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1.
Chron Respir Dis ; 19: 14799731221104095, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35603864

RESUMO

BACKGROUND: Pulmonary hypertension (PH) is associated with decreased exercise tolerance in chronic obstructive pulmonary disease (COPD) patients, but in the altitude the response to exercise in those patients is unknown. Our objective was to compare exercise capacity, gas exchange and ventilatory alterations between COPD patients with PH (COPD-PH) and without PH (COPD-nonPH) residents at high altitude (2640 m). METHODS: One hundred thirty-two COPD-nonPH, 82 COPD-PH, and 47 controls were included. Dyspnea by Borg scale, oxygen consumption (VO2), work rate (WR), ventilatory equivalents (VE/VCO2), dead space to tidal volume ratio (VD/VT), alveolar-arterial oxygen tension gradient (AaPO2), and arterial-end-tidal carbon dioxide pressure gradient (Pa-ETCO2) were measurement during a cardiopulmonary exercise test. For comparison of variables between groups, Kruskal-Wallis or one-way ANOVA tests were used, and stepwise regression analysis to test the association between PH and exercise capacity. RESULTS: All COPD patients had a lower exercise capacity and higher PaCO2, A-aPO2 and VD/VT than controls. The VO2 % predicted (61.3 ± 20.6 vs 75.3 ± 17.9; p < 0.001) and WR % predicted (65.3 ± 17.9 vs 75.3 ± 17.9; p < 0.001) were lower in COPD-PH than in COPD-nonPH. At peak exercise, dyspnea was higher in COPD-PH (p = 0.011). During exercise, in COPD-PH, the PaO2 was lower (p < 0.001), and AaPO2 (p < 0.001), Pa-ETCO2 (p = 0.033), VE/VCO2 (p = 0.019), and VD/VT (p = 0.007) were higher than in COPD-nonPH. In the multivariate analysis, PH was significantly associated with lower peak VO2 and WR (p < 0.001). CONCLUSION: In COPD patients residing at high altitude, the presence of PH was an independent factor related to the exercise capacity. Also, in COPD-PH patients there were more dyspnea and alterations in gas exchange during the exercise than in those without PH.


Assuntos
Hipertensão Pulmonar , Doença Pulmonar Obstrutiva Crônica , Altitude , Dispneia/etiologia , Teste de Esforço , Tolerância ao Exercício/fisiologia , Humanos , Hipertensão Pulmonar/complicações , Doença Pulmonar Obstrutiva Crônica/complicações , Troca Gasosa Pulmonar/fisiologia
2.
Respir Care ; 67(4): 480-493, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-35338096

RESUMO

Acute respiratory failure with inadequate oxygenation and/or ventilation is a common reason for ICU admission in children and adults. Despite the morbidity and mortality associated with acute respiratory failure, few proven treatment options exist beyond invasive ventilation. Attempts to develop intravascular respiratory assist catheters capable of providing clinically important gas exchange have had limited success. Only one device, the IVOX catheter, was tested in human clinical trials before development was halted without FDA approval. Overcoming the technical challenges associated with providing safe and effective gas exchange within the confines of the intravascular space remains a daunting task for physicians and engineers. It requires a detailed understanding of the fundamentals of gas transport and respiratory physiology to optimize the design for a successful device. This article reviews the potential benefits of such respiratory assist catheters, considerations for device design, previous attempts at intravascular gas exchange, and the motivation for continued development efforts.


Assuntos
Síndrome do Desconforto Respiratório , Insuficiência Respiratória , Adulto , Dióxido de Carbono , Criança , Humanos , Troca Gasosa Pulmonar/fisiologia , Respiração , Insuficiência Respiratória/terapia
3.
J Appl Physiol (1985) ; 132(4): 1104-1113, 2022 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-35323050

RESUMO

The common pulmonary consequence of SARS-CoV-2 infection is pneumonia, but vascular clot may also contribute to COVID pathogenesis. Imaging and hemodynamic approaches to identifying diffuse pulmonary vascular obstruction (PVO) in COVID (or acute lung injury generally) are problematic particularly when pneumonia is widespread throughout the lung and hemodynamic consequences are buffered by pulmonary vascular recruitment and distention. Although stimulated by COVID-19, we propose a generally applicable bedside gas exchange approach to identifying PVO occurring alone or in combination with pneumonia, addressing both its theoretical and practical aspects. It is based on knowing that poorly (or non) ventilated regions, as occur in pneumonia, affect O2 more than CO2, whereas poorly (or non) perfused regions, as seen in PVO, affect CO2 more than O2. Exhaled O2 and CO2 concentrations at the mouth are measured over several ambient-air breaths, to determine mean alveolar Po2 and Pco2. A single arterial blood sample is taken over several of these breaths for arterial Po2 and Pco2. The resulting alveolar-arterial Po2 and Pco2 differences (AaPo2, aAPco2) are converted to corresponding physiological shunt and deadspace values using the Riley and Cournand 3-compartment model. For example, a 30% shunt (from pneumonia) with no alveolar deadspace produces an AaPO2 of almost 50 torr, but an aAPco2 of only 3 torr. In contrast, a 30% alveolar deadspace (from PVO) without shunt leads to an AaPO2 of only 12 torr, but an aAPco2 of 9 torr. This approach can identify and quantify physiological shunt and deadspace when present singly or in combination.NEW & NOTEWORTHY Identifying pulmonary vascular obstruction in the presence of pneumonia (e.g., in COVID-19) is difficult. We present here conversion of bedside measurements of arterial and alveolar Po2 and Pco2 into values for shunt and deadspace-when both coexist-using Riley and Cournand's 3-compartment gas exchange model. Deadspace values higher than expected from shunt alone indicate high ventilation/perfusion ratio areas likely reflecting (micro)vascular obstruction.


