We have proposed that unsupported arm exercise alters ventilatory muscle recruitment and precipitates dyspnea in patients with severe chronic airflow obstruction (CAO). To test this hypothesis, we studied 11 patients with CAO during symptom-limited, unsupported arm exercise (UAE) and compared it with supported arm cycling (SAE). During each exercise period, we recorded endoesophageal (PpI), gastric (Pg), and transdiaphragmatic (Pdi) pressures along with heart rate, respiratory rate, and endurance time. Expired gas was collected to determine oxygen uptake (VO2) and minute ventilation (VE). Exercise endurance was shorter for UAE than for SAE (210 +/- 114 versus 270 +/- 120 s, p less than 0.05), even though peak exercise heart rate (113 +/- 5 versus 122 +/- 7 beats/min, p less than 0.05), VO2 (5.9 +/- 0.5 versus 7.1 +/- 0.8 ml/kg/min, p less than 0.05) and VE (16.5 +/- 1.2 versus 19.8 +/- 1.3 L/min, p less than 0.05) were lower for UAE. Mean (+/- SD) values for changes in pleural (delta PpI) and gastric (delta Pg) pressures during either type of arm exercise were significantly greater than at rest (p less than 0.02). In eight of 11 patients during UAE, the changes between end-inspiratory and end-expiratory transdiaphragmatic pressure (delta Pdi) were observed to develop in a similar pattern. In these patients, end-inspiratory Pg was more positive and end-inspiratory PpI was less negative during UAE than during SAE (p less than 0.02). In addition, PpI at end expiration was markedly positive when performing UAE (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)