Effect of cold pressor test on single-breath DLCO in normal subjects

We hypothesized that the decrease in single-breath diffusing capacity of CO (DL(CO)) as observed in patients with Raynaud's phenomenon (P. J. Fahey et al. Am. J. Med. 76: 263-269, 1984) may be present in normal subjects. Therefore, we examined 31 healthy subjects in two different laboratories. Two series of experiments were performed. In the first series DL(CO) was measured in 22 volunteers before (twice) and 5, 10, and 30 min after a cold presser test (CPT), which consisted of immersing both hands in a 12 degrees C water bath for 2 min. In the second series right heart catheterization was performed in nine healthy seated subjects. Cardiac output, mean pulmonary arterial pressure, heart rate, and pulmonary wedge pressure were measured before, during, and 10, 20, and 30 min after the CPT. In every volunteer the CPT induced a decrease in DL(CO) that was still present 30 min after the test. In the nine catheterized subjects DL(CO) increased above control values during the CPT and then decreased below control values for 30 min. The CPT had no effect on cardiac output, heart rate, or pulmonary wedge pressure. In contrast, pulmonary arterial pressure and pulmonary vascular resistance increased during the CPT and then became lower than the control values for at least 30 min. In summary, the CPT induced a biphasic evolution of DL(CO) in normal subjects, being increased during the CPT and decreased after it. Our data are best explained by the West model of the lung. Our data suggest that the pulmonary Raynaud's phenomenon is not specific to patients with primary Raynaud's phenomenon. The decrease in DL(CO) after a CPT is not due to a vasospasm but rather to a vasodilatation of the pulmonary artery.