Sustained increases in blood pressure elicited by prolonged face cooling in humans

Abstract

We tested the hypothesis that increases in blood pressure are sustained throughout 15 min of face cooling. Two independent trials were carried out. In the Face-Cooling Trial, 10 healthy adults underwent 15 min of face cooling where a 2.5-liter bag of ice water (0 ± 0°C) was placed over their cheeks, eyes, and forehead. The Sham Trial was identical except that the temperature of the water was 34 ± 1°C. Primary dependent variables were forehead temperature, mean arterial pressure, and forearm vascular resistance. The square root of the mean of successive differences in R-R interval (RMSSD) provided an index of cardiac parasympathetic activity. In the Face Cooling Trial, forehead temperature fell from 34.1 ± 0.9°C at baseline to 12.9 ± 3.3°C at the end of face cooling (P < 0.01). Mean arterial pressure increased from 83 ± 9 mmHg at baseline to 106 ± 13 mmHg at the end of face cooling (P < 0.01). RMSSD increased from 61 ± 40 ms at baseline to 165 ± 97 ms during the first 2 min of face cooling (P ≤ 0.05), but returned to baseline levels thereafter (65 ± 49 ms, P ≥ 0.46). Forearm vascular resistance increased from 18.3 ± 4.4 mmHg·ml^-1·100 g tissue^-1·min at baseline to 26.6 ± 4.0 mmHg·ml^-1·100 g tissue^-1·min at the end of face cooling (P < 0.01). There were no changes in the Sham Trial. These data indicate that increases in blood pressure are sustained throughout 15 min of face cooling, and face cooling elicits differential time-dependent parasympathetic and likely sympathetic activation.

Keywords: diving reflex; parasympathetic activation; sympathetic activation; trigeminal nerve.