Jan. 3, 2005 — Editor's Note: A novel birth simulator designed by biomedical engineers at Johns Hopkins University in Baltimore, Maryland, helps identify the least traumatic delivery procedure for shoulder dystocia and other problem deliveries and assists in physician training. Results of a study using this simulator, published in the Jan. 4, 2005, issue of the American Journal of Obstetrics and Gynecology, suggest that anterior Rubin's maneuver, in which the fetus is turned so that its spine faces the mother's abdomen, requires less force and exposes the brachial plexus to less trauma than other maneuvers.
The birth simulator, designed by senior author Robert H. Allen, PhD, a senior engineering lecturer and associate research professor of biomedical engineering at Johns Hopkins, consists of a maternal model with a three-dimensional bony pelvis, a fetal model, a force-sensing glove, and a computer-based data acquisition system. In the maternal model, the mock uterus is connected to a pneumatic pump that simulates the natural pattern of uterine contractions and force from a mother's pushing, and flexible legs can be moved to rotate the pelvis. The fetal model is outfitted with a joystick and elements to measure neck extension, rotation, and stretching of the brachial plexus during delivery. The force-sensing glove measures the traction used in delivery through built-in sensors connected via wires to a computer-based data-acquisition system.
To learn more about the implications of the simulator for clinical practice, research, and training, Medscape's Laurie Barclay interviewed lead author Edith D. Gurewitsch, MD, an assistant professor of gynecology and obstetrics in the Division of Maternal Fetal Medicine at Johns Hopkins.
Medscape: What was the impetus behind designing the birth simulator?
Dr. Gurewitsch: There were really two: education and research. Shoulder dystocia is an obstetric emergency in which the fetal head delivers through the vaginal introitus but the shoulders, obstructed behind the maternal pubic symphysis and/or the sacral promontory, fail to deliver without additional manipulation beyond the downward traction that is customarily applied by the delivering clinician. Without expeditious and appropriate management, both mother and fetus are at risk for injury, even death. Up to 27% of shoulder dystocia deliveries are associated with brachial plexus palsy, of which 10% are permanent.
Relatively uncommon and often unpredictable, shoulder dystocias, some more severe than others, are going to be encountered by every obstetric provider in practice; yet these same issues can make it difficult for any single provider to acquire adequate experience and training in its management. Medical training with the use of simulation, particularly for management of uncommon emergencies, is increasing. Presently, commercially available mechanical birth simulators model the normal birth process but fail to capture the shoulder dystocia phenomenon — hence the impetus to develop a mechanical simulator that could be used to research shoulder dystocia and train clinicians specifically in shoulder dystocia management.
At the same time that we aimed to create a device to assist training in specific maneuvers used for shoulder dystocia, it is also true that no single maneuver has proven superiority over another. Yet historical evidence, and more importantly, some biomechanical and geometric considerations, as we discussed in the article, suggest that in fact certain maneuvers could be more effective in resolving shoulder dystocia atraumatically than others. Unfortunately, prospective clinical study of this question is often unfeasible or unethical. For example, it is impossible to instrument a fetus in vivo to measure the stretch in the brachial plexus caused by either the natural birth process or the force applied to the head by the clinician.
A unique feature of our simulator is that it is equipped with bioengineering instrumentation that can measure force applied by the clinician and the mechanical response of the fetus, such as resultant stretch in the brachial plexus. The application then becomes that much more novel and valuable, because direct feedback can be provided to trainees so that they can learn to assess their own traction and evaluate its effect on the fetus. It also enables controlled, objective laboratory evaluation of different shoulder dystocia maneuvers, as was done for this study.
Medscape: What was the purpose of this study?
