Peripheral pulse tracing or plethysmography (PTG) can be conveniently studied by using a photo-electric transducer, which may be applied to the finger nail, or attached to the forehead, in either case, a light beam traverses the vascular bed, to register a rebound from the underlying blood flow. It is technically easy and relatively inexpensive, and can be used at the bedside during intensive care, as out-patients or at out-door locations.

Plethysmographic equipment is conveniently linked to an electrocardiograph or a recorder in out-patients, or attached to a cardiac monitor in the CCU I IOU for quick visual assessment of left ventricular function. PTG may be carried out during medical camps.

In this monograph all recordings were obtained from a fingertip transducer. The recordings have been repro-duced in the original size. The tracings in volunteers at 3780 m have been enlarged. Dedicatedly, Mr. Nasir ud Din Mohmand has redrawn the waveform contours for clarity.