Impact of central hypovolemia on photoplethysmogra

Authors: Aymen A Alian Nicholas J Galante Nina S Stachenfeld David G Silverman Kirk H Shelley

Publish Date: 2011/11/04

Volume: 25, Issue: 6, Pages: 377-385

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Abstract

Our study sought to explore changes in photoplethysmographic PPG waveform param eters during lower body negative pressure LBNP which simulated hypovolemia in spontaneously breathing volunteers We hypothesize that during progressive LBNP there will be a preservation of ear PPG parameters and a decrease in finger PPG parametersWith IRB approval 11 volunteers underwent a LBNP protocol at baseline 30 75 and 90 mm Hg or until the subject became symptomatic Subjects were monitored with finger and ear pulse oximeter probes an ECG and a finger arterial blood pressure monitor The square root of the mean of the squared differences between adjacent NN intervals RMSSD which is the time domain analysis of the heart rate variability HRV was measured PPG waveforms were analyzed for height area width 50 maximum and minimum slope Data are presented as median and interquartile range Friedman ANOVA and Wilcoxon tests were used to identify changes in hemo dynamic and PPG parameters P 0017 was considered statistically significantThere were no significant changes in the blood pressure variables at LBNP30 but at and beyond LBNP75 the decreases in systolic mean and pulse pressure were significant as was the increase in diastolic pressure Heart rate increased significantly at LBNP30 reaching a maximum of 754 above baseline at the symptomatic phase while RMSSD showed significant reduction at LBNP75 Finger PPG height area width 50 and maximum slope decreased significantly at LBNP30 and during symptomatic phase they showed a reduction of 594 769 274 and 516 respectively Ear PPG height area width 50 and maximum slope did not change significantly until the LBNP75 reached During symptomatic phase the respective declines reached 393 610 214 and 349PPG waveform parameters may prove to be sensitive and specific as early indicators of blood loss These PPG changes were observed before profound decreases in arterial blood pressure The relative sparing of central cutaneous blood flow is consistent with the increased parasympathetic innervation of central structures

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