Dr. Gurewitsch: The aim was to compare two "categories" of shoulder dystocia maneuvers: maternal manipulation and fetal manipulation. The representative maternal manipulation in this study was the McRoberts' maneuver, in which the mother's hips and thighs are sharply flexed against the abdomen. The particular fetal maneuver studied was a slight, 30-degree rotation of the fetal shoulders from their pathological anteroposterior orientation within the pelvis to the more physiologic oblique orientation. This maneuver is known as Rubin's maneuver and can be performed by rotating the shoulders to either oblique diameter of the pelvis. We distinguished the two options as anterior Rubin's, in which the shoulders were rotated so that the fetus is oriented with its spine anteriorly, relative to the mother, and posterior Rubin's, in which the shoulders are rotated to the opposite oblique diameter with the fetal spine oriented posteriorly.
Medscape: What were the main findings of this study?
Dr. Gurewitsch: Thirty simulated deliveries were performed, 10 of each maneuver. The experiment was designed so that performance of any of these maneuvers would suffice to resolve the modeled shoulder dystocia when used singly as the initial maneuver. Thus, after performing the maneuver, the delivering clinician would then apply customary traction to complete the delivery and indeed the fetal model would deliver through the maternal model after initially having been obstructed. The clinician applied traction and the resultant neck extension, rotation, and elongation of the brachial plexus were measured and compared among the three maneuver groups: McRoberts', anterior Rubin's, and posterior Rubin's.
We discovered that fetal manipulation, in this instance Rubin's maneuver, required less force and caused less stretch in the brachial plexus than McRoberts' maneuver. Unexpectedly, we also found a difference between anterior Rubin's and posterior Rubin's, with anterior Rubin's requiring the least amount of clinician-applied force and resulting in the least amount of brachial plexus stretch.
Medscape: How well do you believe findings with the simulator will correlate with findings in clinical practice or research?
Dr. Gurewitsch: Although we do not make clinical recommendations based on a laboratory model, we highlight in the discussion section of our article that manipulation of fetal position after delivery of the head had been indeed practiced routinely at all deliveries in the 1950s and 1960s, when dystocia injury rates were at an all-time low. Based on this and now our results, we believe there is justification for reincorporating this practice even at regular deliveries. This should decrease the force applied at any delivery and, more importantly, will increase clinicians' familiarity with fetal manipulation so that they can be more adept and comfortable with its execution before it is truly needed in a shoulder dystocia emergency.
Medscape: Are additional studies planned?
Dr. Gurewitsch: Yes. This is only the first of several studies supported by a grant from the Centers for Disease Control and Prevention, National Center for Injury Prevention and Control's Program of Traumatic Injury Biomechanics Research. We intend to specifically evaluate the simulator for its utility and efficacy in resident training. We also plan other studies to objectively evaluate other shoulder dystocia maneuvers, such as Wood's screw and delivery of the posterior arm.
Medscape: What are other potential uses for the birth simulator, and what modifications would be needed to test the simulator in other types of problem deliveries?
Dr. Gurewitsch: Although initially designed to model the shoulder dystocia phenomenon specifically, in fact, our simulator should be modifiable to model other problem deliveries such as vaginal breech extraction. The maternal component is quite biofidelic already; the fetal model would require additional modifications to more accurately represent the regions of the hips and lower extremities. Since this was already constructed for the maternal model, adaptation to neonatal dimensions should be achievable.
Medscape: What are the hardware and training costs involved in using the simulator, and how widespread do you believe it will become as a research and training tool?
Dr. Gurewitsch: We continue to improve our invention, and one of our goals is to create a robust model that is affordable and can withstand multiple uses. We are also committed to making it "user-friendly" so that clinicians can use it to teach themselves and each other without need for mastery of difficult programming skills or interpretation of data.
Disclosures: The National Center for Injury Prevention and Control, a branch of the federal Centers for Disease Control and Prevention, funded this study. The inventors, including Drs.Gurewitsch and Allen and Paul Gilka, manager of the laboratory that housed the work, have filed a provisional patent on the simulator.
Am J Obstet Gynecol. 2005;192:000-000
Reviewed by Gary D. Vogin, MD
Medscape Medical News © 2005 Medscape
Cite this: Laurie Barclay. Birth Simulator for Shoulder Dystocia: A Newsmaker Interview With Edith D. Gurewitsch, MD - Medscape - Jan 03, 2005.
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