The effect of cold exposure on diffusing capacity in patients with Raynaud's phenomenon.

Pulmonary hypertension is common in progressive systemic sclerosis (PSS), and the presence of "pulmonary Raynaud's phenomenon" has been postulated from a variety of evidence. In this study, the effect of cold-induced Raynaud's phenomenon on carbon monoxide diffusing capacity (Dco), an indicator of pulmonary capillary blood volume, was determined in patients with Raynaud's phenomenon with an without PSS. Cold exposure caused an increase in Dco in patients without PSS, but no change in patients with PSS. We concluded that patients with systemic sclerosis have an altered pulmonary vascular response to cold exposure compared with other Raynaud's patients, which may be due to either structural or functional abnormalities of the pulmonary vascular bed.