Animal model of assessing cerebrovascular functional reserve by imaging photoplethysmography

Figures

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  Figure 1. Layout of the experimental setup for monitoring the response of the cortical-blood-flow and key-physiological parameters to the dorzolamide administration.

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  Figure 2. Spatial distribution of the amplitude (APC) of the optical signal oscillating at the heart rate for one of the rats. (A) One of the recorded frames of the rat’s cortex with a dedicated area (marked by the orange line) in which the photoplethysmographic waveform was assessed. (B) Spatial distribution of APC overlaid with the initial cortex image as estimated at the first second of the experiment. (C) Mapping of APC after the dorzolamide injection calculated at 340th second of the experiment. The color scale on the right shows APC in percent, which is the same for both panels (B) and (C). Colored squares show the position of the selected areas (big ROIs) in which changes in mean APC were estimated.

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  Figure 3. Typical responses of the measured physiological indices on the dorzolamide injection for one of the rats. (A) The normalized amplitude of the pulsatile component (APC) of the photoplethysmographic waveform assessed in the six selected areas shown in Fig. 2. The color of the waveforms coincides with that of the squares in Fig. 2 indicating the position of the big areas of interest. (B) Concentration of end-tidal carbon dioxide (CO2). (C) Dynamics of the heart rate. (D) Systemic arterial pressure (its mean value, ABP). (E) Pulse pressure (PP). ABP and PP were measured invasively through a cannula in the animal’s femoral artery. The timeline (which is the same for all graphs) is displayed at the bottom indicating the stages of the experimental protocol.

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  Figure 4. Response of the physiological parameters averaged over the whole group (n = 15) of animals to the dorzolamide injection. (A) Normalized amplitude of the pulsatile component of (APCN) the photoplethysmographic waveforms. (B) Relative changes in the end-tidal carbon dioxide (CO2) concentration. (C) Relative changes in the heart rate (HR). (D) Relative changes in the mean systemic arterial blood pressure (ABP). (E) Relative changes in the pulse pressure (PP) measured invasively in femoral vein. The circles in all graphs show the mean value whereas the whiskers are standard deviation. In all panels, the data before averaging were normalized to the respective mean value during the baseline for the correctness of averaging the experimental results with different rats.