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Biomedical subjects

F E Block

Publications and source records attributed to F E Block.

35 records · Page 2Linked to original sources
PubMed1991

A clinical evaluation of rapid automatic noninvasive blood pressure determination with the Ohmeda 2120 "return-to-flow" method.

Most commercial noninvasive blood pressure devices use the oscillometric method for determination of blood pressure. The Ohmeda 2120 noninvasive blood pressure monitor uses the oscillometric technique, but it also includes a "Sys Stat" mode for rapid determination of systolic blood pressure up to ten times per minute. This Sys Stat mode uses the "return-to-flow" method, in which the pressure on an upper arm cuff decreases in small steps until a finger sensor detects the first pulse of blood. Data from 16 patients monitored with the Ohmeda 2120 unit and with an arterial cannula were analyzed. The line of regression was Sys Stat = 0.85 (arterial) + 9.49. The Ohmeda 2120 monitor tended to underestimate the arterial pressure, particularly at higher pressures. Several factors could have contributed to this underestimation. Even so, the accuracy is sufficient for clinical use under most circumstances. More importantly, in an urgent situation, the Sys Stat mode can provide a reading of systolic blood pressure within seconds.

Blood Pressure Determination↗
PubMed1991

Evaluation of a single-room, dedicated mass spectrometer.

A single-room dedicated mass spectrometer can be used to measure carbon dioxide, halogenated anesthetic agents, nitrous oxide, nitrogen, and oxygen. This device challenges the multiplexed mass spectrometer, a current standard in measurement. This study compared the single-room dedicated mass spectrometer with a conventional mass spectrometer that is normally used in a multiplexed setting. In this study, a single-room dedicated Ohmeda 6000 Mini-Mass Spectrometer and the Perkin-Elmer MGA-1100 mass spectrometer were calibrated with the same reference gases and both devices sampled various concentrations of dry gases. Regression lines and intercepts were plotted and showed excellent correlation between the two devices. The intraclass correlation test of Lee, Koh, and Ong, showed the devices to be equivalent with regard to the ability to determine various gas concentrations. Various advantages of a single-room dedicated mass spectrometer are discussed.

Anesthesiology↗
PubMed1989

Delayed recognition of an oximeter malfunction.

Most anesthesiologists, relying upon sales presentations from salesmen from oximeter manufacturers, believe that if an oximeter produces a steady signal with a good pulse amplitude, the numbers are always believable in the absence of interference from external light sources or from intravenous dyes. Here I report a case in which an oximeter appeared to be working properly yet displayed values which were falsely low. Trust in the oximeter resulted in delayed identification of the problem.

Aged↗
PubMed1988

A carbon dioxide monitor that does not show the waveform is worthless.

The author suggests that the carbon dioxide waveform should be displayed, as are the electrocardiogram and arterial pressure waveforms. He argues that a carbon dioxide analyzer that does not provide a waveform is not of value, as subtle changes in the carbon dioxide waveform can reflect impending problems. Only when a plateau is present in the capnogram can one be certain that end-tidal gas is being measured, and the author asserts that the presence or absence of this plateau can be detected only by visually inspecting the waveform.

Carbon Dioxide↗
PubMed1987

Analog and digital computer theory.

Analog signals abound in the natural world. With appropriate transducers these signals can be converted to continuous voltages and can be displayed, transmitted, stored, or copied. They can be processed by analog computers, the simplest of which is an audio amplifier. With analog signals, however, there can be errors because of signals loss, interference, and noise. Binary digital signals permit only two values, either 0 ('off' or 'low') or 1 ('on' or 'high'). These signals are much less susceptible to transmission problems. Binary signals are commonly organized into 8-bit groups which can represent 256 different numbers or meanings. These data can be transmitted in either serial or parallel fashion at high rates of speed. Analog-to-digital converters permit analog signals to be transformed to digital signals. A computer consists of the memory, the processor, and the input/output devices. Memory includes the fastest registers, the very fast core memory, the peripheral storage devices such as diskettes and disks, and the very slow peripheral devices such as magnetic tape. The processor can only load and store numbers in memory, add two numbers, test a number, and provide input and output. The program counter indicates the next computer instruction to be performed. Input/output devices allow communication with the outside world and may assume many forms. A computer by itself can do nothing. A program or series of instructions is required. The most simplistic program language is assembler or machine language. Most programming is done in more sophisticated languages, however.(ABSTRACT TRUNCATED AT 250 WORDS)

Analog-Digital Conversion↗
PubMed1986

Minimizing interference and false alarms from electrocautery in the Nellcor N-100 pulse oximeter.

Because the Nellcor N-100 pulse oximeter is generally quite sensitive to electrocautery interference, erroneous oxygen saturation values may be displayed and an audible false alarm may sound. We have discovered, through trial and error, several techniques that may minimize both the interference and the false alarms. Keeping the pulse oximeter sensor and the oximeter unit as far as possible from the surgical site and the electrocautery grounding plate will usually decrease the interference. If this step is inadequate, the incidence of false alarms can be decreased by setting the high pulse rate alarm to approximately 160, operating the unit in mode 2 (the rapid-response mode), and setting the "alarm off" function to 120 seconds. These steps will usually markedly decrease the incidence of false alarms.

