INTERACTION BETWEEN COLD AND HYPOXIA ON PULMONARY CIRCULATION IN COPD

This study was designed to investigate the interaction of mild and loc alized cold exposure and hypoxia on pulmonary hemodynamics in chronic obstructive pulmonary disease (COPD). Nineteen patients with COPD were studied at sea level and seven at an altitude of 2,640 m. For all pat ients, pulmonary hemodynamic measurements were performed 10 min after insertion of a catheter in a femoral vein and following 10 min of cold exposure. Cold exposure was restricted to the forehead, and subjects breathed air at ambient temperature. Flow and temperature of air (1.5 L.s(-1), 5 degrees C) to the forehead were chosen to cool down the for ehead skin to approximately 20 degrees C without discomfort for the su bject. For the seven patients studied at high altitude, the same measu rements were also performed after 5 min of oxygen supplementation with and without cold exposure. At sea level, an increase in pulmonary vas cular resistance (PVR) during cold exposure was inversely related to t he initial Pa-O2. In six severe hypoxic subjects (Pa-O2 < 50 mm Hg), P VR increased by 24%. At high altitude, PVR was significantly increased by 15%. After O-2 supplementation, cold exposure did not induce an in crease in PVR. We concluded that mild and localized cold exposure to t he forehead only induced an increase in PVR in COPD patients with seve re hypoxia. Moreover, in cold exposure responders, O-2 supplementation negated the effect of cold exposure on pulmonary hemodynamics.