Assuntos
COVID-19 , Pneumopatias , Dióxido de Carbono , Humanos , Troca Gasosa Pulmonar/fisiologia , SARS-CoV-2
4.
Sci Rep ; 12(1): 2070, 2022 02 08.
Artigo em Inglês | MEDLINE | ID: mdl-35136116

RESUMO

Outdoor breathing trials with simulated avalanche snow are fundamental for the research of the gas exchange under avalanche snow, which supports the development of the international resuscitation guidelines. However, these studies have to face numerous problems, including unstable weather and variable snow properties. This pilot study examines a mineral material perlite as a potential snow model for studies of ventilation and gas exchange parameters. Thirteen male subjects underwent three breathing phases-into snow, wet perlite and dry perlite. The resulting trends of gas exchange parameters in all tested materials were similar and when there was a significant difference observed, the trends in the parameters for high density snow used in the study lay in between the trends in dry and wet perlite. These findings, together with its stability and accessibility year-round, make perlite a potential avalanche snow model material. Perlite seems suitable especially for simulation and preparation of breathing trials assessing gas exchange under avalanche snow, and potentially for testing of new avalanche safety equipment before their validation in real snow.The study was registered in ClinicalTrials.gov on January 22, 2018; the registration number is NCT03413878.


Assuntos
Óxido de Alumínio , Avalanches , Troca Gasosa Pulmonar/fisiologia , Respiração , Dióxido de Silício , Neve , Adulto , Reanimação Cardiopulmonar/métodos , Estudos Cross-Over , República Tcheca , Método Duplo-Cego , Humanos , Masculino , Modelos Teóricos , Projetos Piloto , Estudos Prospectivos , Treinamento por Simulação , Adulto Jovem
5.
J Appl Physiol (1985) ; 132(3): 632-640, 2022 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-35112932

RESUMO

Heart failure with preserved ejection fraction (HFpEF) is associated with cardiopulmonary abnormalities that may increase physiological dead space to tidal volume (VD/VT) during exercise. However, studies have not corrected VD/VT for apparatus mechanical dead space (VDM), which may confound the accurate calculation of VD/VT. We evaluated whether calculating physiological dead space with (VD/VTVDM) and without (VD/VT) correcting for VDM impacts the interpretation of gas exchange efficiency during exercise in HFpEF. Fifteen HFpEF (age: 69 ± 6 yr; V̇o2peak: 1.34 ± 0.45 L/min) and 12 controls (70 ± 3 yr; V̇o2peak: 1.70 ± 0.51 L/min) were studied. Pulmonary gas exchange and arterial blood gases were analyzed at rest, submaximal (20 W for HFpEF and 40 W for controls), and peak exercise. VD/VT was calculated as [Formula: see text] - [Formula: see text]/[Formula: see text]. VD/VTVDM was calculated as [Formula: see text] - [Formula: see text]/[Formula: see text] - VDM/VT. VD/VT decreased from rest (HFpEF: 0.54 ± 0.07; controls: 0.32 ± 0.07) to submaximal exercise (HFpEF: 0.46 ± 0.07; controls: 0.25 ± 0.06) in both groups (P < 0.05), but remained stable (P > 0.05) thereafter to peak exercise (HFpEF: 0.46 ± 0.09; controls: 0.22 ± 0.05). In HFpEF, VD/VTVDM did not change (P = 0.58) from rest (0.29 ± 0.07) to submaximal exercise (0.29 ± 0.06), but increased (P = 0.02) thereafter to peak exercise (0.33 ± 0.06). In controls, VD/VTVDM remained stable such that no change was observed (P > 0.05) from rest (0.17 ± 0.06) to submaximal exercise (0.14 ± 0.06), or thereafter to peak exercise (0.14 ± 0.05). Calculating physiological dead space with and without a VDM correction yields quantitively and qualitatively different results, which could have impact on the interpretation of gas exchange efficiency in HFpEF. Further investigation is required to uncover the clinical consequences and the mechanism(s) explaining the increase in VD/VTVDM during exercise in HFpEF.NEW & NOTEWORTHY Calculating VD/VT with and without correcting for VDM yields quantitively and qualitatively different results, which could have an important impact on the interpretation of V/Q mismatch in HFpEF. The finding that V/Q mismatch and gas exchange efficiency worsened, as reflected by an increase in VD/VTVDM during exercise, has not been previously demonstrated in HFpEF. Thus, further studies are needed to investigate the mechanisms explaining the increase in VD/VTVDM during exercise in patients with HFpEF.


