Am. J. Respir. Crit. Care Med., Vol 153, No. 4, 04 1996, 1242-1247.
Interaction between cold and hypoxia on pulmonary circulation in COPD
M Bedu, H Giraldo, H Janicot, N Fellmann and J Coudert
Laboratoire d'Explorations Fonctionnelles Respiratoires et Sportives, CHU Clermont-Ferrand, France.
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 subjects (PaO2
< 50 mm Hg), PVR increased by 24%. At high altitude, PVR was
significantly increased by 15%. After O2 supplementation, cold exposure did
not induce an increase in PVR. We concluded that mild and localized cold
exposure to the forehead only induced an increase in PVR in COPD patients
with severe hypoxia. Moreover, in cold exposure responders, O2
supplementation negated the effect of cold exposure on pulmonary
hemodynamics.
