurophysiological studies of single motor unit activity in human subjects during normal and voluntary breathing indicate that the neural drive is not uniform to all muscles. The distribution of neural drive depends on a principle of neuromechanical matching. Those motoneurones that innervate intercostal muscles with greater mechanical advantage are active earlier in the breath and to a greater extent. Inspiratory drive is also distributed differently across different inspiratory muscles, possibly also according to their mechanical effectiveness in developing airway negative pressure. Genioglossus, a muscle of the upper airway, receives various types of neural drive (inspiratory, expiratory and tonic) distributed differentially across the hypoglossal motoneurone pool. The integration of the different inputs results in the overall activity in the muscle to keep the upper airway patent throughout respiration. Integration of respiratory and non-respiratory postural drive can be demonstrated in respiratory muscles, and respiratory drive can even be observed in limb muscles under certain circumstances. Recordings of motor unit activity from the human diaphragm during voluntary respiratory tasks have shown that depending on the task there can be large changes in recruitment threshold and recruitment order of motor units. This suggests that descending drive across the phrenic motoneurone pool is not necessarily consistent. Understanding the integration and distribution of drive to respiratory muscles in automatic breathing and voluntary tasks may have implications for limb motor control.
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Affiliation(s)
- Jane E Butler
- Prince of Wales Medical Research Institute, University of New South Wales, Sydney, NSW 2031, Australia.
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28
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Cherniack NS. Commentary on “Homeostasis of exercise hyperpnea and optimal sensorimotor integration: The internal model paradigm” by Poon et al. Respir Physiol Neurobiol 2007. [DOI: 10.1016/j.resp.2007.04.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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29
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Binks AP, Vovk A, Ferrigno M, Banzett RB. The air hunger response of four elite breath-hold divers. Respir Physiol Neurobiol 2007; 159:171-7. [PMID: 17702673 PMCID: PMC2225349 DOI: 10.1016/j.resp.2007.06.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2006] [Revised: 06/11/2007] [Accepted: 06/18/2007] [Indexed: 10/23/2022]
Abstract
Normal subjects terminate breath-holds due to intolerable 'air hunger'. We hypothesize that competitive breath-hold divers might have increased tolerance of air hunger. We tested the air hunger (AH) response of four divers who could hold their breath for 6-9 min. Tidal volume and respiratory rate were controlled by mechanical ventilation (ventilation approximately 0.16 L min(-1) kg(-1)). AH was induced by raising PCO2 and rated using a visual analog scale whose maximum was defined as intolerable. SpO2 was maintained at >97%. Three divers reported the same uncomfortable urge to breathe as normal subjects; the slopes of their responses were within normal range. Both resting CO2 and AH threshold were shifted to higher CO2 in some divers. Diver 3 was unique amongst neurologically intact subjects we have studied: he denied feeling an urge to breathe, and denied discomfort. We conclude that elite divers' strategies to tolerate intense air hunger are a minor factor in their ability to tolerate long breath-holds.
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Affiliation(s)
- Andrew P Binks
- Physiology Program, Department of Environmental Health, Harvard School of Public Health, and Department of Anesthesiology, Brigham & Women's Hospital, Boston, MA, USA.
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30
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Abstract
This article reviews the basic properties of breath-holding in humans and the possible causes of the breath at breakpoint. The simplest objective measure of breath-holding is its duration, but even this is highly variable. Breath-holding is a voluntary act, but normal subjects appear unable to breath-hold to unconsciousness. A powerful involuntary mechanism normally overrides voluntary breath-holding and causes the breath that defines the breakpoint. The occurrence of the breakpoint breath does not appear to be caused solely by a mechanism involving lung or chest shrinkage, partial pressures of blood gases or the carotid arterial chemoreceptors. This is despite the well-known properties of breath-hold duration being prolonged by large lung inflations, hyperoxia and hypocapnia and being shortened by the converse manoeuvres and by increased metabolic rate. Breath-holding has, however, two much less well-known but important properties. First, the central respiratory rhythm appears to continue throughout breath-holding. Humans cannot therefore stop their central respiratory rhythm voluntarily. Instead, they merely suppress expression of their central respiratory rhythm and voluntarily 'hold' the chest at a chosen volume, possibly assisted by some tonic diaphragm activity. Second, breath-hold duration is prolonged by bilateral paralysis of the phrenic or vagus nerves. Possibly the contribution to the breakpoint from stimulation of diaphragm muscle chemoreceptors is greater than has previously been considered. At present there is no simple explanation for the breakpoint that encompasses all these properties.
