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Morales-Quinteros L, Camprubí-Rimblas M, Bringué J, Bos LD, Schultz MJ, Artigas A. The role of hypercapnia in acute respiratory failure. Intensive Care Med Exp 2019; 7:39. [PMID: 31346806 PMCID: PMC6658637 DOI: 10.1186/s40635-019-0239-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 03/07/2019] [Indexed: 12/16/2022] Open
Abstract
The biological effects and physiological consequences of hypercapnia are increasingly understood. The literature on hypercapnia is confusing, and at times contradictory. On the one hand, it may have protective effects through attenuation of pulmonary inflammation and oxidative stress. On the other hand, it may also have deleterious effects through inhibition of alveolar wound repair, reabsorption of alveolar fluid, and alveolar cell proliferation. Besides, hypercapnia has meaningful effects on lung physiology such as airway resistance, lung oxygenation, diaphragm function, and pulmonary vascular tree. In acute respiratory distress syndrome, lung-protective ventilation strategies using low tidal volume and low airway pressure are strongly advocated as these have strong potential to improve outcome. These strategies may come at a price of hypercapnia and hypercapnic acidosis. One approach is to accept it (permissive hypercapnia); another approach is to treat it through extracorporeal means. At present, it remains uncertain what the best approach is.
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Affiliation(s)
- Luis Morales-Quinteros
- Intensive Care Unit, Hospital Universitario Sagrado Corazón, Carrer de Viladomat, 288, 08029, Barcelona, Spain.
| | - Marta Camprubí-Rimblas
- Department of Medicine, Universitat Autònoma de Barcelona, Bellatera, Spain.,Institut d'Investigació i Innovació Parc Taulí (I3PT), Sabadell, Spain
| | - Josep Bringué
- Department of Medicine, Universitat Autònoma de Barcelona, Bellatera, Spain.,Centro de Investigación en Red de Enfermedades Respiratorias (CIBERES), Madrid, Spain
| | - Lieuwe D Bos
- Department of Intensive Care, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands.,Respiratory Medicine, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands.,Laboratory of Experimental Intensive Care and Anesthesiology (L·E·I·C·A), Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - Marcus J Schultz
- Department of Intensive Care, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands.,Laboratory of Experimental Intensive Care and Anesthesiology (L·E·I·C·A), Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands.,Mahidol Oxford Tropical Medicine Research Unit (MORU), Mahidol University, Bangkok, Thailand
| | - Antonio Artigas
- Intensive Care Unit, Hospital Universitario Sagrado Corazón, Carrer de Viladomat, 288, 08029, Barcelona, Spain.,Department of Medicine, Universitat Autònoma de Barcelona, Bellatera, Spain.,Critical Care Center, Corporació Sanitària I Universitària Parc Taulí, Sabadell, Spain.,Institut d'Investigació i Innovació Parc Taulí (I3PT), Sabadell, Spain.,Centro de Investigación en Red de Enfermedades Respiratorias (CIBERES), Madrid, Spain
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Acid-Base Disturbances in Patients with Asthma: A Literature Review and Comments on Their Pathophysiology. J Clin Med 2019; 8:jcm8040563. [PMID: 31027265 PMCID: PMC6518237 DOI: 10.3390/jcm8040563] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 04/19/2019] [Accepted: 04/23/2019] [Indexed: 01/19/2023] Open
Abstract
Asthma is a common illness throughout the world that affects the respiratory system function, i.e., a system whose operational adequacy determines the respiratory gases exchange. It is therefore expected that acute severe asthma will be associated with respiratory acid-base disorders. In addition, the resulting hypoxemia along with the circulatory compromise due to heart–lung interactions can reduce tissue oxygenation, with a particular impact on respiratory muscles that have increased energy needs due to the increased workload. Thus, anaerobic metabolism may ensue, leading to lactic acidosis. Additionally, chronic hypocapnia in asthma can cause a compensatory drop in plasma bicarbonate concentration, resulting in non-anion gap acidosis. Indeed, studies have shown that in acute severe asthma, metabolic acid-base disorders may occur, i.e., high anion gap or non-anion gap metabolic acidosis. This review briefly presents studies that have investigated acid-base disorders in asthma, with comments on their underlying pathophysiology.
