DIGITAL AND BRACHIAL-ARTERY BLOOD-PRESSURE MEASUREMENTS DURING PERIPHERAL, COLD-INDUCED VASOCONSTRICTION

Measurements of digital artery blood pressure made using an automated photoplethysmographic method (Finapres), in the middle finger of the l eft hands of nine male subjects, were compared with pressure measures in the right brachial artery using a method relying on the abolition o f Karotkoff sounds during occlusion of the upper arm by a pressure cuf f (Dina-map), during a 40-min immersion of the hand in cold (4 degrees C) and thermoneutral (32 degrees C) water. Blood flow in the left ind ex finger was assessed and temperatures of the left and right ring fin gers were also measured. Before immersion, systolic pressures in the d igital artery were higher than systolic pressures in the brachial arte ry (P < 0.05), whereas the corresponding diastolic measurements were s imilar, However, both systolic (P < 0.01) and diastolic (P < 0.05) dig ital artery measurements increased with time. During cold immersion bo th systolic and diastolic pressures increased at both sites (P < 0.01) , although the digital artery systolic readings rose sharply and then declined, whereas the brachial artery readings were stable. The cold-i mmersed digital artery diastolic measurements were greater than the br achial artery measurements (P < 0.01) and showed a continuation of the upward trend noted prior to immersion (P < 0.01). Thermoneutral diast olic digital artery measurements also showed this continued trend (P < 0.001). Some individual photoplethysmograph assessments of index fing er blood flows showed intermittent vasodilatation, but cold immersion caused a decline in mean flow to 22% of pre-immersion value at 15 min, followed by an increase to 40%. It is concluded that digital artery p ressure measurements may not be accurate reflections of more central m easurements of blood pressure either quantitatively or qualitatively u nder conditions could enough to induce peripheral vascular changes.