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Affiliation(s)
- M J Parkes
- School of Sport & Exercise Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
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31
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Jack S, Rossiter HB, Pearson MG, Ward SA, Warburton CJ, Whipp BJ. Ventilatory Responses to Inhaled Carbon Dioxide, Hypoxia, and Exercise in Idiopathic Hyperventilation. Am J Respir Crit Care Med 2004; 170:118-25. [PMID: 15059786 DOI: 10.1164/rccm.200207-720oc] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Idiopathic hyperventilation (IH) is a poorly understood condition of sustained hypocapnia and controversial etiology. Although behavioral/emotional factors may contribute, it is uncertain whether chemosensitivity is altered, hyperventilation is maintained during exercise, and the associated breathlessness reflects the hyperventilation. In 39 patients with IH and 23 control subjects, we described ventilatory responses to isocapnic-hypoxia, hyperoxic-hypercapnia, and exercise; breath-hold tolerance; breathlessness; and psychologic status. Patients demonstrated hyperventilation at rest, with hypocapnia (28 +/- 3.8 mm Hg), a normal (slightly alkaline) arterial pH and [H(+)]a, and a significant base excess (-4.5 +/- 2.7 mEq/L), consistent with compensated respiratory alkalosis. Hyperventilation was sustained during exercise, despite hyperoxic-hypercapnic ventilatory responsiveness being normal and isocapnic-hypoxic ventilatory responsiveness being low relative to control (but exceeding control [2.4 +/- 1.0 vs. 1.6 +/- 0.5 L/min/%, p < 0.05] with acute restoration to normocapnia). Hyperventilation was maintained during exercise, at the resting CO(2) "setpoint." Relative to control, the breath-hold tolerance was attenuated, and dyspnea during exercise was significantly greater and not simply ascribable to the high ventilation. These observations suggest that patients with IH have a sustained hyperventilatory and dyspneic drive that, although not attributable to central chemosensitivity, may possibly have peripheral chemoreflex contributions. The nature and etiology of this chronic hyperventilatory drive remain unclear.
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Affiliation(s)
- Sandy Jack
- Aintree Chest Centre, University Hospital Aintree, Liverpool L9 7AL, UK
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32
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McKay LC, Evans KC, Frackowiak RSJ, Corfield DR. Neural correlates of voluntary breathing in humans. J Appl Physiol (1985) 2003; 95:1170-8. [PMID: 12754178 DOI: 10.1152/japplphysiol.00641.2002] [Citation(s) in RCA: 189] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To investigate the functional neuroanatomy of voluntary respiratory control, blood O2 level-dependent functional magnetic resonance imaging was performed in six healthy right-handed individuals during voluntary hyperpnea. Functional images of the whole brain were acquired during 30-s periods of spontaneous breathing alternated with 30-s periods of isocapnic hyperpnea [spontaneous vs. voluntary: tidal volume = 0.5 +/- 0.01 vs. 1.3 +/- 0.1 (SE) liters and breath duration = 4.0 +/- 0.4 vs. 3.2 +/- 0.4 (SE) s]. For the group, voluntary hyperpnea was associated with significant (P < 0.05, corrected for multiple comparisons) neural activity bilaterally in the primary sensory and motor cortices, supplementary motor area, cerebellum, thalamus, caudate nucleus, and globus pallidum. Significant increases in activity were also identified in the medulla (corrected for multiple comparisons on the basis of a small volume correction for a priori region of interest) in a superior dorsal position (P = 0.012). Activity within the medulla suggests that the brain stem respiratory centers may have a role in mediating the voluntary control of breathing in humans.
