The accuracy of the flowrate in flush-devices of disposable pressure transducers.

Background: Arterial and venous pressure is commonly measured using fluid filled catheters. To avoid obstruction they are continuously spilled by a flush-device. The accuracy of the flowrate has not been investigated previously.
Methods: The accuracy of 5 different flush-devices available in Switzerland was checked for flowrate when factory new, after a single sterilization with ethylen-oxide, in a long-term test over 96 hours, after repeated handling of the integrated bypass and under application of a pulsing counter-pressure.
Results: Flow is linearly related to differential-pressure and is constant over time. The flow of each flush-device at 200 mmHg differential-pressure was below the indicated 3 ml per hour (1.69 - 2.49 ml/h). Sterilization in two types produced a significant but not relevant difference in flowrate. Longtime-use, bypass actuation and pulsing pressure did not alter the flowrate significantly (p <0.05). In two factory-new flush-devices and 4 re-used ones a plugged capillary induced cessation of flow.
Conclusions: Flowrate in flush-devices is accurate under sterilization, longtime use, bypass-actuation and pulsing counter pressure. A plugged capillary occurred in a few new and reused flush-devices, which can be the explanation for clotted catheters in clinical use.