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Carns J, Kawaza K, Liaghati-Mobarhan S, Asibon A, Quinn MK, Chalira A, Lufesi N, Molyneux E, Oden M, Richards-Kortum R. Neonatal CPAP for Respiratory Distress Across Malawi and Mortality. Pediatrics 2019; 144:peds.2019-0668. [PMID: 31540968 DOI: 10.1542/peds.2019-0668] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 07/22/2019] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVES Our aim in this observational study was to monitor continuous positive airway pressure (CPAP) usage and outcomes in newborn wards at 26 government hospitals in Malawi after the introduction of CPAP as part of a quality-improvement initiative. CPAP was implemented in 3 phases from 2013 through 2015. METHODS Survival to discharge was analyzed for neonates treated with nasal oxygen and/or CPAP with admission weights of 1 to 2.49 kg at 24 government hospitals with transfer rates <15%. This analysis includes neonates admitted with respiratory illness for 5.5 months before (621 neonates) and 15 months immediately after CPAP implementation (1836 neonates). A follow-up data analysis was completed for neonates treated with CPAP at all hospitals during an additional 11 months (194 neonates). RESULTS On implementation of CPAP, survival to discharge improved for all neonates admitted with respiratory distress (48.6% vs 54.5%; P = .012) and for those diagnosed with respiratory distress syndrome (39.8% vs 48.3%; P = .042). There were no significant differences in outcomes for neonates treated with CPAP during the implementation and follow-up periods. Hypothermia on admission was pervasive and associated with poor outcomes. Neonates with normal mean temperatures during CPAP treatment experienced the highest survival rates (65.7% for all neonates treated with CPAP and 60.0% for those diagnosed with respiratory distress syndrome). CONCLUSIONS A nurse-led CPAP service can improve outcomes for neonates in respiratory distress in low-resource settings. However, the results show that real-world improvements in survival may be limited without access to comprehensive newborn care, especially for small and sick infants.
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Affiliation(s)
- Jennifer Carns
- Rice 360 Institute for Global Health Technology, Houston, Texas.,Department of Bioengineering, Rice University, Houston, Texas
| | - Kondwani Kawaza
- Department of Pediatrics and Child Health, College of Medicine, Queen Elizabeth Central Hospital, Blantyre, Malawi; and
| | | | - Aba Asibon
- Rice 360 Institute for Global Health Technology, Houston, Texas
| | - Mary K Quinn
- Rice 360 Institute for Global Health Technology, Houston, Texas
| | - Alfred Chalira
- Department of Clinical Services, Ministry of Health, Lilongwe, Malawi
| | - Norman Lufesi
- Department of Clinical Services, Ministry of Health, Lilongwe, Malawi
| | - Elizabeth Molyneux
- Department of Pediatrics and Child Health, College of Medicine, Queen Elizabeth Central Hospital, Blantyre, Malawi; and
| | - Maria Oden
- Rice 360 Institute for Global Health Technology, Houston, Texas.,Department of Bioengineering, Rice University, Houston, Texas
| | - Rebecca Richards-Kortum
- Rice 360 Institute for Global Health Technology, Houston, Texas; .,Department of Bioengineering, Rice University, Houston, Texas
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Haberthür C, Guttmann J. Short-term effects of positive end-expiratory pressure on breathing pattern: an interventional study in adult intensive care patients. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2005; 9:R407-15. [PMID: 16137354 PMCID: PMC1269457 DOI: 10.1186/cc3735] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/13/2005] [Revised: 04/18/2005] [Accepted: 05/11/2005] [Indexed: 11/10/2022]
Abstract
INTRODUCTION Positive end-expiratory pressure (PEEP) is used in mechanically ventilated patients to increase pulmonary volume and improve gas exchange. However, in clinical practice and with respect to adult, ventilator-dependent patients, little is known about the short-term effects of PEEP on breathing patterns. METHODS In 30 tracheally intubated, spontaneously breathing patients, we sequentially applied PEEP to the trachea at 0, 5 and 10 cmH2O, and then again at 5 cmH2O for 30 s each, using the automatic tube compensation mode. RESULTS Increases in PEEP were strongly associated with drops in minute ventilation (P < 0.0001) and respiratory rate (P < 0.0001). For respiratory rate, a 1 cmH2O change in PEEP in either direction resulted in a change in rate of 0.4 breaths/min. The effects were exclusively due to changes in expiratory time. Effects began to manifest during the first breath and became fully established in the second breath for each PEEP level. Identical responses were found when PEEP levels were applied for 10 or 60 s. Post hoc analysis revealed a similar but stronger response in patients with impaired respiratory system compliance. CONCLUSION In tracheally intubated, spontaneously breathing adult patients, the level of PEEP significantly influences the resting short-term breathing pattern by selectively affecting expiratory time. These findings are best explained by the Hering-Breuer inflation/deflation reflex.
