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Biomedical subjects

Johannes H van Oostrom

Publications and source records attributed to Johannes H van Oostrom.

6 recordsLinked to original sources
PubMed2006

An integrated coronary circulation teaching model.

OBJECTIVES: We present in this paper a model of the coronary circulation. This model is integrated with a model of the systemic circulation, and contains models for oxygen supply and demand. METHODS: Three compartments are created: one for the right ventricle, one for the epicardial segment of the left ventricle and one for the endo-cardial segment of the left ventricle. The model was implemented in the Java programming language and contains a visual representation of the left and right ventricles which beat in real time. Color shading is used to represent the partial pressure of oxygen in the segments. A multitude of model parameters can be changed to simulate different scenarios. RESULTS: The output of the model was characterized under different conditions and the results verified by clinicians. CONCLUSIONS: Educational models of human physiology can be very useful for a more in depth understanding of complete physiologic systems. The models must however have enough complexity, interaction with other systems, and realism to show the concepts being taught.

Blood Flow Velocity↗
PubMed2005

The Stealth Station Image Guidance System may interfere with pulse oximetry.

PURPOSE: Interference on pulse oximetry can come from many sources. We found an additional source of interference from the Stealth Station. This article gives an overview of sources of pulse oximeter interference so that clinicians can better prevent them. Technical features: This article discusses the infrared disturbances caused by the Stealth Station. The Stealth Station is a frameless stereotactic positioning system that utilizes a three dimensional location system to measure the position of the patient and the surgical tools, and to relate those positions to previously recorded imaging. To understand the disturbance caused by the Stealth Station, we discuss its operation and that of pulse oximeter monitors. Pulse oximeter interference can come from volume artifacts, electrical and light noise, and can be caused by issues related to the patient. Because the passive Stealth Station contains a strong infrared light source, interference caused by light is a likely reason for the interference we noted. Pulse oximeters rely on the time-variant light signal modulated by arterial volume variations in the finger. Although relatively immune to static light sources, pulse oximeters are extremely sensitive to time-varying light sources. The light emitted by the passive Stealth Station is time-varying at 4 Hz and this is causing the pulse oximeter to provide invalid results. Shielding can generally be used to stop the light from the Stealth Station from being picked up by the pulse oximeter sensor. CONCLUSION: Infrared light interference can be very common, but is easily dealt with if one is aware of it.

Humans↗
PubMed2004

Opioid-induced respiratory depression: a mathematical model for fentanyl.

In this paper, respiratory depressant effects of fentanyl are described quantitatively by a mathematical model. The model is an extension of a previous one, which reproduces the human ventilatory control system on a physiological basis. It includes the following: three compartments for gas storage and exchange (lungs, body tissue, and brain tissue); the main mechanisms involved in ventilation control (peripheral chemoreceptors, central chemoreceptors, and the central hypoxic depression); and local blood flow regulation. The effects of fentanyl on the respiratory system include a decrease in peripheral and central chemoreceptor gains on ventilation and a direct inhibition of respiratory neural activity. All parameters in the model were chosen according to the literature. The model is able to reproduce the ventilatory effects of fentanyl in several conditions: 1) constant levels of fentanyl; 2) after a bolus injection; 3) at fixed levels of P(ETCO2); and 4) after artificial ventilation. According to the model, in spontaneously breathing subjects, minute ventilation depends on two opposing actions: fentanyl inhibitory influences, which depress ventilation, reducing oxygen tension and increasing CO2 tension, and the consequent activation of chemoreceptors, which stimulates ventilation. Simulations of anesthetized patients resuming spontaneous breathing after artificial ventilation demonstrate the risk of prolonged apnea and tissue hypoxemia. A safe transition can be achieved by increasing patient PCO2 toward the end of artificial ventilation, because an advanced chemoreceptor stimulation is produced, which promptly counteracts fentanyl-induced inhibition at cessation of artificial ventilation.

Adaptation, Physiological↗
PubMed2004

Comparative testing of pulse oximeter probes.

UNLABELLED: The testing of pulse oximeter probes is generally limited to the integrity of the electrical circuit and does not include the optical properties of the probes. Few pulse oximeter testers evaluate the accuracy of both the monitor and the probe. We designed a study to compare the accuracy of nonproprietary probes (OSS Medical) designed for use with Nellcor, Datex-Ohmeda, and Criticare pulse oximeter monitors with that of their corresponding proprietary probes by using a commercial off-the-shelf pulse oximeter tester (Index). The Index pulse oximeter tester does include testing of the optical properties of the pulse oximeter probes. The pulse oximeter tester was given a controlled input that simulated acute apnea. Desaturation curves were automatically recorded from the pulse oximeter monitors with a data-collection computer. Comparisons between equivalent proprietary and nonproprietary probes were performed. Data were analyzed by using univariate and multivariate general linear model analysis. Five OSS Medical probe models were statistically better than the equivalent proprietary probes. The remainder of the probes were statistically similar. Comparative and simulation studies can have significant advantages over human studies because they are cost-effective, evaluate equipment in a clinically relevant scenario, and pose no risk to patients, but they are limited by the realism of the simulation. IMPLICATIONS: We studied the performance of pulse oximeter probes in a simulated environment. Our results show significant differences between some probes that affect the accuracy of measurement.

Apnea↗
PubMed2002

Learning about new anesthetics using a model driven, full human simulator.

OBJECTIVE: New pharmacological agents are introduced into medical practice at an ever-increasing pace. Teaching how to use new medications in the clinical setting presents educational challenges and puts patients at risk. METHODS: Patients and clinical settings in which remifentanil might provide clinical advantages over existing anesthetics were identified. A simulator curriculum was developed to demonstrate the use of remifentanil in the sample cases. The simulation was designed to highlight the clinical advantages and potential side effects of remifentanil. A screen displaying the concentrations of remifentanil in plasma and in the hypothetical effector site was developed. A simulator was modified (addition of an infusion pump and a pharmacokinetic screen display) and transported to several cities in the U.S.A. An instructor guided small groups of anesthesiologists and anesthetists through a structured program that enabled participants to observe drug effects in simulated patients. RESULTS: There were 836 participants in the remifentanil program, which was offered in 58 cities in the U.S.A. Surveys were completed by 574 anesthesiologists. There was a significant difference in comfort level for using remifentanil after the session compared to before (Chi-square, p < 0.001.) The statement: "Clinical simulation experience is a means to learn about new agents like remifentanil" was rated as "excellent" by 81% and as "good" by 19% of participants. No participant found the experience to be "not useful." CONCLUSIONS: Patient simulation is a novel method of introducing new drugs to the medical community and is perceived by anesthesia providers as a valuable addition to available teaching methods.

Anesthesiology↗