Date Published: June 15, 2018
Publisher: BioMed Central
Author(s): Silvano R. Gefferie, Anouk W. J. Scholten, Kim A. E. Wijlens, M. Luísa Ferreira Bastos, M. Beatrijs van der Hout-van der Jagt, Hans Zwart, Willem J. van Meurs.
Several models for educational simulation of labor and delivery were published in the literature and incorporated into a commercially available training simulator (CAE Healthcare Lucina). However, the engine of this simulator does not include a model for the clinically relevant indicators: uterine contraction amplitude and frequency, and cervical dilation. In this paper, such a model is presented for the primigravida in normal labor.
The conceptual and mathematical models represent oxytocin release by the hypothalamus, oxytocin pharmacokinetics, and oxytocin effect on uterine contractions, cervical dilation, and (positive) feedback from cervical dilation to oxytocin release by the hypothalamus.
Simulation results for cervical dilation are presented, together with target data for a normal primigravida. Corresponding oxytocin concentrations and amplitude and frequency of uterine contractions are also presented.
An original empirical model for educational simulation of oxytocin concentration, uterine contractions, and cervical dilation in first-stage labor is presented. Simulation results for cervical dilation match target data for a normal patient. The model forms a basis for taking into account more independent variables and patient profiles and can thereby considerably expand the range of training scenarios that can be simulated.
Uterine contractions, fetal descent, and cervical dilation are used to assess progression of labor. These related phenomena vary greatly among parturients and may have an incidence on the condition of the fetus. Simulators allow for practice of normal and critical situations at will and at no risk to real patients. Several models for educational simulation of labor and delivery were published in the literature [1–3] and incorporated into a commercially available training simulator . The cited models make amplitude, frequency, duration, and resting tone of the uterine pressure waveform evolve spontaneously and under the influence of oxytocin and tocolytics. However, the relationships between these variables and cervical dilation are scripted.
Basic assumptions are made, similar to the ones in the article of Bastos et al.  and based on understanding of physiological relations, in order to keep the model as simple as possible, while approaching the target data of Zhang et al. . The subsystems and variables connecting them, as described in the introduction, are reflected in the block diagram of Fig. 1.Fig. 1Conceptual model for educational simulation of cervical dilation during first-stage labor. Oxt.: oxytocin
Figure 2 shows simulation results from the initial conditions d(0) = 2.00 cm, and m(0) = 275 mU, using the parameters listed in Table 1. The stars in Fig. 1 correspond to dilation data for patient A in Zhang et al. . This patient was admitted at 2 cm and labor progressed to 10 cm with labor considered non-protracted.Fig. 2Simulation results and dilation target data
Simulated dilation matches dilation in a normal patient in an approximation that is considered realistic enough for educational simulation. Parameters P2 and P11 were adjusted to achieve this match. Further research could address which parameters are patient- or population-specific and can be used to simulate different labor types. The model parameter estimation procedure could then be formalized so that a clinical instructor can easily use it to meet his or her educational objectives. Ongoing work involves expanding the set of target data and matching simulation results to them, to enhance model validity and demonstrate the possibility to match different patient profiles. Critical analysis of the pharmacokinetic model may be necessary. It would also be interesting to explore validity of the model for exogenous oxytocin administration.
An original empirical model for educational simulation of oxytocin concentrations, uterine contractions, and cervical dilation in first-stage labor is presented. Simulation results for cervical dilation match target data for a normal patient. The proposed model forms a sound, explicit basis for taking into account more independent variables and patient profiles, and thereby considerably expand the range of training scenarios that can be simulated.