Abstract
Concussions have been shown to result in autonomic dysfunction and altered cerebral vascular function. We tested the hypothesis that concussed athletes (CA) would have altered cerebral vascular function during acute decreases and increases in blood pressure compared to healthy controls (HC). Ten CA (age: 20 ± 2 y, 7 females) and 10 HC (age: 21 ± 2 y, 6 females) completed 5 min of lower body negative pressure (LBNP; −40 mmHg) and 5 min of lower body positive pressure (LBPP; 20 mmHg). Protocols were randomized and separated by 10 min. Mean arterial pressure (MAP) and middle cerebral artery blood velocity (MCAv) were continuously recorded. Cerebral vascular resistance (CVR) was calculated as MAP/MCAv. Values are reported as change from baseline to the last minute achieved (LBNP) or 5 min (LBPP). There were no differences in baseline values between groups. During LBNP, there were no differences in the change for MAP (CA: −23 ± 18 vs. HC: −21 ± 17 cm/s; P = 0.80) or MCAv (CA: −13 ± 8 vs. HC: −18 ± 9 cm/s; P = 0.19). The change in CVR was different between groups (CA: −0.08 ± 0.26 vs. HC: 0.18 ± 0.24 mmHg/cm/s; P = 0.04). Total LBNP time was lower for CA (204 ± 92 s) vs. HC (297 ± 64 s; P = 0.04). During LBPP, the change in MAP was not different between groups (CA: 13 ± 6 vs. HC: 10 ± 7 mmHg; P = 0.32). The change in MCAv (CA: 7 ± 6 vs. HC: −4 ± 13 cm/s; P = 0.04) and CVR (CA: −0.06 ± 0.27 vs. HC: 0.38 ± 0.41 mmHg/cm/s; P = 0.03) were different between groups. CA exhibited impaired tolerance to LBNP and had a different cerebral vascular response to LBPP compared to HC.
Highlights
3.8 million individuals sustain a sport-related concussion every year in the United States and many more are sustained via car crashes, falls, and military action [1]
Cardiovascular Responses Mean arterial pressure and systolic blood pressure decreased from baseline in concussed athletes (CA) and healthy controls (HC) during lower body negative pressure (LBNP)
Diastolic blood pressure decreased from baseline in CA at 2 min (P = 0.003), 3 min (P = 0.055), and 4 min (P = 0.003), whereas HC decreased at 3 min (P = 0.019), 4 min (P = 0.045), and 5 min (P = 0.002)
Summary
3.8 million individuals sustain a sport-related concussion every year in the United States and many more are sustained via car crashes, falls, and military action [1]. Cerebral autoregulatory dysfunction was found in acutely concussed athletes (i.e., ice hockey and American football) during squat-to-stand maneuvers [9] and in active professional boxers with mild to moderate chronic brain injury using the thigh cuff deflation technique [10]. These investigations have studied patients at rest [4, 8, 11] or using experimental techniques that induce only acute decreases in blood pressure to assess cBRS [4] and cerebral vascular function [9, 10]. It is important to assess cerebral vascular function and the control of blood pressure during both decreases and increases in blood pressure
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