LAUSR

PURPOSE Camera-based photoplethysmography (cbPPG) remotely detects the volume pulse of cardiac ejection in the peripheral circulation. The cbPPG signal is sourced from the cutaneous microcirculation, yields a two-dimensional intensity map and is therefore an interesting monitoring technique. In this study we investigated, whether cbPPG is in general sufficiently sensitive to discern hemodynamic conditions. METHODS cbPPG recordings of seventy patients recovering from cardiac surgery were analyzed. Photoplethysmograms were processed offline and the optical pulse power (OPP) of cardiac ejection was calculated. Hemodynamic data, image intensity and patient movements were recorded synchronously. The effects of hemodynamic parameters and measurement conditions on the patient's individual OPP variability and their actual OPP values were calculated in mixed-effects regression models. RESULTS Mean arterial pressure, pulse pressure, heart rate and central venous pressure significantly explained the individual OPP variability. Pulse pressure had the highest explanatory power (19.9%). Averaged OPP significantly increased with pulse pressure and mean arterial pressure (p < 0.001, respectively) and decreased with higher heart rate (p = 0.024). Central venous pressure had a two-directional, non-significant effect on averaged OPP. Image intensity and patient movements did significantly affect OPP. After adjustment for hemodynamic co-variables and measurement conditions, the effect of pulse pressure and heart rate remained unchanged, whereas that of mean arterial pressure vanished. CONCLUSION cbPPG is sensitive to hemodynamic parameters in critical care patients. It is a potential application for monitoring the peripheral circulation. Its value in a clinical setting has to be determined.