Introduction: To understand the respiratory work and its components during exercise has important role in exercise limitation in respiratory diseases.
Objective: To evaluate the respiratory work and its components during maximal exercise in interstitial lung disease (ILD) and COPD, compared to controls, using Campbell Diagram.
Methods: 7 ILD patients (47.7±15.4y, FVC 66.1±16.6%pred), 9 COPDs (60.1±8.6y, FEV1 44.2±19.7%pred) and 8 healthy subjects (HS) (53.0±11.2y, FEV1 87.8±13.9%pred) underwent maximal cardiopulmonary cycle ttest and were monitored with esophageal balloon (Pes).
Results: At rest, all groups had similar Pes and tidal volume (Vt). ILD patients had greater Elastic Work, while COPD had the highest Resistive and Expiratory Muscle Work. At intense exercise: (1) HS increased the total Work roughly 3 times, but the Res increased 4 times and the ExpMuscle 11 times; (2) ILD had the worse pressure-volume generation (Pes/Vt); (3) COPD had the lowest increase in ExpMuscle.
Work Of Breathing (J/L) and Pes/Vt at Rest (left) and Final (right) in cycle test
Conclusions: In healthy subjects, the highest increase of work during exercise comes from the expiratory muscles. ILD has the worse inefficiency to generate volume. Severe COPD has already high ExpMuscle even at rest and they could not increase it substantially at intense exercise.