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Burggren W, Fahlman A, Milsom W. Breathing patterns and associated cardiovascular changes in intermittently breathing animals: (Partially) correcting a semantic quagmire. Exp Physiol 2024; 109:1051-1065. [PMID: 38502538 PMCID: PMC11215480 DOI: 10.1113/ep091784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Accepted: 02/29/2024] [Indexed: 03/21/2024]
Abstract
Many animal species do not breathe in a continuous, rhythmic fashion, but rather display a variety of breathing patterns characterized by prolonged periods between breaths (inter-breath intervals), during which the heart continues to beat. Examples of intermittent breathing abound across the animal kingdom, from crustaceans to cetaceans. With respect to human physiology, intermittent breathing-also termed 'periodic' or 'episodic' breathing-is associated with a variety of pathologies. Cardiovascular phenomena associated with intermittent breathing in diving species have been termed 'diving bradycardia', 'submersion bradycardia', 'immersion bradycardia', 'ventilation tachycardia', 'respiratory sinus arrhythmia' and so forth. An examination across the literature of terminology applied to these physiological phenomena indicates, unfortunately, no attempt at standardization. This might be viewed as an esoteric semantic problem except for the fact that many of the terms variously used by different authors carry with them implicit or explicit suggestions of underlying physiological mechanisms and even human-associated pathologies. In this article, we review several phenomena associated with diving and intermittent breathing, indicate the semantic issues arising from the use of each term, and make recommendations for best practice when applying specific terms to particular cardiorespiratory patterns. Ultimately, we emphasize that the biology-not the semantics-is what is important, but also stress that confusion surrounding underlying mechanisms can be avoided by more careful attention to terms describing physiological changes during intermittent breathing and diving.
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Affiliation(s)
- Warren Burggren
- Developmental Integrative Biology Group, Department of Biological SciencesUniversity of North TexasDentonTexasUSA
| | - Andreas Fahlman
- Fundación OceanogràficValenciaSpain
- Kolmården Wildlife ParkKolmårdenSweden
- IFMLinkoping UniversityLinkopingSweden
| | - William Milsom
- Department of ZoologyUniversity of British ColumbiaVancouverBritish ColumbiaCanada
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2
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Dos Santos Ribeiro G, Beltrame T, Fernando Deresz L, Hansen D, Agostoni P, Karsten M. Software development to standardize the clinical diagnosis of exercise oscillatory ventilation in heart failure. J Clin Monit Comput 2023; 37:1247-1253. [PMID: 36735189 DOI: 10.1007/s10877-023-00976-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2022] [Revised: 01/12/2023] [Accepted: 01/18/2023] [Indexed: 02/04/2023]
Abstract
BACKGROUND Exercise oscillatory ventilation (EOV) is characterized by periodic oscillations of minute ventilation during cardiopulmonary exercise testing (CPET). Despite its prognostic value in chronic heart failure (HF), its diagnosis is complex due to technical limitations. An easier and more accurate way of EOV identification can contribute to a better approach and clinical diagnosis. This study aims to describe a software development to standardize the EOV diagnosis from CPET's raw data in heart failure patients and test its reliability (intra- and inter-rater). METHODS The software was developed in the "drag-and-drop" G-language using LabVIEW®. Five EOV definitions (Ben-Dov, Corrà, Kremser, Leite, and Sun definitions), two alternative approaches, one smoothing technique, and some basic statistics were incorporated into the interface to visualize four charts of the ventilatory response. EOV identification was based on a set of criteria verified from the interaction between amplitude, cycle length, and oscillation time. Two raters analyzed the datasets. In addition, repeated measurements were verified after six months using about 25% of the initial data. Cohen's kappa coefficient (κ) was used to investigate the reliability. RESULTS Overall, 391 tests were analyzed in duplicate (inter-rater reliability) and 100 tests were randomized for new analysis (intra-rater reliability). High inter-rater (κ > 0.80) and intra-rater (κ > 0.80) reliability of the five EOV diagnoses were observed. CONCLUSION The present study proposes novel semi-automated software to detect EOV in HF, with high inter and intra-rater agreements. The software project and its tutorial are freely available for download.
