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Biomedical subjects

S B Johnson

Publications and source records attributed to S B Johnson.

At least 91 records · Page 5Linked to original sources
PubMed1994

Closed versus open endotracheal suctioning: costs and physiologic consequences.

OBJECTIVE: To examine the physiologic consequences and costs associated with two methods of endotracheal suctioning: closed vs. open. DESIGN: A prospective, randomized, controlled study. SETTING: An eight-bed trauma intensive care unit (ICU) in a 460-bed level I trauma center. PATIENTS: The study included 35 trauma/general surgery patients (16 in the open suction group, 19 in the closed suction group) who were treated with a total of 276 suctioning procedures (127 open, 149 closed). MEASUREMENTS AND MAIN RESULTS: Physiologic data collected after hyperoxygenation, immediately after suctioning, and 30 secs after suctioning, were compared with baseline values. Open endotracheal suctioning resulted in significant increases in mean arterial pressure throughout the suctioning procedure. Both methods resulted in increased mean heart rates. However, 30 secs after the procedure, the open-suction method was associated with a significantly higher mean heart rate than was the closed method. Closed suctioning was associated with significantly fewer dysrhythmias. Arterial oxygen saturation and systemic venous oxygen saturation decreased with open suctioning. In contrast, arterial oxygen saturation and systemic venous oxygen saturation increased with the closed suction method. There was no difference between the two methods in the occurrence of nosocomial pneumonia. Open endotracheal suctioning cost $1.88 more per patient per day and required more nursing time. CONCLUSIONS: The closed suction method resulted in significantly fewer physiologic disturbances. Closed suctioning appears to be an effective and cost-efficient method of endotracheal suctioning that is associated with fewer suction-induced complications.

Adult↗
PubMed1994

Further experience with transesophageal echocardiography in the evaluation of thoracic aortic injury.

This prospective study sought to further define the role of transesophageal echocardiography (TEE) in diagnosing thoracic aortic injury. We performed TEE, aortography, or both on 160 consecutive patients suspected of having blunt thoracic aortic injury: TEE correctly identified 14 aortic injuries, of which five were confirmed by aortography, seven at thoracotomy, and two at autopsy. The TEE results were suggestive of but not diagnostic for injury in two additional patients with proven aortic injury, and TEE was otherwise 100% sensitive and specific for aortic injury. Aortograms yielded one false positive result and four false negative results, for a sensitivity of 73% and a specificity of 99%. We conclude that TEE is a rapid, safe, and accurate bedside method for evaluating the heart and thoracic aorta for blunt trauma. Negative or positive TEE results obviate the need for aortography. We recommend that aortography be used when TEE results are equivocal, when TEE is not tolerated or contraindicated, or when other suspected vascular injuries require evaluation by arteriography.

Adult↗
PubMed1994

Voltage dependence of beta-adrenergic modulation of conduction in the canine Purkinje fiber.

Although recent voltage-clamp and microelectrode studies have demonstrated beta-adrenergic modulation of Na+ current (INa) the modulation of conduction by catecholamines and the voltage dependence of that process have not been elucidated. To determine whether voltage-dependent modulation of conduction occurs in the presence of a beta-adrenergic agonist, the effect of 1 mumol/L isoproterenol on impulse propagation in canine Purkinje fibers was examined by using a dual-microelectrode technique. At physiological membrane potentials ([K+]o 5.4 mmol/L), isoproterenol increased squared conduction velocity [theta 2, 0.39 +/- 0.25 (m/s)2 (mean +/- SD)] from 3.46 +/- 0.86 to 3.85 +/- 0.98 (m/s)2 (P < .011), an 11% change, without altering the maximum first derivative of the upslope of phase 0 of the action potential (Vmax, 641 +/- 50 versus 657 +/- 47 V/s, P = NS). At transmembrane potential of -65 mV, produced by 12 mmol/L [K+]o titration, theta 2 declined 79% to 0.73 +/- 0.44 (m/s)2 as Vmax decreased 85% to 95 +/- 43 V/s (P < .02). The addition of isoproterenol further decreased theta 2 to 0.49 +/- 0.33 (m/s)2 (P = .02) in parallel with a further decline in Vmax to 51 +/- 25 V/s (P < .05). Isoproterenol produced a 3-mV hyperpolarizing shift of apparent Na+ channel availability curves generated from both theta 2 and Vmax, used as indexes of the fast inward INa, without changing the slopes of the relation. The relation between normalized theta 2 and Vmax over a range of depolarized potentials was linear and was not appreciably altered by isoproterenol.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1994

Direct quantification of apparent binding indices from quinidine-induced in vivo conduction delay in canine myocardium.

