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Biomedical subjects

H A Schwid

Publications and source records attributed to H A Schwid.

At least 19 recordsLinked to original sources
PubMed2001

Screen-based anesthesia simulation with debriefing improves performance in a mannequin-based anesthesia simulator.

BACKGROUND: Previous investigations have established the need for improved training for management of anesthetic emergencies. Training with inexpensive screen-based anesthesia simulators may prove to be helpful. PURPOSES: We measured the effectiveness of screen-based simulator training with debriefing on the response to simulated anesthetic critical incidents. METHODS: Thirty-one 1st-year clinical anesthesia residents were randomized into 2 groups. The intervention group handled 10 anesthetic emergencies using the screen-based anesthesia simulator program and received written feedback on their management, whereas the traditional (control) group was asked to study a handout covering the same 10 emergencies. All residents then were evaluated on their management of 4 standardized scenarios in a mannequin-based simulator using a quantitative scoring system. RESULTS: The average point score for the simulator-with-debriefing group was 52.6 +/- 9.9 out of 95 possible points. The traditional group average point score was 43.4 +/- 5.9, p = .004. CONCLUSIONS: Residents who managed anesthetic problems using a screen-based anesthesia simulator handled the emergencies in a mannequin-based anesthesia simulator better than residents who were asked to study a handout covering the same problems. Computer simulations with feedback are effective as a supplement to traditional residency training methods for the management of medical emergencies.

Anesthesiology↗
PubMed2000

Computers in radiology. The sedation, analgesia, and contrast media computerized simulator: a new approach to train and evaluate radiologists' responses to critical incidents.

BACKGROUND: Awareness and preparedness to handle sedation, analgesia, and contrast-media complications are key in the daily radiology practice. OBJECTIVE: The purpose is to create a computerized simulator (PC-Windows-based) that uses a graphical interface to reproduce critical incidents in pediatric and adult patients undergoing a wide spectrum of radiologic sedation, analgesia and contrast media complications. MATERIALS AND METHODS: The computerized simulator has a comprehensive set of physiologic and pharmacologic models that predict patient response to management of sedation, analgesia, and contrast-media complications. Photorealistic images, real-time monitors, and mouse-driven information demonstrate in a virtual-reality fashion the behavior of the patient in crisis. RESULTS: Thirteen pediatric and adult radiology scenarios are illustrated encompassing areas such as pediatric radiology, neuroradiology, interventional radiology, and body imaging. The multiple case scenarios evaluate randomly the diagnostic and management performance of the radiologist in critical incidents such as oversedation, anaphylaxis, aspiration, airway obstruction, apnea, agitation, bronchospasm, hypotension, hypertension, cardiac arrest, bradycardia, tachycardia, and myocardial ischemia. The user must control the airway, breathing and circulation, and administer medications in a timely manner to save the simulated patient. On-line help is available in the program to suggest diagnostic and treatment steps to save the patient, and provide information about the medications. A printout of the case management can be obtained for evaluation or educational purposes. CONCLUSION: The interactive computerized simulator is a new approach to train and evaluate radiologists' responses to critical incidents encountered during radiologic sedation, analgesia, and contrast-media administration.

Adult↗
PubMed2000

Systolic blood pressure at end-expiration measured by the automated systolic pressure variation monitor is equivalent to systolic blood pressure during apnea.

