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Biomedical subjects

D L Jones

Publications and source records attributed to D L Jones.

At least 145 records · Page 8Linked to original sources
PubMed1990

Somatosensory evoked potential assessment of the inferior alveolar nerve following third molar extraction.

Injury to the inferior alveolar nerve can occur during 3rd molar removal. In this study, 14 patients who had 3rd molars removed were evaluated by 4 methods: 1) threshold to electrical stimulation, 2) visual analogue scale subjective ratings of electrical stimulation, 3) two-point discrimination in mental nerve area, and 4) analysis of somatosensory evoked potentials. The last technique proved to be the most sensitive of the methods, providing an objective evaluation as compared to other methods which require a subjective interpretation by the patient.

Electric Stimulation↗
PubMed1990

Speech production time and judgments of disordered nasalization in speakers with cleft palate.

The purpose of this study was to investigate the effect of production time on the perception of disordered nasalization in children with cleft palate. The subjects with cleft palate included 5 who produced acceptable speech consistently, 5 who produced disordered nasalization consistently, and 10 who were inconsistent in the production of disordered nasalization. We examined a range of production times similar to those for the production of single-word and connected speech tasks. Ten judges used direct magnitude estimation to rate severity of disordered nasalization. An accelerometric ratio technique was used to estimate the extent and timing of nasal acoustic activity. The results showed that reducing the production time did not change perceptible nasalization.

Adolescent↗
PubMed1990

Utility of low energy test shocks for estimation of cardiac and electrode impedance with implantable defibrillators.

We assessed the value and safety of using a low voltage test shock to predict cardiac and electrode impedance during subsequent high voltage, transvenous, sequential pulse shocks. Two transvenous defibrillation catheters were inserted in 15 patients undergoing electrophysiology study for the evaluation of ventricular tachycardia/fibrillation. A sequential pulse test shock at stored voltage of 50 or 100 volts was delivered during sinus rhythm and high voltage therapeutic shocks were delivered during induced ventricular tachycardia/fibrillation. The test shocks were well tolerated and caused only minimal discomfort. Peak delivered voltage for each pulse of the test shock ranged from 34 to 116 volts (mean 62 +/- 27) and for each pulse of the therapeutic shocks from 186 to 778 volts (mean 435 +/- 146). There was a very strong relationship between the impedance of the test and the mean impedance of the therapeutic shocks (R = 0.89, P less than 0.001). The mean impedance of the test shock was slightly greater than the mean impedance of the test shock as slightly greater than the mean impedance of the therapeutic shocks (mean 90 +/- 24 ohms compared to 77 +/- 16 ohms, P less than 0.001), with a maximum difference between test and therapeutic shock impedances of 39 ohms (mean difference 8.4 +/- 10.3 ohms). There was a significant inverse relationship between impedance and peak current (R = -0.49, P = 0.001). Cardiac and electrode impedance during transvenous defibrillation can be predicted reliably and safely by a low voltage test shock. This technique provides a safe and simple method to ensure appropriate connections and electrode function for subsequent countershock therapies.

Adult↗
PubMed1990

Correlation between the ventricular electrogram amplitude in sinus rhythm and in ventricular fibrillation.

During testing of implantable defibrillators, ability to sense ventricular fibrillation is assessed by observing electrograms and the emitted ECG interpretation channel during induced ventricular fibrillation. We hypothesized that ventricular electrogram amplitude in sinus rhythm could be used to predict the ventricular electrogram amplitude in ventricular fibrillation and serve as a first approximation of the "safety margin" for sensing ventricular fibrillation. We compared the peak-to-peak epicardial ventricular electrogram during sinus rhythm and ventricular fibrillation in 12 patients undergoing defibrillator implantation. The ventricular electrogram was recorded with an integrated bipolar lead and filtered at 10-50 Hz. Ventricular fibrillation was induced by alternating current and the ventricular electrogram measured from cessation of alternating current to the first countershock. The mean ventricular electrogram amplitude in sinus rhythm was 15.3 +/- 5.4 mV (range 7.1-25.5) and in 37 episodes of ventricular fibrillation was 8.3 +/- 3.6 mV (range 2.1-16.3). There was a significant relationship between the mean ventricular electrogram amplitude in sinus rhythm and in ventricular fibrillation (R = 0.7, P less than 0.001). There was wide variation among individuals in the decrease in the mean ventricular electrogram amplitude during ventricular fibrillation, with the ratio of mean ventricular electrogram in sinus rhythm to mean ventricular electrogram in ventricular fibrillation ranging from 0.29 to 1.05 (mean 0.55 +/- 0.20). This suggests that up to a fourfold decrease may be expected in the mean ventricular electrogram amplitude during ventricular fibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Pacing, Artificial↗
PubMed1990

Standardization for the reporting of nasopharyngoscopy and multiview videofluoroscopy: a report from an International Working Group.

