A special peristaltic pump, designed and manufactured by Verder Autoclude is an important component in a haemodynamic monitoring system from the LiDCO Group.  This purpose designed, portable pump has unique features including single handed occlusion release.Monitoring key cardiovascular parameters is of critical importance to patient outcome.

In tandem with blood pressure and oxygen delivery, cardiac output is one of these vital indicators.  It is the volume of blood pumped through the heart per minute and has been a difficult parameter to measure.  Prior to the LiDCO system the cardiac output was usually determined with a special haemodynamic monitoring device in the form of a long catheter which is introduced into an artery in the neck, chest or groin and advanced through the heart to the pulmonary artery. This procedure is known as cardiac catheterisation and is one that is both time consuming and not without risk. The LiDCO cardiac sensor system has provided clinicians with a highly effective, minimally invasive alternative.  It assesses a patient’s haemodynamic status by measuring the dilution of lithium from the heart following the injection of small doses of lithium chloride via a venous line. From this results a computation of cardiac output.  As well as eliminating the need for catheterisation it is also a highly portable system that can be used equally well in a war zone as in an intensive care ward.

The special Verder Autoclude pump is responsible for withdrawing blood past a sensor that measures the lithium concentration.  The tested blood then goes into a waste bag.  The main stipulation was that instant tube occlusion – to shut off the blood flow – had to be accomplished single-handedly. This is vital as the nurse’s other hand has to be free to operate the three way valve that allows a gravity fed saline solution to wash the face of sensor in readiness for the next measurement.  

Such a pump simply did not exist as a standard offering.  Verder Autoclude therefore worked with LiDCO to create the optimum lightweight design for the application. The resultant pump has a spring loaded surface against which the tube is occluded.  The tube is released by the single operation of two levers which compress the spring.  

This arrangement ensures the pump remains physically stable during the procedure.To maximise patient safety the pump had to be battery operated but constant flow rate irrespective of battery condition was also a pre-requisite.  Under normal circumstances the performance of the dc motor and therefore the flow rate would decline as the battery runs out.

A battery monitoring circuit is therefore included on LiDCO’s Autoclude pump.  This detects any voltage change and stops the unit so that the battery can be replaced and the constant flow rate assured.
Although Verder Autoclude has a comprehensive range of standard peristaltic pumps for scientific, OEM and industrial applications it is also a UK manufacturer with a lot of experience in bespoke designs.  The LiDCO pump exemplifies this ability. It complements a real-time cardiac output monitoring system that in practice has proven to be both safe and easy to apply.