Progressive Face Cooling does not Reveal a Critical Temperature Eliciting Elevations in Cardiac Parasympathetic Activity
Authors: Mcbryde Muhamed M. , O'Leary Morgan C. , Sackett James , Chapman Chris L. , Schlader Zachary J. , Johnson Blair D. 
Published: June 2021

Placing a plastic bag filled with ice water (0°C) on the forehead, eyes, and cheeks (i.e., face cooling) stimulates the trigeminal nerve, evoking a transient (1–2 min) cardiac parasympathetic response and a concomitant sympathetically mediated increase in blood pressure. However, it is not known if a critical temperature is needed to initiate an increase in cardiac parasympathetic activity and blood pressure.PURPOSETest the hypothesis that a critical bag temperature will elicit an increase cardiac parasympathetic activity and blood pressure.METHODSProgressive face cooling was performed on 11 healthy subjects (24±3 years, 4 women). Following 10 minutes of rest, plastic bags filled with 34°C, 28°C, 21°C, 14°C, 7°C, and 0°C water were placed on the forehead, eyes, and cheeks for 5 minutes each to progressively decrease face temperature. Perceived face pain (0 = no pain, 10 = worst pain imaginable) was quickly obtained between bags. Forehead temperature (thermocouple), heart rate (ECG), and mean arterial pressure (MAP; photoplethysmography) were continuously collected. Stroke volume (Modelflow), cardiac output, and total peripheral resistance were calculated. Root mean squared of successive differences (RMSSD) and high‐frequency spectral analysis (HF) were calculated from the R‐R interval as markers of cardiac parasympathetic activity. Data were analyzed during the first minute of each bag and compared to baseline using one way repeated measures ANOVA.RESULTSForehead temperatures were different from baseline (34.1 ± 0.5°C) during all bag temperatures (34°C: 34.6 ± 0.3°C; 28°C: 32.6 ± 0.5°C; 21°C: 28.3 ± 0.8°C; 14°C: 24.0 ± 1.2°C; 7°C: 19.3 ± 1.2°C; 0°C: 13.5 ± 2.0°C) (P < 0.01 for all). Perceived face pain was greater than baseline (0 ± 0) after the 14°C (2 ± 2), 7°C (4 ± 2), and 0°C (5 ± 3) bag temperatures (P < 0.03 for all). There were no changes in heart rate during the protocol (main effect: P = 0.07). MAP was greater than baseline only during the 0°C bag (84 ± 12 vs. 103 ± 12 mmHg, P = 0.01). There were no changes in stroke volume (main effect: P = 0.79), cardiac output (main effect: P = 0.72), or total peripheral resistance (main effect: P = 0.33) during the protocol. A main effect of bag temperature was observed for RMSSD (P = 0.05) but post hoc analyses were unable to uncover where differences existed (Baseline: 67 ± 40 ms; 34°C: 66 ± 31 ms; 28°C: 53 ± 22 ms; 21°C: 56 ± 23 ms; 14°C: 68 ± 30 ms; 7°C: 79 ± 39 ms; 0°C: 103 ± 69 ms) (P > 0.39 for all). Similarly, a main effect of bag temperature was observed for HF (P = 0.03) but post hoc analyses were unable to uncover where differences existed (Baseline: 710 ± 966 ms2; 34°C: 747 ± 780 ms2; 28°C: 778 ± 1018 ms2; 21°C: 906 ± 1162 ms2; 14°C: 1108 ± 1111 ms2; 7°C: 1312 ± 1295 ms2; 0°C: 4253 ± 4647 ms2) (P > 0.20 for all).CONCLUSIONDespite reductions in forehead temperature, an increase in cardiac parasympathetic activity was not detected at any specific temperature while MAP increased only at the lowest forehead temperature (0°C). We speculate that gradual cooling of the face decreased thermoreactivity downstream of the trigeminal nerve, resulting in a lack of the transient increase in cardiac parasympathetic activity typically seen during face cooling.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.