A multidisciplinary International Working Group of scientists was assembled to address the question of standardizing reporting techniques for multiview videofluoroscopy and nasopharyngoscopy, the generally accepted standards for direct observation of the velopharyngeal valve. This report is a first attempt to propose standards while seeking feedback from the readership in order to further develop a common methodology.

Cineradiography↗
PubMed1990

Intraoperative recording of trigeminal evoked potentials during orthognathic surgery.

The inferior alveolar branch of the trigeminal nerve is at risk during sagittal split osteotomies, a common maxillofacial surgical procedure. The purpose of this study was to evaluate the use of somatosensory evoked potentials to assess the functional state of the nerve during surgery. Ten patients scheduled for bilateral sagittal split osteotomies were studied. Recording electrodes were placed on the scalp overlying vertex and inion, and subcutaneous stimulating electrodes were inserted 1 cm apart over the mental foramina. Recordings were made bilaterally from all patients. Baseline recordings were made after anesthetic induction, prior to the initial incision. Subsequent recordings were made just prior to the mandibular bone cuts, during splitting of the mandible, and after rigid fixation of the mandible. Analysis of the baseline data identified a series of peaks at 20 and 26 milliseconds following stimulation. This biphasic response was consistent across subjects and was chosen for subsequent analysis. Both the amplitude and latency of the response were significantly (P less than .05) affected when the nerve was retracted medially while the medial horizontal bone cuts were made. However, in all patients, the waveforms returned to baseline values within 10 to 20 minutes. No consistent changes were found in the evoked potentials recorded at other times during the surgical procedure. The results indicate that surgical retraction can cause a transient neurapraxia, but they do not account for postsurgical loss of sensation, which could be due to other factors, such as edema and swelling.

Adult↗
PubMed1990

Initial clinical experience with the pacemaker-cardioverter-defibrillator.

The implantation of a new multiprogrammable pacemaker-cardioverter-defibrillator is reported in four patients suffering from drug-refractory ventricular tachycardia or fibrillation. The generator (PCD 7215; Medtronic Inc) was interfaced to the epicardium by three countershock patch electrodes and one ventricular myocardial screw-in lead for sensing/pacing. The device employs separate rate detection criteria for ventricular tachycardia and ventricular fibrillation with automatic delivery of up to four therapies per episode. Therapeutic options include: antitachycardia burst or autodecremental pacing, synchronized cardioversion, defibrillation and ventricular demand pacing at 30 to 90 beats/min. Four men and one woman (ages 29 to 75 years) underwent intraoperative implant evaluation, and the device was implanted in the four men. Over a follow-up of 1.5 to 23 months, 161 spontaneous episodes of ventricular tachycardia and nine episodes meeting ventricular fibrillation criteria (cycle length less than 280 to 290 ms) were detected and treated by the device. Ramp pacing was initially employed to terminate 140 ventricular tachycardia episodes and was successful 88.5% of the time while 10 (7.2%) required low energy epicardial cardioversion (4 to 10 J). Six (4.3%) episodes terminated spontaneously prior to therapy delivery. All nine spontaneous episodes of ventricular fibrillation were defibrillated using 10 to 15 J. Two patients continue to do well with the device functioning reliably. The device was removed at the time of heart transplant in one patient, while another patient died suddenly from drug overdose. No other complications, device malfunctions or inappropriate therapy delivery have been observed. These early results demonstrate the potential usefulness of a programmable device which provides graded therapy for ventricular tachycardia with added defibrillation and bradycardia pacing capability.

Adult↗
PubMed1990

Comparison of methods to assess neurosensory alterations following orthognathic surgery.