OBJECTIVE: It is necessary to define a reference systolic arterial blood pressure (RP) to calculate delta-Up (dUp) and delta-Down (dDown) for systolic pressure variation. Most studies define the reference pressure as the average systolic blood pressure during a short period of apnea. We describe an automated systolic pressure variation monitor that measures airway pressure and defines the reference pressure as the systolic blood pressure at end-expiration. The present study compares the reference systolic blood pressure measured at end-expiration by the automated systolic pressure variation monitor and the reference systolic blood pressure measured during apnea to test whether the end-expiration value is an adequate substitute for the value during apnea. METHODS: After obtaining informed consent, 108 sets of measurements of systolic pressure variation (SPV) were made in 20 intubated, mechanically-ventilated, anesthetized patients by the automated SPV monitor and during apnea. Measurements were taken during periods of hemodynamic stability defined as three consecutive end-expiratory systolic blood pressures within four mmHg of each other. The three systolic pressures at end-expiration were averaged (RPmonitor). Immediately following these measurements, the ventilator was turned off and the systolic blood pressure was measured at 6, 8, 10 and 12 seconds of apnea. The reference pressure during apnea (RPapnea) was defined as the average of the systolic blood pressure at 8, 10 and 12 seconds of apnea. For each measurement set, RPmonitor and the systolic blood pressure at 6 seconds of apnea (SBP6) were compared to RPapnea using Bland-Altman analysis. RESULTS: Bland-Altman analysis for the difference between SBP6 and RPapnea yielded a small bias of -0.3 mmHg with standard deviation of 1.3, indicating that the systolic pressure tends to continue to increase slightly after 6 seconds of apnea. Results were similar for the difference between RPmonitor and RPapnea (-0.2 +/- 3.1 mmHg). CONCLUSIONS: dUp and dDown are calculated using the reference pressure. RPmonitor is an average of 0.2 mm Hg less than RPapnea, thus dUp calculated by the automated SPV monitor is an avenge of 0.2 mm Hg greater than dUp measured by the reference pressure during apnea and dDown is 0.2 mm Hg less. Since the bias of -0.2 mmHg is clinically insignificant, there is acceptable agreement between the reference pressure obtained during apnea and that obtained by the automated SPV monitor at end-expiration. The mean difference between RPmonitor and RPapnea is explained by the continued rise in systolic pressure during the period of apnea as demonstrated by the difference between SBP6 and RPapnea.

Anesthesia↗
PubMed2000

Anesthesia simulators--technology and applications.

Anesthesia simulators are rapidly becoming more prevalent worldwide. Several types of anesthesia simulators utilizing a variety of technologies are available. High fidelity mannequin-based simulators, low fidelity screen-based simulators, and relatively inexpensive intermediate fidelity simulators have found applications in training, assessment of clinical competence, and research. A number of recent studies support the use of anesthesia simulators and may lead to widespread adoption of simulation in other fields of medicine.

Anesthesia↗
PubMed1999

Use of a computerized advanced cardiac life support simulator improves retention of advanced cardiac life support guidelines better than a textbook review.

OBJECTIVE: To determine whether an advanced cardiac life support (ACLS) computer simulation program improves retention of ACLS guidelines more effectively than textbook review. DESIGN: Randomized, controlled trial. SETTING: Academic medical center. PARTICIPANTS: Forty-five anesthesia residents and faculty tested 10 to 11 months after ACLS provider course training. INTERVENTION: Participants were randomized and asked to prepare for a mock resuscitation (Mega Code) with either textbooks or a computerized ACLS simulation program. MAIN OUTCOME MEASURE: Performance on a standardized Mega Code examination that required application of supraventricular tachycardia, ventricular fibrillation, and second-degree Type II atrioventricular block algorithms. Mega Code sessions were administered by an instructor who was blinded as to the subject group. The sessions were videotaped and scored by two evaluators who also were blinded as to the subject group. RESULTS: Participants who used the ACLS simulation program scored significantly higher (mean 34.9 +/- 5.0 [SD] of 47 possible points) than participants who reviewed using a textbook (29.2 +/- 4.9); p < .001. Pass-fail rates for the algorithms were also higher for the group that reviewed with the simulator (mean 2.5 +/- 0.5 of 3 possible passes) than the group that used the textbook (1.6 +/- 1.0); p = .001. CONCLUSIONS: Use of a computerized ACLS simulation program improves retention of ACLS guidelines better than textbook review.

Academic Medical Centers↗
PubMed1995

The effect of graded hemorrhage and intravascular volume replacement on systolic pressure variation in humans during mechanical and spontaneous ventilation.

