Systolic and Diastolic Regulation of the Cerebral Pressure-Flow Relationship Differentially Affected by Acute Sport-Related Concussion

Abstract

Impairments in autoregulatory capacity, observed for a transient period following SRC that persist beyond symptom resolution and clinical recovery, appear to be differentially affected across the cardiac cycle. Similar patterns of impairment were observed for systolic and diastolic phases (response latency); however, normalized gain (response magnitude) impairments were identified only in diastole. These findings may explain the increased cerebral vulnerability as well as exercise-induced symptom exacerbation observed post-SRC.

Dynamic cerebral autoregulation across the cardiac cycle during 8 hr of recovery from acute exercise

“…Ogoh and coworkers (Ogoh, Dalsgaard, et al, ; Ogoh, Fisher, et al, ) found diastolic dynamic CA was impaired during exercise and acute recovery (10 min) within the LF band, despite the 5‐min averaged diastolic MCA blood velocity appearing to be well maintained. These results are similar to those previously reported in athletes who have sustained an acute sports‐related concussion (Wright, Smirl, Bryk, & Donkelaar, ). Both MCA and PCA blood velocities have previously been shown to increase following moderate exercise, likely influenced by the elevated P ET CO2 associated with subanaerobic threshold exercise.…”

“…To prevent BP surges from causing irreversible damage in the cerebrovasculature, CA is thought to act as a buffer to protect the brain from cerebral hyperperfusion (Ogoh, Fisher, et al, ; Smirl et al, ; Wright, Smirl, Bryk, & Donkelaar, ). Ogoh and coworkers (Ogoh, Dalsgaard, et al, ; Ogoh, Fisher, et al, ) found diastolic dynamic CA was impaired during exercise and acute recovery (10 min) within the LF band, despite the 5‐min averaged diastolic MCA blood velocity appearing to be well maintained.…”

“…Moreover, the gain metric was normalized within the current investigation to %/% to enable more appropriate comparisons presented between the various interventions in the study which resulted in alterations to either blood pressure and/or CBV. The input–output nature of the cerebral pressure–flow relationship was examined across the cardiac cycle to obtain a better understanding how each aspect is affected following a controlled bout of exercise as prior research has demonstrated there is differential CA regulation across the cardiac cycle (Ogoh, Dalsgaard, et al, , ; Smirl et al, ; Wright, Smirl, Bryk, & Donkelaar, ). Furthermore, linear elevations to blood pressure are known to occur during increasing intensities of exercise and thus both moderate‐ and high‐intensity exercise bouts were employed to determine how these would have extended effects on CA.…”

“…There are three major limitations to these previous studies: (a) only the short‐term effects of CA during exercise or within 60 min of exercise cessation were examined; the duration of dynamic CA alterations postexercise remain unknown; (b) only two studies have examined the CA relationship across the cardiac cycle (Ogoh, Fadel, et al, ; Ogoh, Fisher, et al, ); as recent research has shown each phase of the cardiac cycle responds differently to a given stimulus, examining the mean may not accurately portray important subtleties between diastolic and systolic components (Smirl, Wright, Ainslie, Tzeng, & Donkelaar, ; Wright, Smirl, Bryk, & Donkelaar, ); and (c) only one of these prior studies employed a research method (oscillatory lower body negative pressure during the exercise intervention) which evoked sufficient coherence to provide reproducible interpretations of the associated phase and gain metrics (Smirl, Hoffman, Tzeng, Hansen, & Ainslie, ). Moreover, recent research has demonstrated when squat–stand maneuvers are employed to quantify CA parameters, coherence values are enhanced to near linear levels (~0.99) (Kostoglou et al, ; Smirl, Haykowsky, et al, ; Smirl et al, , , ; Smirl, Lucas, et al, ; Smirl, Tzeng, Monteleone, & Ainslie, ; Wright, Smirl, Bryk, & Donkelaar, ; Wright et al, , ). This methodological approach leads to greater reproducibility within the CA outcome measures (phase, absolute gain, and normalized gain) (Claassen et al, ; Smirl et al, ), which will enhance the interpretability and application of the findings related to the current investigation.…”

Does depth of squat‐stand maneuver affect estimates of dynamic cerebral autoregulation?

“…The main drawback of SSM is the difficulty of their use in incapacitated subjects, people with mobility issues or those with cognitive impairment (Van Beek et al, 2008;Smirl et al, 2015). Despite the difficulty of applying SSM in some clinical conditions, a number of previous studies have already demonstrated its feasibility (Claassen, Diaz-Arrastia, et al, 2009;Lewis et al, 2019;Smirl et al, 2014;Wright, Smirl, Bryk, & van Donkelaar, 2018).…”