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Affiliation(s)
- Gustavo Dos Santos Ribeiro
- Programa de Pós-Graduação em Ciências da Reabilitação, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Porto Alegre, RS, Brazil
| | - Thomas Beltrame
- Samsung R&D Institute Brazil - SRBR, Universidade Federal de São Carlos (UFSCAR), Campinas, SP, Brazil
| | - Luís Fernando Deresz
- Departamento de Educação Física, Universidade Federal de Juiz de Fora (UFJF), Governador Valadares, MG, Brazil
| | - Dominique Hansen
- Faculty of Rehabilitation Sciences, Hasselt University (UHASSELT), BIOMED/REVAL, Hasselt, Belgium
- Heart Centre Hasselt, Jessa Hospital, Hasselt, Belgium
| | - Piergiuseppe Agostoni
- Centro Cardiologico Monzino, IRCCS, Milan, Italy
- Department of Clinical Sciences of Community Health, Cardiovascular Section, University of Milano, Milano, Italy
| | - Marlus Karsten
- Programa de Pós-Graduação em Ciências da Reabilitação, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Porto Alegre, RS, Brazil
- Departamento de Fisioterapia, Universidade do Estado de Santa Catarina (UDESC), Florianópolis, SC, Brazil
- Programa de Pós-Graduação em Fisioterapia, UDESC, Florianópolis, SC, Brazil
- Centro de Ciências da Saúde e do Esporte, UDESC, Rua Pascoal Simone 358, CEP 88080-350, Florianópolis, SC, Brazil
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Neder JA, Rocha A, Arbex FF, Alencar MCN, Sperandio PA, Hirai DM, Berton DC. Exertional oscillatory ventilation in subjects without heart failure reporting chronic dyspnoea. ERJ Open Res 2023; 9:00324-2022. [PMID: 36726368 PMCID: PMC9885272 DOI: 10.1183/23120541.00324-2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 11/09/2022] [Indexed: 12/24/2022] Open
Abstract
Oscillatory ventilation detected on incremental cardiopulmonary exercise testing might be found in subjects without heart failure reporting exertional dyspnoea despite the best available therapy for their underlying cardiopulmonary disease https://bit.ly/3Tyl7bE.
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Affiliation(s)
- J. Alberto Neder
- Laboratory of Clinical Exercise Physiology (LACEP) and Respiratory Investigation Unit (RIU), Queen's University and Kingston General Hospital, Kingston, ON, Canada,J. Alberto Neder ()
| | - Alcides Rocha
- Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Division of Respirology, Federal University of Sao Paulo, Sao Paulo, Brazil
| | - Flavio F. Arbex
- Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Division of Respirology, Federal University of Sao Paulo, Sao Paulo, Brazil
| | - Maria Clara N. Alencar
- Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Division of Respirology, Federal University of Sao Paulo, Sao Paulo, Brazil
| | - Priscila A. Sperandio
- Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Division of Respirology, Federal University of Sao Paulo, Sao Paulo, Brazil
| | - Daniel M. Hirai
- Department of Health and Kinesiology, Purdue University, West Lafayette, IN, USA
| | - Danilo C. Berton
- Division of Respirology, Federal University of Rio Grande do Sul, Porto Alegre, Brazil
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Ribeiro GDS, Deresz LF, Salvioni E, Hansen D, Agostoni P, Karsten M. Sensitivity and specificity of different exercise oscillatory ventilation definitions to predict 2-year major adverse cardiovascular outcomes in chronic heart failure patients. Int J Cardiol 2022; 360:39-43. [PMID: 35623479 DOI: 10.1016/j.ijcard.2022.05.041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 05/17/2022] [Accepted: 05/18/2022] [Indexed: 11/30/2022]
Abstract
BACKGROUND Exercise oscillatory ventilation (EOV) shows a four-fold greater risk of adverse events. This study aims to analyze the sensitivity and specificity of three EOV diagnostic definitions to predict adverse outcomes at a 2-year follow-up and to compare its EOV prevalence and relations with the patient's profile. METHODS Cardiopulmonary exercise tests from 233 heart failure patients were analyzed. Two blinded reviewers used a semiautomated software to identify EOV cases pattern according to the definitions of Ben-Dov, Corrà, and Leite. Data were grouped in EOV-positive or EOV-negative according to each definition. Baseline characteristics, EOV prevalence, relative risk, sensitivity, and specificity to predict 2-years of major adverse cardiovascular outcomes were analyzed. RESULTS The Corrà definition led to the best prediction of 2-year major cardiovascular adverse outcomes (HR 2.46 [1.16 to 5.25]; p = 0.019, AUC = 0.618; p = 0.007). EOV prevalence was 17.2%, 17.2%, and 9.4% applying Ben-Dov, Corrà, and Leite definition, respectively. The main clinical differences between EOV-positive and EOV-negative patients were: MECKI score and VE/VCO2 slope (all definitions), and BNP levels (Ben-Dov and Leite). BNP levels were correlated with amplitude (rho = 0.255; p = 0.033) and cycle length (rho = 0.388; p = 0.002). CONCLUSION Corrà definition was the only one that exhibited the capacity to predict major adverse cardiovascular outcomes at a 2-year follow-up. Regardless of its definition, EOV was more often prevalent in patients with a greater MECKI score and VE/VCO2 slope values.
