Direct Measurement of Intratracheal Pressure in Pediatric Respiratory Monitoring

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Abstract
We describe a method based on a Fabry-Perot interferometer at the tip of an optic fiber with a diameter of 0.25 mm for direct measurement of tracheal pressure in pediatric respiratory monitoring. The response time of the pressure transducer and its influence on the resistance of pediatric endotracheal tubes (internal diameter, 2.5 to 5 mm) during constant and dynamic flow at different ventilator settings in a lung model were measured. The transducer was positioned at −1.5 (inside), 0, and +1.5 cm (outside) relative to the tip of the endotracheal tube and compared with a reference pressure inside the trachea. The clinical application of the transducer was tested in five pediatric patients. The response time of the transducer was 1.3 ms. The influence of the fiberoptic transducer on tube resistance was negligible during constant flow in inspiratory and expiratory directions for all endotracheal tubes tested. There was no difference in pressure measurements with the transducer positioned at or 1.5 cm below or above the tip of the endotracheal tube during dynamic measurements. During clinical circumstances insertion of the fiberoptic transducer was easy, recordings were stable, and the safety of the patient was not jeopardized. The fiberoptic transducer provided a reliable and promising way of monitoring tracheal pressure in intubated pediatric patients. The presence of the probe did not interfere with either pressure-flow relationship or patient care and safety. The technique is proposed for monitoring of respiratory mechanics and calculation of changes in tube resistance caused by kinking and secretions.