Respiratory response to arm elevation in patients with chronic airflow obstruction

We have shown that patients with chronic airflow obstruction (CAO) complain of disabling dyspnea when performing seemingly trivial tasks with unsupported arms. Surprisingly little is known about the metabolic and ventilatory responses to unsupported upper extremity activity even though some of the muscles of the upper torso and shoulder girdle are used to perform simple and complex everyday tasks as well as partake in ventilation. To determine the effect of simple arm elevation in 20 patients with CAO we studied their lung function, VO2, VCO2, and VE, with arms down at the side (AD), during 2 min with arms extended forward up to shoulder level (AE), and during recovery. To determine the pattern of ventilatory muscle recruitment we also measured endoesophageal (Ppl), gastric (Pg), and transdiaphragmatic (Pdl) pressures. In five of the patients the electromyographic signal (EMG) of the sternocleidomastoid (Sm) muscle was recorded and analyzed in its time domain (amplitude) and power spectrum density (median frequency). Within 30 s of arm elevation VO2, VCO2, and VE rose and remained elevated for 1 min after the arms were lowered. The increase in VE resulted from increases in respiratory rate and minimal rise in tidal volume (VT). With AE, FEV1 decreased by 5% (p less than 0.02) but FRC increased by 2% (p less than 0.05). Peak inspiratory pressure (Pimax) dropped from 54 +/- 4 to 48 +/- 4 cm H2O (p less than 0.005); Pdimax remained unchanged. Immediately after raising the arms Pgi, inspiratory swing in Pdi (delta Pdi), end-expiratory Ppl, and end-expiratory Pg increased significantly.(ABSTRACT TRUNCATED AT 250 WORDS)