Abstract: Device and method for testing the accuracy of pulse oximeters used in estimating arterial blood saturation levels. The device is for use in enabling a pulse oximeter to measure the absorption of the radiation emitted by the oximeter by a pulsatile liquid contained within the device, which device comprises the liquid, a resiliently flexible displaceable member adjacent the liquid which in operation is manually made to rhythmically move with a steady frequency and amplitude so as to effect a change in the depth of a volume of the liquid in the direction acted upon by the radiation such that the liquid is operably provided in pulsatile form while under the influence of the radiation. The device provides a cheap and convenient method of testing the accuracy of the pulse oximeters.

Abstract: Device and method for testing the accuracy of pulse oximeters used in estimating arterial blood saturation levels. The device is for use in enabling a pulse oximeter to measure the absorption of the radiation emitted by the oximeter by a pulsatile liquid contained within the device, which device comprises the liquid, a resiliently flexible displaceable member adjacent the liquid which in operation is made to rhythmically move with a steady frequency and amplitude so as to effect a change in the depth of a volume of liquid in the direction acted upon by the radiation such that the liquid is operably provided in pulsatile form while under the influence of the radiation. The device provides a cheap and convenient method of testing the accuracy of the pulse oximeters.

Abstract: The invention provides a device capable of monitoring the concentration of anaesthetic gas in a breathing mixture being delivered to a patient to cause narcosis and consists essentially of an electronic transducer which provides an output signal proportional to the concentration of anaesthetic gas in a breathing mixture. The transducer includes a sensor having first and second electrical conductors positioned in proximity to one another and defining a space between the conductors. A substantially non-conductive material fills the space between the conductors and has a molecular structure which permits the absorption of the anaesthetic gas thereby causing variations in the electrical characteristics of the sensor. An electrical circuit is provided which is coupled to the sensor to provide the output signal which is proportional to the variations in the electrical characteristics of the sensor.

Abstract: The invention provides apparatus for measuring the rate of flow of liquid being circulated in a closed loop system by a pump using a bolus of indicator injected suddenly into the system upstream of the pump and a sampling station downstream of the pump. The apparatus includes signal means for location at the sampling station to provide an electrical signal proportional to the indicator passing this station. The electrical signal has an increasing portion, a decaying exponential portion, and a distorted portion caused by recirculation of the indicator in the system. A signal analyzer is coupled to the signal means to receive the electrical signal and includes a wave generator sensitive to the exponential portion and including extrapolation means for providing a portion of the exponential curve lost by interference by recirculation. The signal analyzer provides an output signal corresponding to the increasing portion, the exponential portion, and the portion provided by the extrapolation means.