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Finucane KE, Singh B. Role of bronchodilation and pattern of breathing in increasing tidal expiratory flow with progressive induced hypercapnia in chronic obstructive pulmonary disease. J Appl Physiol (1985) 2018; 124:91-98. [PMID: 28982946 DOI: 10.1152/japplphysiol.00752.2016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hypercapnia (HC) in vitro relaxes airway smooth muscle; in vivo, it increases respiratory effort, tidal expiratory flows (V̇exp), and, by decreasing inspiratory duration (Ti), increases elastic recoil pressure (Pel) via lung viscoelasticity; however, its effect on airway resistance is uncertain. We examined the contributions of bronchodilation, Ti, and expiratory effort to increasing V̇exp with progressive HC in 10 subjects with chronic obstructive pulmonary disease (COPD): mean forced expiratory volume in 1 s (FEV1) 53% predicted. Lung volumes (Vl), V̇exp, esophageal pressure (Pes), Ti, and end-tidal Pco2 ([Formula: see text]) were measured during six tidal breaths followed by an inspiratory capacity (IC), breathing air, and at three levels of HC. V̇exp and V̇ with submaximal forced vital capacities breathing air (V̇sFVC) were compared. Pulmonary resistance ( Rl) was measured from the Pes-V̇ relationship. V̇exp and Pes at end-expiratory lung volume (EELV) + 0.3 tidal volume [V̇(0.3Vt) and Pes(0.3Vt), respectively], Ti, and Rl correlated with [Formula: see text] ( P < 0.001 for all) and were independent of tiotropium. [Formula: see text], Ti, and Pes(0.3Vt) predicted the increasing V̇(0.3Vt)/V̇sFVC(0.3Vt) [multiple regression analysis (MRA): P = 0.001, 0.004, and 0.025, respectively]. At [Formula: see text] ≥ 50 Torr, V̇(0.3Vt)/V̇sFVC(0.3Vt) exceeded unity in 30 of 36 measurements and was predicted by [Formula: see text] and Pes(0.3Vt) (MRA: P = 0.02 and 0.025, respectively). Rl decreased at [Formula: see text] 45 Torr ( P < 0.05) and did not change with further HC. IC and Vl(0.3Vt) did not change with HC. We conclude that in COPD HC increases V̇exp due to bronchodilation, increased Pel secondary to decreasing Ti, and increased expiratory effort, all promoting lung emptying and a stable EELV. NEW & NOTEWORTHY The response of airways to intrapulmonary hypercapnia (HC) is uncertain. In chronic obstructive pulmonary disease (COPD), progressive HC increases tidal expiratory flows by inducing bronchodilation and via an increased rate of inspiration and lung viscoelasticity, a probable increase in lung elastic recoil pressure, both changes increasing expiratory flows, promoting lung emptying and a stable end-expiratory volume. Bronchodilation with HC occurred despite optimal standard bronchodilator therapy, suggesting that in COPD further bronchodilation is possible.
