Quantification of the cerebral pressure–flow relationship directional sensitivity: Reliability of shorter repeated squat–stand durations

Figures

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  FIGURE 1. (a) Raw traces of BP, MCAv and PCO2 at 0.05 and 0.10 Hz RSS. (b) Schematic traces of MAP and MCAv during a RSS performed at 0.05 Hz. Enlarged regions depict how the variables were used to calculate ∆MCAvT/∆MAPT. Blue colour indicates variables used to calculate ∆MCAvT/∆MAPT DEC. Red colour indicates variables used to calculate ∆MCAvT/∆MAPT INC. Figure used and modified with permission from P. Brassard (Labrecque, Smirl, et al., 2021). Abbreviations: BP, blood pressure; MAP, mean arterial pressure; MAPmax, maximum MAP value; MAPmin, minimum MAP value; MCAv, middle cerebral artery blood velocity; MCAvmax, maximum MCAv value; MCAvmin, minimum MCAv value; PCO2, partial pressure of carbon dioxide; RSS, repeated squat–stands; TimeMAPmax, time at maximum MAP; TimeMAPmin, time at minimum MAP; TimeMCAvmax, time at maximum MCAv; TimeMCAvmin, time at minimum MCAv; ∆DECMAP, absolute change in MAP during acute decrease in MAP; ∆INCMAP, absolute change in MAP during acute increase in MAP; ∆DECMCAv, absolute change in MCAv during acute decrease in MAP; ∆INCMCAv, absolute change in MCAv during acute increase in MAP.

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  FIGURE 2. ∆MCAvT/∆MAPT and %MCAvT/%MAPT during transient increases (INC; filled circles) and decreases (DEC; open circles) for all repeated squat–stand durations at 0.05 Hz. Left panels (a, c) represent individual values, and right panels (b, d) represent averaged values over the 5 min repeated squat–stand. Differences were assessed via a two‐way repeated‐measures ANOVA (factors: MAP direction and duration as repeated measures). #Significant difference from corresponding value at 300 s. n = 99. Abbreviations: DEC, decrease; INC, increase; MAP, mean arterial pressure; MCA, middle cerebral artery.

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  FIGURE 3. ∆MCAvT/∆MAPT and %MCAvT/%MAPT during transient increases (INC; filled circles) and decreases (DEC; open circles) for all repeated squat–stand durations at 0.10 Hz. Left panels (a, c) represent individual values, and right panels (b, d) represent averaged values over the 5 min repeated squat–stand. Differences were assessed via a two‐way repeated‐measures ANOVA (factors: MAP direction and duration as repeated measures). #Significant difference from corresponding value at 300 s. n = 99. Abbreviations: DEC, decrease; INC, increase; MAP, mean arterial pressure; MCA, middle cerebral artery.

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  FIGURE 4. Bland–Altman plot with 95% LoA of ∆MCAvT/∆MAPT and %MCAvT/%MAPT at 0.05 Hz reported as the relative difference (as a percentage) between durations versus the average. Shorter durations are compared with the 300 s reference standard. n = 99. Abbreviation: LoA, limits of agreement.

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  FIGURE 5. Bland–Altman plot with 95% LoA of ∆MCAvT/∆MAPT and %MCAvT/%MAPT at 0.10 Hz reported as the relative difference (as a percentage) between durations versus the average. Shorter durations are compared with the 300 s reference standard. n = 99. Abbreviation: LoA, limits of agreement.

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  FIGURE 6. Within‐duration ICC of ∆MCAvT/∆MAPT for 60, 120, 180, 240 and 300 s duration RSS. Excellent (>0.90), good (0.75–0.90), moderate (0.50–0.75) and poor (<0.50) ICC are differentiated by blue, yellow, orange and red zones, respectively. n = 99. Abbreviations: DEC, decrease; ICC, intraclass correlation coefficient; INC, increase; RSS, repeated squat–stands.

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  FIGURE 7. Within‐duration ICC of %MCAvT/%MAPT for 60, 120, 180, 240 and 300 s duration RSS. Excellent (>0.90), good (0.75–0.90), moderate (0.50–0.75) and poor (<0.50) ICC are differentiated by blue, yellow, orange and red zones, respectively. n = 99. RSS, Abbreviations: DEC, decrease; ICC, intraclass correlation coefficient; INC, increase; repeated squat–stands.