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Affiliation(s)
- Gustavo Dos Santos Ribeiro
- Programa de Pós-Graduação em Ciências da Reabilitação, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Porto Alegre, Brazil
| | - Luís Fernando Deresz
- Departamento de Educação Física, Universidade Federal de Juiz de Fora (UFJF), Governador Valadares, Brazil
| | | | - Dominique Hansen
- Hasselt University (UHASSELT), Faculty of Rehabilitation Sciences, BIOMED/REVAL, Hasselt, Belgium; Heart Centre Hasselt, Jessa Hospital, Hasselt, Belgium
| | - Piergiuseppe Agostoni
- Centro Cardiologico Monzino, IRCCS, Milan, Italy; Department of Clinical Sciences of Community Health, Cardiovascular Section, University of Milano, Milano, Italy
| | - Marlus Karsten
- Programa de Pós-Graduação em Ciências da Reabilitação, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Porto Alegre, Brazil; Departamento de Fisioterapia, Universidade do Estado de Santa Catarina (UDESC), Florianópolis, Brazil; Programa de Pós-Graduação em Fisioterapia, UDESC, Florianópolis, Brazil.
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da Luz Goulart C, Agostoni P, Salvioni E, Kaminsky LA, Myers J, Arena R, Borghi-Silva A. Exercise Oscillatory Breathing in Heart Failure with reduced ejection fraction: clinical implication. Eur J Prev Cardiol 2022; 29:1692-1698. [PMID: 35708730 DOI: 10.1093/eurjpc/zwac116] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 05/22/2022] [Accepted: 06/01/2022] [Indexed: 01/26/2023]
Abstract
AIM I) to evaluate the impact of exertional oscillatory ventilation (EOV) in patients with heart failure (HF) with reduced left ventricular ejection fraction (HFrEF) during cardiopulmonary exercise testing (CPET) compared with patients without EOV (N-EOV); II) to identify the influence of EOV persistence (P-EOV) and EOV disappearance (D-EOV) during CPET on the outcomes of mortality and hospitalization in HFrEF patients; and III) to identify further predictors of mortality and hospitalization in patients with P-EOV. METHODS AND RESULTS 315 stable HFrEF patients underwent CPET and were followed for 35 months. We identified 202 patients N-EOV and 113 patients with EOV. Patients with EOV presented more symptoms (NYHA III: 35% vs. N-EOV 20%, p < 0.05), worse cardiac function (LVEF: 28 ± 6 vs. N-EOV 39 ± 1, p < 0.05), higher minute ventilation/carbon dioxide production (V̇E/V̇CO2 slope: 41 ± 11 vs. N-EOV 37 ± 8, p < 0.05) and a higher rate of deaths (26% vs. N-EOV 6%, p < 0.05) and hospitalization (29% vs. N-EOV 9%, p < 0.05). P-EOV patients had more severe HFrEF (NYHA IV: 23% vs D-EOV: 9%, p < 0.05), had worse cardiac function (LVEF: 24 ± 5 vs. D-EOV: 34 ± 3, p < 0.05) and had lower peak oxygen consumption (V̇O2) (12.0 ± 3.0 vs D-EOV: 13.3 ± 3.0 mlO2.kg-1.min-1, p < 0.05). Among P-EOV, other independent predictors of mortality were V̇E/V̇CO2 slope ≥36 and V̇O2 peak ≤12 mlO2.kg-1.min-1; a V̇E/V̇CO2 slope≥34 was a significant predictor of hospitalization. Kaplan-Meier survival analysis showed that, HFrEF patients with P-EOV had a higher risk of mortality and higher risk of hospitalization (p < 0.05) than patients with D-EOV and N-EOV. CONCLUSION In HFrEF patients, EOV persistence during exercise had a strong prognostic role. In P-EOV patients V̇E/V̇CO2 ≥36 and V̇O2 peak ≤12 mlO2.kg-1.min-1, had a further additive negative prognostic role.