To characterize quantitatively the quinidine (QUIN)-induced conduction delay (CD) in vivo, canine ventricular activation times were examined with an epicardial mapping technique. A high-resolution index of normalized (N) QUIN CD, derived from all 56 recording sites, was used to quantify QUIN effect. Repetitive stimulation elicited monoexponential increases in CD(N), the rates of which were a linear function of interpulse recovery interval, tr. Steady-state CD(N) was also linearly related to an exponential function of tr and drug uptake rates. The frequency-dependent properties of QUIN in 14 dogs were characterized by apparent binding and unbinding rates of ka = 7.1 +/- 3.5 x 10(6) M-1 s-1, la = 81 +/- 51 s-1 for activated, and kr = 12.6 +/- 11.3 x 10(3) M-1 s-1, lr = 0.51 +/- 0.26 s-1 for resting states. ka and la were similar to values previously derived in canine Purkinje fibers. Drug unbinding at resting potentials was faster in vivo than previously observed in vitro. The time constant of recovery from QUIN block extracted from the interpulse recovery rate was also identical to that determined from post-mature stimulus diastolic scanning. As predicted by the two-state model, similar binding rates were also derived from declining CD(N) elicited by step decreases in heart rate. These findings represent a complete quantitative description of use-dependent QUIN CD in vivo and provide a firm foundation for characterizing antiarrhythmic drug action under physiologic and pathologic conditions.

Action Potentials↗
PubMed1994

Assessing senior residents' knowledge and performance: an integrated evaluation program.

BACKGROUND: Surgical residents have traditionally been evaluated by ward evaluations and multiple-choice testing; overall resident performance has seldom been objectively evaluated. We developed a comprehensive evaluation program for senior residents. The purpose of this study was to determine whether the several different assessment methods included in this program provide similar information about senior residents' clinical knowledge and performance. METHODS: Sixteen senior general surgery residents were evaluated by subjective faculty ward evaluations, a structured oral examination, the American Board of Surgery In-Training Examination, and an objective structured clinical examination (OSCE). The OSCE was divided into two parts: part A required the resident to obtain a directed history or to perform a physical examination; part B required the resident to answer questions about the patient seen in part A. RESULTS: The various evaluation methods differed in their estimates of clinical competence (ward evaluations rated residents highest; the OSCE, lowest). The American Board of Surgery In-Training Examination correlated with both the structured oral examination and OSCE part B, indicating that all are adequate measures of knowledge. Neither the total OSCE score nor OSCE part A correlated with other measures, but the fact that both are highly reliable suggests that they evaluate different clinical skills. Faculty ward evaluations are inflated and do not correlate with other measures. CONCLUSIONS: We conclude that developing a comprehensive program for evaluating resident competence is desirable and feasible.

Employee Performance Appraisal↗
PubMed1994

Accessing the Columbia Clinical Repository.

The Columbia Clinical Repository is the foundation of the Clinical Information System at the Columbia Presbyterian Medical Center (CPMC). The Repository is implemented as a relational database on an IBM mainframe, using a generic design that employs a small number of tables. Client applications on remote platforms send and receive data through Database Access Modules (DAMs), which support the HL7 protocol, while applications on the mainframe manipulate data through DAMs supporting a locally defined "query template". Implementation using static (compiled) SQL is compared to dynamic (ad hoc) SQL in terms of efficiency and flexibility.

Clinical Laboratory Information Systems↗
PubMed1993

Use of transesophageal echocardiography in the evaluation of traumatic aortic injury.

