Acute effects of facial cooling on arterial stiffness and wave reflection

Abstract

Background. It has previously been demonstrated that whole body cooling increases wave reflection and central systolic and pulse pressures. This study tested the hypothesis that local facial cooling would result in an increase in central arterial stiffness, wave reflection, and central blood pressure. Methods. Twelve apparently healthy subjects (23±3 years, 6 male, 6 female) underwent supine measurements of carotid to femoral pulse wave velocity (PWV), brachial artery blood pressure, and the synthesis of a central aortic pressure waveform (by radial artery applanation tonometry and generalized transfer function) during a control (supine rest) trial and a facial cooling trial. Measurements were made at baseline, at 2 minutes, and again 5 minutes later during each trial. Facial cooling consisted of placing a gel pack (0°C) on the forehead. Central aortic augmentation index (AI), systolic time index (STI), diastolic time index (DTI), subendocardial viability ratio (SEVR), and left ventricular wasted energy (LVWE) were calculated from the synthesized central aortic pressure waveform. Carotid-femoral PWV is a measure of central arterial stiffness, and AI is an index of wave reflection. Statistics. A 2 × 3 (condition × time) analysis of variance with repeated measures was used to compare differences among trials. Bonforoni post-hoc analysis was performed to determine differences within and between conditions. Statistical analysis was performed using the SPSS statistical program version 13 (SPSS, Inc.). An alpha level of 0.05 was required for statistical significance. Results. Facial cooling induced increases (P < 0.05) in AI (-1.4±3.8 vs. 21.2±3.0 and 19.9±3.6%), PWV (5.6±0.2 vs. 6.5±0.3 and 6.2±0.2 m-sec^-1), STI (16.7±1.1 vs. 21.2±1.4 and 21.4±1.4 units x 10²), DTI (30.4±0.8 vs. 35.6±0.9 and 36.1±1.1 units x 10²), and LVWE (3.6±1.9 vs. 34.6±5.4 and 30.5±4.6 dyne-sec-cm ^-2 x 10²) from baseline. Additionally, facial cooling increased (P < 0.05) both brachial systolic (114±3 vs.129±4 and 131±4 mmHg) and diastolic (64±2 vs. 76±2 and 77±2 mmHg) blood pressures, central systolic (94±3 vs. 116±4 and 116±4 mmHg) and diastolic (65±2 vs. 77±2 and 78±2 mmHg) blood pressures, and central pulse pressure (30±2 vs. 39±2 and 38±3 mmHg) from baseline. Conclusions. These results demonstrate that facial cooling increases wave reflection and aortic stiffness, resulting in augmented central systolic and pulse pressure. Furthermore, increases in STI and LVWE explain how the increased wave reflection and arterial stiffness seen during facial cooling may lead to greater myocardial oxygen demand and extra energy expenditure by the heart in order to maintain left ventricular ejection.