Orthognathic surgery may damage branches of the trigeminal nerve, resulting in postoperative neurosensory disturbances. Alterations may be due to surgical edema, stretching, or direct trauma to the nerve. Lack of a standard and objective method of assessment hinders efforts to study and/or reduce the incidence of neurosensory disturbances. This study compared three methods of assessing neurosensory disturbances in patients who underwent bilateral mandibular ramus sagittal split osteotomies. Forty patients (26 female, 14 male) ranging in age from 23 to 47 years participated in the study. All of the patients had bilateral mandibular ramus sagittal split osteotomies and were stabilized with rigid skeletal fixation. Neurosensory testing was performed prior to surgery, and at 2 weeks, 1 month, 3 months, 6 months, and 1 year following surgery. Methods of assessment included two-point discrimination, threshold to electrical stimulation, and somatosensory evoked potentials. Threshold to electrical stimulation and two-point discrimination were obtained by the two-alternate forced choice technique.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Contribution of nucleus medianus to the drinking and pressor responses to angiotensin II acting at subfornical organ.

The contribution of neurons in the nucleus medianus (NM) in mediating the drinking and pressor responses elicited by administration of angiotensin II (AII) either directly into the subfornical organ (SFO) or intravenously was investigated in conscious, unrestrained rats. Microinjection of AII into the SFO elicited a robust drinking (7.9 +/- 0.8 ml in 15 min; n = 24) and pressor (peak rise in mean arterial pressure (MAP), 15 +/- 1 mm Hg; n = 20) response. On the other hand, intravenous infusion of AII elicited an increase in MAP (36 +/- 3 mm Hg; n = 14) accompanied by a marked reflex bradycardia (134 +/- 18 beats/min), but not a significant drinking response. Lesions of NM cells, dorsal to the anterior commissure and between the fornical columns, with the neurotoxin kainic acid significantly (P less than 0.05) attenuated the drinking response (prelesion volume, 8.3 +/- 0.8 ml in 15 min; postlesion volume, 1.9 +/- 1.4 ml in 15 min; n = 7), but did not alter the pressor response to AII injected directly into the SFO. Similarly, kainic acid lesions of NM cells did not significantly effect the pressor response or the associated reflex bradycardia to intravenous administration of AII. Sham lesions of NM cells or control kainic acid lesions of adjacent structures did not alter the AII-induced drinking or pressor responses. These data suggest that neurons in the dorsal NM are part of a forebrain neuronal circuit that is involved in the drinking, but not the pressor responses to AII acting at the SFO in the conscious rat.

Angiotensin II↗
PubMed1989

Lipids in breast carcinogenesis.

Excess dietary fat has been identified as a risk factor in the development of human breast carcinoma. However, the quality of fat may be more important than the overall quantity. We have studied the growth of human MCF7 breast carcinoma xenografts in athymic mice treated with dietary supplements of N-6 and N-3 series essential fatty acids given as natural preparations of evening primrose oil and fish oil. Olive oil and normal laboratory diet lacking the essential fatty acids served as controls. Animals treated with essential fatty acids developed tumours which were significantly smaller than both control groups (Mann-Whitney U test, P less than 0.001). Median tumour weights according to diet were: evening primrose oil, 133 mg; fish oil, 70 mg; olive oil, 212 mg; and control, 270 mg. Nutritional intervention to increase the proportion of essential fatty acids in the diet may have a role in the management of breast carcinoma.

Animals↗
PubMed1989

Sequential pulse countershock between two transvenous catheters: feasibility, safety, and efficacy.

We evaluated the feasibility, safety, and efficacy of sequential pulse countershock (SqCS) delivered solely through two endocardial catheters for the termination of ventricular tachycardia (VT) and fibrillation (VF) in patients undergoing electrophysiology studies (EPS). Thirty-four patients (31 men, 3 women) with a mean age of 56.8 +/- 10.1 years were studied. Etiology of VT/VF was ischemic heart disease (n = 26), cardiomyopathy (4) repaired tetralogy of Fallot (n = 1), heart transplant (n = 1), and no identifiable heart disease (n = 2). Catheters were positioned successfully in 29 patients. These were positioned in the right ventricular apex (RVA) and the coronary sinus (CS), respectively. The RVA electrode served as the common cathode for both pulses. The two electrodes located near the right atrium/superior vena cava junction served as anode for pulse 1 while the distal CS electrodes served as anode for pulse 2. Twenty-nine induced VT episodes with cycle length (CL) 220-370 msec were treated. SqCS successfully terminated 15 VT (100-500V) while 14 were accelerated or degenerated to VF. VTCL was longer in successful SqCS episodes than in those that were accelerated (285 +/- 17.3 vs 245 +/- 30.8 msec, P less than .003). Of 26 VF episodes, 21 were terminated with SqCS (500-900V) and 5 were terminated by transthoracic rescue shocks. On 2 occasions, failure to defibrillate was attributable to poor catheter position at the time of shock. No complications occurred. We conclude that SqCS delivered solely between endocardial catheter electrodes is feasible and effective using energy doses within the range of existing implantable cardioverter defibrillators.

