Abstract
A new perfusion and transducer unit for ambulatory blood-pressure recording is described, followed by reports of both the laboratory evaluation of the unit and experience with its clinical use. The major change from earlier systems is the perfusion system, now based on an electrically driven ‘delta’ pump. Pressure is measured by a semiconductor strain-gauge pressure transducer. Laboratory evaluation has shown that the transducer with associated tubing and cannulae has a satisfactory frequency response, considerably better than that of the recording system normally used. Both quantitatively and qualitatively there was a very close correspondence between signals obtained from the entire Oxford system (including recording and replay) and signals obtained directly by means of a catheter-tip transducer. Small, but consistent, signal drifts attributable to battery behaviour are described. The system appears remarkably insensitive to temperature variations within the range of expected ambient temperatures. Delta pump performance is satisfactory, producing essentially constant perfusion rates. Clinically, the system has been used for the recording of ambulatory blood pressures in 110 patients for periods up to 72 h with satisfactory results. Reliability appears good, with minimal artefacts atributable to the equipment. This transducer and perfusion system appears to be fully satisfactory and considerably more reliable than the earlier designs.
Published Version
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