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Biomedical subjects

J H Philip

Publications and source records attributed to J H Philip.

At least 37 records · Page 2Linked to original sources
PubMed1989

Positive end-expiratory pressure: implications for tidal volume changes in anesthesia machine ventilation.

In clinical practice, the addition of positive end-expiratory pressure (PEEP) into a standard anesthesia circle circuit decreases the delivered tidal volume (DTV) to a patient. We studied the magnitude of the delta DTV/delta PEEP relationship in two commonly used anesthesia systems. In addition, the magnitude of the delta DTV/delta PEEP relationship varies with both pulmonary compliance and volume of gas contained in the patient's breathing system between the ventilator and PEEP valve site, and this was also evaluated. Routine monitoring of expired tidal volume should be used whenever PEEP is added to an anesthesia circuit.

Anesthesia, Closed-Circuit↗
PubMed1989

Model for the physics and physiology of fluid administration.

This article describes a model designed to provide an understanding of fluid flow in intravenous systems and human subjects. Experiments were developed which demonstrate that the model can represent common clinical situations. The model depicts physical devices as ideal resistors, pressure sources, and flow sources. The patient's venous system is depicted as a combination of ordinary and Starling resistors. For flows between 0 and 300 ml/hr, both physical devices and patients are adequately represented by a straight line representing the pressure-flow relationship (PFR): pressure = opening pressure + flow X resistance, where the slope is the resistance to fluid flow and the intercept is the opening pressure. The PFR for a normal vein is characterized by a flat slope (vein resistance = 22 +/- 20 mm Hg/L/hr, mean +/- SD) and a low intercept (opening pressure = 15 +/- 8 mm Hg). The PFR for a partially obstructed vein has a resistance equal to that of an unobstructed vein and an opening pressure elevated approximately equal to the pressure obstructing the vein. For perivascular tissue, the PFR has a steep slope (tissue resistance = 1,125 +/- 1,376 mm Hg/L/hr), while tissue opening pressure depends on the amount of fluid infused. At the onset of fluid extravasation (infiltration), tissue pressure usually is lower than venous pressure (8 +/- 8 versus 15 +/- 8 mm Hg), until fluid fills the distensible tissue compartment. In clinical practice, when infiltration or obstruction occurs, flow decreases and the clinician adjusts the roller clamp until correct flow resumes; no problem is obvious. The combined model for the intravenous tubing and venous systems explains the behavior of current clinical infusion devices.

Biophysical Phenomena↗
PubMed1989

The theoretical effect of carboxyhemoglobin on the pulse oximeter.

The relationship between arterial oxygen saturation as measured by the pulse oximeter (SpO2) and the fractional arterial oxygen saturation (SaO2) in the presence and absence of carboxyhemoglobin (COHb) has been derived according to the theory of absorption spectroscopy. We find that our theoretically derived correction equation is similar to that found in the technical literature of Nellcor. However, the correction equations presented by Barker and Tremper and the technical literature of Ohmeda differ substantially from our equation when sufficient quantities of reduced hemoglobin are present and the fractional COHb saturation (SaCO) is high. Our approximated equation, derived from the Lambert-Beer law, is SaO2 = SpO2 (1 - 0.932 SaCO) + 0.032 SaCO. The equation of Barker and Tremper is SaO2 = SpO2 - 0.9 SaCO. The Nellcor equation is SaO2 = SpO2 (1 - SaCO).

Carboxyhemoglobin↗
PubMed1989

An evaluation of the effectiveness of a computer simulation of anaesthetic uptake and distribution as a teaching tool.

Gas Man is an interactive, microcomputer-based simulation and tutorial designed to teach the principles of anaesthetic uptake and distribution. Using two resident groups, one at a primary university-teaching hospital and the other at a medical school affiliated community hospital, the authors compared residents' knowledge of the subject prior to exposure to the tutorial and the average time spent using the program during a self-paced instruction period. Both groups not only significantly improved their knowledge of uptake and distribution 8 weeks after using this program, but wished to spend additional time with it, implying that it was a pleasant and satisfying way to learn. Computer simulation has the potential to be an important teaching tool in an anaesthesia residency training programme.

Anesthesiology↗
PubMed1989

Postanesthesia care unit standards for anesthesiologists. Board of Directors of the American Society of Post Anesthesia Nurses.

The following article describes postanesthesia care unit standards for anesthesiologists as developed by the Harvard Anesthesia Department's Risk Management Committee, Harvard Medical School. The standards were endorsed by the ASPAN Board of Directors, April 10, 1988. It is hoped that publication of these standards will assist PACU nurses in evaluating the anesthesia support they receive in their respective settings.

Anesthesiology↗
PubMed1989

Spinal needles.

Explore the source record for details and available documents.

Anesthesia, Spinal↗
PubMed1988

The prevalence of hypoxemia detected by pulse oximetry during recovery from anesthesia.

Pulse oximetry was used to assess the prevalence of hypoxemia (arterial oxygen saturation of 90% or less) at various times in the immediate postoperative period: five minutes after arrival, 30 minutes later, and just before discharge. Among 149 inpatients studied, one or more hypoxemic measurements were made in 21 (14%) during their postoperative course. Of 92 outpatients, 1 (1%) was found to be hypoxemic. For inpatients, the prevalence of hypoxemia preoperatively, 5 minutes after arrival in recovery, 30 minutes later, and at discharge was 2%, 4%, 6%, and 9%, respectively. Patient factors associated with a significantly higher prevalence of hypoxemia were obesity (22%), body cavity surgical procedures (24%), age over 40 years (18%), American Society of Anesthesiologists physical status (I, 7%; II, 17%; III, 18%; IV, 100%), duration of anesthesia longer than 90 minutes (18%), and intraoperative administration of greater than 1,500 ml of fluid (20%). Unrecognized hypoxemia in postsurgical inpatients with or without these risk factors is common. Therefore routine monitoring of these patients with a pulse oximeter is suggested.