Assuntos
Insuficiência Cardíaca , Idoso , Exercício Físico/fisiologia , Teste de Esforço/métodos , Humanos , Pessoa de Meia-Idade , Troca Gasosa Pulmonar/fisiologia , Espaço Morto Respiratório/fisiologia , Volume Sistólico/fisiologia , Volume de Ventilação Pulmonar/fisiologia
6.
Sports Med ; 52(2): 237-255, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34694596

RESUMO

During incremental exercise, two thresholds may be identified from standard gas exchange and ventilatory measurements. The first signifies the onset of blood lactate accumulation (the lactate threshold, LT) and the second the onset of metabolic acidosis (the respiratory compensation point, RCP). The ability to explain why these thresholds occur and how they are identified, non-invasively, from pulmonary gas exchange and ventilatory variables is fundamental to the field of exercise physiology and requisite to the understanding of core concepts including exercise intensity, assessment, prescription, and performance. This review is intended as a unique and comprehensive theoretical and practical resource for instructors, clinicians, researchers, lab technicians, and students at both undergraduate and graduate levels to facilitate the teaching, comprehension, and proper non-invasive identification of exercise thresholds. Specific objectives are to: (1) explain the underlying physiology that produces the LT and RCP; (2) introduce the classic non-invasive measurements by which these thresholds are identified by connecting variable profiles to underlying physiological behaviour; (3) discuss common issues that can obscure threshold detection and strategies to identify and mitigate these challenges; and (4) introduce an online resource to facilitate learning and standard practices. Specific examples of exercise gas exchange and ventilatory data are provided throughout to illustrate these concepts and a novel online application tool designed specifically to identify the estimated LT (θLT) and RCP is introduced. This application is a unique platform for learners to practice skills on real exercise data and for anyone to analyze incremental exercise data for the purpose of identifying θLT and RCP.


Assuntos
Aplicativos Móveis , Limiar Anaeróbio/fisiologia , Exercício Físico/fisiologia , Teste de Esforço , Humanos , Ácido Láctico , Consumo de Oxigênio/fisiologia , Troca Gasosa Pulmonar/fisiologia
7.
Eur J Appl Physiol ; 122(2): 459-474, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34799752

RESUMO

PURPOSE: Traditional high-intensity interval exercise (HIIE) highly stimulates the cardiorespiratory system and increases energy expenditure (EE) during exercise. High-intensity resistance exercise (HIRE) has become more popular in recreationally active subjects. The physiological responses to HIRE performed with light or moderate load is currently largely unknown. Here, we examined the effect of the type of interval exercise [HIRE at 40% (HIRE40) and 60% (HIRE60) 1-RM vs. traditional HIIE] on the cardiorespiratory response and EE during and after exercise. METHODS: Fifteen recreationally active adults randomly completed traditional HIIE on an ergocyle, HIRE40 and HIRE60. The sessions consisted of two sets of ten 30-s intervals (power at 100% VO2max during HIIE; maximal number of repetitions for 10 different free-weight exercises during HIRE40 and HIRE60) separated by 30-s active recovery periods. Gas exchange, heart rate (HR) and EE were assessed during and after exercise. RESULTS: VO2mean, VO2peak, HRmean, the time spent above 90% VO2max and HRmax, and aerobic EE were lower in both HIRE sessions compared with HIIE (P < 0.05). Anaerobic glycolytic contribution to total exercise EE was higher in HIRE40 and HIRE60 compared with HIIE (P < 0.001). EE from excess post-exercise oxygen consumption (EPOC) was similar after the three sessions. Overall, similar cardiorespiratory responses and EE were found in HIRE40 and HIRE60. CONCLUSIONS: HIRE is not as effective as HIIE for increasing the cardiorespiratory response and EE during exercise, while EPOC remains similar in HIRE and HIIE. These parameters are not substantially different between HIRE40 and HIRE60.


Assuntos
Aptidão Cardiorrespiratória/fisiologia , Metabolismo Energético/fisiologia , Treinamento Intervalado de Alta Intensidade/métodos , Esforço Físico/fisiologia , Treinamento de Força/métodos , Estudos Cross-Over , Teste de Esforço , Feminino , Frequência Cardíaca/fisiologia , Humanos , Masculino , Consumo de Oxigênio/fisiologia , Troca Gasosa Pulmonar/fisiologia , Adulto Jovem
8.
J Vasc Surg Venous Lymphat Disord ; 10(3): 697-704.e4, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-34958976

