Abstract

Cardiopulmonary exercise testing (CPET) equipment, including gas analyzers, is expensive and not always available in sport and clinical medicine. Therefore, a simplified approach may be useful for the identification of the ventilatory compensation point (VCP) in terms of oxygen uptake (V?O2). We analyzed the minute ventilation (V?E) and heart rate (HR) relationship in terms of variations of their slope and absolute values.

Methods. In our study, 19 healthy subjects (14 males, 5 females; age 27.72.9) underwent maximal symptom-limited CPET. We visually detected the VCP through the V?E vs. HR plot and compared it with the ventilatory equivalents method. In addition, we analyzed the slopes in the V?E/HR plot, identifying a trilinear curve, determined by the lactate threshold (LT) and the VCP.

Results. A good agreement in the detection of VCP was found between the V?E/V?CO2 method and the V?E/HR visual slopes changes (16121.6 V?O2 ml/min). In only 3 out of 19 subjects (15.8%) the two methods of VCP detection differed by more than 100 ml/min of V?O2, but less than 200 ml/min.The slopes of the V?E/HR plot pre-LT (S1), between LT and VCP (S2), pre-VCP (S1+S2) and post-VCP (S3) were respectively 0.420.14, 0.790.24, 0.550.10 and 3.771.70. Comparing the slopes, statistically significant differences were found (S1 vs. S2 p=0.002; S2 vs. S3 p<0.001; S1+S2 vs. S3 p<0.001).

Conclusions. The visual analysis of the V?E/HR plot during CPET may result in a simplified approach for the detection of VCP, even in the absence of gas analyzers. Moreover, the standardization in healthy subjects of the V?E/HR slopes before and after LT or VCP may represent a useful tool for future clinical trials.