Mathematical Models for Educational Simulation of Uterine Contractions During Labor

• Main Author: Bastos, Luisa Ferreira
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2010
• Subjects: Anatomy & physiology; Behavioral psychology; Catheters; Childbirth & labor; Communication; Decision making; Design; Drugs; Education; Emergencies; Endocrinology; Family physicians; Fetuses; Health care; Heart rate; Hemorrhage; Hormones; Hospitals; Hyperactivity; Induced labor; Information Technology; Mathematical models; Medical errors; Medical personnel; Medicine; Morphology; Obstetrics; Obstetrics and gynecology; Physiology; Surgery; Training; Virtual reality
• ISBN: 9798382435909

The use of simulation as a tool for teaching diagnostic and therapeutic skills in acute care medicine has increased over the last few years. It provides a controllable environment for training healthcare providers in rare, life-threatening situations, without any risks to real patients. Labor and delivery is a potentially hazardous process for both mother and fetus, and can benefit from educational simulation to increase patient safety and further improve outcomes. However, available obstetric simulators and training programs lack realism and capabilities, impeding fully immersive training of obstetric emergencies.In developed countries, intrapartum monitoring in high-risk cases involves continuous evaluation of the fetal heart rate and uterine contraction signals. A prompt detection of abnormalities in these signals is essential for a timely resolution of potentially harmful situations. Uterine contraction signals provide information on the onset and progress of labor, and assist in the diagnosis of obstetric emergencies, such as placental abruption and uterine rupture. They also aid in the evaluation of the relevance of certain fetal heart rate abnormalities. For example, fetal oxygenation may be compromised by uterine hyperstimulation following labor augmentation with oxytocin. In severe cases this can cause long-term neurological sequelae or fetal death. Immediate oxytocin curtail and rapid administration of drugs that inhibit contractility (tocolysis) are the best approaches to rapidly reverse the situation.This thesis presents an essential component of a high-fidelity simulator for normal and critical situations in labor and delivery: a set of interacting mathematical models for the simulation of uterine contraction signals. These models include a signal generator, scripts of evolving signal features, and continuous-time models of pharmacokinetics and pharmacodynamics of oxytocin and salbutamol. The model underlying the signal generator is a truncated Gaussian curve with programmable contraction amplitude, frequency, duration, and resting tone. Natural variability of these features and of the baseline pressure are approximated by deterministic trends and stationary stochastic processes. Time-and-event based scripts consist of linear interpolations between feature values at given points in time. These values are set based on data published in the scientific literature and/or in accordance with specific educational needs. The pharmacokinetic models for oxytocin and salbutamol consist of independent first order differential equations for drug concentrations normalized to infusion rate. The oxytocin pharmacodynamic model consists of an original adaptation of the traditional Emax model. It takes simulated spontaneously evolving contraction waveform features as a starting point, adding the effect of exogenous oxytocin. The salbutamol pharmacodynamic model consists of an original adaptation of the traditional inhibitory Emax model. It inhibits simulated spontaneously evolving and possibly augmented contraction waveform features in a multiplicative way. The combined models allow for the simulation of spontaneous evolution of uterine activity, labor augmentation with oxytocin, and to colysis with salbutamol. The variability of simulated uterine contraction signals, spontaneous evolution and drug sensitivities can be normal or abnormal, allowing the simulation of uterine contractions that corresponds to different patterns, patients and clinical situations.