Plethysmography: the new wave in haemodynamic monitoring--a review of clinical applications.

The plethysmograph, a useful, non-invasive circulatory assessment capability featured on most modern pulse oximeters, provides a waveform representation of pulsatile peripheral blood flow, from which can be drawn assessments of both the peripheral and central circulation. Implementation and maintenance of plethysmography monitoring is straightforward and uncomplicated by virtue of its non-invasiveness. Yet despite its capabilities, ease of use and widespread availability it remains an underutilised data source. Diagnostic and monitoring capabilities of the device include heart rate and rhythm monitoring, detection of myocardial and valvular dysfunction, assessment of intra-aortic balloon pump performance when pressure waveforms are unobtainable, detection and measurement of pulsus paradoxus, improved performance of the Allen's test and detection of peripheral vascular diseases, peripheral vasoconstriction and developing shock. This paper describes the range of established applications of plethysmography, reviews pertinent literature and describes the directions in which, in the absence of supportive literature, clinical practice is finding applications.