Robert H. Allen

Intrapartum risk factors for permanent brachial plexus injury

OBJECTIVE The purpose of this study was to compare maternal, neonatal, and second stage of labor characteristics in shoulder dystocia deliveries that result in permanent brachial plexus injury with shoulder dystocia deliveries that result in no injury. STUDY DESIGN Our cases were culled from a database of deliveries that resulted in permanent brachial plexus injuries and matched to control cases that were taken from a database of consecutive shoulder dystocia deliveries from one hospital. Deliveries that resulted in injury were excluded from the control cases; those cases with no recorded shoulder dystocia were excluded from the cases. Matching was for birth weight (+/-250 g), parity, and diabetic status. Rates of precipitous and prolonged second stage, operative delivery, neonatal depression, and average number of shoulder dystocia maneuvers used were compared between the two groups with chi(2) test, Fisher exact test, and the Student t test; a probability value of <.05 was considered significant. RESULTS There were 80 matched patients, of which 26 patients were nulliparous and 11 patients were diabetic. Mothers of the uninjured group were younger than those of the injured group (23.7+/-6.2 years vs 27.4+/-5.1 years, P<.001). The injured group had a significantly higher rate of 5-minute Apgar scores of <7 (13.9% vs 3.8%, P=.04). Differences in maternal weight, body mass index, height, race, gestational age, average number of maneuvers, head-to-body delivery interval, operative delivery rate, prolonged second stage rate, precipitous second stage rate, and sex were not significant between groups. The rates of precipitous second stage for both groups (28.0% injured and 35.0% uninjured) were more than triple the rates of prolonged second stage (9.5% injured and 11.3% uninjured). CONCLUSION No characteristic of second-stage of labor predicts permanent brachial plexus injury. Precipitous second stage is the most prevalent labor abnormality that is associated with shoulder dystocia.

Prioritizing posterior arm delivery during severe shoulder dystocia.

BACKGROUND Delivery of the posterior arm, or the Barnum maneuver, is at times used late in shoulder dystocia management algorithms, and is not often a first- or second-line management protocol. CASE A multiparous, diabetic patient, who was morbidly obese and had a residual obstetric brachial plexus injury, experienced a precipitous second stage of labor and severe shoulder dystocia. Attempts at the McRoberts maneuver with traction failed to deliver the fetus. In lieu of alternative maneuvers or continued attempts at traction, the posterior arm was delivered and the fetal trunk followed easily. CONCLUSION A geometric analysis reveals that using posterior arm delivery reduces the obstruction by more than a factor of two, relative to the McRoberts maneuver. We recommend earlier use of this maneuver during shoulder dystocia management.

Temporary Erb-Duchenne palsy without shoulder dystocia or traction to the fetal head.

BACKGROUND: Although many retrospective studies report that brachial plexus palsies occur after vaginal delivery in the absence of recorded shoulder dystocia, there are no known prospective reports by a treating clinician (PubMed, English language only, 1952–June 2004, search terms: shoulder dystocia, nonshoulder dystocia, obstetric brachial plexus injury, Erbs palsy, Erb-Duchenne palsy, spontaneous vaginal delivery). CASE: A multiparous patient presented with a birth plan requesting that the baby be allowed to deliver on its own, without traction on the head and without suctioning. Although induced at term for elevated blood pressure, the otherwise healthy patient experienced a normal labor with a 30-minute second stage. At delivery, which was videotaped by the father, the fetal head presented over an intact perineum in a right-occiput-anterior position. Without traction, the anterior shoulder delivered spontaneously with the next contraction and Valsalva, followed by the posterior shoulder. The trunk followed routinely. The average–weight for gestational age neonate exhibited an Erb-Duchenne palsy of the right (posterior) arm that resolved on the fourth day of life. CONCLUSION: Temporary Erb-Duchenne palsy can occur in the posterior arm after normal labor and spontaneous delivery without shoulder dystocia or traction on the fetal head.