Indications for aortography following blunt chest trauma are broad and ill-defined. This study prospectively assessed the role of transesophageal echocardiography (TEE) in the evaluation of suspected aortic injury. We used both TEE and aortography to evaluate 69 patients with suspected thoracic aortic injury. The studies were performed and interpreted by staff radiologists and cardiologists. The mean study time for TEE was 27 minutes, whereas the mean study time for aortography was 76 minutes (p < 0.05). No complications occurred with either procedure. Both TEE and aortography revealed no evidence of aortic injury in 61 patients. There was one false-positive aortogram. TEE identified seven aortic injuries; four were confirmed by aortography. One patient underwent thoracotomy and aortic repair based on TEE findings alone. Aortograms yielded false-negative results for two patients; one injury was confirmed at thoracotomy, the other at autopsy. TEE accurately predicted the presence or absence of aortic injury in each case, for a diagnostic sensitivity and specificity of 100%. TEE can be performed safely and efficiently on the multiple-injury patient. We conclude that TEE is useful in the evaluation of suspected aortic injury.

Adult↗
PubMed1993

Traumatic ventral abdominal hernia associated with small bowel gangrene: case report.

A rare case is presented of traumatic subcutaneous rupture of the rectus abdominis with ventral herniation and decollement of the jejunum and transverse colon. Irreversible ischemia of the small bowel had occurred following a large mesenteric avulsion. Computed tomographic scanning detected the parietal defect and identified the herniating viscera.

Abdominal Muscles↗
PubMed1993

Full-text document storage and retrieval in a clinical information system.

The overall design of the CIS at CPMC is heavily influenced by the decision support component. The type of automated decision support being implemented dictates the need for highly structured or coded data. The value of decision support systems has been well documented. The current reliance on free-text documents is natural and a rewarding first step to a more valuable mix of coded and free text. While the health care provider might find the textual comments of the various reports extremely useful, the capability of an automated system to vigilantly review every data element for trends and anomalies is becoming invaluable in today's ever more complex health care delivery environment. Other approaches such as optical imaging systems would facilitate human decision support, but do not supply data in a format that can be processed by automated decision support systems. The developers of the CIS at CPMC believe that data are most valuable when available for both human and automated decision support.

Clinical Medicine↗
PubMed1993

Interpreting natural language queries using the UMLS.

This paper describes AQUA (A QUery Analyzer), the natural language front end of a prototype information retrieval system. AQUA translates a user's natural language query into a representation in the Conceptual Graph formalism. The graph is then used by subsequent components to search various resources such as databases of the medical literature. The focus of the parsing method is on semantics rather than syntax, with semantic restrictions being provided by the UMLS Semantic Net. The intent of the approach is to provide a method that can be emulated easily in applications that require simple natural language interfaces.

Humans↗
PubMed1993

Generating MEDLINE search strategies using a librarian knowledge-based system.

We describe a librarian knowledge-based system that generates a search strategy from a query representation based on a user's information need. Together with the natural language parser AQUA, the system functions as a human/computer interface, which translates a user query from free text into a BRS Onsite search formulation, for searching the MEDLINE bibliographic database. In the system, conceptual graphs are used to represent the user's information need. The UMLS Metathesaurus and Semantic Net are used as the key knowledge sources in building the knowledge base.

Artificial Intelligence↗
PubMed1993

Desperately seeking data: knowledge base-database links.

Linking a knowledge-based system (KBS) to a clinical database is a difficult task, but critical if such systems are to achieve widespread use. The Columbia-Presbyterian Medical Center's clinical event monitor provides alerts, interpretations, research screening, and quality assurance functions for the center. Its knowledge base consists of Arden Syntax Medical Logic Modules (MLMs). The knowledge base was analyzed in order to quantify the use and impact of KBS-database links. The MLM data slot, which contains the definition of these links, had almost as many statements (5.8 vs. 8.8, ns with p = 0.15) and more tokens (122 vs. 76, p = 0.037) than the logic slot, which contains the actual medical knowledge. The data slot underwent about twice as many modifications over time as the logic slot (3.0 vs. 1.6 modifications/version, p = 0.010). Database queries and updates accounted for 97.2% of the MLM's total elapsed execution time. Thus, KBS-database links consume substantial resources in an MLM knowledge base, in terms of coding, maintenance, and performance.