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Affiliation(s)
- Christoph Haberthür
- Assistant Professor and head of Surgical Intensive Care Medicine, Department of Anaesthesia, Kantonsspital Luzern, Switzerland
| | - Josef Guttmann
- Professor in Biomedical Engineering, Section of Experimental Anaesthesiology, Department of Anaesthesia and Critical Care Medicine, University of Freiburg, Germany
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Naranjo J, Centeno RA, Galiano D, Beaus M. A nomogram for assessment of breathing patterns during treadmill exercise. Br J Sports Med 2005; 39:80-3. [PMID: 15665202 PMCID: PMC1725107 DOI: 10.1136/bjsm.2003.009316] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
OBJECTIVE To assess the breathing patterns of trained athletes under different conditions. The hypothesis is that the breathing pattern during a progressive treadmill exercise is independent of the protocol, at least in healthy people, and can be assessed using a nomogram. METHODS A total of 43 male and 21 female athletes from different sports were studied. They performed one of two different protocols (steps or ramp) on a treadmill. The two protocols started at the same speed and had the same rate of increase in work. During the test, the expired air was analysed for CO2 and O2. Ventilation (VE) was continuously recorded, and tidal volume (Vt) and breathing frequency (BF) at the same intensity were analysed for both protocols, as well as Vt/T(i) and T(i)/T(tot). RESULTS No significant differences were observed in Vt and BF between the two protocols in either the men or women at any level (confidence intervals up to 0.958 in all the groups). T(i)/T(tot) remained constant, and all increases in VE were strongly related to the respective increases in Vt/T(i). Plots of data for men and women showed a curvilinear relation between Vt and BF which could be fitted with an exponential function with a strong correlation (R2 = 0.98 for men and 0.97 for women). CONCLUSIONS Graphic expression of Vt v BF is a useful nomogram for the routine assessment of ventilatory response during exercise in healthy trained subjects.
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Affiliation(s)
- J Naranjo
- Centro Andaluz de Medicina del Deporte, Exercise Physiology, CAR La Cartuja, Isla de la Cartuja s/n, Sevilla 41092, Spain.
