Effect of temperature on finger artery pressure evaluated by volume clamp technique

We examined the effect of temperature on digital arterial blood pressure obtained by continuous beat-to-beat non-invasive monitoring with a volume-clamp technique (Finapres). In 10 normal volunteers and 13 patients with symptoms of vasospasm, digital pressure and brachial artery pressure (cuff method) was simultaneously recorded in control conditions at room temperature, during body cooling, finger heating, and truncal heating. In the control condition digital systolic blood pressure was significantly higher (16.1 +/- 14.2 mmHg) than brachial systolic pressure. The augmentation of digital systolic pressure correlated inversely with finger tip temperature. Diastolic and mean arterial pressure did not differ significantly between the two methods. Body cooling augmented the systolic finger-arm gradient while truncal heating and finger heating had the opposite effect. Finger heating reduced systolic augmentation without changing the mean and diastolic blood pressure. Similar changes were also observed in the patients with vasospasm except in one case with a pronounced Raynaud syndrome where digital blood pressure was lower than brachial artery pressure. We conclude that augmentation of finger systolic pressure seems to be dependent on local vasoconstriction of A/V shunts and that finger heating may be a useful procedure to improve the reliability of Finapres readings.