RELIABILITY OF INSPIRATORY CAPACITY FOR ESTIMATING END-EXPIRATORY LUNG-VOLUME CHANGES DURING EXERCISE IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

The inspiratory capacity (IC) maneuver is increasingly used to monitor exercise-induced dynamic hyperinflation in patients with COPD. Howeve r, the reliability of this method in patients with COPD exercising to symptom limitation has not been systematically studied and presented. The purpose of the present study was therefore to evaluate the reliabi lity of the IC maneuver in assessing changes in end-expiratory lung vo lume (EELV) by assessing the pressure developed during IC maneuvers, i n patients with COPD during incremental bicycle exercise to exhaustion . Fifteen patients with stable COPD performed bicycle exercise to symp tom limitation. During the experiment, the patients performed IC effor ts during resting breathing and at the end of each exercise work load. Esophageal pressure (Pes) measured at peak inspired volume plateau (z ero flow) was -13.5 +/- 1.9 and -13.4 +/- 1.9 cm H2O (p = 0.79) during IC maneuvers at resting breathing and during the final exercise work load, respectively. When the Pes values at the peak inspired volume pl ateau during IC efforts at each exercise level were expressed as a per centage of those during resting breathing, the great majority of the r atios were above 90% with the lowest at 84%, and these ratios were ind ependent of exercise intensity. Despite a constant Pes during IC, ther e was a progressive decrease in IC with increasing exercise work load in most patients, suggesting an increase in EELV. At the highest exerc ise work load achieved, Delta EELV calculated as the decrease in IC wa s 0.26 +/- 0.06 L (p < 0.001). We conclude that repeated IC maneuver i s a simple and reliable method for estimating EELV changes during exer cise to exhaustion in patients with COPD.