RESUMO

OBJECTIVE: Pulmonary oxygen uptake (V˙O2) kinetics measured during the initiation of exercise mirror energetic transition during daily activity. The aim of this study was to elucidate the pathophysiological mechanisms of exercise limitation of patients with chronic iliofemoral vein obstruction after deep vein thrombosis by measuring V˙O2 kinetics compared with patients with peripheral arterial disease (PAD) and healthy individuals. METHODS: Eleven patients with iliofemoral vein obstruction (7 men; age, 20-65 years), seven patients with PAD (all men; age 44-60 years) and eight healthy participants (5 men; age 28-58 years) were studied. Participants performed upper and lower limb symptom-limited cardiopulmonary exercise tests on cycle ergometers; and four repeat lower limb tests at a constant work rate corresponding with 90% of the gas exchange threshold for determining V˙O2 kinetics. RESULTS: Phase I V˙O2 amplitude in the constant work rate tests (percent increase over resting V˙O2), representing the initial surge in cardiac output caused by the emptying of leg veins, was 59 ± 19% in the iliofemoral vein obstruction group, 73 ± 22% in PAD, and 85 ± 26% in healthy participants (P = .055 for iliofemoral vein obstruction vs healthy). Phase II V˙O2 kinetics, which largely reflect the kinetics of O2 consumption in the exercising muscles, were slower in iliofemoral vein obstruction (tau = 42 ± 6 seconds), and PAD (tau = 49 ± 19 seconds), compared with healthy participants (23 ± 4 seconds; P < .01). CONCLUSIONS: Slow phase II V˙O2 kinetics reflect a slow onset of muscular aerobic metabolism in both iliofemoral vein obstruction and PAD. The low amplitude phase I of V˙O2 kinetics observed in iliofemoral vein obstruction suggests a damped cardiodynamic phase, consistent with decreased venous return from the obstructed veins. These abnormalities of V˙O2 kinetics may contribute to exercise intolerance in iliofemoral vein obstruction and PAD.


Assuntos
Doença Arterial Periférica , Troca Gasosa Pulmonar , Adulto , Idoso , Exercício Físico/fisiologia , Feminino , Humanos , Cinética , Masculino , Pessoa de Meia-Idade , Oxigênio , Consumo de Oxigênio/fisiologia , Doença Arterial Periférica/diagnóstico , Troca Gasosa Pulmonar/fisiologia , Adulto Jovem
9.
J Physiol ; 600(3): 463-482, 2022 02.
Artigo em Inglês | MEDLINE | ID: mdl-34961925

RESUMO

Progressive improvements in perinatal care and respiratory management of preterm infants have resulted in increased survival of newborns of extremely low gestational age over the past few decades. However, the incidence of bronchopulmonary dysplasia, the chronic lung disease after preterm birth, has not changed. Studies of the long-term follow-up of adults born preterm have shown persistent abnormalities of respiratory, cardiovascular and cardiopulmonary function, possibly leading to a lower exercise capacity. The underlying causes of these abnormalities are incompletely known, but we hypothesize that dysanapsis, i.e. discordant growth and development, in the respiratory and cardiovascular systems is a central structural feature that leads to a lower exercise capacity in young adults born preterm than those born at term. We discuss how the hypothesized system dysanapsis underscores the observed respiratory, cardiovascular and cardiopulmonary limitations. Specifically, adults born preterm have: (1) normal lung volumes but smaller airways, which causes expiratory airflow limitation and abnormal respiratory mechanics but without impacts on pulmonary gas exchange efficiency; (2) normal total cardiac size but smaller cardiac chambers; and (3) in some cases, evidence of pulmonary hypertension, particularly during exercise, suggesting a reduced pulmonary vascular capacity despite reduced cardiac output. We speculate that these underlying developmental abnormalities may accelerate the normal age-associated decline in exercise capacity, via an accelerated decline in respiratory, cardiovascular and cardiopulmonary function. Finally, we suggest areas of future research, especially the need for longitudinal and interventional studies from infancy into adulthood to better understand how preterm birth alters exercise capacity across the lifespan.


Assuntos
Displasia Broncopulmonar , Nascimento Prematuro , Adulto , Exercício Físico/fisiologia , Feminino , Humanos , Lactente , Recém-Nascido , Recém-Nascido Prematuro , Gravidez , Troca Gasosa Pulmonar/fisiologia , Adulto Jovem
11.
BMC Pulm Med ; 22(1): 71, 2022 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-35216579

