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Biomedical subjects

A R Shapiro

Publications and source records attributed to A R Shapiro.

15 recordsLinked to original sources
PubMed1989

Thermal compression and molding of atherosclerotic vascular tissue with use of radiofrequency energy: implications for radiofrequency balloon angioplasty.

The combined delivery of pressure and thermal energy may effectively remodel intraluminal atherosclerotic plaque and fuse intimal tears. To test these hypotheses with use of a non-laser thermal energy source, radiofrequency energy was delivered to postmortem human atherosclerotic vessels from a metal "hot-tip" catheter, block-mounted bipolar electrodes and from a prototype radiofrequency balloon catheter. Sixty-two radiofrequency doses delivered from a metal electrode tip produced dose-dependent ablation of atherosclerotic plaque, ranging from clean and shallow craters with histologic evidence of thermal compression at doses less than 40 J to tissue charring and vaporization at higher (greater than 80 J) doses. Lesion dimensions ranged between 3.14 and 3.79 mm in diameter and 0.20 and 0.47 mm in depth. Tissue perforation was not observed. To test the potential for radiofrequency fusion of intimal tears, 5 atm of pressure and 200 J radiofrequency energy were delivered from block-mounted bipolar electrodes to 48 segments of human atherosclerotic aorta, which had been manually separated into intima-media and media-adventitial layers. Significantly stronger tissue fusion resulted (28.5 +/- 3.3 g) with radiofrequency compared with that with pressure alone (4.8 +/- 0.26 g; p less than 0.0001). A prototype radiofrequency balloon catheter was used to deliver 3 atm of balloon pressure with or without 200 J radiofrequency energy to 20 postmortem human atherosclerotic arterial segments. In 10 of 10 radiofrequency-treated vessels, thermal "molding" of both normal and atherosclerotic vessel wall segments resulted with increased luminal diameter and histologic evidence of medial myocyte damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1983

The SCAMP system for patient and practice management.

SCAMP is a comprehensive clinical information system for ambulatory care. Four design goals distinguish this system: ease of use, comprehensiveness, the incorporation of medical knowledge into system functions, and ease of modification of system capabilities by clinicians. Major subsystems are dedicated to billing, administrative reports, entry, retrieval and analysis of the medical record, clinical research, and provision of clinical reminders. Because clinicians differ in their needs and preferences, SCAMP has been designed to let clinicians modify aspects of the content, format, and processing of information available on the system. The SCAMP system has become increasingly accepted by many primary care physicians as a practical and useful tool for managing their information needs in ambulatory care.

Accounts Payable and Receivable↗
PubMed1977

The evaluation of clinical predictions. A method and initial application.

Clinical predictions are never certain but are inherently probablisitc. The accuracy coefficient, a measure of probabilistic accuracy based on probability assigned to outcomes that occur, was used to assess the skill of clinical rheumatologists in predicting patient outcomes. Physicians' scores correlated well with degree of clinical experience. An approach to evaluation based on the measure provides a sensitive assessment of marginal benefit of technologies such as laboratory tests, diagnostic procedures or computer consultations. Most currently used methods of computer prediction were not as accurate as the best physicians tested. By allowing measurement of ability to individualize predictions to each patient's unique characteristics, the accuracy-coefficient approach has potential use in physician assessment.

Bayes Theorem↗
PubMed1977

A nomogram for planning respiratory therapy.

A nomogram is presented which aids in monitoring and selecting therapy in the treatment of the patient with hypoxemia. It facilitates accurate bedside determination of total shunt fraction and estimation of the arterial oxygen tension (PaO2) attainable at inspired oxygen concentrations of 21 percent to 100 percent. The nomogram permits rapid consideration of changes in hemoglobin concentration, arteriovenous oxygen content difference, and shunt fraction on the PaO2. The uses of the nomogram in several therapeutic contexts are discussed.

Carbon Dioxide↗
PubMed1977

Interpretation of alveolar-arterial oxygen tension difference.