In dogs and humans, the magnitude of the variation in systolic pressure (SPV) over the respiratory cycle during mechanical ventilation appears to be inversely related to intravascular volume. Also reported to correlate with changes in volume status is delta down, the difference between systolic pressure at end-expiration and the lowest value during the respiratory cycle. These variables were examined during graded hemorrhage in eight anesthetized, mechanically ventilated subjects, and seven awake, spontaneously breathing subjects. SPV and delta down were measured in sequence at baseline, after 500 mL blood removal, after 1000 mL (total) blood removal, after 500 mL hetastarch replacement, after 1000 mL (total) hetastarch replacement, and after 500 mL normal saline (NS). Repeated-measures analysis of variance was used to test the significance of the change in SPV and delta down among the interventions. During mechanical ventilation, each 500-mL hemorrhage significantly increased SPV and delta down, and each 500-mL hetastarch infusion significantly decreased SPV and delta down. After hetastarch, both SPV and delta down were smaller than at baseline and may explain why the infusion of NS caused nonsignificant reductions in SPV and delta down. A SPV of 5 mm Hg or less, or a delta down of 2 mm Hg or less appeared to indicate minimal intravascular volume depletion. During spontaneous ventilation, delta down could not be determined accurately in several subjects, and SPV did not change in the appropriate direction in all cases of hemorrhage and volume infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Educational computer simulation of malignant hyperthermia.

An educational graphic simulator was developed to provide an interactive learning environment to practice the diagnosis and treatment of malignant hyperthermia. The program incorporates a set of dynamically interacting models to present the physiologic changes associated with malignant hyperthermia and the simulated patient's response to management. Cardiovascular, respiratory, and temperature changes are presented through a graphic display of the operating room monitors. Mouse-driven input is used to manage the airway, control ventilation, manage cardiovascular and rhythm disturbances, and control fluids, electrolytes, and temperature. Medications, including dantrolene, antidysrhythmics, diuretics, and sodium bicarbonate, can be administered. Four simulated patients with different presentations of malignant hyperthermia are included to illustrate variations in the syndrome. Two of these patients are described in detail.

Adult↗
PubMed1992

Anesthesiologists' management of simulated critical incidents.

Human error is believed to contribute to the majority of negative anesthesia outcomes. Because retrospective analysis of critical incidents has several shortcomings and prospective studies are limited by the low frequency of critical incidents, an anesthesia simulator was used to evaluate the management of simulated emergency situations by ten anesthesia residents, ten faculty anesthesiologists, and ten anesthesiologists in private practice in order to identify specific patterns of errors in diagnosis and treatment. The simulator is a computer program that presents the patient, monitors, and management choices in a graphical display on an IBM or compatible personal computer. Many errors were observed in the management of these emergency situations, and even anesthesiologists with years of experience made serious errors. Although all experienced anesthesiologists correctly diagnosed simulated esophageal intubation, two residents misinterpreted the lack of end-tidal carbon dioxide. Only 40% of subjects correctly diagnosed simulated anaphylactic reaction; 27% adequately treated simulated myocardial ischemia; and 30% managed a simulated cardiac arrest according to Advanced Cardiac Life Support (ACLS) guidelines. Problems with continuous infusions of vasoactive agents were common. Fixation errors or failure to revise a plan in the presence of inconsistent cues were made by 63% of subjects. The subjects that gathered more information during simulated anaphylaxis made the correct diagnosis more often and made fewer treatment errors. The time since the last ACLS training was found to be an important predictor of correct management of simulated cardiac arrest.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaphylaxis↗
PubMed1991

An objective comparison of intrathecal lidocaine versus fentanyl for the treatment of lower extremity spasticity.

The reduction of spasticity after administration of intrathecal fentanyl, 35 micrograms, and intrathecal lidocaine, 50 mg, was compared with preinjection spasticity levels in ten subjects with central nervous system disease or injury. Spasticity was objectively assessed by an electronic instrument that simultaneously measures degrees of extension and force during passive knee extension. Duration of spasticity relief and adverse effects were recorded. Both drugs equally reduced spasticity and increased the range of motion. There were no supraspinal side effects from the fentanyl, whereas three subjects became hypotensive after receiving lidocaine. The reduction of spasticity with intrathecal fentanyl lasted at least 3 h. The authors postulate that fentanyl reduced spasticity by an effect on spinal pathways. Intrathecal fentanyl should be considered as an alternative to lidocaine for diagnostic blocks in patients with spasticity.

