RESUMEN
Cardiopulmonary exercise testing (CPET) is a procedure widely used in daily clinical activity to investigate cardiac and pulmonary disorders. Peak oxygen consumption (VO2 peak) is the most validated and clinically accepted parameter used to report aerobic capacity in healthy individuals and in different clinical settings. However, peak VO2 is influenced by several factors, whose variability is nowadays particularly evident due to the extensive use of CPET even in very young and very old subgroups of patients. Thus, its diagnostic and prognostic significance may be improved by the use of % of predicted VO2. At present, many sets of normal values are available, making the identification of the most proper max VO2 predicted value a challenging problem. In fact, normal value sets have been obtained from studies whose accuracy was reduced by important limitations, such as small sample size, low grade of heterogeneity of the population enrolled, poor rigorousness of methods, or difficulty in interpreting results. Accordingly, the aim of the present review is threefold: (A) to report some illustrative cases to show how the choice of the normal value set can influence the report of CPET; (B) to describe the most known and used reference value sets, highlighting the main characteristics of sample population, the most important methodological aspects, and the major limitations of the studies; (C) to suggest which equation should be used, if any, and to underline its weakness.
Asunto(s)
Prueba de Esfuerzo/métodos , Tolerancia al Ejercicio/fisiología , Insuficiencia Cardíaca/fisiopatología , Consumo de Oxígeno/fisiología , Humanos , Pronóstico , Valores de ReferenciaRESUMEN
BACKGROUND: Cardiac output (QË) is a key parameter in the assessment of cardiac function, its measurement being crucial for the diagnosis, treatment, and prognostic evaluation of all heart diseases. Until recently, QË determination at peak exercise has been possible through invasive methods, so that normal values were obtained in studies based on small populations. METHODS: Nowadays, peak QË can be measured noninvasively by means of the inert gas rebreathing (IGR) technique. The present study was undertaken to provide reference values for peak QË in the normal general population and to obtain a formula able to estimate peak exercise QË from measured peak oxygen uptake (VËo2). RESULTS: We studied 500 normal subjects (age, 44.9 ± 1.5 years; range, 18-77 years; 260 men, 240 women) who underwent a maximal cardiopulmonary exercise test with peak QË measurement by IGR. In the overall study sample, peak QË was 13.2 ± 3.5 L/min (men, 15.3 ± 3.3 L/min; women, 11.0 ± 2.0 L/min; P < .001) and peak VËo2 was 95% ± 18% of the maximum predicted value (men, 95% ± 19%; women, 95% ± 18%). Peak VËo2 and peak QË progressively decreased with age (R2, 0.082; P < .001; and R2, 0.144; P < .001, respectively). The VËo2-derived formula to measure QË at peak exercise was (4.4 × peak VËo2) + 4.3 in the overall study cohort, (4.3 × peak VËo2) + 4.5 in men, and (4.9 × peak VËo2) + 3.6 in women. CONCLUSIONS: The simultaneous measurement of QË and VËo2 at peak exercise in a large sample of healthy subjects provided an equation to predict peak QË from peak VËo2 values.