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Affiliation(s)
- Kevin E Finucane
- Department of Pulmonary Physiology and Sleep Medicine, Sir Charles Gairdner Hospital , Nedlands, Western Australia , Australia.,West Australian Sleep Disorders Research Institute, Queen Elizabeth II Medical Centre , Perth, Western Australia , Australia
| | - Bhajan Singh
- Department of Pulmonary Physiology and Sleep Medicine, Sir Charles Gairdner Hospital , Nedlands, Western Australia , Australia.,West Australian Sleep Disorders Research Institute, Queen Elizabeth II Medical Centre , Perth, Western Australia , Australia.,Faculty of Science, University of Western Australia, Perth, Western Australia, Australia
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Kennedy MD, Steinback CD, Skow R, Parent EC. Is Performance of a Modified Eucapnic Voluntary Hyperpnea Test in High Ventilation Athletes Reproducible? ALLERGY, ASTHMA & IMMUNOLOGY RESEARCH 2017; 9:229-236. [PMID: 28293929 PMCID: PMC5352574 DOI: 10.4168/aair.2017.9.3.229] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 07/11/2016] [Accepted: 08/01/2016] [Indexed: 12/02/2022]
Abstract
Purpose Exercise-induced bronchoconstriction (EIB) is common in “high ventilation” athletes, and the Eucapnic Voluntary Hyperpnea (EVH) airway provocation test is the standard EIB screen. Although the EVH test is widely used, the in-test performance in high ventilation athletes as well as the reproducibility of that performance has not been determined. Reproducibility of pre- and post-test spirometry and self-reported atopy/cough was also examined. Methods High ventilation athletes (competitive swimmers; n=11, 5 males) completed an atopy/cough questionnaire and EVH testing (operator controlled FiCO2) on 2 consecutive days. Results Swimmers achieved 85%±9% and 87%±9% of target FEV1 volume on days 1 and 2, respectively, (P=0.45; ICC 0.57 [0.00-0.86]) resulting in a total ventilation of 687 vs 684 L [P=0.89, ICC 0.89 (0.65-0.97]) equating to 83%±8% and 84%±9% of predicted total volume (ICC 0.54 [0.00-0.85]) between days 1 and 2. FiCO2 required to maintain eucapnic conditions was 2.5%. Pre-test FEV1 was less on day 2 (P=0.04; ICC >0.90). Day 1 to 2 post-test FEV1 was not different, and 4 swimmers were EIB positive (>10% fall in pre-post FEV1) on day 1 (3 on day 2). Conclusions EVH in-test performance is reproducible however required less FiCO2 than standard protocol and the swimmers under-ventilated by 125 and 139 L/min for days 1 and 2, respectively. How this affects EIB diagnosis remains to be determined; however, our results indicate a post-test FEV1 fall of ≥20% may be recommended as the most consistent diagnostic criterion.
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Affiliation(s)
- Michael D Kennedy
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada.
| | - Craig D Steinback
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Rachel Skow
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Eric C Parent
- Department of Physical Therapy, University of Alberta, Edmonton, Alberta, Canada
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Palla A, Marconi L, Bigazzi F, Pistolesi M. Lung scintigraphy in the diagnosis of pulmonary embolism: pathophysiological and practical evidence. Clin Transl Imaging 2014. [DOI: 10.1007/s40336-014-0083-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Tsang JYC, Hogg JC. Gas exchange and pulmonary hypertension following acute pulmonary thromboembolism: has the emperor got some new clothes yet? Pulm Circ 2014; 4:220-36. [PMID: 25006441 DOI: 10.1086/675985] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Accepted: 02/17/2014] [Indexed: 01/09/2023] Open
Abstract
Patients present with a wide range of hypoxemia after acute pulmonary thromboembolism (APTE). Recent studies using fluorescent microspheres demonstrated that the scattering of regional blood flows after APTE, created by the embolic obstruction unique in each patient, significantly worsened regional ventilation/perfusion (V/Q) heterogeneity and explained the variability in gas exchange. Furthermore, earlier investigators suggested the roles of released vasoactive mediators in affecting pulmonary hypertension after APTE, but their quantification remained challenging. The latest study reported that mechanical obstruction by clots accounted for most of the increase in pulmonary vascular resistance, but that endothelin-mediated vasoconstriction also persisted at significant level during the early phase.
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Affiliation(s)
- John Y C Tsang
- Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - James C Hogg
- Department of Pathology, University of British Columbia, Vancouver, British Columbia, Canada
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Glenny RW, Robertson HT. Spatial distribution of ventilation and perfusion: mechanisms and regulation. Compr Physiol 2013; 1:375-95. [PMID: 23737178 DOI: 10.1002/cphy.c100002] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
With increasing spatial resolution of regional ventilation and perfusion, it has become more apparent that ventilation and blood flow are quite heterogeneous in the lung. A number of mechanisms contribute to this regional variability, including hydrostatic gradients, pleural pressure gradients, lung compressibility, and the geometry of the airway and vascular trees. Despite this marked heterogeneity in both ventilation and perfusion, efficient gas exchange is possible through the close regional matching of the two. Passive mechanisms, such as the shared effect of gravity and the matched branching of vascular and airway trees, create efficient gas exchange through the strong correlation between ventilation and perfusion. Active mechanisms that match local ventilation and perfusion play little if no role in the normal healthy lung but are important under pathologic conditions.
