Cardiopulmonary exercise test with ramp protocol in adults with heart failure

Abstracts

INTRODUÇÃO E OBJETIVO: O teste de esforço com protocolo de rampa é descrito como o que mais se adéqua à condição física de indivíduos com insuficiência cardíaca (IC). Porém, não há padronização descrita sobre incrementos de velocidade e inclinação. Este estudo teve como objetivo descrever resultados encontrados a partir da aplicação de um teste de esforço com protocolo de rampa adaptado para indivíduos com IC, classes II e III da New York Heart Association (NYHA). MÉTODOS: 41 indivíduos com média de idade de 46,37 ± 8,98 anos e fração de ejeção de 31,51 ± 9,45% fizeram o teste de esforço com análise de gases expirados em esteira, com protocolo de rampa desenvolvido a partir de critérios definidos pelo estudo de Barbosa e Silva e Sobral. Análise estatística: Foi realizada análise descritiva com distribuição de frequência e o tempo de teste foi apresentado como média ± desvio padrão. Foi realizado o modelo de regressão linear incluindo classe da NYHA, idade e fração de ejeção como variáveis explicativas para tempo de teste. Foi considerado significativo p < 0,05. RESULTADOS: O tempo médio do teste foi 8,89 ± 3,57 minutos e o R alcançado foi 1,12 ± 0,11. Sessenta e um porcento da amostra apresentou duração do teste entre seis e 12 minutos, considerando intervalo de média ± 1 desvio padrão, e 73,2% da amostra apresentou duração entre seis e 15 minutos. CONCLUSÃO: Os achados deste estudo demonstraram que a maioria dos indivíduos com IC finalizou o teste com o protocolo de rampa adaptado dentro da duração considerada adequada pela literatura.

teste em esteira; consumo de oxigênio; capacidade física

ORIGINAL ARTICLE

EXERCISE AND SPORTS MEDICINE CLINIC

Cardiopulmonary exercise test with ramp protocol in adults with heart failure

Danielle Aparecida Gomes Pereira^I; Giane Amorim Ribeiro Samora^II; Maria Clara Noman Alencar^III; Danielle Soares Rocha Vieira^IV; Verônica Franco Parreira^I; Leani Souza Máximo Pereira^I; Maria da Consolação Vieira Moreira^V; Nadja Carvalho Pereira^VI; Camila Camargos Zampa^IV; Raquel Rodrigues Britto^I

^IDepartment of Physiotherapy, Federal University of Minas Gerais - UFMG - Belo Horizonte, MG

^IIUniversity Center of Belo Horizonte - Uni-BH - Belo Horizonte, MG

^IIIHospital and Clinics/UFMG and Socor Hospital - Belo Horizonte, MG

^IVPost-Graduation Program in Rehabilitation Sciences, Federal University of Minas Gerais - UFMG - Belo Horizonte, MG

^VDepartment of Medical Clinics, Federal University of Minas Gerais - UFMG - Belo Horizonte, MG

^VITechnician of the Laboratory of Evaluation and Research in Cardiorespiratory Performance, Federal University of Minas Gerais - UFMG - Belo Horizonte, MG

Correspondence

ABSTRACT

Introduction and objective: The exercise test with ramp protocol is described as the one which best adapts to physical condition of subjects with heart failure (HF). However, velocity and inclination standard increments have not been described yet. This study aimed to describe the results found after application of an exercise test with ramp protocol adjusted for subjects with HF, New York Heart Association (NYHA) class II and III. Methods: 41 subjects with mean age 46.37 ± 8.98 years and ejection fraction of 31.51 ± 9.45% performed the exercise test with expired gas analysis on treadmill with ramp protocol developed from criteria defined in a study by Barbosa and Silva et al. Statistical Analysis: descriptive analysis was performed with frequency distribution and the test time was presented as mean ± standard deviation. Linear regression model was used and NYHA class, age and ejection fraction were included as explanation variables for the test time. A p value of < 0.05 was considered statistically significant. Results: Mean test time was 8.89 ± 3.57 minutes and the R was 1.12 ± 0.11. Sixty-one percent of the sample presented test duration between 6 and 12 minutes - mean ± 1 standard deviation interval - and 73.2% presented duration between 6 and 15 minutes. Conclusion: This study demonstrated that the majority of the subjects with HF concluded the test with ramp protocol adjusted in time considered adequate in the literature.

Keywords: treadmill test, oxygen consumption, physical endurance.

