Advances in photoplethysmography: beyond arterial oxygen saturation

Abstract

Purpose Photoplethysmography permits continuous measurement of heart rate and peripheral oxygen saturation and has been widely used to inform clinical decisions. Recently, a myriad of noninvasive hemodynamic monitoring devices using this same technology have been increasingly available. This narrative review aims to summarize the principles that form the basis for the function of these devices as well as to comment on trials evaluating their accuracy and clinical application. Principal findings Advanced monitoring devices extend photoplethysmography technology beyond measuring oxygen concentration and heart rate. Quantification of respiratory variation of the photoplethysmographic waveform reflects respiratory variation of the arterial pressure waveform and can be used to gauge volume responsiveness. Both the volume-clamp and physiocal techniques are extensions of conventional photoplethysmography and permit continuous measurement of finger arterial blood pressure. Finger arterial pressure waveforms can subsequently inform estimations of cardiac output. Conclusions Although respiratory variations of the plethysmographic waveform correlate only modestly with the arterial blood pressure waveform, fluid responsiveness can be relatively consistently assessed using both approaches. Continuous blood pressure measurements obtained using the volume-clamp technique may be as accurate as conventional brachial noninvasive blood pressure measurements. Most importantly, clinical comparative effectiveness studies are still needed in order to determine if these technologies can be translated into improvement of relevant patient outcomes. RésuméObjectif La photopléthysmographie permet la mesure continue de la fréquence cardiaque et de la saturation en oxygène périphérique, et elle est largement utilisée pour les prises de décisions cliniques. Depuis peu, un très grand nombre de dispositifs non invasifs de surveillance hémodynamique utilisant la même technologie envahit le marché. Cette synthèse narrative vise à résumer les principes à la base du fonctionnement de ces dispositifs et à commenter les essais évaluant leur exactitude ainsi que leurs applications cliniques. Constatations principales Les dispositifs de surveillance avancée étendent la technologie de photopléthysmographie au-delà de la mesure de la concentration en oxygène et de la fréquence cardiaque. La quantification de la variation respiratoire du tracé photopléthysmographique reflète la variation respiratoire du tracé de pression artérielle et peut servir à jauger la réactivité au volume. Les deux techniques de compression volumique (volume-clamp) au doigt et la technique physiocal sont des prolongements de Author contributions Karsten Bartels wrote approximately 50% of the manuscript and critically edited the remainder. Robert H. Thiele wrote approximately 50% of the manuscript and critically edited the remainder.

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