The “Respiratory Vasomotor Reelex” in the Eorehead and Einger

The so‐called respiratory vasomotor reflex, long observed in plethysmography of the extremities, was examined in seven normal S s ranging in age from 17 to 38 years. With a photometric method, the vascular responses of the skin of the forehead and the finger were found to differ following a deep breath like a sigh. These responses were quite similar to the vascular components of the orienting reflex, i.e., vasodilation in the forehead and vasoconstriction in the hand. A polyphasic response in the forehead in some S s followed the deliberate deep inspirations. This polyphasic response has also been observed during the orieinting reflex but without changes in respiration. This type of response appears to be associated with bradycardia, and may be related to similar vascular responses observed following cardiac arrhythmias.