RESUMO

BACKGROUND: Prone positioning enables the redistribution of lung weight, leading to the improvement of gas exchange and respiratory mechanics. We aimed to evaluate whether the initial findings of acute respiratory distress syndrome (ARDS) on computed tomography (CT) are associated with the subsequent response to prone positioning in terms of oxygenation and 60-day mortality. METHODS: We retrospectively included patients who underwent prone positioning for moderate to severe ARDS from October 2014 to November 2020 at a medical center in Taiwan. A semiquantitative CT rating scale was used to quantify the extent of consolidation and ground-glass opacification (GGO) in the sternal, central and vertebral regions at three levels (apex, hilum and base) of the lungs. A prone responder was identified by a 20% increase in the ratio of arterial oxygen pressure (PaO2) to the fraction of oxygen (FiO2) or a 20 mmHg increase in PaO2. RESULTS: Ninety-six patients were included, of whom 68 (70.8%) were responders. Compared with nonresponders, responders had a significantly greater median dorsal-ventral difference in CT-consolidation scores (10 vs. 7, p = 0.046) but not in CT-GGO scores (- 1 vs. - 1, p = 0.974). Although dorsal-ventral differences in neither CT-consolidation scores nor CT-GGO scores were associated with 60-day mortality, high total CT-GGO scores (≥ 15) were an independent factor associated with 60-day mortality (odds ratio = 4.07, 95% confidence interval, 1.39-11.89, p = 0.010). CONCLUSIONS: In patients with moderate to severe ARDS, a greater difference in the extent of consolidation along the dependent-independent axis on CT scan is associated with subsequent prone positioning oxygenation response, but not clinical outcome regarding survival. High total CT-GGO scores were independently associated with 60-day mortality.


Assuntos
Troca Gasosa Pulmonar , Síndrome do Desconforto Respiratório , Humanos , Prognóstico , Decúbito Ventral/fisiologia , Troca Gasosa Pulmonar/fisiologia , Síndrome do Desconforto Respiratório/diagnóstico por imagem , Síndrome do Desconforto Respiratório/terapia , Estudos Retrospectivos , Tomografia Computadorizada por Raios X
12.
PLoS One ; 16(11): e0257349, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34748555

RESUMO

Pulmonary acini represent the functional gas-exchanging units of the lung. Due to technical limitations, individual acini cannot be identified on microscopic lung sections. To overcome these limitations, we imaged the right lower lobes of instillation-fixed rat lungs from postnatal days P4, P10, P21, and P60 at the TOMCAT beamline of the Swiss Light Source synchrotron facility at a voxel size of 1.48 µm. Individual acini were segmented from the three-dimensional data by closing the airways at the transition from conducting to gas exchanging airways. For a subset of acini (N = 268), we followed the acinar development by stereologically assessing their volume and their number of alveoli. We found that the mean volume of the acini increases 23 times during the observed time-frame. The coefficients of variation dropped from 1.26 to 0.49 and the difference between the mean volumes of the fraction of the 20% smallest to the 20% largest acini decreased from a factor of 27.26 (day 4) to a factor of 4.07 (day 60), i.e. shows a smaller dispersion at later time points. The acinar volumes show a large variation early in lung development and homogenize during maturation of the lung by reducing their size distribution by a factor of 7 until adulthood. The homogenization of the acinar sizes hints at an optimization of the gas-exchange region in the lungs of adult animals and that acini of different size are not evenly distributed in the lungs. This likely leads to more homogeneous ventilation at later stages in lung development.


Assuntos
Pulmão/ultraestrutura , Alvéolos Pulmonares/ultraestrutura , Troca Gasosa Pulmonar/fisiologia , Respiração , Células Acinares/fisiologia , Células Acinares/ultraestrutura , Animais , Animais Recém-Nascidos/fisiologia , Humanos , Pulmão/fisiologia , Alvéolos Pulmonares/fisiologia , Ratos
13.
Sci Rep ; 11(1): 17862, 2021 09 09.
Artigo em Inglês | MEDLINE | ID: mdl-34504252

RESUMO

When hemoglobin (Hb) is fully saturated with oxygen, the additional gain in oxygen delivery (DO2) achieved by increasing the fraction of inspired oxygen (FiO2) is often considered clinically insignificant. In this study, we evaluated the change in DO2, interrogated by mixed venous oxygen saturation (SvO2), in response to a change in FiO2 of 0.5 during cardiac surgery. When patients were hemodynamically stable, FiO2 was alternated between 0.5 and 1.0 in on-pump cardiac surgery patients (pilot study), and between 0.3 and 0.8 in off-pump coronary artery bypass grafting patients (substudy of the CARROT trial). After the patient had stabilized, a blood gas analysis was performed to measure SvO2. The observed change in SvO2 (ΔSvO2) was compared to the expected ΔSvO2 calculated using Fick's equation. A total 106 changes in FiO2 (two changes per patient; total 53 patients; on-pump, n = 36; off-pump, n = 17) were finally analyzed. While Hb saturation remained near 100% (on-pump, 100%; off-pump, mean [SD] = 98.1% [1.5] when FiO2 was 0.3 and 99.9% [0.2] when FiO2 was 0.8), SvO2 changed significantly as FiO2 was changed (the first and second changes in on-pump, 7.7%p [3.8] and 7.6%p [3.5], respectively; off-pump, 7.9%p [4.9] and 6.2%p [3.9]; all P < 0.001). As a total, regardless of the surgery type, the observed ΔSvO2 after the FiO2 change of 0.5 was ≥ 5%p in 82 (77.4%) changes and ≥ 10%p in 31 (29.2%) changes (mean [SD], 7.5%p [3.9]). Hb concentration was not correlated with the observed ΔSvO2 (the first changes, r = - 0.06, P = 0.677; the second changes, r = - 0.21, P = 0.138). The mean (SD) residual ΔSvO2 (observed - expected ΔSvO2) was 0%p (4). Residual ΔSvO2 was more than 5%p in 14 (13.2%) changes and exceeded 10%p in 2 (1.9%) changes. Residual ΔSvO2 was greater in patients with chronic kidney disease than in those without (median [IQR], 5%p [0 to 7] vs. 0%p [- 3 to 2]; P = 0.049). DO2, interrogated by SvO2, may increase to a clinically significant degree as FiO2 is increased during cardiac surgery, and the increase of SvO2 is not related to Hb concentration. SvO2 increases more than expected in patients with chronic kidney disease. Increasing FiO2 can be used to increase DO2 during cardiac surgery.