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Affiliation(s)
- Robb W Glenny
- Department of Medicine, University of Washington, USA.
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Finucane KE, Singh B. Diaphragm efficiency estimated as power output relative to activation in chronic obstructive pulmonary disease. J Appl Physiol (1985) 2012; 113:1567-75. [PMID: 22995393 DOI: 10.1152/japplphysiol.01453.2011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Muscle efficiency increases with fiber length and decreases with load. Diaphragm efficiency (Eff(di)) in healthy humans, measured as power output (Wdi) relative to the root mean square of diaphragm electromyogram (RMS(di)), increases with hyperpnea due to phasic activity of abdominal muscles acting to increase diaphragm length at end expiration (L(di ee)) and decrease inspiratory load. In chronic obstructive pulmonary disease (COPD), hyperpnea may decrease Eff(di) if L(di ee) decreases and load increases due to airflow obstruction and dynamic hyperinflation. To examine this hypothesis, we measured Eff(di) in six COPD subjects (mean forced expiratory volume in 1 s: 54% predicted) when breathing air and at intervals during progressive hypercapnic hyperpnea. Wdi was measured as the product of mean inspiratory transdiaphragmatic pressure (ΔPdi(mean)), diaphragm tidal volume measured fluoroscopically, and 1/inspiratory duration. Results were compared with those of six healthy subjects reported previously. In COPD, L(di ee) was normal when breathing air. ΔPdi(mean) and Wdi increased normally, and RMS(di) increased disproportionately (P = 0.01) with hyperpnea, and, unlike health, inspiratory capacity (IC), L(di ee), and Eff(di) did not increase. IC and L(di ee) were constant with hyperpnea because mean expiratory flow increased as expiratory duration decreased (r(2) = 0.65), and because expiratory flow was terminated actively by the balance between expiratory and inspiratory muscle forces near end expiration, and these forces increased proportionately with hyperpnea (r(2) = 0.49). At maximum ventilation, diaphragm radius of curvature at end inspiration increased in COPD (P = 0.04) but not controls; diaphragm radius of curvature at end inspiration and ln(Eff(di)) were negatively correlated (P = 0.01). Thus in COPD with modest airflow obstruction, Eff(di) did not increase normally with hyperpnea due to a constant L(di ee) and inspiratory flattening of the diaphragm.
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Affiliation(s)
- Kevin E Finucane
- Department of Pulmonary Physiology and Sleep Medicine, Sir Charles Gairdner Hospital, Nedlands, WA 6009, Australia.
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Subject specific effects of hyperpnea but not hypocapnia on airway conductance. Respir Physiol Neurobiol 2011; 177:127-32. [DOI: 10.1016/j.resp.2011.03.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Revised: 03/22/2011] [Accepted: 03/23/2011] [Indexed: 11/23/2022]
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Chen Y, Marchenko V, Rogers RF. Pulmonary stretch receptor spike time precision increases with lung inflation amplitude and airway smooth muscle tension. J Neurophysiol 2011; 105:2590-600. [PMID: 21411567 DOI: 10.1152/jn.00514.2010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Slowly adapting pulmonary stretch receptors (SARs) respond to different lung inflation volumes with distinct spike counts and patterns, conveying information regarding the rate and depth of breathing to the cardiovascular and respiratory control systems. Previous studies demonstrated that SARs respond to repetitions of the same lung inflation faithfully, suggesting the possibility of modeling an SAR's discrete response pattern to a stimulus using a statistically based method. Urethane-anesthetized rabbit SAR spike trains were recorded in response to repeated 9-, 12-, and 15-ml lung inflations, and used to construct model spike trains using K-means clustering. Analysis of the statistics of the responses to different lung inflation volumes revealed that SARs fire with more temporal precision in response to larger lung inflations, because the standard deviations of real spikes clustered around the modeled spike times of responses to 15-ml stimuli were smaller than those produced by 12 or 9 ml, even at the same absolute firing frequencies. This implied that the mechanical coupling of SAR endings with pulmonary tissue is critical in determining spike time reliability. To test this, we collected SAR responses during bronchial constriction, compared them with those produced by the same SARs under normal airway resistance, and found that their firing reliability improved during bronchial constriction. These results suggest that airway distension and mechanical coupling of the receptor endings with the airway wall (partially determined by smooth muscle tone) are important determinants of SAR spike time reliability.
