Dwayne R. Westenskow - US grants

When unilateral or asymmetric lung injuries are treated with conventional respiratory therapy, the results can be very unsatisfactory. At times it becomes necessary to separate the two lungs with an endobronchial tube and treat each lung individually. Though differential lung ventilation is used in many centers, little is known about how to divide the tidal volumes and adjust airway pressures in the two lungs to obtain the best outcome. Our work in dogs has shown that expiratory airway pressure (PEEP) allocation is critical. Oxygenation is profoundly better if PEEP levels are properly chosen. This proposal is aimed at defining the consequences of unilateral PEEP allocation during differential ventilation. Using an asymmetric pulmonary injury dog model, PEEP will be given in increments while outcome is measured in terms of shunt, PaO2, and gas exchange. Procedures will be introduced which are expected to alter the optimum PEEP allocation, changes in body position and vasoactive drugs, and the studies repeated. We expect the results from this project will define criteria for PEEP allocation during the acute phase following asymmetric pulmonary injury. Once techniques are found to optimize PEEP we plan to extend these results to a much wider population by studying diffuse bilateral pulmonary disease. The PEEP allocation results will be applied to a porcein model of diffuse injury. It will be determined it position induced changes in ventilation-perfusion can be reversed by unilateral PEEP. Further investigation will examine the use of asynchronous differential ventilation (ventilators 180 degrees out of phase) to lower mean airway pressure and reduce the adverse effects of PEEP in treatment of diffuse disease.

There is a growing need to better monitor neuromuscular blockage during and immediately after anesthesia. Experts state that the only reliable method of monitoring neuromuscular function is by stimulating a peripheral nerve and measuring the evoked response of a skeletal muscle. Neuromuscular monitoring helps the anesthesiologist with a more predictable and rational approach to the use of muscle relaxants, and hence in better patient care. Monitoring measures whether a patient is adequately paralyzed during surgery, and if he will be capable of breathing on his own after surgery is over. We plan to develop a handheld neuromuscular monitor to be used in the operating room. The monitor will deliver an electrical stimulus under computer control and will measure the patient's resultant muscle movement with a piezo-film sensor. the disposable, proprietary motion sensor conveniently attaches to the patient, making the unit much easier to use than currently available monitors. After completion of the prototype, it will be tested clinically in 10 patients to compare its accuracy with a standard measurement system. The ease of application gives considerable advantage to the motion sensor over currently available techniques, making it the preferred method of monitoring neuromuscular relaxation.

Present anesthesia machines have many displays and alarms but in fact do little to support the anesthesiologist's decision making in a crisis. The objective of this proposal is to develop an anesthesia workstation which includes an expert alarm system and central display in an effort to significantly reduce the anesthesiologists reaction time to of the anesthesiologist critical events. This system would detect critical events very quickly and provide a clearly defined cause for the problem. Phase I studies demonstrated in animals that an expert alarm system can detect 94% of the anesthesia machine failures and 89.4% of the breathing circuit failures. Phase II studies are planned to complete the development of the alarm system, focusing effort on training the alarms algorithm and developing simple disposable sensors. The alarm system will use neural network type artificial intelligence to identify failures in the patient breathing circuit and in the anesthesia machine. Input to the system will come from a small CO2/flow/pressure transducer array. Phase II includes the animal and clinical testing required to obtain FDA marketing approval.

minority institution research support;

Fetal monitoring is useful in assessing the progress of pregnancy and labor and can identify conditions that, if not corrected, lead to fetal or maternal mortality or morbidity. Monitors used to predict preterm labor are important in preventing prematurity from idiopathic premature labor. Commercially available sensors for monitoring intrauterine contractions and fetal heart rate use cumbersome belts and large and bulky sensors, which are uncomfortable and limit the patient's mobility. We plan to develop three devices for fetal monitoring. The first is uterine activity monitor. The sensor is an air-filled bubble, attached to the abdomen with adhesive. The adhesive presses the bubble slightly into the abdominal wall so changes in the uterine activity can be measured. The device shows excellent correlation when compared with a commercial monitor for the measurement of contraction duration (r2= .86 and for frequency of contractions (r2 = .99). The second device holds an ultrasonic Doppler transducer to the abdomen for the monitoring of fetal heart rate. The two products combine pressure and heart rate monitoring to provide a beltless system which can be conveniently and comfortably worn by the mother. Our third product will he a portable, battery-powered monitor for use in home health care. It will use both transducers and advanced signal processing to provide monitoring of preterm labor at home.

The plan is to develop a new technique for epidural blockade using an objective measure. The current "loss of resistance" technique depends on subjective feel of the anesthesiologist. Misinterpretation of this feel can result in complications such as dural puncture and misplacement of the needle tip. The spinal cord ends at L1 or L2. During puncture above this level may cause irreversible damage to the spinal cord. The electrical resistance of the epidural space in higher than the overlying ligaments. The electrical resistance of the epidural space in higher than the overlying ligaments. The epidural space can be identified by a sudden increase in tissue impedance. To measure the tissue impedance, a constant current will be passed between an epidural needle and a reference electrode. The configuration of the electrode will be used to identify the epidural space. The impedance technique will be considered effective if the time to start surgery can be shortened. Misplacement can be recognized immediately and the needle reinserted. It will not be necessary to wait to see whether the block works and repeat the procedure if not. We expect to see a reduction in the rate of complications, (dural puncture, failed blocks, etc).

bioengineering /biomedical engineering; biomedical equipment