Oxygen Consumption – ABC CARDIOL

IJCS

Editorial

Cardiorespiratory Optimal Point: A New Kid in the Block or an Established Star?

Summary

COP researchers have already conducted very important research that must be expanded, including larger and more diverse and better defined populations, with patients around the world, different cardiovascular and non-cardiovascular diseases, tests using a treadmill (more experience with treadmill CPET is needed), and evaluation of the prognostic values of sub-maximal parameters, such as COP and eventually VO ₂ at VT1, versus the maximal parameters, such as pVO ₂ , VE/VCO ₂ slope, and OUES.

A clear answer is needed: Is the information obtained from a submaximal CPET enough, or should it be considered only as an alternative when it is not possible to perform a maximal CPET or when peak VO ₂ was not reached?

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IJCS

Original Article

Comparative Analysis of Direct and Indirect Methods for the Determination of Maximal Oxygen Uptake in Sedentary Young Adults

Alfredo Moreira da Rocha Neto et al. Artur Haddad Herdy Pablo de Souza

Abstract

Background:

Maximal oxygen uptake is a powerful prognostic indicator and a reliable measure of physical conditioning. It can be measured directly by cardiopulmonary exercise testing (CPET) or indirectly by formulas derived from conventional protocols.

Objective:

We compared the VO₂ max obtained by formula using exercise testing with Bruce protocol (BP) with the VO₂ max obtained by CPET on the treadmill.

Methods:

We selected 41 healthy, non-obese, physically inactive young volunteers, aged between 21 and 50 years, residents of Florianópolis, Brazil.

Results:

Twenty-one women (52%) with mean age of 35.62 ± 8.83 years, and 20 males, with mean age of 32.5 ± 7.18 years participated in the study. Statistically significant differences were found for VO₂ max between the two methods (BP – 42.31 ± 5.21 ml/kg.min vs. CPET – 30.46 ± 5.50 ml/kg.min., p < 0.0001). The Bruce formula overestimated the result by 34.1% (BP – 45.95 ± 3.94 ml/kg.min vs. CPX – 34.27 ± 4.20 ml/kg.min, p < 0.0001) for men, and by 44.8% (BP – 38.84 ± 3.72 ml/kg.min vs. CPX – 26.83 ± 3.90, p < 0.0001) for women. A moderate correlation was observed between the methods (r = 0.65). When classifying the results according to the table of aerobic capacity of the American Heart Association, the agreement was null (kappa = 0.0034; Pearson chi2 = 0.001).

Conclusion:

VO₂ estimated by BP is not capable of demonstrating the true aerobic capacity in these individuals, while CPET is an important tool for early detection of diminished functional capacity in sedentary young men and women.

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IJCS

Original Article

Classification System for Cardiorespiratory Fitness Based on a Sample of the Brazilian Population

Antonio Eduardo Monteiro de Almeida et al. Igor Rafael Miranda Ferreira Santander Maria Izabel Macedo Campos Jorge René Garcia Arévalo … João Agnaldo do Nascimento Luiz Eduardo Fonteles Ritt Karlyse Claudino Belli Jorge Pinto Ribeiro Ricardo Stein

Abstract

Background:

Peak oxygen consumption (VO_2peak) is an important prognostic marker and its classification helps the cardiologist in the therapeutic decision-making process. The most commonly used cardiorespiratory fitness (CRF) classification has not been validated for the Brazilian population.

Objective:

To elaborate a CRF classification using a Brazilian sample and to compare it with the American Heart Association (AHA), Cooper and UNIFESP classifications.

Methods:

A total of 6,568 healthy subjects were analyzed through cardiopulmonary exercise testing (CPET). They were distributed by sex and the following age groups (years): 7-12, 13-19, 20-79 (per decades) and > 80 years. After measurement of the VO_2peak, participants were distributed into quintiles of CRF in very poor, poor, moderate, high and very high (AEMA Table). The CRF classifications by AEMA, AHA, Cooper, and UNIFESP were compared using the Wilcoxon, Kappa and concordance percentages.

Results:

VO_2peak presented an inverse and moderate correlation with age considering both sexes (R = -0.488, p < 0.001). All paired comparisons between CRF classification systems showed differences (p < 0.001) and disagreement percentage – AEMA versus AHA (k = 0.291, 56.7%), AEMA versus Cooper (k = 0.220, 62.4%) and AEMA versus UNIFESP (k = 0.201, 63.9 %).

Conclusion:

The AEMA table showed important discrepancies in the classification of CRF when compared to other tables widely used in our setting. Because it was obtained from a large sample of the Brazilian population, the AEMA table should be preferred over other classification systems in our population.

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IJCS

Original Article

Correlation between Exercise Stress Test and Echocardiographic Parameters in Elderly Individuals

Liz Andréa Villela Baroncini et al. Camila Varotto Baroncini Juliana Ferreira Leal

Abstract

Background:

Maximum oxygen consumption (VO₂ max) in healthy individuals decreases approximately 10% per decade of life, and such decrease is more pronounced after the seventh decade.

