Biomedical subjects

B A Houtchens

Publications and source records attributed to B A Houtchens.

10 recordsLinked to original sources

PubMed1995

Telemedicine protocols and standards: development and implementation.

Telemedicine is likely to adopt rather than create most of its protocols and standards as it becomes an integral part of medical practice. To optimize this process, it will be necessary to understand how to use existing protocols and standards, and influence the development, evaluation, and modification of new ones. We have identified key participants in standards setting activities under the titles of international government, United States government, professional certifying organizations, and independent institutes. We have reviewed their roles in establishing standards for identification of patients and providers, content and structure of patient records, terminology and codes of medical information and records, and transfer of messages and data. We have addressed requirements for storing and viewing images, the impact of image resolution on accuracy of clinical interpretation, the choice of communications protocols to satisfy transmission requirements, the need to link images and text data, and the evaluation of telemedicine systems.

Computer Communication Networks↗

PubMed1993

Medical-care systems for long-duration space missions.

As in the opening of frontiers on Earth, human physiological maladaptation, illness, and injury--rather than defective transportation systems--are likely to be the pace-limiting variables in efforts to expand the presence of humans into the solar system. Because of the inability of individuals to return to Earth rapidly and conveniently, the capability of delivering medical care on site will be key to the success of a manned space station, lunar base, and Mars mission. Spaceflight medical care equipment must meet stringent constraints of size, weight, and power requirements, and then must function accurately in remote, self-contained, microgravity settings after extended intervals of storage, with neither expert operators nor repair technicians on site. Satisfying these unusually rigorous requirements will require sustained direct involvement of clinically up-to-date health-care providers, medical scientists, and biomedical engineers, as well as astronauts and aerospace engineers and managers. Solutions will require validation in clinical settings with real patients, as well as in simulated operational settings.

Aerospace Medicine↗

PubMed1992

Management of trauma and emergency surgery in space.

Trauma may cause morbidity or mortality in expeditionary spaceflight settings. Physiologic and mechanical changes related to microgravity may increase susceptibility to and complicate the management of injuries in spaceflight. Limited surgical experience in microgravity suggests that special apparatuses and techniques will be needed to maintain the stability of patients, surgeons, and equipment, and to control fluids. A prototype microgravity surgical workstation and suction unit and modifications of standard procedures were devised to address these needs. Using these devices and methods and selected surgical supplies during repeated 25-second intervals of microgravity generated by parabolic arc flight, the "ABCs" of trauma management, limb traction and immobilization, and minor surgical procedures were performed in flight and problems were identified. Convincing "qualification" of spaceflight surgical equipment and protocols will require evaluations in continuous microgravity. As on Earth, the major determinant of emergency surgical care in spaceflight may be the presence or absence of a well-trained surgeon.

Emergencies↗

PubMed1988

Effect of a rotating bed on the incidence of pulmonary complications in critically ill patients.

The risk of nosocomial pneumonia and atelectasis is high among critically ill immobilized patients. We hypothesized that continuous turning on the kinetic treatment table would reduce their incidence. Sixty-five critically ill patients, immobilized because of head injury or traction, were prospectively randomized for treatment in a conventional bed (n = 38) or the kinetic treatment table (n = 27). Patients were well matched for baseline demographic and pulmonary risk factors. Patients in the conventional bed group had a higher incidence of cigarette smoking. The combined incidence of significant atelectasis or pneumonia was higher (66%) in the conventional vs. kinetic treatment table (33%) groups (p less than .01). Atelectasis, pneumonia, adult respiratory distress syndrome, requirements for ventilator treatment, for PEEP, and for an FIO2 greater than 0.50 were not significantly different, but tended to be higher in the control group. Survival and the incidence of decubitus ulcers were similar.

Adult↗

PubMed1985

Measured and predicted caloric expenditure in the acutely ill.

Predicted energy requirements calculated from the Harris-Benedict basal energy expenditure (BEE) formulas, and caloric allowances recommended by the Food and Nutrition Board National Research Council, were compared to metabolic expenditures measured by indirect calorimetry, using a feedback-controlled gas replenishment technique with a prototype device for the continuous determination of oxygen consumption (VO2) and carbon dioxide production (VCO2). In a group of 50 acutely ill surgical patients, predicted metabolic requirements based on ideal body weight (1.75 BEE) averaged 59% greater than metabolic expenditures measured by indirect calorimetry. Metabolic requirements based on actual body weight averaged 52% greater; recommended caloric allowances averaged 39% greater. Thus, accepted methods of predicting metabolic requirements significantly overestimated the caloric needs of these acutely ill patients. These results should encourage the development of new bedside equipment for measuring VO2 and VCO2, so that indirect calorimetry can be used to guide nutritional support in the clinical setting.

Acute Disease↗

PubMed1984

Oxygen consumption in septic shock: collective review.