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Fernandez R, Mendez M, Younes M. Effect of ventilator flow rate on respiratory timing in normal humans. Am J Respir Crit Care Med 1999; 159:710-9. [PMID: 10051241 DOI: 10.1164/ajrccm.159.3.9709090] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Respiratory rate (RR) increases as a function of ventilator flow rate (V). We wished to determine whether this is due to a decrease in neural inspiratory time (T In), neural expiratory time (TEn), or both. To accomplish this, we ventilated 15 normal subjects in the assist, volume cycled mode. Ventilator flow rate was varied at random, at four breaths with each step, over the flow range from 0.8 (Vmin) to 2.5 (Vmax) L/s. V T was kept constant. The pressure developed by respiratory muscles (Pmus) was calculated with the equation of motion (Pmus = V. R + V. E - Paw, where R = resistance, V = volume, E = elastance, and Paw = airway pressure). Electromyography of the diaphragm (Edi) was also done in five subjects. TIn and TEn were determined from the Pmus or Edi waveform. TIn decreased progressively as a function of V, from 1.44 +/- 0.34 s at Vmin to 0.62 +/- 0.26 s at Vmax (p < 0.00001). Changes in TEn were inconsistent and not significant. TIn/Ttot decreased significantly (0.30 +/- 0.06 at Vmin to 0.18 +/- 0.09 at Vmax; p < 0. 00001). We conclude that TI is highly sensitive to ventilator flow, and that the RR response to V is primarily related to this T In response. Because an increase in V progressively reduces T In/Ttot, and this variable is an important determinant of inspiratory muscle energetics, we further conclude that inspiratory muscle energy expenditure is quite sensitive to V over the range from 0.8 to 2.5 L/s.
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Affiliation(s)
- R Fernandez
- Section of Respiratory Diseases, Department of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada
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Delacourt C, Canet E, Praud JP, Bureau MA. Influence of vagal afferents on diphasic ventilatory response to hypoxia in newborn lambs. RESPIRATION PHYSIOLOGY 1995; 99:29-39. [PMID: 7740209 DOI: 10.1016/0034-5687(94)00078-e] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The effect of vagal afferents on the ventilatory response to hypoxia was studied in eleven awake newborn lambs. Tests were repeated before and after vagotomy in the same lambs in two conditions: with intact upper airways and after intubation. During hypoxia, a diphasic pattern of ventilatory response was observed in both vagotomized and intact lambs. However, face mask-breathing vagotomized lambs had a blunted increase in ventilation (VI) to hypoxia as compared with intact lambs (P = 0.0001) and they showed an expiratory braking during all hypoxic time. Furthermore, the normal increase in frequency (f) to hypoxia was abolished after vagotomy. After intubation, expiratory braking disappeared and, consequently, magnitude of the VI response to hypoxia was similar in intact and vagotomized lambs. These changes were due to improved tidal volume response in vagotomized intubated lambs (P < 0.002) with no significant change in f response. We concluded that, in awake newborn lambs, vagal afferents are essential for maintaining the pattern and the magnitude of the ventilatory response to hypoxia, the latter by controlling the motor output to the larynx.
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Affiliation(s)
- C Delacourt
- Jeremy Rill Center, Département de Pédiatrie, Université de Sherbrooke, Québec, Canada
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O'Donnell DE, Sanii R, Dubo H, Loveridge B, Younes M. Steady-state ventilatory responses to expiratory resistive loading in quadriplegics. THE AMERICAN REVIEW OF RESPIRATORY DISEASE 1993; 147:54-9. [PMID: 8420432 DOI: 10.1164/ajrccm/147.1.54] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Patients with quadriplegia have a limited capacity to recruit expiratory muscles and are deprived of respiratory-related feedback from the rib cage and abdominal wall. We wished to evaluate the compensatory strategies available to such patients during expiratory resistive loading (ERL) and to compare their responses with those of normal healthy individuals. In addition, to determine whether the quadriplegic subjects have a blunted sensory appreciation of added ERL, we also compared sensory detection thresholds (delta R50). Steady-state ventilatory responses to ERL (delta R = 12 cm H2O/L/s) were compared in seven quadriplegic patients (level of injury, C6, C7) and six age-matched normal subjects. Highly significant intergroup differences were evident in the extent of prolongation of expiratory time (TE) and total cycle duration (Ttot) during ERL; values of delta TE and delta Ttot in quadriplegics were, on average, 46% of those of normals (p < 0.001). Minute ventilation (VE) was defended to an equal or better extent in quadriplegics. ERL-induced changes in tidal volume, inspiratory duration, mean inspiratory and expiratory flows, and end-expiratory lung volume (EELV) were not significantly different. Average delta R50 in quadriplegics and normals were (mean +/- SD), 1.73 +/- 0.039 cm H2O/L/s and 1.62 +/- 0.4 cm H2O/L/s, respectively (p = ns). Quadriplegics, therefore, despite substantial sensory and motor deficits, defend ventilation and EELV as effectively as normal individuals and show no attenuation in the ability to detect an added expiratory resistance.
