The effect of hypercapnia on static cerebral autoregulation

• Published in: Physiological reports 2014-06, Vol.2 (6), p.e12059-n/a
• Main Authors: Perry, Blake G., Lucas, Samuel J. E., Thomas, Kate N., Cochrane, Darryl J., Mündel, Toby
• Format: Article
• Language: English
• Subjects: Blood pressure; Body mass; Carbon dioxide; Cerebral blood flow; Experiments; Flow velocity; Heart rate; Hypercapnia; Hypertension; Laboratories; lower body positive pressure; Original Research; Physiology; Software; static cerebral autoregulation; Ultrasonic imaging; Veins & arteries
• ISSN: 2051-817X; 2051-817X
• DOI: 10.14814/phy2.12059

Hypercapnia impairs cerebrovascular control during rapid changes in blood pressure (BP); however, data concerning the effect of hypercapnia on steady state, nonpharmacological increases in BP is scarce. We recruited fifteen healthy volunteers (mean ± SD: age, 28 ± 6 years; body mass, 77 ± 12 kg) to assess the effect of hypercapnia on cerebrovascular control during steady‐state elevations in mean arterial BP (MAP), induced via lower body positive pressure (LBPP). Following 20 min of supine rest, participants completed 5 min of eucapnic 20 and 40 mm Hg LBPP (order randomized) followed by 5 min of hypercapnia (5% CO2 in air) with and without LBPP (order randomized), and each stage was separated by ≥5 min to allow for recovery. Middle cerebral artery blood velocity (MCAv), BP, partial pressure of end‐tidal carbon dioxide (PETCO2) and heart rate were recorded and presented as the change from the preceding baseline. No difference in MCAv was apparent between eupcapnic baseline and LBPPs (grouped mean 65 ± 11 cm·s−1, all P > 0.05), despite the increased MAP with LBPP (Δ6 ± 5 and Δ8 ± 3 mm Hg for 20 and 40 mm Hg, respectively, both P