Adult↗
PubMed1991

The dynamic flexometer: an instrument for the objective evaluation of spasticity.

Anesthesiologists may care for patients who have spasticity in the operating room or pain clinic. A number of therapeutic modalities for treatment of spasticity exist, but there are few simple objective methods for evaluating their effect. We describe one instrument, the Dynamic Flexometer, that measures the force required to move the limb passively through its maximum range of motion. The data presented validate the instrument's reliability. Two clinical cases presented here demonstrate the instrument's utility. This device may be of value to anesthesiologists involved in the care of patients with spasticity.

Disability Evaluation↗
PubMed1990

Microcomputer-based data acquisition system for clinical research.

We have described a computerized data acquisition system for clinical investigation that can record over fifty physiologic variables from up to twenty-four electronic monitors. The information is acquired by a personal computer using RS-232C serial communications and analog-to-digital conversion. In its present configuration the system records information from a Spacelabs 500 series physiologic monitor, Hewlett-Packard physiologic monitor with the Careport computer interface, SARA mass spectrometer, Nellcor pulse oximeter, Neurotrac processed EEG, Lawrence cardiac output monitor, Hewlett-Packard capnometer, and Bourns spirometer. The software can be easily modified to accommodate other physiologic monitors. The system records parameter or waveform information and writes the data into a file that can be accessed by commercially available graphical and statistical packages. The data acquisition system is easy to use, transportable, and inexpensive.

Humans↗
PubMed1990

Computer simulation of the hemodynamic determinants of myocardial oxygen supply and demand.

A computer program was developed that uses a mathematical model of the cardiovascular system to predict myocardial oxygen supply and demand as well as cardiac hemodynamics. This model combines the time-varying elastance model of the left ventricle, the modified Windkessel model of the arterial system, and the left ventricular pressure-volume area prediction of myocardial oxygen demand. The computer simulation permits independent control of variables, thus providing the opportunity to design "experiments" and to observe the results. The model predicts that tachycardia leads to reduced myocardial oxygen supply and increased demand. Hypertension caused by increased systemic vascular resistance increases supply more than it increases demand. On the other hand, increased contractility or left ventricular end-diastolic pressure increases demand more than supply, and may cause ischemia in the presence of coronary artery stenosis. The model is an aid in understanding how hemodynamic variables affect the balance between myocardial oxygen supply and demand. It can be used for education and to analyze study protocols prior to animal experimentation.

Animals↗
PubMed1990

The Anesthesia Simulator-Recorder: a device to train and evaluate anesthesiologists' responses to critical incidents.

The Anesthesia Simulator-Recorder is a computer program that trains and evaluates anesthesiologists' management of critical incidents. The program executes on IBM compatible personal computers, combining a graphic display of the operating room with mouse-driven input and using an integrated set of physiological and pharmacological models to predict patient responses. The program records the simulated patient's vital signs and all management decisions, and produces a printed case summary. The Anesthesia Simulator-Recorder was evaluated by 44 resident and attending anesthesiologists at seven different anesthesia training centers. These anesthesiologists found the simulator easy to use with clear presentation of the case and management options. The physiological and pharmacological models produced clinically realistic predictions of patient behavior (mean score = 8.5, where 10 is highly realistic and 1 is unrealistic). The Anesthesia Simulator-Recorder was appraised as an excellent training device (mean score = 8.5, where 10 is outstanding and 1 is poor) because it provides the ability to repeatedly practice the management of critical incidents. The simulator was judged to be a good evaluation device (mean score = 6.6, where 10 is outstanding and 1 is poor). No significant differences were found in evaluations between the institution where the program was developed and other institutions, or between residents and attendings.

Anesthesiology↗
PubMed1988

Frequency response evaluation of radial artery catheter-manometer systems: sinusoidal frequency analysis versus flush method.

