Influence of a neck compression collar on cerebrovascular and autonomic function in men and women

OBJECTIVE: Neck compression collars have been proposed to reduce injury to the brain caused by head impacts. Our objective was to test if compression of the carotid artery affected the baroreflex and influenced blood pressure control. METHODS: Cerebrovascular and autonomic responses of healthy young men and women (n = 8 each) to paced deep breathing, Valsalva, and 70(o) head-up tilt with or without use of a Q-collar were determined. Continuous measurements of heart rate, beat-to-beat blood pressure, transcranial Doppler, and end-tidal gases were obtained. Heart rate variability was measured during supine rest and head-up tilt. Carotid artery and jugular vein cross-sectional area were measured at end-inhalation and end-exhalation using cross-sectional ultrasound images at diastole. RESULTS: Wearing the collar reduced carotid cross-sectional area (CSA; P = 0.022; η(2) = 0.03) and increased jugular CSA (P = 0.001; η (2) = 0.30). In both men and women, wearing the collar increased systolic blood pressure during Valsalva (P<0.05; η (2) = 0.38). In only men, wearing the collar resulted in prolonged pressure recovery time during Valsalva (P = 0.02; η (2) = 0.05). In only women, wearing the collar increased baseline diastolic (P = 0.026; η (2) = 0.09) and mean (P = 0.041; η (2) = 0.06) middle cerebral artery (MCA) blood flow velocity, which attenuated the normal increase of diastolic (P = 0.01; η (2) = 0.03) and mean (P = 0.038; η (2) = 0.02) MCA blood flow velocity during Valsalva. There were no effects of sex or collar on the responses to deep breathing (P>0.05), and there were no effects of the collar on cerebrovascular function, hemodynamics, cardiovagal baroreceptor sensitivity, or heart rate variability (P>0.05) during upright tilt. CONCLUSION: Use of the Q-collar compresses both the jugular vein and carotid artery influencing sympathetic nerve activity in both men and women while influencing brain blood flow in women.