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Comparative Study
. 2005 Dec 1;569(Pt 2):697-704.
doi: 10.1113/jphysiol.2005.095836. Epub 2005 Oct 6.

The effect of changes in cardiac output on middle cerebral artery mean blood velocity at rest and during exercise

Shigehiko Ogoh  1 , R Matthew Brothers, Quinton Barnes, Wendy L Eubank, Megan N Hawkins, Sushmita Purkayastha, Albert O-Yurvati, Peter B Raven
Affiliations
Comparative Study

The effect of changes in cardiac output on middle cerebral artery mean blood velocity at rest and during exercise

Shigehiko Ogoh et al. J Physiol. .

Abstract

We examined the relationship between changes in cardiac output and middle cerebral artery mean blood velocity (MCA V(mean)) in seven healthy volunteer men at rest and during 50% maximal oxygen uptake steady-state submaximal cycling exercise. Reductions in were accomplished using lower body negative pressure (LBNP), while increases in were accomplished using infusions of 25% human serum albumin. Heart rate (HR), arterial blood pressure and MCA V(mean) were continuously recorded. At each stage of LBNP and albumin infusion was measured using an acetylene rebreathing technique. Arterial blood samples were analysed for partial pressure of carbon dioxide tension (P(a,CO2). During exercise HR and were increased above rest (P < 0.001), while neither MCA V(mean) nor P(a,CO2) was altered (P > 0.05). The MCA V(mean) and were linearly related at rest (P < 0.001) and during exercise (P = 0.035). The slope of the regression relationship between MCA V(mean) and at rest was greater (P = 0.035) than during exercise. In addition, the phase and gain between MCA V(mean) and mean arterial pressure in the low frequency range were not altered from rest to exercise indicating that the cerebral autoregulation was maintained. These data suggest that the associated with the changes in central blood volume influence the MCA V(mean) at rest and during exercise and its regulation is independent of cerebral autoregulation. It appears that the exercise induced sympathoexcitation and the change in the distribution of between the cerebral and the systemic circulation modifies the relationship between MCA V(mean) and .

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Figures

Figure 1
Figure 1. A summary of the linear relationships between and FBF (A) or MCA Vmean (B) at rest (•) and during exercise (○)
Symbols denote actual group data for all subjects (means ± s.e.m.). The lines represent the linear regressions calculated from the group average data. The significant relationship between formula image (in l min−1) and percentage FBF (where control FBF at rest was equal to 100%) was linear; Rest, FBF (%) = 11.9 ×formula image+ 19.4, R = 0.93, P = 0.023; Exercise, FBF (%) = 10.0 ×formula image– 37.3, R = 0.98, P = 0.003. The significant relationship between formula image (in l min−1) and MCA Vmean (in cm s−1) was linear; Rest, MCA Vmean = 3.4 ×formula image+ 44.0, R = 0.99, P < 0.001; Exercise, MCA Vmean = 1.2 ×formula image+ 52.9, R = 0.90, P = 0.035.
Figure 2
Figure 2. Group averaged responses of FBF (A) and MCA Vmean (B) to the change in at rest and during exercise
Bars represent the average slope of the linear regression line between percentage FBF and formula image (A) and between percentage MCA Vmean and formula image (B) for all subjects (means ± s.e.m.) at rest and during exercise.
Figure 3
Figure 3. Grouped-averaged low-frequency (LF) transfer function phase (A), gain (B) and coherence (C) between MAP and MCA Vmean at rest (filled bars) and during exercise (open bars)
Values are means ± s.e.m.†Different from rest.
See this image and copyright information in PMC

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