INTRODUCTION

Heart failure (HF) is a limiting health condition responsible for approximately two million cases in Brazil¹. The compromising of the heart function associated to the skeletal muscular alterations as well as to the reduction of capillary density contribute to the intolerance to exercise and reduction of functional capacity in this population², evidenced by approximate reduction of 50% in oxygen uptake peak (VO₂peak), if compared with healthy individuals^2,3.

The cardiopulmonary exertion test with expired gas analysis is an efficient way of evaluating functional capacity of individuals with HF which permits that the cause to intolerance to exertion is established, the exercise intensity is prescribed in an individualized and safe manner, heart transplant is indicated, as well as prognostic is evaluated^4-14. Many test parameters are used in the HF evaluation, such as VO₂peak, carbon dioxide production (VCO₂), anaerobic threshold (AT), ventilation-minute (VE), carbon dioxide ventilatory equivalent (VE/VCO₂), oxygen ventilatory equivalent (VE/VO₂) and respiratory exchange ratio (R)^2-5,7,14.

Many protocols of exertion test are used in HF evaluation^3,5,7,8. The protocols are different in their majority concerning load increment volume, duration of each stage and total exercise time⁷. In the individuals with HF, the exertion test may be early interrupted due to their low tolerance to exertion and to the dyspnea and fatigue symptoms^2,3,7. Thus, the ramp protocol is described as a conservative protocol which best adapts to the reduced physical condition of this population^2,7. It is already described in the literature that the increments for performance of test with ramp protocol in cycle ergometer should vary between 10 and 15 watts per minute⁷. However, there is no described standardization about velocity increment and inclination on treadmill for each age group and sex. The most consistent recommendation establishes that the increments should not be higher than a metabolic equivalent^7,15. Thus, the aim of this study was to describe the results found from the application of a cardiopulmonary exertion test with ramp protocol adapted for individuals with HF, classes II and III of the NYHA.

METHODS

Subjects

The study was approved by the Ethics in Research Committee of the Institution (legal opinion ETIC 489/06 - Ad 01/07) and all volunteers signed a Free and Clarified Consent Form. Individuals with HF, stage C^16,17, classes II and III of the NYHA were included, regardless of their sex and ethnic group, who did not practice regular physical activity, were aged between 25 and 59 years, presented clinical stability for at least two months, ejection fraction of the left ventricle (EFLV) at rest < 45% and who did not present orthopedic or neurological dysfunction which limit walking performance, pulmonary disease history, unstable angina, uncontrolled arrhythmia or peripheral obstructive arterial disease.

Experimental protocol

The cardiopulmonary exertion test with expired gas analysis (CPX Ultima^®, Medical Graphics, the USA) and electrocardiographic record was performed on ergometric treadmill with ramp protocol developed from criteria suggested by the study by Barbosa and Silva and Sobral for healthy individuals¹⁸. In that study, a table with minimum and maximum velocity and inclination to be reached in the exertion test for each age decade and sex was proposed, so that the test had duration of approximately 10 minutes. In an attempt to adapt the protocol for individuals with HF, polynomial extrapolation of fourth order was initially performed and the reference values for each specific age and sex were determined. On a second moment a pilot study was conducted with five individuals with HF for initial evaluation of the protocol. Since in the pilot study the test was interrupted before six minutes, and in order to also have its duration of approximately 10 minutes in this population, the total velocity and inclination increment was redistributed for duration of 15 minutes, and the velocity and inclination increase at every 10 seconds during the test was recalculated. The increments used as reference for te ramp protocol proposed are described in tables 1 and 2.

The volunteers were told to keep their usual medication, to observe 2-hour fast and avoid food and drink with caffeine, besides smoking and physical exercise on the day of the test¹⁹. The exertion test was preceded by three minutes of rest with the individual in orthostatism on the ergometric treadmill (Millenium Classic CI^®, Inbramed/Inbrasport, Brazil). Subsequently, a three-minute warm-up was initiated, and was followed by the incremental period with the proposed protocol. The heart rate and oxygen peripheral saturation were continuously recorded as well as the blood pressure at every two minutes and at the end of the test. The test was interrupted in case the individual requested it for fatigue or presented any of the absolute criteria for the test interruption, according to the guidelines of the American College Cardiology/American Heart Association 2002²⁰. All tests were performed at room temperature of 20 ± 2ºC and relative air humidity between 50 and 70%²¹ and followed by a cardiologist with ergometry and life advanced support degree.

STATISTICAL ANALYSIS

Data descriptive analysis was performed with frequency distribution considering the entire sample and later the classes II and III of NYHA. Shapiro-Wilk test was performed to evaluate the data distribution. The test time was presented as mean ± standard for the entire sample and separately for each functional class. The multivariate analysis was performed through the linear regression model including the class of the NYHA, age and ejection fraction as explanatory variables for the test time. A p < 0.05 was considered significant. The SPSS^® software (SPSS Inc, the USA) version 13.0 was used for the analyses.

