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Medical Instrumentation

S T Blanks, P King, B E Smith
Two approaches to intraoperative anesthetic gas monitoring exist today. Central, mass-spectrometer-based systems share cost and analyzer time among several remote locations. Stand-alone monitors are usually infrared analyzers and are dedicated to a single monitoring location. The advantages and disadvantages of each are due primarily to the shared versus dedicated approaches. Dedicated analyzers, while limited somewhat by infrared technology, offer uninterrupted, real-time analysis of anesthetic and respiratory gases...
June 1988: Medical Instrumentation
G R Wodicka, A Aguirre, S K Burns, D C Shannon
A scheme to reduce the data corruption caused by tape-speed variation in cassette recorders used for monitoring infant apnea was developed. Low-frequency timing information is recorded on the tape, under the constraints of the frequency response of the recorder, simultaneously with the other signals. This information is extracted during playback and multiplied to a frequency suitable for data sampling, using an electronic, phase-locked loop. Analog-to-digital conversion of the data is performed at a rate proportional to the tape speed, resulting in compensation for speed variation...
June 1988: Medical Instrumentation
L D Metcalf
Much attention has been focused on the response to victims of injuries in the last two decades. During those twenty years, tremendous strides have been made in the medical community's ability to meet the needs of patients in the acute phase of treatment for traumatic injuries. Recent research has reflected these advances in treatment as well as equipment design and development that enable rapid response and access to the injured. Even with these modern miracles of treatment, injuries kill more citizens of the United States 1-34 yr of age than all diseases combined...
June 1988: Medical Instrumentation
J J Weinberg, A D Smith
Over the past 10 years, endourology and ureteroscopy have revolutionized the field of urinary endoscopy. No longer limited to cystoscopic examination of the lower genitourinary tract, endoscopy incorporates the upper tracts as well. With this surge in upper tract endoscopy has come a rise in the variety of medical instruments available to the endourologist. Beginning with rigid instruments that offered only a limited view, technology has advanced both flexible and rigid instruments that allow access to the entire urinary tract for examination and treatment...
April 1988: Medical Instrumentation
C R Williams, L A Geddes, J D Bourland, E S Furgason
We have designed a high-impedance (5000 omega-cm), tapered, gelled-pad, external cardiac pacing electrode that limits the migration of charges to the perimeter of a circular electrode and produces a more uniform current-density distribution than external cardiac pacing electrodes in clinical use. A computer simulation was developed that uses cylindrical coordinates to analyze the current-density distribution at the interface between the electrode and human tissue. Our computer simulation analyzed 32 different electrodes, and the results showed that the gelled-pad thickness, the gelled-pad taper, and the radius of the conducting disk were not significant parameters in determining the current-density distributions for low-resistivity electrodes...
December 1987: Medical Instrumentation
D W Harrison, P L Kelly
This study provides a detailed comparison of 22 digital, blood pressure monitors intended for home use. Blood pressure and pulse-rate readings from each electronic monitor were compared with concurrent measures obtained using the mercury column and auscultation. Correlation coefficients and linear regressions were performed to evaluate accuracy. Separate analyses of variance were used to determine significant calibration errors for each model. The results showed considerable disparity among available home monitors under controlled testing conditions...
December 1987: Medical Instrumentation
G F Harris, D C Jeutter, B C Bergner, D V Matesi, N J Pelc
A multichannel biotelemetry system using pulse-width modulation-frequency modulation (PWM-FM) is described in detail for laboratory construction. Its application in a kinematic gait-analysis system is demonstrated, employing minimally encumbering electrogoniometry and foot-contact switches. The triaxial electrogoniometers sense rotational joint motion, and four foot-switches under the sole of each foot provide information on placement and temporal contact. Signals from the multiple sensors are amplified, encoded by pulse-width modulation, and transmitted at an FM radio frequency of 107 MHz...
December 1987: Medical Instrumentation
J M Bruner, P F Leonard
No abstract text is available yet for this article.
October 1987: Medical Instrumentation
L L Weed
No abstract text is available yet for this article.
October 1987: Medical Instrumentation
N Daikuzono, S N Joffe, H Tajiri, S Suzuki, H Tsunekawa, M Ohyama
Contact Nd:YAG laser surgery is assuming a role of greater importance in endoscopic and open surgery, allowing coagulation, cutting, and vaporization with greater precision and safety. A synthetic sapphire probe allows a wider angle of irradiation and diffusion of low power laser energy (less than 5 W) using an interstitial technique for producing local hyperthermia. Sensors placed directly into surrounding tissue or tumor continuously monitor temperature, and a pertinent computer program produces a controlled and stable temperature (e...