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Affiliation(s)
- Cássia da Luz Goulart
- Cardiopulmonary Physiotherapy Laboratory, Physiotherapy Department, Federal University of Sao Carlos, UFSCar, Rodovia Washington Luis, KM 235, Monjolinho, CEP: 13565-905, Sao Carlos, SP, Brazil
| | - Piergiuseppe Agostoni
- Centro Cardiologico Monzino, IRCCS, Via Parea 4, Milan20138, Italy.,Department of Clinical Sciences and Community Health, Cardiovascular Section, University of Milano, Milano, Italy
| | | | | | - Jon Myers
- Division of Cardiovascular Medicine, Department of Medicine, Stanford University, Stanford, California, USA
| | - Ross Arena
- Department of Physical Therapy, College of Applied Health Sciences, University of Illinois Chicago, Chicago, IL, USA
| | - Audrey Borghi-Silva
- Cardiopulmonary Physiotherapy Laboratory, Physiotherapy Department, Federal University of Sao Carlos, UFSCar, Rodovia Washington Luis, KM 235, Monjolinho, CEP: 13565-905, Sao Carlos, SP, Brazil
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Ministro G, Castaño JB, Barboza CA, Moura EG, Ferreira-Melo SE, Mostarda CT, Fattori A, Moreno-Junior H, Rodrigues B. ACUTE TRANSCRANIAL DIRECT CURRENT STIMULATION (tDCS) IMPROVES VENTILATORY VARIABILITY AND AUTONOMIC MODULATION IN RESISTANT HYPERTENSIVE PATIENTS. Respir Physiol Neurobiol 2021; 297:103830. [PMID: 34915178 DOI: 10.1016/j.resp.2021.103830] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 11/29/2021] [Accepted: 12/13/2021] [Indexed: 10/19/2022]
Abstract
Here, we assessed the impact of one session of transcranial direct current stimulation (tDCS) or SHAM (20 min, each) on ventilatory responses to cardiopulmonary exercise test, central and peripheral blood pressure (BP), and autonomic modulation in resistant hypertensive (RHT) patients. RHT subjects (n = 13) were randomly submitted to SHAM and tDCS crossing sessions (1 week of "washout"). Patients and a technician who set the tDCS/Sham room up were both blind. After brain stimulation, patients were submitted to a cardiopulmonary exercise test to evaluate ventilatory and cardiovascular response to exercise. Hemodynamic (Finometer®, Beatscope), and autonomic variables were measured at baseline (before tDCS/Sham) and after incremental exercise. RESULTS: Our study shows that tDCS condition improved heart rate recovery, VO2 peak, and vagal modulation (after cardiopulmonary exercise test); attenuated the ventilatory variability response, central and peripheral blood pressure well as sympathetic modulation (after cardiopulmonary exercise test) in comparison with SHAM. These data suggest that acute tDCS sessions prevented oscillatory ventilation behavior during the cardiopulmonary exercise test and mitigated the increase of systolic blood pressure in RHT patients. After the exercise test, tDCS promotes better vagal reentry and improved autonomic modulation, possibly reducing central blood pressure and aortic augmentation index compared to SHAM. Brazilian Registry of Clinical Trials (ReBEC): https://ensaiosclinicos.gov.br/rg/RBR-8n7c9p.
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Affiliation(s)
- Gabriela Ministro
- Laboratory of Cardiovascular Investigation & Exercise, School of Physical Education, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Javier B Castaño
- Laboratory of Cardiovascular Investigation & Exercise, School of Physical Education, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Catarina A Barboza
- Laboratory of Cardiovascular Investigation & Exercise, School of Physical Education, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Eliezer G Moura
- Laboratory of Cardiovascular Investigation & Exercise, School of Physical Education, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Silvia E Ferreira-Melo
- Laboratory of Cardiovascular Pharmacology & Hypertension, School of Medical Sciences, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | | | - André Fattori
- Department of Clinical Medicine, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Heitor Moreno-Junior
- Laboratory of Cardiovascular Pharmacology & Hypertension, School of Medical Sciences, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Bruno Rodrigues
- Laboratory of Cardiovascular Investigation & Exercise, School of Physical Education, University of Campinas (UNICAMP), Campinas, SP, Brazil; Laboratory of Cardiovascular Pharmacology & Hypertension, School of Medical Sciences, University of Campinas (UNICAMP), Campinas, SP, Brazil.