Academic Medical Centers↗
PubMed1993

From ICD9-CM to MeSH using the UMLS: a how-to guide.

One purpose of the Unified Medical Language System (UMLS) is to facilitate conversion of terms from one controlled medical vocabulary to another. We examined our ability to convert International Classification of Diseases, 9th Edition, Clinical Modifications (ICD9-CM) to Medical Subject Headings (MeSH) using the UMLS. We describe a method which mapped 30.4% of ICD9-CM to UMLS. Of these, 95.0% were linked to MeSH, of which translation was straightforward in 90.4%. We discuss the use of these translations for retrieval from MeSH-indexed databases, such as Medline.

Disease↗
PubMed1993

A conceptual model for clinical radiology reports.

The structural and informational content of clinical radiology reports was examined to develop a comprehensive representational schema of the concepts in the domain. The model involves several different conceptual levels, ranging from the high level description of the report to the lower level description of the clinical concepts contained in the reports and the specification of the terms used to express the concepts. The design of an adequate structured representation for the domain has important implications for the design of the electronic patient record, for the unification of different controlled vocabularies by enabling them to be mapped to one common representation, and for the facilitation of natural language processing of clinical reports so that coded data may be obtained.

Humans↗
PubMed1993

Use of an Objective Structured Clinical Examination (OSCE) to measure improvement in clinical competence during the surgical internship.

BACKGROUND: Traditional ward ratings and multiple-choice tests do not reliably assess clinical competence. This study determined the reliability of the Objective Structured Clinical Examination (OSCE) and its sensitivity in detecting the performance gains and deficits in surgical interns. METHODS: A comprehensive 35-station OSCE was administered to 23 incoming interns and seven outgoing interns. The OSCE comprised 17 two-part clinical problems, relying primarily on actual or simulated patients. The reliability of the examination was assessed by coefficient alpha. Significant differences in performance between the two intern groups, between parts A and B, and among the 17 problems were determined by a three-way ANOVA: OSCE performance was also correlated with National Board of Medical Examiners Part II scores. RESULTS: The reliabilities of part A, part B, and parts A and B combined were 0.72, 0.70, and 0.82, respectively. Overall, the outgoing interns performed significantly better than the incoming interns: 58% +/- 1% mean OSCE score versus 47% +/- 1% (p = 0.0001). The 17 clinical problems differed significantly in difficulty; major performance deficits were seen in both groups of trainees. The correlation of OSCE scores with National Board of Medical Examiners Part II scores was not significant (r = 0.11, p = 0.633). CONCLUSIONS: We conclude that the OSCE is an innovative, reliable tool for evaluating resident competence. Although outgoing interns performed better than did incoming interns, the OSCE scores clearly indicated major performance deficits in all interns.

Clinical Competence↗
PubMed1993

Generic queries for meeting clinical information needs.

This paper describes a model for automated information retrieval in which questions posed by clinical users are analyzed to establish common syntactic and semantic patterns. The patterns are used to develop a set of general-purpose questions called generic queries. These generic queries are used in responding to specific clinical information needs. Users select generic queries in one of two ways. The user may type in questions, which are then analyzed, using natural language processing techniques, to identify the most relevant generic query; or the user may indicate patient data of interest and then pick one of several potentially relevant questions. Once the query and medical concepts have been determined, an information source is selected automatically, a retrieval strategy is composed and executed, and the results are sorted and filtered for presentation to the user. This work makes extensive use of the National Library of Medicine's Unified Medical Language System (UMLS): medical concepts are derived from the Metathesaurus, medical queries are based on semantic relations drawn from the UMLS Semantic Network, and automated source selection makes use of the Information Sources Map. The paper describes research currently under way to implement this model and reports on experience and results to date.

Algorithms↗