In this study, an assessment is given of errors resulting from the use of the alveolar-arterial oxygen difference determined on both room air and 100% oxygen in estimating changes in total shunt fraction of 41 patients hospitalized with long bone fractures. In 113 studies, changes in alveolar-arterial oxygen difference in 29 patients were in the opposite direction to changes in shunt fraction. Based upon these studies, changes of less than 45 millimeters in the arterial oxygen tension determined with a patient breathing 100% oxygen are not reliable indicators of direction of change in shunt fraction. In 126 studies, the shunt fraction determined from arterial and mixed venous oxygen contents in 71 patients was greater when determined on 100% oxygen than when determined on room air, a possible indication of the induction of alveolar or small airway collapse. The errors in estimation of shunt fraction due to assuming a value for arteriovenous oxygen content difference become larger as total shunt fraction increases; in particular, use of the alveolar-arterial oxygen difference as a guide to serial changes in pulmonary dysfunction can be particularly misleading when the alveolar-arterial oxygen tension difference is so large that the arterial hemoglobin is less than fully saturated on 100% oxygen. Use of mixed venous samples was found necessary, in these instances, to avoid large errors in estimation of total shunt fraction.

Adult↗
PubMed1976

An analysis of direct and indirect measurements of left atrial filling pressure.

Left ventricular function may be assessed by direct catheter measurements of left atrial pressure or by indirect measurements of pulmonary artery wedge pressure or pulmonary artery end-diastolic pressure. Controversy exists as to how closely the indirect measurements correlate with true left atrial pressure and to which is the most accurate. To clarify this probelm, we studied 43 patients undergoing cardiac surgical procedures with cardiopulmonary bypass. Both left atrial catheters for direct measurement and Swan-Ganz catheters were placed at the time of surgery. All patients were monitored continuously for 48 hours and hourly measurements were recorded. The resultant 1,620 left atrial pressure and pulmonary artery wedge pressure figures and 1,860 left atrial pressure and pulmonary artery end-diastolic wedge pressure measurements were subjected to computer analysis. The following conclusions have been found: (1) Pulmonary artery wedge pressure is a better indirect measure of left atrial pressure than is pulmonary artery end-diastolic wedge pressure (pooled correlation coefficient 0.629); (2) direct left atrial pressure measurement is more reliable and has fewer complications than indirect measurements; (3) there is no consistent correlation between left atrial pressure and central venous pressure (pooled correlation coefficient 0.3). A discussion of our results and the problems associated with left atrial catheters and Swan-Ganz catheters is presented.

Atrial Function↗
PubMed1975

Hemodynamic alterations with positive end-expiratory pressure: the contribution of the pulmonary vasculature.

The hemodynamic responses to positive end-expiratory pressure (PEEP) ventilation have been evaluated. A rise in pulmonary capillary wedge pressure which follows the use of PEEP may not reflect changes in left atrial pressure and may be associated with a fall in cardiac output. This increase in pulmonary capillary wedge pressure suggests that there is a high resistance to flow in the pulmonary circulation and that a lower level of PEEP should be used.

Adult↗
PubMedDate not supplied

Exploratory analysis of the medical record.

Current patient information systems such as SCAMP have the capacity to store not only highly-structured information such as problem codes, drug lists and laboratory values, but also richer, clinically-descriptive information such as comprehensive natural language problem summaries and other textual data that retain the full clinical information used by physicians in managing their patients. The clinical importance, richness, and extensiveness of this information suggest that techniques which allow computers to process textual data may play a helpful role in clinical research. The analysis programs of the SCAMP system have been developed to explore the potential of this approach.

Ambulatory Care Information Systems↗
PubMedDate not supplied

Central venous catheter placement using electromagnetic position sensing: a clinical evaluation.

A critical step in placing a central venous catheter (CVC) is positioning the catheter tip in a location just outside the heart in the lower superior vena cava. The authors report the clinical evaluation of a new commercially available system that uses electromagnetic technology to sense the position of a catheter tip during CVC insertion. Fifty catheters were implanted using fluoroscopy to monitor system accuracy. The catheters were accurately placed (within 2.5 cm of the desired optimal position) in 46 of the 50 cases (92%). In two patients with abnormal chest geometry (short, barrel chests), catheter tip location was difficult to determine. In two other cases, procedural difficulties unrelated to the system (difficulty in external landmark determination and unclear fluoroscopic view of the optimal position) resulted in catheter placement outside the targeted range. The electromagnetic system provides an opportunity to eliminate "blind" CVC placement procedures and to reduce or omit perioperative fluoroscopy of x-ray during CVC insertion.

Adult↗