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Ribeiro GS, Cargnin C, Dal Lago P, Hansen D, Agostoni P, Karsten M. Exercise training effects on metabolic and ventilatory changes in heart failure patients with exercise oscillatory ventilation: systematic review and meta-analysis. Eur J Prev Cardiol 2021; 29:e233-e236. [PMID: 34849706 DOI: 10.1093/eurjpc/zwab195] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 10/14/2021] [Accepted: 11/05/2021] [Indexed: 11/13/2022]
Affiliation(s)
- Gustavo S Ribeiro
- Programa de Pós-Graduação em Ciências da Reabilitação, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rua Sarmento Leite 245, 90050-170 Porto Alegre, Brazil
| | - Camila Cargnin
- Programa de Pós-Graduação em Ciências da Reabilitação, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rua Sarmento Leite 245, 90050-170 Porto Alegre, Brazil
| | - Pedro Dal Lago
- Programa de Pós-Graduação em Ciências da Reabilitação, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rua Sarmento Leite 245, 90050-170 Porto Alegre, Brazil.,Departamento de Fisioterapia, UFCSPA, Rua Sarmento Leite 245, 90050-170 Porto Alegre, Brazil
| | - Dominique Hansen
- Faculty of Rehabilitation Sciences, Hasselt University (UHASSELT), BIOMED/REVAL, Agoralaan, Building A, 3590 Diepenbeek, Hasselt, Belgium.,Heart Centre Hasselt, Jessa Hospital, Jessa Ziekenhuis, Stadsomvaart 11, 3500 Hasselt, Belgium
| | - Piergiuseppe Agostoni
- Centro Cardiologico Monzino, IRCCS, Via Carlo Parea 4, 20138 Milano, Italy.,Department of Clinical Sciences of Community Health, Cardiovascular Section, University of Milano, Via Festa del Perdono 7, 20122 Milano, Italy
| | - Marlus Karsten
- Programa de Pós-Graduação em Ciências da Reabilitação, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rua Sarmento Leite 245, 90050-170 Porto Alegre, Brazil.,Departamento de Fisioterapia, Universidade do Estado de Santa Catarina (UDESC), Rua Pascoal Simone 358, 88080-350 Florianópolis, Brazil.,Programa de Pós-Graduação em Fisioterapia, UDESC, Rua Pascoal Simone 358, 88080-350 Florianópolis, Brazil
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Exercising in Hypoxia and Other Stimuli: Heart Rate Variability and Ventilatory Oscillations. Life (Basel) 2021; 11:life11070625. [PMID: 34203350 PMCID: PMC8306822 DOI: 10.3390/life11070625] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 06/22/2021] [Accepted: 06/27/2021] [Indexed: 12/24/2022] Open
Abstract
Periodic breathing is a respiratory phenomenon frequently observed in patients with heart failure and in normal subjects sleeping at high altitude. However, until recently, periodic breathing has not been studied in wakefulness and during exercise. This review relates the latest findings describing this ventilatory disorder when a healthy subject is submitted to simultaneous physiological (exercise) and environmental (hypoxia, hyperoxia, hypercapnia) or pharmacological (acetazolamide) stimuli. Preliminary studies have unveiled fundamental physiological mechanisms related to the genesis of periodic breathing characterized by a shorter period than those observed in patients (11~12 vs. 30~60 s). A mathematical model of the respiratory system functioning under the aforementioned stressors corroborated these data and pointed out other parameters, such as dead space, later confirmed in further research protocols. Finally, a cardiorespiratory interdependence between ventilatory oscillations and heart rate variability in the low frequency band may partly explain the origin of the augmented sympathetic activation at exercise in hypoxia. These nonlinear instabilities highlight the intrinsic "homeodynamic" system that allows any living organism to adapt, to a certain extent, to permanent environmental and internal perturbations.
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Abstract
In cardiopulmonary medicine, residual exertional dyspnea (RED) can be defined by the persistence of limiting breathlessness in a patient who is already under the best available therapy for the underlying heart and/or lung disease. RED is a challenge to the pulmonologist because the patient (and the referring physician) assumes that the "lung doctor" should invariably provide a successful plan to fight the symptom. After presenting a simplified framework to understand the neurobiological underpinnings of dyspnea in cardiorespiratory disease, I discuss the seeds of RED associated with 1) increased metabolic cost of work, 2) increased inspiratory constraints, 3) diaphragm dysfunction, 4) impaired right ventricle preload, 5) increased central and/or peripheral chemosensitivity, 6) increased physiological dead space, 7) increased pulmonary venous and/or high left ventricle filling pressures, 8) impaired chronotropic response to exertion, and 9) increased activation of the cortical-limbic circuits. I finalize by outlining the following two common coexistence of diseases in which these multiple mechanisms interact to produce severe RED: chronic obstructive pulmonary disease-heart failure with reduced ejection fraction and chronic pulmonary fibrosis-emphysema. RED exposes the important limitations of the current reductionist approach focused only on the (over)treatment of the poorly reversible cardiopulmonary disease(s). Conversely, recognizing the existence of RED sets the stage for a more holistic approach toward one of the most devastating symptoms known to man.
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