EVALUATION OF CATHETER-MOUNTED TRANSDUCERS FOR INTRA-ESOPHAGEAL PRESSURE RECORDING IN RESPIRATORY-FUNCTION TESTS

Oesophageal pressure measurements in respiratory function tests are co mmonly performed using a balloon-catheter system. This study investiga tes the usefulness of catheter-mounted pressure transducers as an alte rnative to balloon-catheter systems. Calibration related physical prop erties of the catheter mounted pressure transducers are evaluated in v itro. The behaviour of these transducers in vivo is evaluated in ten v olunteers by relating pressures measured in the oesophagus to airway o pening pressures and by comparing these relationships with those seque ntially obtained by a balloon-catheter system. The catheter-mounted pr essure transducers show no drift after a proper preparation procedure. These catheters, with integrated pressure transducers, are tolerated significantly better by the subjects than are balloon catheters. The c atheter-mounted pressure transducers are found to give an equivalent p erformance compared with the balloon-catheter system, if relative pres sures are of interest. However, unpredictable and uncontrollable shift s in offset occur during the in vivo measurements, disturbing absolute pressure readings. Possible explanations for these shifts are the pre sence of bubbles and adhesion of mucus to the transducers, exerting Va n der Waals forces, and contact with the tissue of the oesophageal wal l. These shifts are found to be quite stable throughout a period of me asurement and therefore of minor disturbance to relative pressure meas urements, for instance in assessing the elastic properties of lungs.