Assessment of cerebral autoregulation using continuous-wave near-infrared spectroscopy during squat-stand maneuvers in subjects with symptoms of orthostatic intolerance

Figures

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  Figure 1. Experimental design. (A) Data acquisition setup (B) Experimental protocol (C) Optode position (D) Channel position. R = right; L = left; Fpz = frontal pole zero; CW-NIRS = continuous-wave near-infrared spectroscopy.

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  Figure 2. Total hemoglobin (HbT) and time-derivative of HbT (DHbT) change during squat-stand maneuver. (A) An example of the block averaged (5-block) HbT change and DHbT with parameters evaluated from HbT; the decrease time (DT), increase time (IT) and recovery time (RT). (B) Closer view of DHbT change during the task with objective parameters obtained from DHbT; the maximum and minimum slope variations (Max SV, Min SV) and the peak-time of the slopes (Max PT, Min PT). (C) Measured sections from the prefrontal region of the brain (The channels were grouped into eight sections).

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  Figure 3. Systolic, diastolic, and mean arterial blood pressure (SBP, DBP, and MAP respectively) and heart rate (HR) during the squat-stand maneuver. Mean and standard deviation values were extracted in each group from the pre-defined time-intervals such as baseline (BL), squatting-rest (sqR), T1, T2, and T3 (150 to 180 seconds, 210 to 240 seconds, 295 to 300 seconds, 355 to 360 seconds, and 415 to 420 seconds, respectively). Initial minimum and maximum peak (MinP and MaxP) of the response immediately after standing. (A) An example SBP, DBP, MAP and HR responses measured from the finger artery. (B) Between-group comparison of cardiovascular variables. Asterisks: significant differences (*P < 0.05, **P < 0.01) between BL and other time intervals (i.e. sqR, T1, T2, and T3) in each group. Error bars indicate the standard deviation of the mean.

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  Figure 4. Between-group comparison of cardiovascular responses. Graphs of (A) deviation from BL values at sqR, T1, T2, and T3. (B) Deviation from sqR values at T1, T2, and T3. (C) Transient variation of cardiovascular responses. Asterisks: significant differences (*P < 0.05, **P < 0.01) between groups. Error bars indicate the standard deviation of the mean. BL = baseline; sqR = squatting-rest.

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  Figure 5. Transient grand-average of DHbT response between control and symptom group. The figure shows transient signal of grand-averaged DHbT of each groups. The blue and red lines indicate the grand-averaged waveform of the control and symptom groups. The shaded red and blue bands represent ± standard deviation. The quarter circle in the waveform represents significance, whereby filled red indicates statistical significance of each parameter (Max/Min SV, Max/Min PT) measured from DHbT. Fpz = frontal pole zero; SV = slope variation; PT = peak time.