October 1987: Medical Instrumentation
D J McMahon, G E Thompson
Although the amount and complexity of equipment and supplies used in the practice of anesthesia have sharply increased in the past decade, the role of technical support personnel dealing with this technology has not been assessed. In an effort to determine that role, a questionnaire survey was conducted of the apportionment, direction, duties, and training of anesthesia technicians in teaching departments. Two-thirds of the inquiries were returned, disclosing a typical allocation of three anesthetizing locations (or 2000 annual anesthetics) per technician...
October 1987: Medical Instrumentation
J C Schuder, H Stoeckle, W C McDaniel, M Dbeis
Studies involving 240 fibrillation-defibrillation episodes via epicardial patch electrodes in 21-27-kg dogs and 480 transthoracic episodes in 100-kg calves are reported. In dogs, 120 episodes involving shocks by a 3.7-A, 5-ms unidirectional rectangular wave of one polarity were interlaced with 120 similar episodes of the reverse polarity. When the upper right ventricular patch was positive with respect to the left ventricular apex patch, 85% of the episodes yielded defibrillation; 78% defibrillated with the reverse polarity...
October 1987: Medical Instrumentation
W J Levy
Monitoring of the nervous system using evoked potentials is a developing tool. A new evoked potential, the motor-evoked potential (MEP), based on a traditional test, uses brain stimulation to monitor the motor system. The MEP complements the existing modalities, which are wholly sensory. The MEP can be prompted by direct stimulation of the motor cortex, but, in a more general way, by transcranial stimulation. Electric or magnetic means can be used. One electric system involves placement of an electrode on the scalp over the motor cortex, paired with a cathodal plate on the roof of the hard palate...
October 1987: Medical Instrumentation
J C Buckey, R L Goble, C G Blomqvist
We have developed a device for continuous direct measurement of human central venous pressure (CVP) during space flight. Normal resting CVP is typically in the range of 5-10 mmHg; in zero gravity, the expected changes are +/- 5 mmHg or less. A 1-mm Hg change in CVP can represent a substantial intravascular fluid shift. The device is small, battery powered, and designed to run for at least 24 hr. Pressure is measured in a saline solution-filled catheter inserted into a central vein. The transducer is placed in the axilla at the level of the catheter tip to offset hydrostatic gradients...
August 1987: Medical Instrumentation
S Thomsen, J R Morris, C R Neblett, J Mueller
A low energy, CO2 laser adapted specifically for microsurgery can be used to assist in anastomosis by "welding" tissue through thermal coagulation. Which tissue constituents contribute to the bond are not known, and different constituents may be important in welding different organs.
August 1987: Medical Instrumentation
F W Cross, T J Bowker
The current controversy regarding the interaction between the output of the excimer laser and human tissue concerns the relative importance of photothermal and photoablative effects. Two experiments using an excimer laser on vascular tissue, aimed at defining the precise laser-tissue interaction, were performed. The experiments argue strongly in favor of photoablative effects that result from multiple photon interactions with ablated tissue.
August 1987: Medical Instrumentation
S R Mordon, A H Cornil, B Buys, J P Sozanski, J M Brunetaud, Y Moschetto
Several medical fields are concerned with applications of thermal lasers such as neodymium-doped, yttrium aluminum garnet (Nd:YAG), argon, and CO2. However, quantification of the necrotic volume of Nd:YAG laser-induced damage is not possible at the time of treatment. Mathematic models and feedback control can help to optimize Nd:YAG laser treatments. We therefore formulated mathematic models for coagulation processes and developed an intelligent Nd:YAG laser system with closed-loop feedback control. Surface temperature evolution proved to be valuable data for real-time control of coagulation and ablation...
August 1987: Medical Instrumentation
O T Tan, T J Stafford
A pulsed, dye laser at 577 nm was used to treat 65 patients with port-wine stains. Results clearly indicate that the laser parameters of dose, wavelength, and pulse duration contribute to the outcome of laser treatment of port-wine stains.
August 1987: Medical Instrumentation
M J van Gemert, A J Welch
Port-wine stains (PWS) are bluish red skin stains that are caused by enlarged, ectatic blood vessels in the dermis. Laser treatment of PWS is analyzed from computation of the spatial distribution of heat production by direct absorption of the laser light and subsequent heat conduction. The absorption and scattering caused by oxyhemoglobin, epidermis, and dermis as a function of wavelength are utilized in this analysis. Ideal treatment is defined as coagulating the ectatic blood vessels without irreversible damage to the epidermis and dermis...
August 1987: Medical Instrumentation
J A Pearce
Laser energy sources have been used in a wide range of clinical applications over the last decade to obtain cutting, coagulation, and denaturization of tissue. The therapeutic effect depends on complex interaction among the optical and thermal properties of tissue and damage accumulation. In applications where localized white coagulum is required, there are trade-offs between continuous activation using a large spot size and repetitive pulses with a small spot size as well as between a highly scattered, deep penetration source and a highly absorbed, shallow penetration laser source...
August 1987: Medical Instrumentation
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