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Affiliation(s)
- L C McKay
- National Heart and Lung Instiute, Imperial College London, London W6 8RP, United Kingdom
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33
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Reilly KJ, Moore CA. Respiratory sinus arrhythmia during speech production. JOURNAL OF SPEECH, LANGUAGE, AND HEARING RESEARCH : JSLHR 2003; 46:164-177. [PMID: 12647896 PMCID: PMC3976417 DOI: 10.1044/1092-4388(2003/013)] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The amplitude of the respiratory sinus arrhythmia (RSA) was investigated during a reading aloud task to determine whether alterations in respiratory control during speech production affect the amplitude of RSA. Changes in RSA amplitude associated with speech were evaluated by comparing RSA amplitudes during reading aloud with those obtained during rest breathing. A third condition, silent reading, was included to control for potentially confounding effects of cardiovascular responses to cognitive processes involved in the process of reading. Calibrated respiratory kinematics, electrocardiograms (ECGs), and speech audio signals were recorded from 18 adults (9 men, 9 women) during 5-min trials of each condition. The results indicated that the increases in respiratory duration, lung volume, and inspiratory velocity associated with reading aloud were accompanied by similar increases in the amplitude of RSA. This finding provides support for the premise that sensorimotor pathways mediating metabolic respiration are actively modulated during speech production.
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Affiliation(s)
- Kevin J Reilly
- Department of Speech and Hearing Sciences, University of Washington, Seattle 98105-6246, USA.
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Abstract
Although recent evidence demonstrates considerable neuroplasticity in the respiratory control system, a comprehensive conceptual framework is lacking. Our goals in this review are to define plasticity (and related neural properties) as it pertains to respiratory control and to discuss potential sites, mechanisms, and known categories of respiratory plasticity. Respiratory plasticity is defined as a persistent change in the neural control system based on prior experience. Plasticity may involve structural and/or functional alterations (most commonly both) and can arise from multiple cellular/synaptic mechanisms at different sites in the respiratory control system. Respiratory neuroplasticity is critically dependent on the establishment of necessary preconditions, the stimulus paradigm, the balance between opposing modulatory systems, age, gender, and genetics. Respiratory plasticity can be induced by hypoxia, hypercapnia, exercise, injury, stress, and pharmacological interventions or conditioning and occurs during development as well as in adults. Developmental plasticity is induced by experiences (e.g., altered respiratory gases) during sensitive developmental periods, thereby altering mature respiratory control. The same experience later in life has little or no effect. In adults, neuromodulation plays a prominent role in several forms of respiratory plasticity. For example, serotonergic modulation is thought to initiate and/or maintain respiratory plasticity following intermittent hypoxia, repeated hypercapnic exercise, spinal sensory denervation, spinal cord injury, and at least some conditioned reflexes. Considerable work is necessary before we fully appreciate the biological significance of respiratory plasticity, its underlying cellular/molecular and network mechanisms, and the potential to harness respiratory plasticity as a therapeutic tool.
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Affiliation(s)
- Gordon S Mitchell
- Department of Comparative Biosciences, University of Wisconsin, Madison 53706, USA.
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Dempsey JA, Sheel AW, St Croix CM, Morgan BJ. Respiratory influences on sympathetic vasomotor outflow in humans. Respir Physiol Neurobiol 2002; 130:3-20. [PMID: 12380012 DOI: 10.1016/s0034-5687(01)00327-9] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We have attempted to synthesize findings dealing with four types of respiratory system influences on sympathetic outflow in the human. First, a powerful lung volume-dependent modulation of muscle sympathetic nerve activity (MSNA) occurs within each respiratory cycle showing late-inspiratory inhibition and late-expiratory excitation. Secondly, in the intact human, neither reductions in spontaneous respiratory motor output nor voluntary near-maximum increases in central respiratory motor output and inspiratory effort, per sec, influence MSNA modulation within a breath, MSNA total activity or limb vascular conductance. Thirdly, carotid chemoreceptor stimuli markedly increase total MSNA; but most of the MSNA response to chemoreceptor activation appears to be mediated independently of increased central respiratory motor output. Fourthly, repeated fatiguing contractions of the diaphragm or expiratory muscles in the human show a metaboreflex mediated time-dependent increase in MSNA and reduced vascular conductance and blood flow in the resting limb. Recent evidence suggests that these respiratory influences contribute significantly to sympathetic vasomotor outflow and to the distribution of systemic vascular conductances and blood flow in the exercising human.
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Affiliation(s)
- Jerome A Dempsey
- John Rankin Laboratory of Pulmonary Medicine, Department of Population Health Sciences, University of Wisconsin, 504 N. Walnut Street, Madison, WI 53706, USA.
