OXYGEN DESATURATION AND BREATHLESSNESS DURING CORRIDOR WALKING IN CHRONIC OBSTRUCTIVE PULMONARY-DISEASE - EFFECT OF OXITROPIUM BROMIDE

Background-Although exercise induced desaturation can occur in patient s with chronic obstructive pulmonary disease (COPD), little is known a bout its frequency during everyday exercise, or how it relates to dysp noea or prior drug treatment. Methods-The effects of 200 mug inhaled o xitropium bromide, an anticholinergic bronchodilator drug, on spiromet ric values, dyspnoea score, and oxygen saturation during corridor walk ing and cycle ergometry were studied in a double blind, randomised, pl acebo controlled study. Results-Oxitropium produced a small increase i n forced expired volume in one second (FEV1) from 0-76 (0.28) 1 to 0.9 3 (0.69) 1 and in six minute walking distance from 311 (93) m to 332 ( 86) m, but did not change progressive cycle exercise duration. Resting and end exercise breathlessness levels were reduced in both forms of exercise after oxitropium. Resting oxygen saturation fell significantl y after active bronchodilator from 92.9% (3.7%) to 92.0% (4.1%) but th e nadir saturation during exercise was unchanged. The patients desatur ated more during corridor walking than cycle ergometry [walking 7.8% ( 4.4%), cycle ergometry 2.1% (2.1%)]. Baseline walking distance was rel ated to FVC, resting breathlessness and resting oxygen saturation (mul tiple r2 = 0.46) but only resting saturation correlated with end exerc ise breathlessness (r2 = -0.25). Improvements in symptoms or exercise performance after oxitropium could not be predicted by changes in spir ometric indices or oxygen saturation. Conclusions-In patients with COP D arterial oxygen desaturation during self-paced walking is common, of greater severity than that during cycle ergometry, but is unaffected by inhaled oxitropium bromide. The factors that predict initial perfor mance are not appropriate markers of functional improvement after an a ctive bronchodilator drug.