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Biomedical subjects

J M Jenkins

Publications and source records attributed to J M Jenkins.

156 records · Page 9Linked to original sources
PubMed1983

Automatic computer processing of digital 2-dimensional echocardiograms.

Quantitative studies of left ventricular function using 2-dimensional echocardiography have been limited because of a lack of computerized methods to automatically analyze the echocardiographic images. Previous computer efforts have been directed at digitizing the video output of the 2-D echocardiogram, but this digitizing method has significant limitations. A direct digitization method that produces improvement in signal-to-noise ratio and, subsequently, improved automatic detection of endocardial and epicardial borders, was developed. With definition of these edges, left ventricular global and regional analysis is possible frame by frame so that dynamic changes in cardiac function may be assessed throughout the cardiac cycle. Further technologic advances in 2-D echocardiographic acquisition and image processing should allow computer processing of 2-D echocardiographic data in real time.

Computers↗
PubMed1981

Ultrasonic detection of renal calculi: accuracy tested in an in vitro porcine kidney model.

Porcine kidneys containing human calculi of known size and composition were used to study the ability of ultrasound to localize intrarenal calculi. The study conducted in a blind fashion demonstrated that stones as small as 2 mm could be detected. The chemical composition was not related to the ability to detect the stone. Early trials in the operating room have been encouraging. The porcine kidney model is useful for training purposes.

Animals↗
PubMed1979

Computer diagnosis of supraventricular and ventricular arrhythmias. A new esophageal technique.

Computerized arrhythmia monitors recognize only a few of the significant arrhythmias and generally fail to detect arrhythmias of supraventricular origin. This is because conventional surface leads, which are sufficient for QRS recognition, are highly inadequate for automated P-wave detection. A new two-lead system, which includes a swallowable capsule-electrode for esophageal monitoring of atrial activity, is used in an on-line arrhythmia monitor. Three interval measurements (AA, AR and RR) and a QRS shape measurement provide the foundation for a detailed interpretation of each beat. Building on the single-beat analysis, a contextual diagnostic algorithm then recognizes and reports on-line the following arrhythmias: couplets, bigeminy, trigeminy, ventricular tachycardia, supraventricular tachycardia, atrial flutter, atrial fibrillation, ventricular tachycardia with retrograde conduction to the atria, first-degree block, second-degree block, Wenckebach periodicity, advanced block, third-degree block and sinus bradycardia.

Arrhythmias, Cardiac↗
PubMedDate not supplied

A comparative study of the percutaneous versus intraoral technique for mental nerve block.

OBJECTIVE: Mental nerve block is frequently used to aid repair of facial lacerations; both percutaneous and intraoral approaches to blocking this nerve are used, but have never been compared. The authors compared the two techniques for pain of administration and effectiveness of anesthesia. METHODS: A prospective, randomized, single-blind, crossover study was conducted using ten healthy volunteers aged 22 to 33 years. Patients having prior experience with mental nerve blocks, lidocaine allergy, active oral/facial infection, or previous facial fractures were excluded. Bilateral mental nerve blocks were done using intraoral technique on one side and percutaneous technique on the other. Both techniques were used by the same investigator and were carried out with 27-gauge needles and 2.5 mL of 2% buffered lidocaine at room temperature injected over 20 seconds. The oral mucosa was topically anesthetized with viscous lidocaine for 1 minute prior to intraoral injection. The orders of the blocks and sides of the face anesthetized were randomized. Subjective and objective pain (visual-analog scale), efficacy (anesthesia of lower lip), time to onset, and duration of anesthesia were evaluated. RESULTS: The intraoral technique was subjectively less painful than the percutaneous approach in nine of ten subjects (p = 0.02). Scores on the visual-analog pain scale were significantly lower for the intraoral technique (p = 0.03). Intraoral injection produced lower-lip anesthesia in 10/10 subjects versus 7/10 for percutaneous (p = 0.25). Times to onset (approximately 1-2 minutes) and durations of anesthesia (approximately one hour) were similar for the two techniques. CONCLUSION: The intraoral approach to the mental nerve block with adjunctive topical anesthesia was subjectively and objectively less painful than the percutaneous approach without adjunctive anesthesia. While the intraoral approach had a greater efficacy of lower-lip anesthesia and a longer duration of action, these differences were not statistically significant.

Adult↗
PubMedDate not supplied

Comparison of intraoral and percutaneous approaches for infraorbital nerve block.

