Variations in pulse oximetry plethysmographic waveform amplitude induced by passive leg raising in spontaneously breathing volunteers

PurposeNoninvasive methods that could predict preload responsiveness are lacking. Our objective was to evaluate variations in pulse oximetry plethysmographic (POP) waveform amplitude (ΔPOP) induced by passive leg raising (PLR).MethodsWe attached a pulse oximeter to the middle finger of 25 spontaneously breathing volunteers at several time points: baseline (ie, semirecumbent position), during PLR at 60° while each subject's trunk was lowered in a supine position at 1 minute, and after putting the patient back in the semirecumbent position (5-minute rest). Heart rate, noninvasive arterial pressures (mean arterial pressure and pulse pressure), maximal POP (POPmax), minimal POP (POPmin), and ΔPOP defined as [POPmax − POPmin]/[(POPmax + POPmin)/2] were recorded using a monitor.ResultsHeart rate, mean arterial pressure, pulse pressure, POPmax, and POPmin values were not different at baseline, during PLR at 1 minute, and after the 5-minute rest (repeated-measures analysis of variance). The median ΔPOP significantly decreased from 16% (95% confidence interval = 11%-23%) to 11% (95% confidence interval = 8%-14%) (P < .05) and then increased to 13% (95% confidence interval = 10%-21%) after the 5-minute rest (P = nonsignificant).ConclusionPassive leg raising induces a significant decrease in ΔPOP among spontaneously breathing volunteers.