Autonomic Activation During Face Cooling is Not Attenuated in Healthy Adults with a History of Concussion
Authors: Bloomfield Adam C , Reed Emma L , Horn Emily C , Johnson Blair D 
Published: April 2020

Recent evidence indicates that physiological recovery from a concussion appears to take longer than clinical recovery. We have shown that symptomatic concussed patients have impaired cardiac parasympathetic activity and attenuated sympathetically‐mediated increases in blood pressure during face cooling (FC) vs. healthy controls. However, it is not known if the attenuated responses to FC persist in asymptomatic healthy adults who reported experiencing a concussion more than one year ago.PURPOSEWe tested the hypothesis that asymptomatic healthy active adults who experienced a concussion more than one year ago have diminished autonomic activation during FC vs. healthy active adults without a history of concussion.METHODSThirteen healthy adults without a history of concussion within one year of testing performed a FC test. Subjects were retrospectively grouped into those who reported experiencing a concussion more than a year ago (n=5, CH) and those without a history of concussion (n=8, NH). After 10 min of supine rest, a pliable plastic bag filled with ice water (~0° C) was placed on the forehead, eyes and cheeks for 3 min. Heart rate (HR, 3‐lead ECG), mean arterial pressure (MAP, finger photoplethysmography), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were continuously recorded. Total peripheral resistance (TPR) was calculated as MAP/cardiac output. Root mean square of successive differences in R‐R interval (RMSSD) and high‐frequency power (HF) were calculated from spectral analysis of the R‐R interval (RRI) to estimate cardiac parasympathetic activity. Data were analyzed every 1 min and reported as the mean of the change from baseline (D) ± SD.RESULTSAt baseline, there were no differences between groups for HR (NH: 65±14; CH: 65±5 bpm, P=0.95), MAP (NH: 96± 7; CH: 94 ± 10 mmHg, P=0.67), SBP (NH: 130 ± 15; CH: 132 ± 13 mmHg, P=0.84), DBP (NH: 75 ± 5; CH: 74± 8 mmHg, P=0.77), TPR (NH: 17 ± 8; CH: 13± 1 mmHg, P=0.32), and RRI (NH: 990 ± 510; CH: 666 ± 407 ms, P=0.34). RMSSD (NH: 155 ± 85; CH: 50 ± 30 ms, P=0.05) and HF (NH: 3965 ± 1283; CH: 430± 550 ms2, P=0.01) were lower at baseline in CH. During FC, there were no main effects of group for DMAP (P=0.69), DSBP (P=0.86), DDBP (P=0.31), DTPR (P=0.22), DRMSSD (P=0.27), or DHF (P=0.97). During FC, DHR for NH was different vs. CH at Min 1 (NH: 5±4; CH: −4±7 bpm, P=0.01), Min 2 (NH: 1 ± 5; CH: −12 ± 9 bpm, P<0.01), and Min 3 (NH: 3 ± 9; CH: −9 ± 5 bpm, P<0.01). During FC, DRRI in NH was different vs. CH at Min 1 (NH: −68 ± 81; CH: 188 ± 240 ms, P=0.06), Min 2 (NH: −8 ± 130; CH: 253 ± 264 ms, P=0.06), and Min 3 (NH: −67 ± 210; CH: 31 ± 55 ms, P=0.06).CONCLUSIONThese preliminary data indicate that resting cardiac parasympathetic activity is lower in patients with a history of concussion. Despite a greater decrease in heart rate, there were no differences in markers of cardiac parasympathetic activity and sympathetically‐mediated increases in blood pressure during FC between individuals with a history of concussion vs. individuals with no history of concussion. More frequent assessments of the autonomic responses to FC are warranted to determine the normal progression of physiological recovery from concussion.Support or Funding InformationSupported by the National Center for Advancing Translational Sciences of the NIH Pilot Grants Award Program UL1TR001412