Cardiopulmonary exercise testing (CPET)
To evaluate exercise capacity, a treadmill (Technogym Run Race 1400HC)
maximum test was performed. The protocol started with an initial speed
and slope of 2.5 km h−1 and 0.5%, respectively. Increases in both
variables of 0.1 km.h−1 and 0.5%, respectively, were
used every 15 s. Gas exchange data were measured breath‐by‐breath using
open‐circuit spirometry (Vmax 29C; Sensor Medics). The variables
collected included VO2peak, maximum minute ventilation
(VE), respiratory exchange ratio (RER),
VE/VO2,
VE/VCO2, BR, peripheral oxygen
saturation (SpO2), and maximum heart rate (HRmax). HRmax
was measured using a heart rate monitor (Polar®) and
SpO2 was monitored with a pulse oximeter
(TrueSatTM, GE Healthcare, Finland).
VO2peak was recorded as the highest value obtained for
any continuous 20 s period. The ventilatory threshold
(VT1) was determined using the criteria of an increase
in both the VE/VO2 and end‐tidal
pressure of oxygen, with no increase in the
VE/VCO2. BR was calculated as the
difference between MVV and the maximum ventilation at peak exercise. An
indirect estimate was used to predict MVV by multiplying
FEV1 by 35. The test was considered as maximum if the
following criteria were met: (i) heart rate greater than 180 beats per
minute, (ii) respiratory exchange ratio above 1.0, and (iii) clear
exhaustion according to the perceived exertion (RPE).