Reducing the Risk of Shoulder Dystocia and Associated Brachial Plexus Injury

Despite persisting controversy over shoulder dystocia prediction, prevention, and injury causation, the authors find considerable evidence in recent research in the field to recommend additional guidelines beyond the current American College of Obstetricians and Gynecologists and Royal College of Obstetricians and Gynecologists guidelines to improve clinical practice in managing patients at risk for experiencing shoulder dystocia. In this article, the authors offer health care providers information, practical direction, and advice on how to limit shoulder dystocia risk and, more importantly, to reduce adverse outcome risk.

Cost-effective therapeutic hypothermia treatment device for hypoxic ischemic encephalopathy

Despite recent advances in neonatal care and monitoring, asphyxia globally accounts for 23% of the 4 million annual deaths of newborns, and leads to hypoxic-ischemic encephalopathy (HIE). Occurring in five of 1000 live-born infants globally and even more in developing countries, HIE is a serious problem that causes death in 25%–50% of affected neonates and neurological disability to at least 25% of survivors. In order to prevent the damage caused by HIE, our invention provides an effective whole-body cooling of the neonates by utilizing evaporation and an endothermic reaction. Our device is composed of basic electronics, clay pots, sand, and urea-based instant cold pack powder. A larger clay pot, lined with nearly 5 cm of sand, contains a smaller pot, where the neonate will be placed for therapeutic treatment. When the sand is mixed with instant cold pack urea powder and wetted with water, the device can extract heat from inside to outside and maintain the inner pot at 17°C for more than 24 hours with monitoring by LED lights and thermistors. Using a piglet model, we confirmed that our device fits the specific parameters of therapeutic hypothermia, lowering the body temperature to 33.5°C with a 1°C margin of error. After the therapeutic hypothermia treatment, warming is regulated by adjusting the amount of water added and the location of baby inside the device. Our invention uniquely limits the amount of electricity required to power and operate the device compared with current expensive and high-tech devices available in the United States. Our device costs a maximum of 40 dollars and is simple enough to be used in neonatal intensive care units in developing countries.

A biofidelic birthing simulator

The design, testing, and implementation of a novel birthing simulator (patent pending, 6 September 2005) developed specifically to research the delivery process and improve clinical training in uncommon but inevitable complicated human births is reported on. The simulator consists of a maternal model and an instrumented fetal model that are used in conjunction with an existing force-sensing system and a data-acquisition system. The maternal model includes a bony, rotatable pelvis, flexible legs, and an optional uterine expulsive system. The fetal model, which can be delivered repeatedly through the maternal model, is instrumented with potentiometers to measure neck extension, rotation, and flexion during delivery. Simulation of the brachial plexus within the model fetal neck allows measurement of stretch in those nerves at risk for injury during difficult deliveries. Elements mimic the range-of-motion properties of neonate. Two methods for measuring clinician-applied force during simulated deliveries provide trainees with the real-time assessment of their own traction force and allow researchers to correlate fetal neck motion and nerve stretch parameters with clinician-applied traction. Preliminary testing indicates the system is biofidelic for the final stages of the birthing process and can be used for training and research in obstetrics.

Simulating complicated human birth for research and training

We report on the design, testing and implementation of a novel birthing simulator developed specifically to research the delivery process and improve clinical training in uncommon but inevitable complicated human births. The simulator consists of a maternal model and an instrumented fetal model, used in conjunction with an existing force-sensing system and a data-acquisition system. The maternal model includes a bony, rotatable pelvis, flexible legs, and a uterine expulsive system. The fetal model, which can be delivered repeatedly through the maternal model, is instrumented with potentiometers to measure neck extension, rotation and flexion during delivery. Simulation of the brachial plexus within the model fetal neck allows measurement of stretch in those nerves at risk for injury during difficult deliveries. Wooden elements mimic the properties of neonatal bone and can break either spontaneously or purposely. Two methods for measuring clinician-applied force during simulated deliveries provide trainees with real-time assessment of their own traction force and allow researchers to correlate fetal neck motion and nerve stretch parameters with clinician-applied traction. Preliminary testing indicates the system is biofidelic for the final stages of the birthing process, and can be used for training and research in obstetrics.

