Interaction between cold and hypoxia on pulmonary circulation in COPD

This study was designed to investigate the interaction of mild and localized 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 patients, 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 forehead skin to approximately 20 degrees C without discomfort for the subject. For the seven patients studied at high altitude, the same measurements were also performed after 5 min of oxygen supplementation with and without cold exposure. At sea level, an increase in pulmonary vascular resistance (PVR) during cold exposure was inversely related to the initial PaO2. In six severe hypoxic s...