Traditionally, ventilatory limitation to exercise is assessed by measuring the breathing reserve (BRR) [ie, the difference between minute ventilation at peak exercise and maximum voluntary ventilation measured at rest]. Recent studies have however, documented important abnormalities in ventilatory adaptation with a remarkable potential to limit exercise even in the presence of a normal BRR. Among these abnormalities is lung hyperinflation and expiratory flow limitation. This was documented by comparing tidal to maximum flow-volume loops (FVLs) collected throughout the test. In the present study, we wondered whether the advantages of using such a technique within the classic cardiopulmonary exercise test (CPET) might be obscured by the maneuvers interfering with the main functional parameters of the test, and eventually with interpretation of the CPET.
We studied 18 healthy subjects, 19 patients affected by COPD, and 19 patients with chronic heart failure during a maximum exercise test on three different study days in a random order. On one occasion, the CPET was conducted with no FVLs (control test [CTRL]), whereas on the other occasions FVLs were incorporated every 1 min during exercise (FVL1-min) or every 2 min during exercise (FVL2-min).
None of the classic cardiovascular parameters recorded at ventilatory anaerobic threshold or at peak exercise differed between the study days (by analysis of variance). Furthermore, the coefficients of variation of the main parameters between FVL1-min and FVL2-min days vs CTRL day were well within the natural variability thresholds reported in the literature.
The FVLs appear to not interfere with the main functional parameters used for the interpretation of CPET.