θL lactate threshold 6MWD 6-min walk distance 6MWT 6-min walk test BMI body mass index BP blood pressure CO 2 carbon dioxide COPD chronic obstructive pulmonary disease CPET cardiopulmonary exercise testing DLCO diffusing capacity of the lung for carbon monoxide EELV end-expiratory lung volume EILV end-inspiratory lung volume FEV1 forced expiratory volume in 1 s FRC functional residual capacity FVC forced vital capacity HR heart rate IC inspiratory capacity ILD interstitial lung disease IRV inspiratory reserve volume MCID minimally clinically important difference MVV maximum voluntary ventilation O 2 oxygen PaCO 2 arterial carbon dioxide tension PAH pulmonary arterial hypertension PaO 2 arterial oxygen tension PETCO 2 end-tidal carbon dioxide tension PETO 2 end-tidal oxygen tension RV residual volume SaO 2 arterial oxygen saturation SpO 2 arterial oxygen saturation measured by pulse oximetry tE expiratory time tI inspiratory time TLC total lung capacity V’CO 2 carbon dioxide output VD dead space volume VE expired volume V’E minute ventilation V’O 2 oxygen uptake VT tidal volume WR work rate List of abbreviations