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Affiliation(s)
- Yan Chen
- Department of Electrical and Computer Engineering, University of Delaware, Newark, Delaware, USA
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Lele EE, Hantos Z, Bitay M, Szívós B, Bogáts G, Peták F, Babik B. Bronchoconstriction during alveolar hypocapnia and systemic hypercapnia in dogs with a cardiopulmonary bypass. Respir Physiol Neurobiol 2011; 175:140-5. [DOI: 10.1016/j.resp.2010.10.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 10/19/2010] [Accepted: 10/20/2010] [Indexed: 11/30/2022]
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Tsang JYC, Lamm WJE, Swenson ER. Regional CO2 tension quantitatively mediates homeostatic redistribution of ventilation following acute pulmonary thromboembolism in pigs. J Appl Physiol (1985) 2009; 107:755-62. [PMID: 19608933 DOI: 10.1152/japplphysiol.00245.2009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous studies reported that regional CO(2) tension might affect regional ventilation (V) following acute pulmonary thromboembolism (APTE). We investigated the pathophysiology and magnitude of these changes. Eight anesthetized and ventilated piglets received autologous clots at time = 0 min until mean pulmonary artery pressure was 2.5 times baseline. The distribution of V and perfusion (Q) at four different times (-5, 30, 60, 120 min) was mapped by fluorescent microspheres. Regional V and Q were examined postmortem by sectioning the air-dried lung into 900-1,000 samples of approximately 2 cm(3) each. After the redistribution of regional Q by APTE, but in the scenario assuming that no V shift had yet occurred, CO(2) tension in different lung regions at 30 min post-APTE (P(X)CO(2)) was estimated from the V/Q data and divided into four distinct clusters: i.e., P(X)CO(2) < 10 Torr; 10 < P(X)CO(2) < 25 Torr; 25 < P(X)CO(2) < 50 Torr; P(X)CO(2) > 50 Torr. Our data showed that the clusters in higher V/Q regions (with a P(X)CO(2) < 25 Torr) received approximately 35% less V when measured within 30 min of APTE, whereas, in contrast, the lower V/Q regions showed no statistically significant increases in their V. However, after 30 min, there was minimal further redistribution of V. We conclude that there are significant compensatory V shifts out of regions of low CO(2) tension soon following APTE, and that these variations in regional CO(2) tension, which initiate CO(2)-dependent changes in airway resistance and lung parenchymal compliance, can lead to improved gas exchange.
