Dynamics of middle cerebral artery blood flow velocity during moderate-intensity exercise

Abstract

The dynamic response to a stimulus such as exercise can reveal valuable insights into systems control in health and disease that are not evident from the steady-state perturbation. However, the dynamic response profile and kinetics of cerebrovascular function have not been determined to date. We tested the hypotheses that bilateral middle cerebral artery blood flow mean velocity (MCA) increases exponentially following the onset of moderate-intensity exercise in 10 healthy young subjects. The MCA response profiles were well fit to a delay (TD) + exponential (time constant, τ) model with substantial agreement for baseline [left (L): 69, right (R): 64 cm/s, coefficient of variation (CV) 11%], response amplitude (L: 16, R: 13 cm/s, CV 23%), TD (L: 54, R: 52 s, CV 9%), τ (L: 30, R: 30 s, CV 22%), and mean response time (MRT) (L: 83, R: 82 s, CV 8%) between left and right MCA as supported by the high correlations (e.g., MRT = 0.82, < 0.05) and low CVs. Test-retest reliability was high with CVs for the baseline, amplitude, and MRT of 3, 14, and 12%, respectively. These responses contrasted markedly with those of three healthy older subjects in whom the MCA baseline and exercise response amplitude were far lower and the kinetics slowed. A single older stroke patient showed baseline ipsilateral MCA that was lower still and devoid of any exercise response whatsoever. We conclude that kinetics analysis of MCA during exercise has significant potential to unveil novel aspects of cerebrovascular function in health and disease. Resolution of the dynamic stimulus-response profile provides a greater understanding of the underlying the physiological control processes than steady-state measurements alone. We report a novel method of measuring cerebrovascular blood velocity (MCAv) kinetics under ecologically valid conditions from rest to moderate-intensity exercise. This technique reveals that brain blood flow increases exponentially following the onset of exercise with ) a strong bilateral coherence in young healthy individuals, and) a potential for unique age- and disease-specific profiles.

Blunted cerebrovascular response is associated with elevated beta-amyloid

“…10,11 Quantitative measurement of cerebral blood flow at rest provides valuable steady state information. However, examining the dynamic response, CVR, from rest to moderate intensity exercise can provide unique information regarding cerebrovascular control mechanisms 29 especially in a well-characterized cohort. All of our participants were sedentary 26 and were classified as moderate or high cardiac risk.…”

“…26 The laboratory room for the experimental session was dimly lit, quiet, and temperature maintained between 22 and 24 C. 27,28 External stimuli were kept to a minimum during the testing session. 29 The left MCA was used for the transcranial Doppler (TCD) ultrasound with a 2-MHz probe (RobotoC2MD, Multigon Industries) placed over the temporal window and fixed in place using a robotic TCD headpiece. If the left MCA was not obtainable, then the right side was used.…”

Swimming‐related effects on cerebrovascular and cognitive function

“…It has been proposed that the cognitive benefit from exercise may be associated with the acute, exercise-related increase in cerebral blood flow (Ogoh, 2017). Leg-based dynamic exercise, such as cycling (Jorgensen et al, 1992;Hellstrom et al, 1996;Ogoh and Ainslie, 2009), recumbent stepping (Billinger et al, 2017), and treadmill running (Jiang et al, 1995) increase cerebral blood velocity (CBV) through the independent and interactive factors involved in cerebral blood flow regulation (e.g., blood pressure [BP], cardiac output, and alterations in arterial CO 2 ; Ide andSecher, 2000, Ogoh andAinslie, 2009). Furthermore, upright leg-based, aquatic exercise has recently been shown to augment the increase in CBV compared to intensity-matched land exercise (Parfitt et al, 2017).…”

Middle cerebral artery velocity dynamic response profile during exercise is attenuated following multiple ischemic strokes: a case report

“…Another potential mechanism known to influence CBF is partial pressure of carbon dioxide (PaCO 2 ) in the arterial blood. As discussed in our prior work, we acknowledge that P ET CO 2 is not identical to PaCO 2 (Billinger et al ), but we can expect an approximate 3–5 mmHg increase in P ET CO 2 from rest to moderate‐intensity exercise. We observed a consistent increase in P ET CO 2 from rest to exercise at all study visits.…”

“…We published a novel method for measuring cerebrovascular response to a change in demand from rest to moderate‐intensity exercise in the middle cerebral artery (MCA) (Billinger et al ). The resolution of the MCA velocity (MCAv) kinetics provided unique information for age‐ and sex‐differences and revealed that the kinetics profile was blunted in older adults when compared to their younger counterparts (Ward et al ).…”