INTRAUTERINE PRESSURE CATHETER PERFORMANCE IN AN IN-VITRO UTERINE MODEL - A SIMULATION OF PROBLEMS FOR INTRAPARTUM MONITORING

Objective: To compare pressure recordings from fluid-filled and sensor -tip catheters under varying intrauterine conditions in a uterine mode l. Methods: The uterine model was a 4.1-L dual-walled polyurethane bla dder with ports for dual catheter insertion. ''Contractions,'' generat ed by a programmable pump, were analyzed by computer. The first three experiments used an internal volume of normal saline and included eith er ''normal'' catheter placement, distal end of the catheter coated wi th petroleum jelly, or distal end of the catheter kinked at 150-degree s. The fourth and fifth experiments were similar to the first except t hat the internal volume was either pea soup or bovine blood. Each stud y had at least 20 consecutive pressure waveform sequences with peaks o f 100, 60, and 20 mmHg, and a resting baseline of 10 mmHg. Ascent and descent phases were each 25 seconds. Peak and baseline pressure phases were each 10 seconds. Results: Each catheter generated satisfactory p ressure waveforms, which were similar in all experiments except for th e one involving simulated meconium. In this trial, significant wavefor m damping occurred when pea soup filled the fluid catheter line (P < . 05, t test). Conclusions: In most extreme experimental conditions, the catheter types behaved similarly when detecting ''intrauterine'' pres sure. The sole exception, thick meconium simulation, suggests that flu id-filled catheters would be less reliable in this condition unless fl ushed continuously with saline.