Electricity↗
PubMed1986

Do we monitor enough? We don't monitor enough.

The choice of which intraoperative monitors to use for routine cases is difficult, because a multitude of monitors is available today. Monitoring is deemed necessary to avoid problems, although there is little hard evidence that a specific monitor will improve outcome. The risk associated with modern noninvasive monitors, however, is negligible, and they should be considered for routine use in all patients. Although errors in the variables displayed or misuse of correct information can cause difficulties, these result from a lack of education and are not a valid reason to abandon a particular monitoring modality. Regular use of such monitoring tools as the electroencephalogram would allow clinicians to become familiar with how to interpret it in normal and crisis situations. The cost of a disaster during anesthesia (such as unrecognized hypoxia) is high. The dollars spent to cover a single major malpractice award could buy a tremendous number of monitors. The state of the art in the mid-1980s demands traditional anesthesia monitors plus continuous capnography and measurement of peripheral oxygenation. Other negligible-risk monitors should also be used when feasible. Improvement in monitoring design, particularly in output formats and in integration of monitored data, will be essential in the next few years, as will training in the proper use of monitors.

Electrocardiography↗
PubMed1986

A simple automatic record of oxygenation and ventilation with a pulse oximeter and a carbon dioxide monitor.

Many cases have come to medicolegal attention in which a healthy patient undergoing a routine, elective operation has had an unexpected cardiac arrest attributed to hypoxia or hypercarbia. A simple, objective, automatic, inexpensive record of the adequacy of oxygenation and ventilation was obtained by using the Nellcor N-100 pulse oximeter, the Puritan-Bennett/Datex carbon dioxide monitor, and the Nellcor N-9000 recorder in combination. The required interface is described, and a sample record is presented. A second interface allows the recorder to work with the Puritan-Bennett anesthesia and brain activity monitor (ABM-1). Oxygen saturation can also be displayed on the video screen of the anesthesia and brain activity monitor.

Automation↗
PubMed1985

The computer-based anesthetic monitors: the Duke Automatic Monitoring Equipment (DAME) system and the microDAME.

From 1972 to 1983 the Duke University Department of Anesthesiology designed, built, and maintained most of its own operating room patient monitoring equipment. Construction of a new hospital facility in 1980 provided the opportunity to design and test a new computer-based system, the Duke Automatic Monitoring Equipment (DAME) System. The system consist of microcomputer-based instrumentation on monitoring carts, which communicate with a central minicomputer that allows selection of different software monitoring packages based on the needs of the patient. Multiple problems, including frequent total monitoring failures during surgery, plagued the DAME System in its first year of operation. Despite resolution of many of these problems, user acceptance was poor because of the large size and weight of the monitoring carts, the inadequate quality of displayed physiological waveforms, and inability to overcome the difficulties of the man-machine interface. Because the remaining problems could not be rectified with the existing monitoring carts, a new generation of monitors was designed. The smaller, multiprocessor microDAME was designed to be as automatic and user tolerant as possible. It would omit much of the flexibility that had proved undesirable in the DAME system. When the microDAME was nearly completed, however, departmental research in that area ceased. It remains for others to apply our experiences to further improve operating room patient monitors.

Anesthesiology↗
PubMed1979

[67Ga]citrate scintiscanning in active inflammatory bowel disease.

Twenty-five hospitalized patients were studied prospectively with [67Ga]citrate (GA) abdominal scintillation scanning in an attempt to define its role in the evaluation of patients with active inflammatory bowel disease (IBD). There were nine patients with ulcerative colitis (UC), seven with Crohn's disease (CD), and nine controls. In four patients, two with UC and two with CD, a tissue/plasma radioactivity ratio was obtained and compared to normals. All the UC patients had positive GA scans and only one of seven of the CD patients had a positive scan. There were no false positive scans. Scans performed after a 3- or 5-day delay were more accurate than 6-hr scans alone. Well-delineated colinic radioactivity 6 hr after injection which persists for 3 to 5 days indicates the presence of UC in patients with IBD, while a negative scan is more consistent with active CD. Colonic uptake at 6 hr which clears by 48 or 72 hr is not indicative of UC. This procedure aided in following the course of UC, delineating the extent of disease, and in differentiating active CD from an intraabdominal abscess. Tissues from UC patients had increased tissue/plasma ratioactivity ratios while tissues from CD patients had normal or decreased ratios which were consistent with the imaging data.

Adolescent↗
PubMed1977

Self-instructional emergency medicine program for medical students.

A self-instructional program in emergency medicine has been developed for freshmen medical students at the University of Virginia School of Medicine. The cognitive objective of the course is to give the student the minimum level of knowledge to diagnose emergency medical conditions. Performance of the appropriate practical treatment is the course's psychomotor objective. Evaluation of the student's grasp of the program's cognitive and psychomotor objectives is accomplished by the written and practical examination for certification of emergency medical technicians and practical tests in basic life-support. Self-instructional guides, algorithms, videotapes and reading materials are the educational resources for the course. As a result of successful completion of the training program, the student is certified as an emergency medical technician in the Commonwealth of Virginia.

Audiovisual Aids↗