Adult↗
PubMed1987

Hypoxemia during ambulatory gynecologic surgery as evaluated by the pulse oximeter.

Pulse oximetry was used to determine the incidence of intraoperative hypoxemia in 108 patients undergoing ambulatory gynecologic operation. Eleven (10%) experienced moderate desaturation (arterial oxygen saturation less than 90%), and 5 (5%) suffered severe hypoxemic episodes (arterial oxygen saturation less than 85%). Among patient risk factors--including operation, body habitus, smoking habits, history of asthma, age, and airway characteristics--an association with moderate hypoxemia was found only with nonlaparoscopic gynecologic operation, obesity, and age over 35 years, and an association with severe hypoxemia was found only with obesity and age over 35. Among operative events--including inspired oxygen concentration, position, mode of ventilation, and anesthesia phase--an association with moderate hypoxemia was found only with the lithotomy position, manual ventilation, and arousal. The cost per patient of monitoring with a pulse oximeter is about +1.35. A cost-benefit analysis reveals that a mortality rate of 1 in 40,000 among patients who actually become moderately hypoxemic would justify the cost of monitoring arterial oxygen saturation. We conclude that pulse oximetry should be part of routine anesthetic monitoring.

Adult↗
PubMed1987

Studies of nontraumatic osteonecrosis. The role of core decompression in the treatment of nontraumatic osteonecrosis of the femoral head.

This study reports a five-year experience with core decompression for treatment of nontraumatic osteonecrosis of the femoral head. There were 25 patients (39 hips) with predominantly steroid-associated osteonecrosis followed postoperatively for a minimum of two years. All patients were evaluated functionally, roentgenographically, histologically, and hemodynamically. At latest follow-up examination, two of 12 hips (17%) with Stage I disease, seven of 12 hips (58%) with Stage IIA disease, four of four hips with Stage IIB disease, and nine of 11 hips (82%) with Stage III disease have progressed roentgenographically and/or clinically. A lack of correlation between pressure manometrics, venography, and clinical outcome in this study suggests that mechanisms other than progressive ischemia may be involved. Current indications for core decompression are Ficat Stage 0, I, and IIA (sclerotic predominant) disease.

Adult↗
PubMed1987

Studies of nontraumatic osteonecrosis. Manometric and histologic studies of the femoral head after chronic steroid treatment: an experimental study in rabbits.

High-dose methylprednisolone was administered to adult rabbits over a five- to nine-week period, according to previously described experimental models of nontraumatic osteonecrosis (NON). Manometric studies were performed using a sensitive computer-directed microvolume flow system. Osteocyte viability within the femoral head was assessed by counting empty osteocyte lacunae in five random high-power fields of hematoxylin- and eosin-stained sections. There was no significant elevation of intramedullary pressure or venous outflow resistance in femoral heads of animals receiving steroids, and a significant random loss of osteocytes was observed in these femoral heads. The clinical relevance of these studies is as follows. NON associated with steroids may not simply be the result of progressive ischemia. Ischemia and elevated intramedullary pressure may be epiphenomena, and a direct cytotoxic effect of steroids on osteocytes may be the earliest event in the development of nontraumatic osteonecrosis. The stress test, as it is currently being used in the clinical setting, may be unreliable.

Animals↗
PubMed1986

An electronic stethoscope is judged better than conventional stethoscopes for anesthesia monitoring.

A prototype electronic monitoring stethoscope was constructed from readily available, high-quality components. It consisted of a conventional precordial or esophageal probe connected to a microphone by a rubber adapter. The microphone was connected by lightweight wire to an amplifier and headphones. Twenty-one anesthesia clinicians evaluated the stethoscope and responded to a multiple-choice preference questionnaire. The electronic stethoscope was judged to perform better than the conventional stethoscope in most categories evaluated. The electronic device was perceived to be louder, clearer in sound reproduction, more efficacious for monitoring, and easier to use continuously, and its headphones were considered more comfortable than the conventional earpiece. Based on our results, we conclude that amplified stethoscopes have the potential to improve monitoring. Further development of electronic stethoscope monitoring seems warranted and is continuing.

Anesthesia↗
PubMed1986

Gas Man--an example of goal oriented computer-assisted teaching which results in learning.

Gas Man is an educational computer simulation program. The goal of the program is for the user to learn the theory and application of inhalation anesthesia uptake and distribution. The program and accompanying text are designed to be used by medical students, pharmacy students, anesthesia residents, nurses, practicing anesthesiologists, and medical equipment technicians and engineers. After using the program, the learner should understand the time course of patient response to inhalation anesthesia. He should know the factors which influence patient response and be able to predict their impact in specific situations. The key to Gas Man's success are: A well-defined and valid educational goal, teaching anesthesia uptake and distribution. An identifiable and testable set of educational objectives. A specific set of learner tasks to achieve those objectives, the actual simulation exercises. The appropriate educational medium, computer simulation and graphics. Effective software implementation, the Gas Man Program.

Anesthesia, Inhalation↗