Assuntos
Débito Cardíaco/fisiologia , Consumo de Oxigênio/fisiologia , Oxigênio/sangue , Troca Gasosa Pulmonar/fisiologia , Cirurgia Torácica , Idoso , Gasometria/métodos , Ponte de Artéria Coronária sem Circulação Extracorpórea/métodos , Daucus carota/metabolismo , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Oximetria/métodos
14.
Br J Anaesth ; 127(5): 807-814, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34507822

RESUMO

BACKGROUND: Lung rest has been recommended during extracorporeal membrane oxygenation (ECMO) for severe acute respiratory distress syndrome (ARDS). Whether positive end-expiratory pressure (PEEP) confers lung protection during ECMO for severe ARDS is unclear. We compared the effects of three different PEEP levels whilst applying near-apnoeic ventilation in a model of severe ARDS treated with ECMO. METHODS: Acute respiratory distress syndrome was induced in anaesthetised adult male pigs by repeated saline lavage and injurious ventilation for 1.5 h. After ECMO was commenced, the pigs received standardised near-apnoeic ventilation for 24 h to maintain similar driving pressures and were randomly assigned to PEEP of 0, 10, or 20 cm H2O (n=7 per group). Respiratory and haemodynamic data were collected throughout the study. Histological injury was assessed by a pathologist masked to PEEP allocation. Lung oedema was estimated by wet-to-dry-weight ratio. RESULTS: All pigs developed severe ARDS. Oxygenation on ECMO improved with PEEP of 10 or 20 cm H2O, but did not in pigs allocated to PEEP of 0 cm H2O. Haemodynamic collapse refractory to norepinephrine (n=4) and early death (n=3) occurred after PEEP 20 cm H2O. The severity of lung injury was lowest after PEEP of 10 cm H2O in both dependent and non-dependent lung regions, compared with PEEP of 0 or 20 cm H2O. A higher wet-to-dry-weight ratio, indicating worse lung injury, was observed with PEEP of 0 cm H2O. Histological assessment suggested that lung injury was minimised with PEEP of 10 cm H2O. CONCLUSIONS: During near-apnoeic ventilation and ECMO in experimental severe ARDS, 10 cm H2O PEEP minimised lung injury and improved gas exchange without compromising haemodynamic stability.


Assuntos
Oxigenação por Membrana Extracorpórea/métodos , Lesão Pulmonar/fisiopatologia , Respiração com Pressão Positiva/métodos , Síndrome do Desconforto Respiratório/terapia , Animais , Modelos Animais de Doenças , Hemodinâmica , Masculino , Troca Gasosa Pulmonar/fisiologia , Respiração Artificial/métodos , Síndrome do Desconforto Respiratório/fisiopatologia , Índice de Gravidade de Doença , Suínos
15.
Respir Physiol Neurobiol ; 294: 103735, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34229064

