Abstract: A pulse oximeter and method of determining the oxygen saturation level of a patient's blood wherein a heartbeat related signal is used, as a reference to guide the averaging of optical pulse waveforms. The oximeter and method assign different weighting to different optical pulses based upon the amplitude of new pulse waveforms and the degree of similarity between it and the preceding waveform. A composite, averaged pulse waveform is then used in computing oxygen saturation level.

Abstract: A water trap for a gas analyzer includes self-sealing filters formed of a porous polymer that includes a cellulose extract that causes the polymer to become impermeable on contact with water. The water trap in this way automatically protects the gas analyzer from liquid contamination. Preferably, the gas analyzer monitors a pressure parameter of a pneumatic line connected to the water trap and provides an indication that the water trap should be replaced in the event this pressure parameter indicates an abnormal operating condition.

Abstract: An air tunnel device is provided for use in combination with a thermohygrter of the type where the change of resistance of the probe in response to changes in the ambient atmosphere is used to measure the temperature and humidity of the atmosphere. The device includes a housing which defines an air passageway therethrough, a probe support for mounting the probe of the thermohygrometer so that the probe is exposed to the air passagement in the housing and a fan mounted in the housing below the probe support for drawing air into the air passageway and thus providing air flow at a constant velocity past the probe.