RESISTIVE UNLOADING IN OLDER MEN AND WOMEN WITH MILD CHRONIC AIRFLOW LIMITATION

Abstract

1031 We had previously observed an increase in maximal ventilation (VE) with resistive unloading (HeO2 breathing) in healthy elderly subjects. To investigate the effects of resistive unloading in elderly individuals with mild chronic airflow limitation (CAL, FEV1/FVC: 61 ± 4%), we studied ten Elderly (70 ± 3 yr) men and women. These subjects performed graded cycle ergometry to exhaustion, once breathing room air and once breathing a HeO2 gas mixture (79% He, 21% O2). Pulmonary mechanics and PetCO2 were measured during each 1 min increment in work rate. Data were analyzed by paired T-test at rest, ventilatory threshold (VTh), and maximal exercise. VE was significantly (p<0.05) increased at VTh (3.4 ± 4.0 L/min, 12 ± 15%) and maximal exercise (15.2 ± 9.7 L/min, 22 ± 13%) while breathing HeO2. Concomitant to the increase in VE, PetCO2 was decreased at all levels (p<0.01), while total work of breathing against the lung (WOBT) was not different. End expiratory lung volume was decreased at rest, VTh, and maximal exercise (p<0.05), although tidal volume was only increased (p<0.01) during maximal exercise. Despite the significant increase in maximal VE while breathing HeO2, there were no significant differences in maximal work rate, or exercise time between the room air and HeO2 tests. We conclude that VE is increased during HeO2 breathing due to resistive unloading of the airways and the maintenance of the relationship between WOBT and exercise level. Supported by NIA AG-11805