RESUMO

The aim of this study was to test the utility and effectiveness of an alternative computational approach to threshold-intensities based on time dependent change-points in minute ventilation divided by end-tidal partial pressure of CO2 (VE/PETCO2) to reveal whether respiratory compensation point (RCP) is a third ventilatory threshold, or not. Ten recreationally active young adults and ten well-trained athletes volunteered to take part in this study. Following incremental ramp tests, gas exchange threshold (GET) and respiratory compensation point (RCP) were respectively evaluated by the slopes of VCO2-VO2 and VE-VCO2 using the Innocor system automatically. Respiratory threshold (RT) was analysed based on time dependent change-points in the VE/PETCO2 using binary segmentation algorithm. Additionally, those intersections were analysed independently by two experienced investigators using a visual identification technique in a double-blind design. According to the results, in the recreationally active group, there were the first (GET1) and the second (GET2) gas exchange thresholds which were identical with the RT1 (139 W; 1.9 L⋅min-1 of VO2; 1.73 L⋅min-1 of VCO2; 49.9 L⋅min-1 of VE versus 139 W; 1.88 L⋅min-1; 1.7 L⋅min-1; 49 L⋅min-1, respectively) and RT2 (186 W; 2.39 L⋅min-1 of VO2; 2.44 L⋅min-1 of VCO2; 66 L⋅min-1 of VE versus 187 W; 2.41 L⋅min-1; 2.49 L⋅min-1; 65.7 L⋅min-1, respectively). However, there were three threshold intensities which were determined by GET1, GET2, and RCP in well-trained athletes. Additionally, RT1, RT2, and RT3 were determined as valid surrogates of the GET1 (194 W; 2.56 L⋅min-1 of VO2; 1.99 L⋅min-1 of VCO2; 57.5 L⋅min-1 of VE versus 192 W; 2.61 L⋅min-1; 1.99 Lmin-1; 57.7 L⋅min-1, respectively), GET2 (267 W; 3.6 L⋅min-1 of VO2; 3.29 L⋅min-1 of VCO2; 94.5 L⋅min-1 of VE versus 266 W; 3.58 L⋅min-1; 3.26 L⋅min-1; 93.4 L⋅min-1, respectively), and RCP (324 W; 4.05 L⋅min-1 of VO2; 4.13 L⋅min-1 of VCO2; 124 L⋅min-1 of VE versus 322 W; 4.02 L⋅min-1; 4.07 L⋅min-1; 122 L⋅min-1, respectively) in well-trained athletes. There were high levels of agreements between the power outputs determined by traditional techniques and newly proposed change-points in RT. All markers were strongly correlated (p < 0.001). It was shown that RT technique can provide an accurate threshold determination. Furthermore, the RCP was observed as a third threshold-intensity for well-trained athletes but not for recreationally active young adults.


Assuntos
Dióxido de Carbono/metabolismo , Troca Gasosa Pulmonar/fisiologia , Ventilação Pulmonar/fisiologia , Adulto , Atletas , Humanos , Masculino , Adulto Jovem
16.
Respir Physiol Neurobiol ; 294: 103767, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34329768

RESUMO

A computational model of the transport of gases involved in spontaneous breathing, from the trachea inlet to the alveoli was developed for healthy patients. Convective and diffusive transport mechanisms were considered simultaneously, using a diffusion coefficient (D) that has considered the four main species of gases present in the exchange carried out by the human lung, nitrogen (N2), oxygen (O2), carbon dioxide (CO2) and water vapor (H2O). A Matlab® script was programmed to simulate the trachea-alveolus gas exchange model under three respiratory frequencies: 12, 24 and 40 breaths per minute (BPM), each with three diaphragmatic movements of 2 cm, 4 cm, and 6 cm. During the simulations, the CO2 inlet concentrations in the alveoli and the O2 concentration at the inlet of the trachea were kept constant. A simplified but stable model of mass transport between the trachea and alveoli was obtained, allowing the concentrations to be determined dynamically at the selected test points in the airway.


Assuntos
Modelos Teóricos , Alvéolos Pulmonares/fisiologia , Troca Gasosa Pulmonar/fisiologia , Respiração , Traqueia/fisiologia , Humanos
17.
Nutrients ; 13(7)2021 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-34209600

RESUMO

The relation between changes in respiratory quotient (RQ) following dietary interventions and clinical parameters and body fat pools remains unknown. In this randomized controlled trial, participants with moderate abdominal obesity or/and dyslipidemia (n = 159) were randomly assigned to a Mediterranean/low carbohydrate (MED/LC, n = 80) or a low fat (LF, n = 79) isocaloric weight loss diet and completed a metabolic assessment. Changes in RQ (measured by indirect calorimeter), adipose-tissue pools (MRI), and clinical measurements were assessed at baseline and after 6 months of intervention. An elevated RQ at baseline was significantly associated with increased visceral adipose tissue, hepatic fat, higher levels of insulin and homeostatic insulin resistance. After 6 months, body weight had decreased similarly between the diet groups (-6 ± 6 kg). However, the MED/LC diet, which greatly improved metabolic health, decreased RQ significantly more than the LF diet (-0.022 ± 0.007 vs. -0.002 ± 0.008, p = 0.005). Total cholesterol and diastolic blood pressure were independently associated with RQ changes (p = 0.045). RQ was positively associated with increased superficial subcutaneous-adipose-tissue but decreased renal sinus, pancreatic, and intramuscular fats after adjusting for confounders. Fasting RQ may reflect differences in metabolic characteristics between subjects affecting their potential individual response to the diet.