Objectives:

To assess functional capacity of individuals aged 75 years or older, submitted to ergometric test and transthoracic echocardiogram exam, by means of metabolic equivalent (MET) and VO₂ max measurements.

Methods:

A total of 381 patients (205 women; 79 ± 3.7 years) were evaluated. Exclusion criteria were: presence of left ventricular (LV) systolic dysfunction, LV diastolic dysfunction grade II and III, significant valve disease, or coronary artery disease with systolic LV dysfunction or dilatation. Associations between quantitative variables were analyzed by Pearson and Spearman correlation coefficients, and comparisons of quantitative data by Student’s t-test for independent samples.

Results:

Increasing age was associated with a progressive decrease in the distance covered (p = 0.021), in the expected increase in HR (p < 0.001), in VO₂ max (p < 0.001), and METs (p < 0.001) in both genders. There was no correlation of exercise test parameters with the echocardiographic parameters.

Conclusions:

Relatively healthy older individuals, with global systolic and diastolic functions of the left ventricle preserved, presented a progressive decrease in their functional capacity due to their natural aging process, comorbidities related to their age range and physical deconditioning.

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Original Article

Influence of Pulmonary Rehabilitation on Clinical Characteristics in Patients with Chronic Heart Failure and Chronic Obstructive Pulmonary Disease

Ganna S. Smyrnova et al. Tetiana M. Babkina Gennadii G. Taradin Mykola T. Vatutin

Abstract

Background:

The improvement of treatment strategies in patients with chronic obstructive pulmonary disease (COPD) and especially with comorbid pathology should provide rational conversion of standard schemes of therapy and rehabilitation in accordance with their clinical, pathogenic, functional and economic feasibility.

Objective:

To assess the influence of pulmonary rehabilitation on clinical characteristics in patients with chronic heart failure (CHF) and concomitant COPD.

Methods:

The study included 102 patients with CHF and concomitant COPD (males, 62%; mean age, 68.2 ± 4.5 years). All patients were divided into two groups: control group (CG) (n = 54), received only standard therapy of CHF and COPD; and intervention group (IG) (n = 48) were additionally taught the full yogic breathing as a program of pulmonary rehabilitation. Calculation of points by clinical evaluation scale (CES), assessment of CHF functional class (FC) (NYHA) and 6-minute walk test (6MWT – with the evaluation of dyspnea by the Borg scale) were performed in all patients on admission to the department and at discharge. Significant association was defined by p value < 0.05.

Results:

At baseline, there were no significant differences in clinical characteristics of the patients and studied parameters between the groups. At discharge both groups showed significant reduction of dyspnea by the Borg scale (in CG: from 7.2 ± 0.8 points to 5.2 ± 0.3; in IG: from 7.4 ± 0.6 points to 3.2 ± 0.4), the number of points by CES (in CG: from 10.8 ± 0.3 points to 7.2 ± 0.4; in IG: from 10.7 ± 0.6 points to 5.9 ± 0.6). Increase in exercise tolerance (by the distance of 6MWT) was observed in both groups (in CG: from 215 ± 24 m to 275 ± 22 m; in IG: from 219 ± 21 m to 308 ± 24 m). The changes were more significant in IG compared to CG. We observed the prominent decrease in CHF FC and length of hospital stay in IG.

Conclusions:

Application of full yogic breathing as the program of pulmonary rehabilitation in addition to standard therapy of the patients with CHF and COPD is associated with a significant decrease in CHF FC, an increase in exercise tolerance and a reduced length of hospital stay.

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Original Article

Can the Cardiopulmonary 6-Minute Walk Test Reproduce the Usual Activities of Patients with Heart Failure?

Guilherme Veiga Guimarães et al. Giovanni Bellotti Fernando Bacal Amilcar Mocelin Edimar Alcides Bocchi

OBJECTIVE: The 6-minute walk test is an way of assessing exercise capacity and predicting survival in heart failure. The 6-minute walk test was suggested to be similar to that of daily activities. We investigated the effect of motivation during the 6-minute walk test in heart failure. METHODS: We studied 12 males, age 45±12 years, ejection fraction 23±7%, and functional class III. Patients underwent the following tests: maximal cardiopulmonary exercise test on the treadmill (max), cardiopulmonary 6-minute walk test with the walking rhythm maintained between relatively easy and slightly tiring (levels 11 and 13 on the Borg scale) (6EB), and cardiopulmonary 6-minute walk test using the usual recommendations (6RU). The 6EB and 6RU tests were performed on a treadmill with zero inclination and control of the velocity by the patient. RESULTS: The values obtained in the max, 6EB, and 6RU tests were, respectively, as follows: O2 consumption (ml.kg-1.min-1) 15.4±1.8, 9.8±1.9 (60±10%), and 13.3±2.2 (90±10%); heart rate (bpm) 142±12, 110±13 (77±9%), and 126±11 (89±7%); distance walked (m) 733±147, 332±66, and 470±48; and respiratory exchange ratio (R) 1.13±0.06, 0.9±0.06, and 1.06±0.12. Significant differences were observed in the values of the variables cited between the max and 6EB tests, the max and 6RU tests, and the 6EB and 6RU tests (p<0.05). CONCLUSION: Patients, who undergo the cardiopulmonary 6-minute walk test and are motivated to walk as much as they possibly can, usually walk almost to their maximum capacity, which may not correspond to that of their daily activities. The use of the Borg scale during the cardiopulmonary 6-minute walk test seems to better correspond to the metabolic demand of the usual activities in this group of patients.