It is well recognized that catheter-manometer systems significantly distort direct radial artery pressure measurements. Sinusoidal frequency analysis and the flush method of assessing the degree of distortion caused by the monitoring system were compared to determine whether these two methods agree in the estimation of natural frequency and damping coefficient. The frequency response of 30 radial artery catheter-manometer systems used for intensive-care unit patients was measured by the flush method and sinusoidal frequency analysis. The monitoring system consisted of a 20-gauge cannula, 150-cm pressure tubing, two plastic stopcocks, a continuous infusion device with fast flush valve, an American Edwards dome, a Hewlett-Packard quartz transducer, and a Hewlett-Packard blood pressure amplifier. Sinusoidal frequency analysis demonstrated second-order underdamped response for all 30 catheter-manometer systems. No secondary resonance peaks were observed up to a frequency of 200 Hz. The measured frequency response demonstrated that the average catheter-manometer system in use in our intensive care unit would cause significant distortion of the radial artery pressure, with the mean natural frequency (fn) of 14.7 +/- 3.7 Hz and the mean damping coefficient (zeta) of 0.24 +/- 0.07. Although the 30 monitoring systems had identical configurations and visible bubbles were carefully removed, a wide range of frequency responses was found (fn = 10.2 to 25.3; zeta = 0.15 to 0.44).(ABSTRACT TRUNCATED AT 250 WORDS)

Arm↗
PubMed1988

Electrocardiogram simulation using a personal computer.

A personal computer with a digital-to-analog converter is used as an electrocardiogram simulator. A TurboPascal procedure, given the heart rate, rhythm, and ST segment levels, generates the voltages for Leads II and V5. A simple circuit reduces the voltages to the physiologic range and smoothes the waveforms, removing the staircase effects of digitalization. The procedure can be manually controlled using a software interface or driven by other programs for use in a full-scale operating room simulator.

Computer Simulation↗
PubMed1987

Computer model analysis of the radial artery pressure waveform.

Simultaneous measurements of aortic and radial artery pressures are reviewed, and a model of the cardiovascular system is presented. The model is based on resonant networks for the aorta and axillo-brachial-radial arterial system. The model chosen is a simple one, in order to make interpretation of the observed relationships clear. Despite its simplicity, the model produces realistic aortic and radial artery pressure waveforms. It demonstrates that the resonant properties of the arterial wall significantly alter the pressure waveform as it is propagated from the aorta to the radial artery. Although the mean and end-diastolic radial pressures are usually accurate estimates of the corresponding aortic pressures, the systolic pressure at the radial artery is often much higher than that of the aorta due to overshoot caused by the resonant behavior of the radial artery. The radial artery dicrotic notch is predominantly dependent on the axillo-brachial-radial arterial wall properties, rather than on the aortic valve or peripheral resistance. Hence the use of the radial artery dicrotic notch as an estimate of end systole is unreliable. The rate of systolic upstroke, dP/dt, of the radial artery waveform is a function of many factors, making it difficult to interpret. The radial artery waveform usually provides accurate estimates for mean and diastolic aortic pressures; for all other measurements it is an inadequate substitute for the aortic pressure waveform. In the presence of low forearm peripheral resistance the mean radial artery pressure may significantly underestimate the mean aortic pressure, as explained by a voltage divider model.

Blood Pressure↗
PubMed1987

A flight simulator for general anesthesia training.

A simulator of general anesthesia is described. It consists of an integrated set of physiologic computer models and a graphics display. The model predicts many of the physiologic and pharmacodynamic changes associated with general anesthesia. It is a multiple model consisting of circulatory, respiratory, pharmacokinetic, and pharmacodynamic models and their interactions. The model can account for many pathologic states of the cardiorespiratory system plus poor renal and hepatic function. Both intravenous and inhalation agents are included. Examples of its capabilities are presented, including pharmacokinetic changes associated with thiopental administration to a hypovolemic subject, administration of oxygen in several pulmonary pathologic conditions, and a simulation of an induction using fentanyl or thiopental. The model, combined with the graphics interface, becomes a real-time simulator useful for training students and residents.

Anesthesia, General↗