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Affiliation(s)
- D E O'Donnell
- Department of Medicine, University of Manitoba, Winnipeg, Canada
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Fenik VB. Mechanoreceptor system of the respiratory center and its contribution to respiratory control. NEUROPHYSIOLOGY+ 1992. [DOI: 10.1007/bf01057171] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Muza SR, Lee LY, Pan CP, Zechman FW, Frazier DT. Respiratory volume-timing relationship during sustained elevation of functional residual capacity. RESPIRATION PHYSIOLOGY 1984; 58:77-86. [PMID: 6515153 DOI: 10.1016/0034-5687(84)90046-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
In 7 spontaneously breathing dial-urethane anesthetized cats a negative pressure was produced around the thorax and abdomen to increase the functional residual capacity (FRC) by about 1 tidal volume for up to 60 min. A tracheal cannula was connected to a resistive manifold for selective loading of inspiration or expiration. Two resistive loads and tracheal occlusion were presented six times each at control FRC (FRCc), after 60 min at elevated FRC (FRCe) and 30 min after return to FRCc. Inspiratory and expiratory durations (TI and TE) were measured from diaphragmatic EMG. We observed that TI at FRCe (0.88 +/- 0.11 sec) was not significantly shorter than TI at FRCc (1.06 +/- 0.14 sec). Tracheal occlusion at FRCe caused a shorter TI (1.37 +/- 0.15 sec) than at FRCc (1.79 +/- 0.21 sec) (P less than 0.05). The slope (m) of the VI-TI relationship generated by the resistive loads at FRCe was steeper (m = -65 +/- 7 ml X sec-1) and shifted upward from the VI-TI curve at FRCc (-50 +/- 6 ml X sec-1) (P less than 0.05). The VE-TE relationship at FRCe was not significantly changed from control. Thirty minutes following return to FRCc, TI was still slightly shorter (0.96 +/- 0.11 sec) than the initial TI at FRCc. We conclude: (1) The slope of the VI-TI relationship is determined to a great extent by the total lung volume. However, under the conditions of sustained elevation of FRC, this relationship is influenced by the partial adaptation of slowly adapting pulmonary receptors SARs. (2) The increased SAR activity at end expiration during FRCe may not influence the control of TE.
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Abstract
The interrelationships of ventilation (V), tidal volume (VT), inspiratory (T1), expiratory (TE) and total breath (Ttot) durations, mean inspiratory (VT/TI) and expiratory (VT/TE) flows, and lung volumes were studied in normal subjects at rest and during exercise on a cycle ergometer. The ergometric load was increased by 10 W every minute, from zero W to 200 W. The TI/Ttot ratio increased with V in the range 15 to 60 1 X min-1, indicating that with increasing V the rate of increase of VT/TI decreased whereas that of VT/TE increased. Possible mechanisms responsible for the difference in behaviour of VT/TI and VT/TE are discussed. The VT-TI and VT-TE relationships both displayed three ranges with breakpoints at tidal volumes of about 1.4 and 2.4 1. The relations of TI and TE to end-inspiratory volume were approximately linear over the entire VT range studied, whereas the relations of TI and TE to end-expiratory volume showed three ranges with different characteristics. We conclude that the termination of inspiration during cycle exercise is dependent on volume-related afferent feedback from the lungs and/or chest walls, not only in the high but also in the low volume range.
