COMPUTING TECHNIQUES FOR INTRAPARTUM PHYSIOLOGICAL DATA REDUCTION .1. UTERINE ACTIVITY

This and a succeeding paper describe real-time Computing techniques for data reduction and presentation, intended to assist clinical personnel in their management of labour. Active Pressure Area (APA), that is, the area under individual uterine contractions above baseline (Fig. 1), provides a single, quantitative index of uterine activity. It is independent of errors due to hydrostatic pressure and patient movement, which are inherent in intrauterine pressure (IUP) measurement by transcervical catheter. APA is simply measured by digital Integration. When used for clinical purposes, the term ‘ENERGY’ is used instead of APA, while ‘POWER’ refers to the amount of ‘energy’ expended during an epoch. Power is expressed in torr-seconds per second, so that vaiues are independent of epoch length. The POWERGRAM (Fjg. 2) provides a graphical summary of uterine activity by plotting Power against time. The probable effect of Power vaiues on labour progress and condition of mother and fetus are interpreted with respect to two ‘power limits’ (Fig. 3). An individual ‘frame’ of the POWERGRAM can display the results from up to 10 hours of data. The Powergram provides a summary of uterine activity which can be interpreted clinically to show trends in uterine activity which cannot be easily appreciated from visual inspection of an IUP chart recording. It has been shown to be of particular use to inexperienced clinical personnel and in induced/augmented labour where oxytocic drugs are used to control labour. From a technical point of view, the technique requires modest processing facilities, and is suitable for on-line, real-time purposes. Although the Powergram employs a graphical presentation it can be implemented using relatively simple, low cost, low resolution alphanumeric Output devices. © 1979, Walter de Gruyter. All rights reserved.