Evaluation of the cerebral hemodynamic response to rhythmic handgrip

Abstract

The response of the cerebral circulation to exercise has been studied with transcranial Doppler ultrasound (TCD) because this modality provides continuous measurements of blood velocity and is well suited for the exercise environment. The use of TCD as an index of cerebral blood flow, however, requires the assumption that the diameter of the insonated vessel is constant. Here, we examine this assumption for rhythmic handgrip using a spectral index designed to measure trends in vessel flow. Nineteen normal subjects were studied during 5 min of volitional maximum rhythmic right handgrip at 1 Hz. TCD velocities from both middle arteries (left and right), blood pressure, and end-tidal PCO(2) were recorded every 10 s. A spectral weighted sum was also calculated as a flow index (FI). Averages were computed from the last 2 min of handgrip. Relative changes in velocity, FI, and pressure were calculated. The validity of FI was tested by comparing the change in diameter derived from equations relating flow and diameter. Mean blood pressure increased 23.8 +/- 17.8% (SD), and velocity increased 13.3 +/- 9.8% (left) and 9.6 +/- 8.3% (right). Although the mean change in FI was small [2.0 +/- 18. 2% (left) and 4.7 +/- 29.7% (right)], the variation was high: some subjects showed a significant increase in FI and others a significant decrease. Diameter estimates from two equations relating flow and luminal area were not significantly different. Decreases in FI were associated with estimated diameter decreases of 10%. Our data suggest that the cerebral blood flow (CBF) response to rhythmic handgrip is heterogeneous and that middle cerebral artery flow can decrease in some subjects, in agreement with prior studies using the Kety-Schmidt technique. We speculate that the velocity increase is due to sympathetically mediated vasoconstriction rather than a ubiquitous flow increase. Our data suggest that the use of ordinary TCD velocities to interpret the CBF response during exercise may be invalid.

Cerebral Autoregulation: An Overview of Current Concepts and Methodology with Special Focus on the Elderly

“…Both methods have been used for the assessment of dCA (Micieli et al, 1994;Roatta et al, 1998;Giller et al, 2000). However, the CBFV response to these tests is very heterogeneous.…”

A review on continuous wave functional near-infrared spectroscopy and imaging instrumentation and methodology

“…These BP changes affect hemodynamics in the extracerebral compartment, measured as stimulus/task-related changes in SBF and/or volume (SBV) (Kirilina et al, 2012;Takahashi et al, 2011), or even in the cerebral compartment itself (Minati et al, 2011 Another source of systemic component is the influence of the autonomic nervous system (ANS) on the cerebral vasculature (Hamel, 2006;Wahl and Schilling, 1993). For example, Giller et al (2000) showed that a rhythmic handgrip exercise causes a sympathetic-mediated modulation of the hemodynamics in the middle cerebral artery. Cerebral hemodynamics is also affected by parasympathetic and trigemino-vascular activity (Goadsby et al, 1997;Wahl and Schilling, 1993).…”

“…The superficial layer of the extracerebral compartment, i.e. the skin, is also under the influence of the ANS; a good example for this is facial flushing (Drummond, 1999;Drummond and Lance, 1987), which takes place even during a simple static handgrip task (Giller et al, 2000), for example. Kirilina et al (2012) suggest that stimulus/ task-evoked sympathetic arterial vasoconstriction may influence fNIRI signals.…”

Effect of Isometric Hand Grip Exercise Training on Cardiovascular and Echocardiographic Parameters Among Healthy Young Males

“…This may help to ease some of the barriers to exercise, and increase patient adherence. This form of exercise has been found to result similar reduction in resting arterial blood pressure as that of conventional aerobic therapy, (6) and have beneficial effects, on autonomic nervous system regulation of blood pressure, (7) in improving cerebral haemodynamics (8) and forearm vascular response. (9) In spite of the above fact, very few studies have been conducted to evaluate the effect of IHG training on cardiovascular system, especially on cardiac morphology & functioning.…”