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Muza SR, Frazier DT. Response of pulmonary stretch receptors to shifts of functional residual capacity. RESPIRATION PHYSIOLOGY 1983; 52:371-86. [PMID: 6612107 DOI: 10.1016/0034-5687(83)90092-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The response of slowly adapting pulmonary stretch receptors (PSRs) to sustained elevations of functional residual capacity (FRC) was investigated in spontaneous breathing anesthetized cats. A subatmospheric pressure was produced around the thorax and abdomen to increase FRC by approximately one tidal volume (VT) for up to 60 min. During eupneic breathing the PSR frequency (fPSR) was closely related to changes in transpulmonary pressure (PTP), but occasionally hysteresis was observed in the FPSR - PTP relationship. Elevation of FRC caused most phasic PSRs to discharge continuously for a few breaths before returning to a phasic discharge pattern. During the shift in FRC there were increases in mean fPSR, peak fPSR firing threshold which were sustained throughout the period of elevated FRC. PSRs that normally showed discharges at FRC similarly increased their mean and peak firing rates. For all PSRs the y-intercept (fPSR at PTP = 0) of the fPSR - PTP relationship was decreased but the sensitivity of the PSR as defined by delta fPSR/delta PTP was not changed until the period of elevated FRC exceeded 30 min. Thereafter, PSR sensitivity tended to decline. These results suggest that PSRs undergo some modification of their discharge parameters during prolonged elevation of FRC.
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Moomjian AS, Schwartz JG, Wagaman MJ, Shutack JG, Shaffer TH, Fox WW. The effect of external expiratory resistance on lung volume and pulmonary function in the neonate. J Pediatr 1980; 96:908-11. [PMID: 6988558 DOI: 10.1016/s0022-3476(80)80576-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
To investigate the acute physiologic effects of external expiratory resistance on lung function in extubated neonates recovering from respiratory disease, lung mechanics, respiratory patterns, and functional residual capacity were measured in ten neonates dueing a control period and immediately after application of an external expiratory resistance of 30 cm H2O/l/second via a face mask. Following application of EER, mean FRC increased by 40.8% (P less than 0.05). The work of breathing was significantly increased after the EER was applied; there was also a significant increase in measured expiratory resistance and a decrease in inspiratory-expiratory time ratio. The change in lung volume was rapid, requiring less than five seconds for the new end-expiratory level to be reached. Dynamic lung compliance, inspiratory resistance, and respiratory rate did not change during any phase of the study. The application of external expiratory resistance may have potential therapeutic value by increasing lung volume in infants recovering from respiratory disease.
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Coleridge HM, Coleridge JC, Banzett RB. II. Effect of CO2 on afferent vagal endings in the canine lung. RESPIRATION PHYSIOLOGY 1978; 34:135-51. [PMID: 705075 DOI: 10.1016/0034-5687(78)90053-1] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
We have attempted to identify the afferent endings responsible for the pulmonary-CO2 ventilatory reflex. We recorded afferent vagal impulses arising from the left lung in anesthetized dogs with separately ventilated lungs. When the left pulmonary artery was occluded, left lung PCO2 fell to 3 mm Hg and slowly-adapting pulmonary stretch receptor activity increased 46%. Firing declined to its original intensity when left lung PCO2 was raised in steps by administration of CO2, firing decreasing most between 2 and 19 mm Hg, and least between 30 and 50 mm Hg. Irritant receptor activity also increased (from 2.8 to 7.4 impulses/sec) after pulmonary arterial occlusion, the effect being reversed by administration of CO2. These procedures caused trivial changes in pulmonary and bronchial C-fiber activity. Effects on both slowly-adapting stretch receptors and irritant receptors appeared to result from a direct action of CO2 on the endings themselves, rather than from mechanical changes in the lung. Changes in slowly-adapting stretch receptor activity provide an adequate explanation for the pulmonary-CO2 ventilatory reflex, the relationship between impulse frequency and lung PCO2 suggesting that these afferents may have a role in limiting CO2 loss under conditions causing hypocapnia, but be less effective in stimulating breathing during hypercapnia.
