Abstract: A microprocessor controlled volumetric infusion pump is set as to volume and rate of infusion by two digipots (shaft encoders) each having sixteen detented positioned in 360 degrees. The microprocessor is programmed such that the extent to which the parameter is changed for a given rotation of its setting digipot depends on the speed with which the digipot is rotated. For slow or normal rotation, unit change in parameter is produced for each detented position traversed. Faster rotation causes the setting to jump from one to the next of a series of preselected preferred settings, irrespective of the number of detented positions traversed. The direction of rotation determines whether the setting increases or decreases.

Abstract: A device for detecting air in large bore thin walled transparent tubing, including a body providing accommodation for the tubing; an LED in a passage body for transmitting light energy towards the tubing; a phototransistor mounted in an orthogonally extending passage for receiving light transmitted by LED and modified by changes in the constituency of fluid passing through tubing; and an optical spacer in the form of a slotted collar of material optically matched to the material of tubing occupying space between LED and the tubing and phototransistor.

Abstract: A pumping arrangement including a squeezing device for deforming a length of pliant p.v.c. tubing first in one direction locally to reduce its volume and in another tending to restore its original cross-section and, on either side of squeezing device, inlet and outlet valves which operate by occluding the tubing. The squeezing device and the valves are controlled by a microprocessor control unit such that inlet valve is open and outlet valve shut while the squeezing device is relaxed and thereafter outlet valve is open and inlet valve shut while the squeezing device is operated to deform the tubing, this sequence repeating. Downstream of the output valve is a pressure responsive device providing input to the control unit whereby upon a rise in pressure in the delivery portion of tubing due to a restriction, the squeezing device is disabled and valves are open together to allow excess fluid to pass back towards the fluid source.

Abstract: An arrangement for monitoring the pressure of fluid flowing through pliant tubing forming part of a system for the intravenous supply of fluids to a patient under medical treatment in which the tubing is caused to assume an elongate cross-section and a linear voltage displacement transducer having a spring loaded plunger is arranged to apply pressure in a flattened region of the tubing wall to provide indications of contact area movement and thus variations in fluid pressure. Compensation for movement of the contact area after pressure is applied due other than to variations in pressure is provided by a sampler which regularly samples the output of tranducer and provides inputs to a comparator directly and via a shift register so that one sample is compared with an immediately preceding sample. If the difference exceeds the threshold of a threshold circuit, which is indicative of fluid pressure change, an alarm is sounded.