Assuntos
Tecido Adiposo/fisiopatologia , Dieta Redutora/métodos , Obesidade Abdominal/dietoterapia , Troca Gasosa Pulmonar/fisiologia , Perda de Peso/fisiologia , Adulto , Calorimetria Indireta , Dieta com Restrição de Carboidratos/métodos , Dieta com Restrição de Gorduras/métodos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Obesidade Abdominal/fisiopatologia , Resultado do Tratamento
19.
Crit Care ; 25(1): 248, 2021 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-34266454

RESUMO

BACKGROUND: Differences in physiology of ARDS have been described between COVID-19 and non-COVID-19 patients. This study aimed to compare initial values and longitudinal changes in respiratory system compliance (CRS), oxygenation parameters and ventilatory ratio (VR) in patients with COVID-19 and non-COVID-19 pulmonary ARDS matched on oxygenation. METHODS: 135 patients with COVID-19 ARDS from two centers were included in a physiological study; 767 non-COVID-19 ARDS from a clinical trial were used for the purpose of at least 1:2 matching. A propensity-matching was based on age, severity score, oxygenation, positive end-expiratory pressure (PEEP) and pulmonary cause of ARDS and allowed to include 112 COVID-19 and 198 non-COVID pulmonary ARDS. RESULTS: The two groups were similar on initial oxygenation. COVID-19 patients had a higher body mass index, higher CRS at day 1 (median [IQR], 35 [28-44] vs 32 [26-38] ml cmH2O-1, p = 0.037). At day 1, CRS was correlated with oxygenation only in non-COVID-19 patients; 61.6% and 68.2% of COVID-19 and non-COVID-19 pulmonary ARDS were still ventilated at day 7 (p = 0.241). Oxygenation became lower in COVID-19 than in non-COVID-19 patients at days 3 and 7, while CRS became similar. VR was lower at day 1 in COVID-19 than in non-COVID-19 patients but increased from day 1 to 7 only in COVID-19 patients. VR was higher at days 1, 3 and 7 in the COVID-19 patients ventilated using heat and moisture exchangers compared to heated humidifiers. After adjustment on PaO2/FiO2, PEEP and humidification device, CRS and VR were found not different between COVID-19 and non-COVID-19 patients at day 7. Day-28 mortality did not differ between COVID-19 and non-COVID-19 patients (25.9% and 23.7%, respectively, p = 0.666). CONCLUSIONS: For a similar initial oxygenation, COVID-19 ARDS initially differs from classical ARDS by a higher CRS, dissociated from oxygenation. CRS become similar for patients remaining on mechanical ventilation during the first week of evolution, but oxygenation becomes lower in COVID-19 patients. TRIAL REGISTRATION: clinicaltrials.gov NCT04385004.


Assuntos
COVID-19/terapia , Respiração com Pressão Positiva/métodos , Síndrome do Desconforto Respiratório/terapia , Idoso , Gasometria , Índice de Massa Corporal , COVID-19/fisiopatologia , Feminino , Humanos , Unidades de Terapia Intensiva , Masculino , Pessoa de Meia-Idade , Pontuação de Propensão , Troca Gasosa Pulmonar/fisiologia , Respiração Artificial/métodos , Síndrome do Desconforto Respiratório/fisiopatologia , Testes de Função Respiratória , Mecânica Respiratória/fisiologia , SARS-CoV-2
20.
Artigo em Inglês | MEDLINE | ID: mdl-34256130

RESUMO

The use of assisted ventilation is required in anesthetized reptiles as their respiratory drive is lost at surgical depths of anesthesia. The minute volume of the assisted ventilation influences arterial blood gases and acid-base regulation. Meanwhile, the ventilatory pattern may also affect hemodynamics in chelonians, which, given their large capacity for cardiac shunts, may impact the efficacy of the ventilation in terms of gas exchange. Hence, there is a need for primary information on the influence of assisted ventilation on chelonian physiology, and we, therefore, performed a randomized study into the effects of recumbency and maximum airway pressure on pressure-cycled ventilation in nine female Trachemys scripta scripta. Pronounced effects of ventilation pressure on arterial PCO2 and pH regardless of recumbency were revealed, whilst dorsal recumbency led to a larger Arterial-alveolar (A-a) O2 difference, suggesting compromised pulmonary gas exchange. Plasma [Na+] and [K+] balance was also significantly correlated with maximum airway pressure. Computed tomography (CT) scanning at a range of end-inspiratory pressures and ventral and dorsal recumbencies in eight T. scripta scripta showed that lung volumes increase with maximum ventilatory pressure, while recumbency did not influence volume at pressures above 5 cmH2O. Static compliance of the lungs was influenced by recumbency at neutral pressures. In conclusion, dorsal recumbency reduces pulmonary efficacy during positive pressure ventilation and tends to lower lung volume when ventilation is not provided. However, lung volumes and function - even in dorsal recumbency - can be adequately supported by assisted ventilation, and an end inspiratory pressure of 10 cmH2O at 4 breaths min-1 provided the most physiologically appropriate ventilation of anesthetized T. scripta scripta.


Assuntos
Gasometria , Pulmão/fisiologia , Respiração com Pressão Positiva/métodos , Troca Gasosa Pulmonar/fisiologia , Respiração Artificial , Tartarugas/fisiologia , Anestésicos , Animais , Eletrólitos , Feminino , Água Doce , Hemodinâmica , Concentração de Íons de Hidrogênio , Pulmão/diagnóstico por imagem , Pulmão/patologia , Pressão , Taxa Respiratória , Tomografia Computadorizada por Raios X
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