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Grunstein MM, Milic-Emili J. Analysis of interactions between central and vagal respiratory control mechanisms in cats. IEEE Trans Biomed Eng 1978; 25:225-35. [PMID: 680751 DOI: 10.1109/tbme.1978.326326] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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D'Angelo E. Effects of single breath lung inflation on the pattern of subsequent breaths. RESPIRATION PHYSIOLOGY 1977; 31:1-18. [PMID: 918408 DOI: 10.1016/0034-5687(77)90061-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
In rabbits, on release of lung inflations 0.4 to 3.3 times control VT and lasting 1 to 30 sec, VT, peak diaphragmatic activity (Ep) and inspiratory duration (Ti) increased, whereas expiratory duration (Te) decreased relative to pre-inflation values. Similar changes occurred between pre- and postinflation occluded breaths. These changes lasted from a few breaths up to 30 sec, and were positively correlated with magnitude and duration of inflations. Postinflation changes of pulmonary stretch receptor activity were relatively small and limited to 1-3 breaths. At chemical drive close to control: (a) postinflation VT vs Ti relationship moved to the right without changing its slope, Ti occluded eventually exceeding Ti after vagotomy; (b) the Te vs Ti relationship moved downwards, its slope being decreased and eventually abolished; (c) the average rate of rise of E was decreased. An increase of VT, Ep and Ti, and a decrease Te also occurred on release of stimulation of the central ends of the cut vagi producing apnea at FRC in mono- and bilateral vagotomized rabbits. Postinflation effects were mainly of central origin and tentatively explained as rebound phenomena within the respiratory center.
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Martin RJ, Nearman HS, Katona PG, Klaus MH. The effect of a low continuous positive airway pressure on the reflex control of respiration in the preterm infant. J Pediatr 1977; 90:976-81. [PMID: 323448 DOI: 10.1016/s0022-3476(77)80575-1] [Citation(s) in RCA: 64] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The airway occlusion technique was used to measure the strength of the Hering-Breuer inflation reflex before and during the administration of low pressure CPAP. In five of 12 preterm infants studied in the first two weeks of life, CPAP did not alter the inflation reflex. In the other seven premature infants, shortened rather than lengthened inspiratory efforts were observed on occlusion 32 times of CPAP but only twice on CPAP. In seven term infants at 1 to 2.5 hours of age this shortening was noted only twice in 58 occlusions. In the preterm infants exhibiting short responses, the peak inspiratory pressure generated in response to occlusion rose on CPAP from 3.4 to 7.1 cm H2O (p less than 0.005), while respiratory rate fell from 61 to 49 breaths/minute (p less than 0.025). This data suggests that CPAP enhances these infants' ability to adjust to increased respiratory loads, possibly by the elimination of a Hering-Breuer deflation reflex.
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Bishop B. Vagal control of diaphragm timing in cat while breathing at elevated lung volumes. RESPIRATION PHYSIOLOGY 1977; 30:169-84. [PMID: 195322 DOI: 10.1016/0034-5687(77)90029-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
This paper proposes and tests an hypothesis to account for the roles of the volume and rate components of vagal feedback in determining the steady-state pattern of breathing during continuous positive pressure breathing (PPB) and expiratory threshold loading (ETL) in Dial anesthetized cats. During PPB the duration of diaphragm activity (Tdi) is shortened; the duration of its expiratory pause (Tep) is lengthened with little or no change in cycle duration (Tt); with onset of inspiration, flow (dV/dt) is increased; as inspiration proceeds, flow decelerates (d2V/dt2). During ETL Tdi, Tep and Tt are all prolonged; dV/dt is decreased at onset of inspiration, with either no change or an acceleration in flow as inspiration proceeds. PPB and ETL cause similar increases in resting lung volume and Tep, and high negative correlations between Tdi and flow. These relationship suggest that the 'volume component' of vagal feedback is one important factor controlling Tep whereas the 'rate component' contributes to the restraint of Tdi.
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