An infra-red reflectance system for ambulatory characterization of left ventricular function.

An optical method of detecting the arterial pulse is described. The system employs an infra-red light emitting diode (LED) and phototransistor arranged to operate in the reflectance mode and sited over the superficial temporal artery. The LED is pulsed and the signal recovery system performs a synchronous sample-and-hold function on the phototransistor output. This arrangement improves peak light output relative to ambient light and extends battery life. The transducer, used at its site of application over the temporal artery produces an arterial pulse-wave relatively resistant to motion artefact, and is thus suitable for ambulatory monitoring applications. The pulsewave can be used to obtain measurements of left ventricular ejection time with the accuracy required for clinical systolic time interval investigations.