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Extremes of cerebral blood flow during hypercapnic squat‐stand maneuvers

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posted on 2021-11-17, 10:13 authored by Samuel C Barnes, Victoria J Haunton, Lucy Beishon, Osian Llwyd, Thompson G Robinson, Ronney B Panerai
Squat-stand maneuvers (SSMs) are a popular method of inducing blood pressure (BP) oscillations to reliably assess dynamic cerebral autoregulation (dCA), but their effects on the cerebral circulation remain controversial. We designed a protocol whereby participants would perform SSMs under hypercapnic conditions. Alarmingly high values of cerebral blood flow velocity (CBFV) were recorded, leading to early study termination after the recruitment of a single participant.

One healthy subject underwent recordings at rest (5 min sitting, 5 min standing) and during two SSMs (fixed and random frequency). Two sets of recordings were collected; one while breathing room air, one while breathing 5% CO2. Continuous recordings of bilateral CBFV (transcranial Doppler), heart rate (ECG), BP (Finometer), and end-tidal CO2 (capnography) were collected.

Peak values of systolic CBFV were significantly higher during hypercapnia (p < 0.01), and maximal values exceeded 200 cm.s−1. Estimates of dCA (ARI) during hypercapnia were impaired relative to poikilocapnia (p = 0.03). The phase was significantly reduced under hypercapnic conditions (p = 0.03).

Here we report extremely high values of CBFV in response to repeated SSMs during induced hypercapnia, in an otherwise healthy subject. Our findings suggest that protocols performing hypercapnic SSMs are potentially dangerous. We, therefore, urge caution if other research groups plan to undertake similar protocols.

History

Citation

Physiological Reports, 9 (19), 2021, e15021

Author affiliation

Department of Cardiovascular Sciences, University of Leicester

Version

  • VoR (Version of Record)

Published in

Physiological Reports

Volume

9

Issue

19

Publisher

Wiley

issn

2051-817X

eissn

2051-817X

Acceptance date

2021-08-09

Copyright date

2021

Available date

2021-11-17

Language

en

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