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Howard RS, Rudd AG, Wolfe CD, Williams AJ. Pathophysiological and clinical aspects of breathing after stroke. Postgrad Med J 2001; 77:700-2. [PMID: 11677278 PMCID: PMC1742182 DOI: 10.1136/pmj.77.913.700] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- R S Howard
- Department of Neurology, Guy's and St. Thomas' Hospital Trust, London, UK
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Computational Modeling of Integration of Voluntarybehavioral and Automatic Mechanisms Forbreathing Control. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2001. [DOI: 10.1007/978-1-4615-1375-9_68] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Poon CS, Siniaia MS. Plasticity of cardiorespiratory neural processing: classification and computational functions. RESPIRATION PHYSIOLOGY 2000; 122:83-109. [PMID: 10967337 DOI: 10.1016/s0034-5687(00)00152-3] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Neural plasticity, or malleability of neuronal structure and function, is an important attribute of the mammalian forebrain and is generally thought to be a kernel of biological intelligence. In this review, we examine some reported manifestations of neural plasticity in the cardiorespiratory system and classify them into four functional categories, integral; differential; memory; and statistical-type plasticity. At the cellular and systems level the myriad forms of cardiorespiratory plasticity display emergent and self-organization properties, use- and disuse-dependent and pairing-specific properties, short-term and long-term potentiation or depression, as well as redundancy in series or parallel structures, convergent pathways or backup and fail-safe surrogate pathways. At the behavioral level, the cardiorespiratory system demonstrates the capability of associative and nonassociative learning, classical and operant conditioning as well as short-term and long-term memory. The remarkable similarity and consistency of the various types of plasticity exhibited at all levels of organization suggest that neural plasticity is integral to cardiorespiratory control and may subserve important physiological functions.
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Affiliation(s)
- C S Poon
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Bldg. E25-501, Cambridge, MA 02139, USA.
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Evans KC, Shea SA, Saykin AJ. Functional MRI localisation of central nervous system regions associated with volitional inspiration in humans. J Physiol 1999; 520 Pt 2:383-92. [PMID: 10523407 PMCID: PMC2269603 DOI: 10.1111/j.1469-7793.1999.00383.x] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/1999] [Accepted: 07/27/1999] [Indexed: 11/28/2022] Open
Abstract
1. Functional magnetic resonance imaging (fMRI) provides a means of studying neuronal circuits that control respiratory muscles in humans with better spatial and temporal resolution than in previous positron emission tomography (PET) studies. 2. Whole brain blood oxygenation level-dependent (BOLD) changes determined by fMRI were used to identify areas of neuronal activation associated with volitional inspiration in five healthy men. Four series of scans of each subject were acquired during voluntary breathing (active task) and mechanical ventilation (passive task). Ventilation and end-tidal PCO2 were similar between tasks. Scan data were re-aligned to correct for movement artefacts and cross-referenced breath by breath to respiratory data for selective averaging of inspiratory and expiratory images. 3. Group analysis identified significant increases in the fMRI signal with volitional inspiration in the superior motor cortex, premotor cortex and supplementary motor area at loci similar to those detected in earlier studies that used PET. Additional regions activated by volitional inspiration included inferolateral sensorimotor cortex, prefrontal cortex and striatum (these foci were only revealed by PET under significant inspiratory load). 4. This study represents the first synchronised breath-by-breath analysis of respiratory-related neuronal activity with whole brain imaging in humans. Temporal resolution is sufficient to distinguish individual breaths at a normal breathing frequency.
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Affiliation(s)
- K C Evans
- Brain Imaging Laboratory, Departments of Psychiatry and Radiology, Dartmouth-Hitchcock Medical Center, 1 Medical Center Drive, Lebanon, NH 03756, USA
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Corne S, Webster K, McGinn G, Walter S, Younes M. Medullary metastasis causing impairment of respiratory pressure output with intact respiratory rhythm. Am J Respir Crit Care Med 1999; 159:315-20. [PMID: 9872856 DOI: 10.1164/ajrccm.159.1.9803051] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
We present an unusual case of weaning failure. A 67-yr-old man presented with confusion, hyponatremia, and hypercapnic respiratory failure that necessitated mechanical ventilation. CXR revealed a right hilar mass (non-small-cell carcinoma on biopsy). Level of consciousness improved with treatment of his hyponatremia. However, attempts at weaning were complicated by hypercapnia with no overt distress. Resistance and elastance were only slightly abnormal, excluding mechanics as a cause of respiratory failure. Maximal inspiratory pressure (MIP) and vital capacity (VC) were reduced at -15 cm H2O and 0.97 L, respectively. Limb muscle strength was well preserved, suggesting isolated respiratory muscle weakness. During a weaning trial respiratory rate increased from 7 to 40 breaths/min as PCO2 increased from 56 to 89 mm Hg, confirming an intact respiratory pacemaker and good response to CO2. However, spontaneous Pdi was only 1 to 2 cm H2O (< 20% of Pdimax) despite profound hypercapnia. The fact that the patient did not utilize a greater fraction of his pressure-generating capacity suggested preferential impairment of the automatic respiratory centers. MRI showed a large central metastatic lesion in the rostral medulla with only a thin rim of uninvolved tissue. This case illustrates the utility of relating the magnitude of spontaneous efforts to maximal voluntary efforts as a means of localizing the site of involvement in cases of respiratory muscle weakness. It also demonstrates that a large medullary mass lesion may selectively impair brainstem modulation of respiratory pressure output while sparing other medullary functions, and in particular the pacemaking function of the respiratory centers.