Measuring bioimpedance in the human uterine cervix: towards early detection of preterm labor

We have created a bioimpedance probe designed to detect subtle changes in human cervical tissue composition in vivo, and thereby detect the onset of cervical remodeling in a noninvasive manner sooner than existing clinical methods allow. Our cervical bioimpedance measurement device, which can be used during a routine pelvic examination, is composed of a contoured probe with disposable tip and, within the probes handle, a bioimpedance sensor equipped with an integrated chip capable of generating sinusoidal voltage of varying frequencies. A constant force spring assures consistent measurements through a range of contact forces applied. An activation switch allows the operator to control the application of current. The sensor can be synchronized with a computer data storage and analysis system, which interfaces with the device. With the probe placed in contact with a collagen gels of varying concentration, the relationship between measured bioimpedance and collagen concentration is verified to be positive exponential (R/sup 2/=0.94) and repeatability in saline solution showed that measurements varied by less than /spl plusmn/10% over 20 trials. Finally, a variety of user-applied forces showed that impedance values plateau when forces exceed 1N.

The descent curve of the grand multiparous woman

OBJECTIVE The purpose of this study was to compare the descent curves and second-stage length among grand multiparous, nulliparous, and lower parity multiparous women. STUDY DESIGN Retrospective cohorts of spontaneously laboring, vertex-presenting, term, grand multiparous women (parity >or=5) from two medical centers over 5.5 years were matched randomly to nulliparous women and lower parity multiparous women controlled for age, hospital, and year of delivery. Descent curves were modeled from serial cervical examination data by the estimation of the probability of a given station occurring at a given time before delivery with the use of ordinal logistic regression. Curves were compared by Wald tests and adjusted for possible confounders. Second-stage lengths were compared by a Cox proportional hazards model. A probability value of <.05 was considered significant. RESULTS Grand multiparous women and lower parity multiparous women maintain a high station up to 1.5 hour before delivery and then rapidly transition to delivery. Nulliparous women transition to lower stations at a more gradual rate throughout the first and second stages. Descent curves differ among parity groups, with grand multiparous women maintaining a higher station for a longer time compared with either lower parity multiparous women or nulliparous women (P<.001). Once full dilation is reached, the median length of the second stage is 0.75, 0.85, and 1.75 hours for grand multiparous women, lower parity multiparous women, and nulliparous women, respectively (hazard ratios were 0.39 for nulliparous women vs grand multiparous women and 0.9 for lower parity multiparous women vs grand multiparous women). CONCLUSIONS Compared with lower parity multiparous women or nulliparous women, grand multiparous women maintain a higher station for a longer time before delivery but transition rapidly to delivery once full dilation is reached.

A wireless device for measuring hand-applied forces

We report on a wireless, electromyography (EMG)-based, force-measuring system developed to quantify hand-applied loads without interfering with grasping function. A portable surface EMG device detects and converts to voltage output biopotentials generated by muscle contractions in the forearm and upper arm during hand-gripping and traction activities. After amplifying and bandpass filtering, our radio frequency (RF)-based design operating at /spl sim/916 MHz wirelessly transmits those voltages to a data acquisition (DAQ) system up to 20 meters away. A separate calibration system is used to relate an individual users EMG signal to known pull and clenching forces during specific applications. Real-time EMG data is processed and displayed in software developed with LabView/spl trade/ (National Instruments, Austin, TX). Data is then converted to force data using individual calibration curves. With EMG electrodes placed over any major forearm muscle, calibration curves for seven subjects demonstrated linearity (R/sup 2/ > 0.9) and repeatability (<10% of average slope) to 110 newtons (N). Preliminary results in clinical application on newborn delivery suggest that this approach may be effective in providing an unobtrusive and accurate method of measuring hand-applied forces in applications such as rehabilitation and training.