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Affiliation(s)
- John Y C Tsang
- James Hogg iCAPTURE Research Laboratory, Division of Critical Care Medicine, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada V6Z 1Y6
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Is the lung scan alive and well? Facts and controversies in defining the role of lung scintigraphy for the diagnosis of pulmonary embolism in the era of MDCT. Eur J Nucl Med Mol Imaging 2009; 36:505-21. [DOI: 10.1007/s00259-008-1014-8] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Accepted: 11/07/2008] [Indexed: 11/26/2022]
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Wang Z, Su F, Bruhn A, Yang X, Vincent JL. Acute hypercapnia improves indices of tissue oxygenation more than dobutamine in septic shock. Am J Respir Crit Care Med 2007; 177:178-83. [PMID: 17947612 DOI: 10.1164/rccm.200706-906oc] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
RATIONALE Hypercapnia has similar hemodynamic effects to those of a dobutamine infusion and may have relevance in the management of septic shock. OBJECTIVES To compare the effects induced by hypercapnia with those of dobutamine in a clinically relevant model of septic shock. METHODS Fecal peritonitis was induced in 21 anesthetized, invasively monitored, mechanically ventilated female sheep. A combination of Ringer's lactate and 6% hydroxyethyl starch solution was titrated to maintain constant cardiac filling throughout the experiments. Two hours after feces spillage, animals were randomized to one of three groups (each, n = 7): (1) hypercapnia: carbon dioxide given to maintain partial pressure of carbon dioxide between 55 and 65 mm Hg throughout the experiment; (2) dobutamine: dobutamine infused intravenously (7 microg/kg/min); (3) control: no treatment. In the dobutamine and control groups, the partial pressure of carbon dioxide was kept between 35 and 45 mm Hg. All animals were monitored until spontaneous death. MEASUREMENTS AND MAIN RESULTS The animals in the hypercapnia group had significantly lower arterial pH than the other two groups (P < 0.05). Hypercapnic and dobutamine-treated animals developed significantly higher heart rate, cardiac index, and oxygen delivery, and lower lactate concentrations than control animals (P < 0.05). Hypercapnic animals had lower post mortem lung wet/dry ratio than the control animals (P < 0.05). The alveolar-arterial oxygen partial pressure difference and shunt fraction were significantly lower in hypercapnic animals than in the other groups (P < 0.05). CONCLUSIONS In this clinically relevant ovine model of septic shock, hypercapnia had similar effects to dobutamine on hemodynamic variables and lactic acidosis. Hypercapnia improved tissue oxygenation and reduced lung edema formation more than dobutamine administration.
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Affiliation(s)
- Zhen Wang
- Department of Intensive Care, Erasme Hospital, Route de Lennik 808, 1070-B Brussels, Belgium.
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Bishop A, Rawle M, Bruton A. The use of mouth taping in people with asthma: a pilot study examining the effects on end-tidal carbon dioxide levels. Physiotherapy 2007. [DOI: 10.1016/j.physio.2006.11.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Koutsoukou A, Perraki H, Raftopoulou A, Koulouris N, Sotiropoulou C, Kotanidou A, Orfanos S, Roussos C. Respiratory mechanics in brain-damaged patients. Intensive Care Med 2006; 32:1947-54. [PMID: 17053881 DOI: 10.1007/s00134-006-0406-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2005] [Accepted: 09/18/2006] [Indexed: 10/24/2022]
Abstract
OBJECTIVE To assess respiratory mechanics on the 1st and 5th days of mechanical ventilation in a cohort of brain-damaged patients on positive end-expiratory pressure (PEEP) of 8 cmH(2)O or zero PEEP (ZEEP). DESIGN AND SETTING Physiological study with randomized control trial design in a multidisciplinary intensive care unit of a university hospital. PATIENTS AND MEASUREMENTS Twenty-one consecutive mechanically ventilated patients with severe brain damage and no acute lung injury were randomly assigned to be ventilated with ZEEP (n = 10) or with 8 cmH(2)O of PEEP (n = 11). Respiratory mechanics and arterial blood gases were assessed on days 1 and day 5 of mechanical ventilation. RESULTS In the ZEEP group on day 1 static elastance and minimal resistance were above normal limits (18.9 +/- 3.8 cmH(2)O/l and 5.6 +/- 2.2 cmH(2)O/l per second, respectively); on day 5 static elastance and iso-CO(2) minimal resistance values were higher than on day 1 (21.2 +/- 4.1 cmH(2)O/l; 7.0 +/- 1.9 cmH(2)O/l per second, respectively). In the PEEP group these parameters did not change significantly. One of the ten patients on ZEEP developed acute lung injury. On day 5 there was a significant decrease in PaO(2)/FIO(2) in both groups. CONCLUSIONS On day 1 of mechanical ventilation patients with brain damage exhibit abnormal respiratory mechanics. After 5 days of mechanical ventilation on ZEEP static elastance and minimal resistance increased significantly, perhaps reflecting "low lung volume" injury. Both could be prevented by administration of moderate levels of PEEP.
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Affiliation(s)
- Antonia Koutsoukou
- Department of Critical Care and Pulmonary Services, Evangelismos General Hospital and M Simou Laboratory, Medical School, University of Athens, Athens, Greece.