RESULTS

43 individuals were selected for the study, and, out of these, two were excluded: one for presenting ventricular tachycardia and the other, supraventricular tachycardia, during the warm-up phase which preceded the test protocol. Therefore, 41 individuals (31 men and 10 women; 20 in class II and 21 in class III of NYHA) with age mean of 46.37 ± 8.98 years and EFLV of 31.51 ± 9.45%, performed cardiopulmonary exertion test with expired gas analysis with the proposed ramp protocol. The VO₂peak reached was in mean 22.35 ± 6.63mL/kg·min^-1.

The mean test time was 8.89 ± 3.57 minutes and the R reached was 1.12 ± 0.11. Sixty-one percent of the sample presented test duration between six and 12 minutes, considering the mean ± one standard deviation interval (table 3). 73.2% out of the total of the sample presented test duration between six and 15 minutes.

Linear regression model was used and evidenced that age and ejection fraction did not contribute to the time variation in the exertion test. The class of the NYHA isolatedly contributed with 16.9% of the variation of the test duration (R² = 0.169; p = 0.008).

The individuals of the class II of the NYHA ended the protocol in mean time of 10.37 ± 3.61 minutes with mean R of 1.16 ± 0.11 and 15% performed the test in more than 15 minutes (table 3). The test mean duration in the individuals of the class III of the NYHA was of 7.47 ± 2.97 minutes with mean R of 1.08 ± 0.08. Test end in time shorter than six minutes occurred in 28.6% of this population and one individual performed the protocol in time longer than 12 minutes (table 3).

DISCUSSION

In the present study, the mean duration of the cardiopulmonary exertion test with the ramp protocol proposed, performed in adults with HF classes II and III of the NYHA, non-practitioners of regular physical activity, was of 8.89 ± 3.57 minutes and 73.2% of the sample presented test duration between six and 15 minutes. Such findings indicate that the test performed with the ramp protocol developed presented suitable duration for the cardiopulmonary evaluation in the individuals with HF evaluated as described in the literature^{1,3,7,8,15,18,22-24}. The application of the proposed protocol is possible on treadmills which present external command with possibility of concomitant velocity and inclination adjustment.

This study evaluated the percentage of the sample in which the target-duration was successfully reached, going beyond the mean of the results. Considering the absolute values of test duration for each individual, it is necessary to be careful in the application of this protocol, since 25% of the individuals from class II and 28.6% from class III presented the time without the maximum and minimum thresholds described as suitable in the literature. Ten percent of the individuals from class II finished the test in less than six minutes, while 15% finished in more than 15 minutes. In the subjects from class III, 28.6% interrupted the test in less than six minutes.

A study by Myers et al.²⁵ described results of the application of a ramp protocol on treadmill in 200 apparently healthy individuals, individualized from the measurement of the maximum velocity of each participant of the research different from the test application. This way of defining the maximum velocity may be accurate, but it requires repeated visits to the health service office, which could make the HF evaluation unviable in the clinical practice. The present study provides an alternative to adapt velocity and inclination of the ramp protocol to the performance of the cardiopulmonary exertion test in this population.

The regression analysis performed demonstrated that the functional class of the NYHA influenced on the test duration, which was expected. It is already described in the literature that the worse the functional class, the worse the exercise capacity and consequently, the exertion test duration would be shorter²⁶. On the other hand, correlation between age and test duration was not observed during the test, indicating that in these individuals with HF the functional capacity stopped exclusively correlating with age, due to the differentiated impact of the disease. As expected, the ejection fraction was not a variable which contributed to the test duration in the proposed model. It has been demonstrated in the literature that the physical capacity is not directly related to the systolic function which, isolatedly, presents moderate to weak correlations with the capacity to perform exercise²⁷.

Further studies in individuals of different functional classes of the NYHA are necessary to corroborate the applicability of this ramp protocol.

CONCLUSION

The findings of this study demonstrated that the majority of the individuals with HF ended the cardiopulmonary exertion test with the adapted ramp protocol within the duration considered suitable by the literature. However, it is necessary to carefully generalize these results, considering the sample's characteristics and the inclusion of only individuals from classes II and III of the NYHA.

ACKNOWLEDGEMENTS

This study was partially sponsored by the FAPEMIG and CNPq.

REFERENCES

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Publication Dates

• Publication in this collection
  14 Feb 2013
• Date of issue
  Dec 2012