The concept of Raynaud's phenomenon of the lung revisited

Having observed that a cold pressor test (CPT) induces a decrease in carbon monoxide single breath diffusing capacity (DLco) in normal subjects contrary to the findings of Fahey et al (Am J Med. 1984; 76:263-269), we compared the response to CPT for the two types of Raynaud's phenomenon.

Two groups of 8 patients suffering from primary or secondary Raynaud's phenomenon were examined.

Single breath diffusing capacity, mean pulmonary artery pressure (PAP), cardiac output (CO), pulmonary capillary wedge pressure (PwP), and pulmonary vascular resistance (PVR) were measured before and 30 minutes after CPT, which consisted of immersing both hands in a water bath at 12 degrees C for 2 minutes.

Cold pressor testing induced no change in DLco or cardiovascular parameters in patients with secondary Raynaud's phenomenon. Conversely, in patients with the primary form, it induced a significant decrease in DLco (16%), PAP (20%), and PVR (27%), whereas CO and PwP remained unaltered.

The concept of pulmonary Raynaud's phenomenon had to be reconsidered, as it is also observed in normal subjects, and is due to a vasodilatation and not to a vasoconstriction of the pulmonary artery (Frans et al, J Appl Physiol. 1994; 76:750-755). In patients with primary Raynaud's phenomenon, the decrease in DLco is not only a physiological response, but a pathological response to a CPT, as it is significantly more marked in patients than in control subjects (16% versus 10% for controls, same reference). The contribution by Fahey et al remains important, however, in that it allows assessing whether a patient with Raynaud's phenomenon suffers from the primary or secondary form of the disease.