Medline ® Abstracts for References 1,2

The reliability of intrauterine pressure measurements was studied by placing two catheters in the same uterus in women in labor. Nineteen parturients were studied, five with two Intran I catheters in different pockets of amniotic fluid, five with two Intran II catheters in different pockets, and nine with two Intran II catheters in the same pocket of amniotic fluid. Among 1429 contractions studied, the catheters showed differences of pressure of less than 5 mmHg in 86% of contractions and of less than 10 mmHg in 94%. When cumulative uterine activity was calculated for each labor, the difference in the total active pressures shown by the two catheters was less than 5% in 17 cases and 5% or more in two cases. These differences are unlikely to be of any importance in the management of labor.

OBJECTIVE: To assess the reliability of intrauterine pressure measurements in labour with transducer tipped catheters.

DESIGN: Prospective clinical study.

SETTING: Delivery ward, National University Hospital, Singapore.

SUBJECTS: 20 women admitted in early labour were randomly allocated to two groups.

INTERVENTIONS: Women in the first group had two catheters that had been tied together introduced transcervically into the same amniotic fluid pocket. The second group had two catheters introduced in different directions so that each catheter tip was in a different pocket of amniotic fluid.

MAIN OUTCOME MEASURE: The contraction to contraction pressure difference recorded by the two catheters in the same uterus. In addition, thecumulative uterine active pressure generated by one catheter was compared with that of the other.

RESULTS: There were differences in peak pressure of up to 4-5.3 kPa (30-40 mmHg) during some contractions. The difference in pressure recordings between the two catheters could not be explained by effects of loculation of amniotic fluid. However, the pressures recorded were not systematically higher in one catheter than in the other. Cumulative uterine activity was very similar when assessed by each catheter in the same uterus.

CONCLUSION: Intrauterine pressure measurements using transducer tipped catheters provide reliable information on the cumulative pressure wherever the catheter tip was sited in the uterus, but there are variations in pressures recorded during individual contractions.