That a decline in oxygen consumption (VO2) might herald onset of septic shock prior to hemodynamic collapse is suggested by previous observations in humans and animals in which VO2 appeared to be suppressed in systemic sepsis, despite normal or supranormal cardiac output, and in cellular and mitochondrial preparations exposed to endotoxin, despite adequate flow of perfusate. That a supranormal VO2 might be one of the best predictors of ultimate survival is suggested by data collected from humans during various stages of septic shock. To evaluate VO2 as an early indicator of sepsis, the effect of endotoxemia was observed in 20 rhesus monkeys divided into groups according to hypodynamic, normodynamic, and hyperdynamic blood flow states; the effect of sepsis was observed in seven preterminal septic humans during the final hours of their lives. VO2 was measured using a new device that evaluates expired gases by means of a relatively simple feedback-controlled gas replenishment technique. In neither the primates nor the humans was it possible to demonstrate a flow-independent depression of VO2. VO2 was distinctly elevated in each of the humans over some interval during the final day of life. These observations, plus an in-depth review of the literature, suggest that other variables, particularly peripheral vascular resistance, systemic and regional blood flow, and oxygen extraction fraction attempt to accommodate in an effort to sustain VO2. Probability of survival in sepsis appears to be enhanced by VO2 and cardiac output that are supranormal; yet even when VO2 is elevated, death can ensue within minutes to hours. Significant decline in VO2 is a grave prognostic sign, almost always preceded by a relatively easily detected hemodynamic change. Systemic VO2 appears to represent neither a specific early indicator of sepsis nor a certain prognosticator of survival outcome; it might provide useful information regarding adequacy of resuscitation.

Adult↗

PubMed1982

Automatic vs manual injections for thermodilution cardiac output determinations.

To investigate the effects of operator variability on thermodilution cardiac output determinations, a group of physicians and nurses made a series of manual indicator injections and automatic injections using a gas powered injector in a simulated clinical situation. The data show significant variability in injection time, injectate flow rate, consistency of injection, and cardiac output values obtained during manual injections. There was little variability in these parameters during automatic injections. When other variables are properly controlled, the automatic injector may improve the precision of cardiac output measurements by controlling the consistency of injection and variables introduced by different operators performing manual injections. However, despite significant variation in parameters associated with manual injection, it is interesting to note that 8 out of 10 operators obtained cardiac output values by hand injection using room temperature injectate, which did not differ significantly from those obtained by automatic injection.

Animals↗

PubMed1982

Oxygen consumption and optimum PEEP in acute respiratory failure.

The effect of PEEP on oxygen consumption (VO2) was observed in 3 groups of dogs. In addition to intermittent and indirect measurements using the expired gas collection and Fick methods, VO2 was measured continuously and directly using the "oxiconsumeter", a device utilizing a relatively simple feedback controlled gas replenishment technique which adapts to standard ventilator circuits. One group of dogs served as controls, while the other 2 groups developed acute respiratory failure (ARF) subsequent to an acute pulmonary injury (API) induced by iv administration of oleic acid. In animals without API, there were no PEEP-induced changes in gas exchange variables; whereas the 2 API groups showed graded improvement in arterial oxygen tension (PaO2), shunt fraction (Qsp/Qt), and alveolar-arterial oxygen tension gradient [P(A-a)O2] during mechanical ventilation with PEEP. In the absence of vascular volume loading, increasing PEEP was associated with decreased cardiac output in dogs with or without API. In contrast, when concurrently fluid resuscitated, the dogs receiving the most severe API showed all of the classic signs of progressive ARF but did not evidence decreased cardiac output with increasing PEEP. VO2 decreased at high PEEP when oxygen transport decreased. The following conclusions were reached: The oxiconsumeter provides a safe cost-effective means for VO2 monitoring, whose convenience and rapidity exceed those of expired gas collections and whose accuracy and reliability far exceeds those of Fick determinations. In general, PEEP has little effect on VO2 provided cardiac output is adequate; in particular, VO2 cannot be used to optimize PEEP via correlation with lung compliance or intrapulmonary shunt fraction. Decreased VO2 during PEEP therapy reflects a significant decrease in cardiac output, and is indication to support cardiac output, or reduce PEEP, or both.

Acute Disease↗

PubMed1981

Continuous monitoring of interstitial fluid potassium during hemorrhagic shock in dogs.

It appears that ISFET probes can reliably and continuously monitor IF K+ in vivo for intervals of at least several hours. The consistently observed increase in IF K+ in response to hemorrhage, a phenomenon invisible systemically, suggests that such probes may provide clinically valuable information regarding perfusion related events at the cellular level during onset of and resuscitation from hypoperfusion states. Precise correlation of ISFET signal to specific cellular dysfunction awaits investigation in which muscle cell membrane potential, muscle surface pH, and postexperiment cellular histology are studied concurrently.

Animals↗

PubMed1977

Major trauma in the rural mountain West.

A disproportionately high percentage of trauma fatalities occur in rural areas. Almost half of these fatalities occur after arrival at a community hospital. A review of the initial evaluation and management of major trauma victims in rural community hospitals in the intermountain West revealed a surprisingly high incidence of departure from well defined standards. Reducing the magnitude of this rural hospital component of trauma facilities will require application of the same standards of initial evaluation and management which have proved effective in major medical center emergency department settings.

Abdominal Injuries↗