TABLE 2

Common cardiopulmonary exercise test features at peak exercise in interstitial lung disease (ILD) patients compared to healthy subjects

Healthy subjectsILD patientsCause
Peak VO2 L·min−1≥85%<85%Hypoxia, ventilatory limitation, deconditioning
Maximum work W≥85%<85%Hypoxia, ventilatory limitation, deconditioning
Heart rate beats·min−1≥85%<85%Ventilator limitation to exercise, deconditioning
Oxygen saturationPreservedReducedIncreased V/Q mismatch, diffusion limitation, shunt, reduced mixed venous oxygen concentration
Respiratory frequency breaths·min−1<50>50Respiratory muscle elastic loading, stimulation of peripheral mechanoreceptors
VT LIncreasedReducedReduced lung compliance
VE L·min−150–80% of MVV>90% of MVVVentilator limitation to exercise
VD/VTReducedUnchanged or increasedIncreased V/Q mismatch, rapid, shallow breathing pattern
VE/VCO2 slope25–35>35Increased V/Q mismatch
Anaerobic threshold L·min−1>45% peak VO2<45% peak VO2Hypoxia, pulmonary hypertension
  • Data are presented as n, unless otherwise stated. VO2: oxygen uptake; VT: tidal volume; VE: minute ventilation; VD: dead space volume; VCO2: carbon dioxide production; MVV: maximal voluntary ventilation; V/Q: ventilation/perfusion.