Digital and brachial artery blood pressure measurements during peripheral, cold-induced vasoconstriction

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Abstract
Measurements of digital artery blood pressure made using an automated photoplethysmographic method (Finapres), in the middle finger of the left hands of nine male subjects, were compared with pressure measures in the right brachial artery using a method relying on the abolition of Karotkoff sounds during occlusion of the upper arm by a pressure cuff (Dinamap), during a 40-min immersion of the hand in cold (4° C) and thermoneutral (32° C) water. Blood flow in the left index finger was assessed and temperatures of the left and right ring fingers were also measured. Before immersion, systolic pressures in the digital artery were higher than systolic pressures in the brachial artery (P < 0.05), whereas the corresponding diastolic measurements were similar. However, both systolic (P < 0.01) and diastolic (P < 0.05) digital artery measurements increased with time. During cold immersion both 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-immersed digital artery diastolic measurements were greater than the brachial artery measurements (P < 0.01) and showed a continuation of the upward trend noted prior to immersion (P < 0.01). Thermoneutral diastolic digital artery measurements also showed this continued trend (P < 0.001). Some individual photoplethysmograph assessments of index finger 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 pressure measurements may not be accurate reflections of more central measurements of blood pressure either quantitatively or qualitatively under conditions could enough to induce peripheral vascular changes.