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Affiliation(s)
- S Corne
- Department of Medicine, University of Manitoba, and Department of Radiology, St. Boniface Hospital, Winnipeg, Canada
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Corfield DR, Murphy K, Guz A. Does the motor cortical control of the diaphragm 'bypass' the brain stem respiratory centres in man? RESPIRATION PHYSIOLOGY 1998; 114:109-17. [PMID: 9865585 DOI: 10.1016/s0034-5687(98)00083-8] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In humans, cortico-motor excitation of the diaphragm may act directly on the phrenic motor nucleus via the cortico-spinal tract 'bypassing' brain stem respiratory centres (RC); alternatively, or in addition, this control may be indirect via the RC and bulbo-spinal paths. To investigate this, we stimulated the motor cortex using transcranial magnetic stimulation (TMS) in six subjects at end-expiration (diaphragm relaxed) and during voluntary inspiration. The sizes of the evoked compound action potentials in the diaphragm and also, as a control, in the thumb were no different whether TMS was delivered during normocapnia or during hypocapnia (PET(CO2) = 25 mmHg) when, presumably, the respiratory 'oscillator' was silent. In a further six subjects, TMS was performed during relaxed spontaneous breathing at three different points in the respiratory cycle. No perturbations in respiratory pattern (either tidal volume or respiratory timing) were seen. Thus we have been unable to demonstrate that the cortico-motor excitation of the diaphragm acts via the brain stem RC.
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Affiliation(s)
- D R Corfield
- Imperial College School of Medicine, National Heart and Lung Institute, Charing Cross Campus, London, UK.
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42
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Abstract
This review attempts to summarize: (i) evidence on how man voluntarily or behaviourally (as in speech) alters breathing; and (ii) evidence on how the breathlessness induced by CO2 inhalation, is perceived. The application of new methods to study these problems, e.g. functional brain imaging and transcranial focal brain stimulation, is summarized. Studies of patients with specific neurological lesions have shed considerable light in this area. The key requirement for the ponto-medullary respiratory oscillator to be both 'intact' and 'responsive' for the perception of CO2-induced air hunger is emphasized. We are ignorant as to how the voluntary/behavioural control system interacts with the automatic system at any site above the final common pathway of the respiratory anterior horn cells in the cervical and thoracic spinal cord. The opportunities for further work are outlined.
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Affiliation(s)
- A Guz
- Charing Cross and Westminster Medical School, London, UK.
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Abstract
We studied in conscious humans the relative strength of mechanisms controlling timing and drive components of the respiratory cycle around their resting set points. A system of auditory feedback with end-tidal PCO2 held constant in mild hyperoxia via an open circuit was used to induce subjects independently to change inspiratory time (TI) and tidal volume (VTI) over a wide range above and below the resting values for every breath for up to 1 h. Four protocols were studied in various levels of hypercapnia (1-5% inspired CO2). We found that TI (and expiratory time) could be changed over a wide range (1.17 - 2.86 s, P < 0.01 for TI) and VTI increased by > or = 500 ml (P < 0.01) without difficulty. However, in no protocol was it possible to decrease VTI below the free-breathing resting value in response to reduction of auditory feedback thresholds by up to 600 ml. This applied at all levels of chemical drive studied, with resting VTI values varying from 1.06 to 1.74 liters. When reduction in VTI was forced by the more "programmed" procedure of isocapnic panting, end-expiratory of volume was sacrificed to ensure that peak tidal volume reached a fixed absolute lung volume. These results suggest that the imperative for control of resting breathing is to prevent reduction of VTI below the level dictated by the prevailing chemical drive, presumably to sustain metabolic requirements of the body, whereas respiratory timing is weakly controlled consistent with the needs for speech and other nonmetabolic functions of breathing.