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Original Article

Exercise and heart failure. Relation of the severity of the disease to the anaerobic threshold and the respiratory compensation point

Guilherme Veiga Guimarães et al. Giovanni Bellotti Mauricio Wajngarten Luzimar Teixeira … José Franchini Ramires Edimar Alcides Bocchi

OBJECTIVE – To identify, the anaerobic threshold and respiratory compensation point in patients with heart failure. METHODS – The study comprised 42 Men,divided according to the functional class (FC) as follows: group I (GI) – 15 patients in FC I; group II (GII) – 15 patients in FC II; and group III (GIII) – 12 patients in FC III. Patients underwent a treadmill cardiopulmonary exercise test, where the expired gases were analyzed. RESULTS – The values for the heart rate (in bpm) at the anaerobic threshold were the following: GI, 122±27; GII, 117±17; GIII, 114±22. At the respiratory compensation point, the heart rates (in bpm) were as follows: GI, 145±33; GII, 133±14; GIII 123±22. The values for the heart rates at the respiratory compensation point in GI and GIII showed statistical difference. The values of oxygen consumption (VO2) at the anaerobic threshold were the following (in ml/kg/min): GI, 13.6±3.25; GII, 10.77±1.89; GIII, 8.7±1.44 and, at the respiratory compensation point, they were as follows: GI, 19.1±2.2; GII, 14.22±2.63; GIII, 10.27±1.85. CONCLUSION – Patients with stable functional class I, II, and III heart failure reached the anaerobic threshold and the respiratory compensation point at different levels of oxygen consumption and heart rate. The role played by these thresholds in physical activity for this group of patients needs to be better clarified.

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Original Article

Gas exchange during exercise in different evolutional stages of chronic Chagas' heart disease

Fátima Palha de Oliveira et al. Roberto Coury Pedrosa Antonio Giannella-Neto

OBJECTIVE: To compare gas exchange at rest and during exercise in patients with chronic Chagas’ heart disease grouped according to the Los Andes clinical/hemodynamic classification. METHODS: We studied 15 healthy volunteers and 52 patients grouped according to the Los Andes clinical/hemodynamic classification as follows: 17 patients in group IA (normal electrocardiogram/echocardiogram), 9 patients in group IB (normal electrocardiogram and abnormal echocardiogram), 14 patients in group II (abnormal electrocardiogram/echocardiogram, without congestive heart failure), and 12 patients in group III (abnormal electrocardiogram/echocardiogram with congestive heart failure). The following variables were analyzed: oxygen consumption (V O2), carbon dioxide production (V CO2), gas exchange rate (R), inspiratory current volume (V IC), expiratory current volume (V EC), respiratory frequency, minute volume (V E), heart rate (HR), maximum load, O2 pulse, and ventilatory anaerobic threshold (AT). RESULTS: When compared with the healthy group, patients in groups II and III showed significant changes in the following variables: V O2peak, V CO2peak, V ICpeak, V ECpeak, E, HR, and maximum load. Group IA showed significantly better results for these same variables as compared with group III. CONCLUSION: The functional capacity of patients in the initial phase of chronic Chagas’ heart disease is higher than that of patients in an advanced phase and shows a decrease that follows the loss in cardiac-hemodynamic performance.

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Original Article

Assessment of functional capacity through oxygen consumption in patients with asymptomatic probable heart disease

Luiz Oswaldo Carneiro Rodrigues et al. Emerson Silami-Garcia Maria da Consolação Vieira Moreira Giane Amorim Ribeiro

PURPOSE: To compare peak exercise oxygen consumption (VO2peak) of healthy individuals with asymptomatic individuals with probable heart disease. METHODS: Ninety-eight men were evaluated. They were divided into two groups: 1) 39 healthy individuals (group N) with an age range of 50±4.6 years; and 2) 59 asymptomatic individuals with signs of atherosclerotic and/or hypertensive heart disease (group C) with an age range of 51.9±10.4 years. In regard to age, height, body surface area, percentage of fat, lean body mass, and daily physical activity, both groups were statistically similar. Environmental conditions during the ergometric test were also controlled. RESULTS: Maximal aerobic power (watts), VO2peak, maximal heart rate, and maximal pulmonary ventilation were lower in group C (p<0.01) than in group N; weight, however, was lower in group N (p=0.031) than in group C. Differences in the respiratory gas exchange index, heart rate at rest, and the maximal double product of the two groups were not statistically significant. CONCLUSION: Signs of probable heart disease, even though asymptomatic, may reduce the functional capacity, perhaps due to the lower maximal cardiac output and/or muscle metabolic changes.

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