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D'Angelo E, Pecchiari M, Gentile G. Dependence of lung injury on surface tension during low-volume ventilation in normal open-chest rabbits. J Appl Physiol (1985) 2006; 102:174-82. [PMID: 16959911 DOI: 10.1152/japplphysiol.00405.2006] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
To evaluate the role of pulmonary surfactant in the prevention of lung injury caused by mechanical ventilation (MV) at low end-expiratory volumes, lung mechanics and morphometry were assessed in three groups of eight normal, open-chest rabbits ventilated for 3-4 h at zero end-expiratory pressure (ZEEP) with physiological tidal volumes (Vt = 10 ml/kg). One group was left untreated (group A); the other two received surfactant intratracheally (group B) or aerosolized dioctylsodiumsulfosuccinate (group C) before MV on ZEEP. Relative to initial MV on positive end-expiratory pressure (PEEP; 2.3 cmH(2)O), quasi-static elastance (Est) and airway (Rint) and viscoelastic resistance (Rvisc) increased on ZEEP in all groups. After restoration of PEEP, only Rint (124%) remained elevated in group A, only Est (36%) was significantly increased in group B, whereas in group C, Est, Rint, and Rvisc were all markedly augmented (274, 253, and 343%). In contrast, prolonged MV on PEEP had no effect on lung mechanics of eight open-chest rabbits (group D). Lung edema developed in group C (wet-to-dry ratio = 7.1), but not in the other groups. Relative to group D, both groups A and C, but not B, showed histological indexes of bronchiolar injury, whereas all groups exhibited an increased number of polymorphonuclear leukocytes in alveolar septa, which was significantly greater in group C. In conclusion, administration of exogenous surfactant largely prevents the histological and functional damage of prolonged MV at low lung volumes, whereas surfactant dysfunction worsens the functional alterations, also because of edema formation and, possibly, increased inflammatory response.
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Affiliation(s)
- Edgardo D'Angelo
- Istituto di Fisiologia Umana I, Università di Milano, Milan, Italy.
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Abstract
There is some evidence that breathing retraining may be beneficial for patients with asthma, but the mechanism behind this benefit is still unknown. One hypothesis is that individuals can be trained to raise carbon dioxide levels and thereby reverse the bronchoconstrictive effects of hypocapnia and utilize the bronchodilatory effects of hypercapnia. This theory presupposes that individuals with asthma have lower carbon dioxide levels than the healthy population. This article reviews the available evidence supporting the hypothesis and concludes that although attractive, there is currently insufficient evidence to attribute the benefits of breathing retraining to this mechanism.
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Affiliation(s)
- Anne Bruton
- University of Southampton, Highfield, Southampton, SO17 1BJ, UK.
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Bruton A, Lewith GT. The Buteyko breathing technique for asthma: a review. Complement Ther Med 2005; 13:41-6. [PMID: 15907677 DOI: 10.1016/j.ctim.2005.01.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2004] [Accepted: 01/19/2005] [Indexed: 10/25/2022] Open
Abstract
Breathing exercises and breathing retraining are often used in the management of asthma. One specific form of breathing therapy, known as the Buteyko breathing technique (BBT) has received considerable attention, but there is a paucity of rigorous research evidence to support its recommendation for asthma patients. There are only four published clinical trials and two conference abstracts evaluating BBT. Although all have reported improvements in one or more outcome measures, results have not been consistent. This article provides the background to the BBT, reviews the available evidence for its use and examines the physiological hypothesis claimed to underpin it. In common with other therapies, BBT is not a standardised treatment modality. The BBT 'package' is complex, as it also includes advice and education about medication use, nutrition and exercise, and general relaxation. This makes it difficult, and possibly inappropriate, to attempt to tease out a single mechanism. Buteyko's theory relating to carbon dioxide levels and airway calibre is an attractive one, and has some basis in evidence from experimental studies. However, it is not known whether altering breathing patterns can raise carbon dioxide levels significantly, and there is currently insufficient evidence to confirm that this is the mechanism behind any effect that BBT may exert. Further research is necessary to establish unequivocally whether BBT is effective, and if so, how it may work.