OBJECTIVE: The infraorbital nerve block is frequently used during repair of facial lacerations; both percutaneous and intraoral approaches are used. The authors compared the two techniques for pain of administration and anesthetic effectiveness. METHODS: A prospective, randomized, single-blind, crossover study was conducted using 12 healthy volunteers, aged 25-41 years. No patient had prior experience with infraorbital nerve anesthesia, lidocaine allergy, active oral/facial infection, or previous facial fractures. Bilateral infraorbital nerve blocks were done using the intraoral technique on one side and the percutaneous technique on the other. Both techniques were used by the same investigator and were carried out with 27-gauge needles and 2.5 mL of 2% buffered lidocaine at room temperature injected over 20 seconds. The oral mucosa was topically anesthetized with viscous lidocaine for 1 minute prior to intraoral injection. The orders of the blocks and sides of the face anesthetized were randomized. Pain of injection, anesthetic efficacy (anesthesia of upper lip), time to anesthetic onset, and duration of anesthesia were evaluated. RESULTS: By visual-analog pain scale scores, there was less pain by the intraoral approach, although this difference did not achieve significance (p = 0.08). Overall, nine of the 12 subjects considered the intraoral technique less painful than the percutaneous approach (p = 0.14). The intraoral approach produced upper-lip anesthesia in 12 of 12 subjects, versus nine of 12 for the percutaneous technique (p = 0.25). The duration of anesthesia was longer with the intraoral approach (1.6 +/- 0.8 hours versus 0.9 +/- 0.4 hours) than with the percutaneous approach (p = 0.04). The two techniques were similar in times to anesthetic onset. CONCLUSION: The intraoral approach to the infraorbital nerve block after adjunctive topical anesthesia appeared at least as effective in producing upper-lip anesthesia as the percutaneous approach without adjunctive topical anesthesia. Although the volunteers subjectively preferred the intraoral approach and visual-analog pain scores were lower for this approach, these differences did not achieve statistical significance. The intraoral approach was associated with a longer duration of upper-lip anesthesia.

Adult↗
PubMedDate not supplied

Analysis of a decade of carotid reconstructive operations.

Carotid artery reconstruction surgery for atherosclerotic lesions of the extracranial cerebral circulation has become the most common peripheral vascular operation. A better understanding of the indications for operative intervention, enhanced monitoring during surgery, and more precise management of intraoperative anesthesia have all decreased the risks associated with internal carotid endarterectomy (ICA). In an effort to evaluate the safety and efficacy of extracranial carotid reconstructive surgery, we reviewed 3028 operations performed in 2198 patients during the past decade (1977-1986). Operation was recommended because of hemispheric symptoms in 59% of cases. Fourteen percent were advised to have endarterectomy because of an asymptomatic, significant ICA stenosis. Postoperative hemiparesis occurred in 24 patients (1.1%) and was associated with thrombosis at the operative site in 18 patients. Antiplatelet drugs utilized during the last four years were effective in preventing thrombosis at the operative site. Operative mortality during the decade was 1.2%. Follow-up has ranged from one to. 104 months with 86% of the patients alive and 87% symptom free.

Aged↗
PubMedDate not supplied

Transesophageal atrial pacing: importance of the atrial-esophageal relationship.

To determine the thresholds for transesophageal atrial capture, as well as factors that might influence the thresholds, the authors measured the minimal current and pulse duration required to pace the atrium through transesophageal bipolar lead systems in 32 patients during 42 trials. Mathematical modeling suggested that the current density at the posterior atrial wall was dependent upon the current delivered, the electrode distance, and, most importantly, the esophageal-atrial geometry, expressed as the distance from the esophagus to the excitable tissue. To examine this esophageal-atrial distance, 17 different patients, aged 11 months to 44 years, were studied concurrently with either computerized tomography or magnetic resonance imaging of the chest. The thresholds needed to capture the atrium from the esophagus were 13.2 +/- 3.7 mA at a pulse duration of 5.8 +/- 3.1 msec. Further, the data demonstrated that the threshold for transesophageal atrial pacing was poorly related to the patient's age or size. The fit between these data and the mathematical model suggested that the distance between the left atrial posterior wall and the esophagus was approximately 5-6 mm. Likewise, the minimal esophageal-atrial distance as measured by the two imaging techniques was equal to or less than 3.3 mm. These observations suggest that the distance (anterior-posterior dimension) between left atrial posterior wall and the esophagus is small and remains constant despite obvious changes in somatic and linear growth.

Adolescent↗