Wave reflection augments central systolic and pulse pressures during facial cooling

Abstract

Cardiovascular events are more common in the winter months, possibly because of hemodynamic alterations in response to cold exposure. The purpose of this study was to determine the effect of acute facial cooling on central aortic pressure, arterial stiffness, and wave reflection. Twelve healthy subjects (age 23 +/- 3 yr; 6 men, 6 women) underwent supine measurements of carotid-femoral pulse wave velocity (PWV), brachial artery blood pressure, and central aortic pressure (via the synthesis of a central aortic pressure waveform by radial artery applanation tonometry and generalized transfer function) during a control trial (supine rest) and a facial cooling trial (0 degrees C gel pack). Aortic augmentation index (AI), an index of wave reflection, was calculated from the aortic pressure waveform. Measurements were made at baseline, 2 min, and 7 min during each trial. Facial cooling increased (P < 0.05) peripheral and central diastolic and systolic pressures. Central systolic pressure increased more than peripheral systolic pressure (22 +/- 3 vs. 15 +/- 2 mmHg; P < 0.05), resulting in decreased pulse pressure amplification ratio. Facial cooling resulted in a robust increase in AI and a modest increase in PWV (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/s; P < 0.05). Change in mean arterial pressure but not PWV predicted the change in AI, suggesting that facial cooling may increase AI independent of aortic PWV. Facial cooling and the resulting peripheral vasoconstriction are associated with an increase in wave reflection and augmentation of central systolic pressure, potentially explaining ischemia and cardiovascular events in the cold.

Increased cardiovascular reactivity to the cold pressor test is not associated with increased reactivity to isometric handgrip exercise

“…Thus, the time course was similar to that of MSNA (Victor et al 1987;Yamamoto et al 1992), suggesting that coldand/or pain-induced vasoconstriction increases arterial stiffness and the PWV, which leads to increases in wave reflection from the periphery, the AIx@75 (Nichols 2005;Edwards et al 2008a). Similarly, in isometric handgrip exercise, both PWV and AIx@75 remained unchanged during the first 30 s, but increased from the control value at 60 s of exercise and remained elevated until 30 s after exercise, following almost the same time course as MSNA (Mark et al1985;Seals and Victor 1991;Hashimoto et al 1998).…”

Effect of healthy aging on renal vascular responses to local cooling and apnea

“…Care was taken to avoid contact with the eyes (i.e., to avoid the oculocardiac reflex), and subjects were monitored to ensure normal breathing. This foreheadcooling procedure is thought to stimulate trigeminal afferents that are involved in the diving reflex (i.e., bradycardia and peripheral vasoconstriction), but bradycardia is not a universal finding in healthy people (11,22,65). Because forehead cooling at 1°C was expected to be painful, we also performed forehead cooling at 15°C in all subjects, which is a temperature that stimulates cold-sensitive afferents but does not elicit pain (23,32,35).…”

Evaluation of effect of highly standardized aqueous extract of roots and leaves of Withania somnifera on cold pressor test induced cardiovascular changes in healthy human subjects

“…26 The cold exposure also increases aortic augmentation index (AIx), a measure of wave reflection, leading to augmented central systolic pressure. 27 Cold pressor test conducted in healthy individuals demonstrated that stress exerted through the cold pressor for a minute stimulated the sympathetic nervous system resulting in accelerated heart rate and elevated blood pressure, both systolic and diastolic, in comparison to those recorded before the foregoing test in all the normotensive volunteers. 28 In our study, similar observations have been recorded.…”