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Affiliation(s)
- G F Rafferty
- Department of Physiology, Kings College London, United Kingdom
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Heywood P, Murphy K, Corfield DR, Morrell MJ, Howard RS, Guz A. Control of breathing in man; insights from the 'locked-in' syndrome. RESPIRATION PHYSIOLOGY 1996; 106:13-20. [PMID: 8946573 DOI: 10.1016/0034-5687(96)00060-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Control of breathing was studied in a patient with a lesion in the ventral pons; no volitional behaviour, including voluntary breathing acts, was possible (locked-in syndrome, LIS). Spontaneous breathing via a tracheostomy maintained a normal PETCO2 of 39-40 mmHg. Variability of ventilatory parameters awake was similar to that seen in five tracheostomized control subjects during stage IV sleep but much smaller than during resting wakefulness. Emotion associated with laughter caused disturbances of breathing. The ventilatory response to CO2 was normal and was associated with 'hunger for air' when the PETCO2 was 49-50 mmHg. Mechanical ventilation to reduce PETCO2 by as little as 1 mmHg resulted in apnoea when the ventilator was disconnected; breathing resumed when PETCO2 crossed the threshold of 39-40 mmHg. These results demonstrate the functional dependence of the human medullary respiratory oscillator on a threshold level of PCO2 in the absence of cortico-bulbar input, even during wakefulness. The absence of such input may explain the regularity of breathing.
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Affiliation(s)
- P Heywood
- Department of Medicine, Charing Cross and Westminster Medical School, London, UK
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46
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Oku Y, Saidel GM, Cherniack NS, Altose MD. Model of respiratory sensation and wilful control of ventilation. Med Biol Eng Comput 1995; 33:252-6. [PMID: 7475359 DOI: 10.1007/bf02510496] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A mathematical model has been developed that includes sensations of breathlessness and a dynamic CO2 respiratory controller. Breathing sensations, which are represented as a discomfort index, are assumed to depend on arterial PCO2 level, automatic and wilful motor commands and mechanoreceptor feedback. Wilful control is assumed to arise from cortical centres of the brain and is independent of the reflex control system. The bulbopontine respiratory controller produces the automatic motor command, which is determined by chemical and mechanical feedback. Simulations demonstrate how the controller output and breathing sensations change when wilful motor commands disturb spontaneous breathing. Simulations include isocapnic hyper- and hypoventilation and deliberate hypoventilation during CO2 rebreathing. Simulations are compared with experimental data from human subjects. Simulations predict that the discomfort index intensifies when ventilation is either voluntarily raised or lowered from the optimal level; and discomfort is greater when ventilation is lowered than when it is raised at a given level of PCO2. The simulated results agree with those obtained experimentally. The simulations suggest that respiratory drive integration may depend not only on the direct effects of chemical and mechanical feedback, but also on the perceptual consequences of these stimuli.
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Affiliation(s)
- Y Oku
- Department of Medicine, Case Western Reserve University, USA
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47
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McKenzie DK, Bellemare F. Respiratory muscle fatigue. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1995; 384:401-14. [PMID: 8585468 DOI: 10.1007/978-1-4899-1016-5_32] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Ventilatory failure may accompany a variety of pulmonary and neuromuscular diseases. There has been much controversy about whether this failure is due to respiratory muscle fatigue at peripheral sites or a failure of drive at sites within the central nervous system. The chapter reviews this topic.