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Affiliation(s)
- A Bruton
- School of Health Professions and Rehabilitation Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
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Bruton A, Clark R. A pilot study measuring mixed venous carbon dioxide levels in students with and without a diagnosis of asthma. Physiotherapy 2004. [DOI: 10.1016/j.physio.2004.05.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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D'Angelo E, Pecchiari M, Saetta M, Balestro E, Milic-Emili J. Dependence of lung injury on inflation rate during low-volume ventilation in normal open-chest rabbits. J Appl Physiol (1985) 2004; 97:260-8. [PMID: 15020576 DOI: 10.1152/japplphysiol.01175.2003] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Lung mechanics and morphometry were assessed in two groups of nine normal open-chest rabbits mechanically ventilated (MV) for 3-4 h at zero end-expiratory pressure (ZEEP) with physiological tidal volumes (Vt; 11 ml/kg) and high (group A) or low (group B) inflation flow (44 and 6.1 ml x kg(-1) x s(-1), respectively). Relative to initial MV on positive end-expiratory pressure (PEEP; 2.3 cmH(2)O), MV on ZEEP increased quasi-static elastance and airway and viscoelastic resistance more in group A (+251, +393, and +225%, respectively) than in group B (+180, +247, and +183%, respectively), with no change in viscoelastic time constant. After restoration of PEEP, quasi-static elastance and viscoelastic resistance returned to control, whereas airway resistance, still relative to initial values, remained elevated more in group A (+86%) than in group B (+33%). In contrast, prolonged high-flow MV on PEEP had no effect on lung mechanics of seven open-chest rabbits (group C). Gas exchange on PEEP was equally preserved in all groups, and the lung wet-to-dry ratios were normal. Relative to group C, both groups A and B had an increased percentage of abnormal alveolar-bronchiolar attachments and number of polymorphonuclear leukocytes in alveolar septa, the latter being significantly larger in group A than in group B. Thus prolonged MV on ZEEP with cyclic opening-closing of peripheral airways causes alveolar-bronchiolar uncoupling and parenchymal inflammation with concurrent, persistent increase in airway resistance, which are worsened by high-inflation flow.
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Affiliation(s)
- Edgardo D'Angelo
- Istituto di Fisiologia Umana I, via Mangiagalli 32, 20133 Milan, Italy.
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Cummings KJ, Pendlebury JD, Sherwood NM, Wilson RJA. Sudden neonatal death in PACAP-deficient mice is associated with reduced respiratory chemoresponse and susceptibility to apnoea. J Physiol 2003; 555:15-26. [PMID: 14608012 PMCID: PMC1664827 DOI: 10.1113/jphysiol.2003.052514] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Pituitary adenylate cyclase-activating polypeptide (PACAP)-deficient mice are more prone to sudden death during postnatal weeks 1-3 than wild-type littermates. Given that PACAP is localized in brainstem regions associated with respiratory chemosensitivity, we examined whether PACAP-null neonates have reduced respiratory responses to hypoxia and hypercapnia. Using unrestrained, whole-body, flow-through plethysmography we found that, by postnatal day 4, the PACAP-null neonates had significantly reduced ventilation during baseline breathing, and blunted responses to both hypoxia (10% O2-90% N2) and hypercapnia (8% CO2-92% air). To determine whether the respiratory phenotype of the PACAP-null mice may contribute to their greater neonatal mortality, we used ECG to examine respiration and cardiovascular function of littermates. We demonstrate that, under conditions that exacerbate mortality of knockout but not wild-type animals, PACAP-deficient mice experience prolonged apnoeas that precede atrio-ventricular block. Both apnoeas and atrio-ventricular block were absent in wild-type littermates. These data suggest that PACAP-deficiency results in higher neonatal mortality primarily as a result of respiratory control defects and raise the possibility that mutations in genes encoding components of the PACAP signalling pathways may contribute to neonatal breathing disorders in humans.
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Affiliation(s)
- Kevin J Cummings
- Respiratory Research Group, Department of Physiology and Biophysics, University of Calgary, 3330 Hospital Dr NW, Calgary, Alberta T2N 4N1, Canada
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