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Affiliation(s)
- D K McKenzie
- Department of Respiratory Medicine, University of New South Wales, Sydney, Australia
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48
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Chang FC. Modification of medullary respiratory-related discharge patterns by behaviors and states of arousal. Brain Res 1992; 571:281-92. [PMID: 1611499 DOI: 10.1016/0006-8993(92)90666-w] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The modulatory influences of behaviors and states of arousal on bulbar respiratory-related unit (RRU) discharge patterns were studied in an unanesthetized, freely behaving guinea pig respiratory model system. When fully instrumented, this model system permits concurrent monitoring and recording of (i) single units from either Bötzinger complex or nucleus para-ambiguus; (ii) electrocorticogram; and, (iii) diaphragmatic EMG. In addition to being used in surveys of RRU discharge patterns in freely behaving states, the model system also offered a unique opportunity in investigating the effects of pentobarbital on RRU discharge patterns before, throughout the course of, and during recovery from anesthesia. In anesthetized preparations, a particular RRU discharge pattern (such as tonic, incrementing or decrementing) typically displayed little, if any notable variation. The most striking development following pentobarbital was a state of progressive bradypnea attributable to a significantly augmented RRU cycle duration, burst duration and an increase in the RRU spike frequencies during anesthesia. In freely behaving states, medullary RRU activities rarely adhered to a fixed, immutable discharge pattern. More specifically, the temporal organization (such as burst duration, cycle duration, and the extent of modulation of within-burst spike frequencies) of RRU discharge patterns regularly showed complex and striking variations, not only with states of arousal (sleep/wakefulness, anesthesia) but also with discrete alterations in electrocorticogram (ECoG) activities and a multitude of on-going behavioral repertoires such as volitional movement, postural modification, phonation, mastication, deglutition, sniffing/exploratory behavior, alerting/startle reflexes. Only during sleep, and on occasions when the animal assumed a motionless, resting posture, could burst patterns of relatively invariable periodicity and uniform temporal attributes be observed. RRU activities during sniffing reflex is worthy of further note in that, based on power spectrum analyses of concurrently recorded ECoG activities, this particular discharge pattern was clearly associated with the activation of a 6-10 Hz theta rhythm. These findings indicated that bulbar RRU activity patterns are subject to change by not only behaviors and sleep/wakefulness cycles, but also a variety of modulatory influences and feedback/feedforward biases from other central and peripheral physiological control mechanisms.
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Affiliation(s)
- F C Chang
- Neurotoxicology Branch, U.S. Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010-5425
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49
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Macefield G, Gandevia SC. The cortical drive to human respiratory muscles in the awake state assessed by premotor cerebral potentials. J Physiol 1991; 439:545-58. [PMID: 1895244 PMCID: PMC1180123 DOI: 10.1113/jphysiol.1991.sp018681] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
1. We investigated the possibility of a cortical contribution to human respiration by recording from the scalp of awake subjects the premotor cerebral potentials that are known to precede voluntary limb movements. 2. Electroencephalographic activity (EEG) was recorded from scalp electrodes and averaged for 1.8-2.0 s before the time at which airway pressure exceeded an inspiratory or expiratory threshold. Clear premotor cerebral potentials were recorded during brisk, self-paced nasal inhalations or exhalations. In ten subjects, a slow cortical negativity (Bereitschaftspotential) was apparent in the averaged EEG, commencing 1.2 +/- 0.3 s before the onset of inspiratory (scalene) or expiratory (abdominal) muscle activity (EMG). It was maximal at the vertex, with a mean slope of 12.3 +/- 5.8 microV/s, and was followed by a post-movement positivity. 3. In four subjects the inspiratory premotor potential culminated in a large negativity, the motor potential, which began 24 +/- 15 ms before the onset of scalene EMG. It is argued that such a short latency is consistent with a volitionally generated respiratory command which travels relatively directly to the respiratory muscles, having a total central delay which is no longer than that for voluntary finger movements. 4. That the respiratory premotor and motor potentials did not originate in subcortical structures was supported by their absence in a patient suffering from chronic reflexogenic hiccups, in whom cerebral activity was back-averaged from each brisk hiccup. 5. During quiet breathing, in which subjects were relaxed and distracted from thinking about their respiration, no premotor cerebral potentials preceding inspiration could be detected. This failure was not due to the slow rate of rise of inspiratory activity during quiet breathing as compared with a brisk sniff, because premotor potentials were detected when subjects intermittently generated slow active expiratory efforts. 6. These observations suggest that during quiet breathing the cerebral cortex does not contribute to respiratory drive on a breath-by-breath basis. Conversely, the presence of clear premotor cerebral potentials when subjects performed self-paced inspiratory or expiratory manoeuvres illustrates the powerful cortical projection to human respiratory muscles.
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Affiliation(s)
- G Macefield
- Department of Clinical Neurophysiology, Prince Henry Hospital, Matraville, NSW, Australia
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50
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Affiliation(s)
- R Monteau
- Biologie des Rythmes et du Développement', Département de Physiologie et Neurophysiologie, Faculté des Sciences et Techniques St. Jérôme, Marseille, France
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