Adult↗
PubMed1989

Effects of time to defibrillation and subthreshold preshocks on defibrillation success in pigs.

The purpose of this study was to examine the effects of: (1) time to defibrillation and (2) subthreshold preshocks on defibrillation success. We conducted two separate experiments in 19 anaesthetized, open-chested pigs. Defibrillation was attempted using the sequential pulse technique approximately 10 s after electrically induced ventricular fibrillation. Each sequential pulse shock consisted of two trapezoidal pulses (approximately 3 ms duration), separated by 0.2 ms. Current was delivered to three mesh electrodes (TX-7, Medtronic) sutured over the anterior right ventricle, posterior right ventricle, and lateral left ventricle. For each animal, defibrillation threshold (DFT) defined as the lowest delivered energy that defibrillated the heart, was measured twice and the average was designated as mean DFT. The energy at 1.4 times the specific mean DFT for each pig was designated as the test shock and 100 volts less than the mean DFT was designated as the preshock. In the first experiment, test shocks were delivered at five different fibrillation intervals (10, 20, 40, 60, and 90 s). Time to test shock delivery was randomized for 10 to 60 s, but, 90 s was always tested at the end of the study. Percentages of success at 10, 20, 40, 60, and 90 s were 94, 78, 94, 83, and 100%, respectively (p = NS). The 12 pigs in which all initial test shocks were successful were selected for the evaluation of post defibrillation arrhythmias. The cumulative incidence of complete heart block lasting at least 5 s were 8, 33, 83, 83, and 83%, respectively. The incidence of complete heart block increased significantly at 40 s (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Vena caval filter splaying: potential complication of use of the titanium Greenfield filter.

Significant structural and mechanical differences exist between the titanium and stainless steel versions of the Greenfield filter (GF). The titanium GF has a longer leg length (49 mm vs 43 mm), a greater span (38.5 mm vs 28.0 mm), and a larger hook angle (41 degrees vs 23.5 degrees). In vitro tests demonstrated approximately sevenfold greater filter length shortening (a measure of filter splaying) for the titanium GF in response to a given applied load. These differences resulted in marked filter splaying and inferior vena cava (IVC) perforation in three patients in whom a titanium GF had been inserted. The aorta was penetrated by a filter leg in one patient, and abdominal or back pain was present in all three patients. In vitro tests involving thrombosis within a latex balloon revealed that the titanium GF, but not the stainless steel GF, remained splayed even in the face of clot retraction. Design modifications, possibly using shorter, thicker filter legs and using reduced hook angles, should be made in the titanium GF to decrease the risk of filter splaying and IVC perforation before widespread use of this device.

Adult↗
PubMed1989

A new microbioassay for the measurement of lactogenic hormones in human serum.

The standard Nb2 assay for biologically active prolactin has been modified to allow a rapid convenient microbioassay without loss of specificity or accuracy. Lactogenic hormones specifically stimulate the replication of Nb2 node rat lymphoma cells in suspension culture and form the basis of a currently available bioassay to measure prolactin and growth hormone in human serum. A new microbioassay was developed using microtest plates enabling a large number of samples to be assayed simultaneously whilst maintaining the overall sensitivity of the bioassay for lactogenic hormones. Growth of the Nb2 node lymphoma cells, measured by a light scattering technique using optical density on a spectrophotometer, was shown to be closely correlated with the cell number determined on a Coulter counter. Addition of excess anti-human prolactin and anti-human growth hormone completely inhibited the growth stimulatory effects of both human prolactin and human growth hormone. This new microbioassay (BA) and conventional radioimmunoassay (RIA) were used to measure lactogenic hormones in 48 normal subjects. There was a close correlation between the results of both assays for each hormone studied in the control sera. The mean basal BA/RIA ratio was 1.5 (range 0.8-2.0) for prolactin, 0.7 (range 0-4.5) for growth hormone and 1.3 (range 0.5-1.9) for total lactogenic activity.

Adult↗
PubMed1988

Sequential pulse defibrillation in humans: orthogonal sequential pulse defibrillation with epicardial electrodes.

A newly described sequential pulse technique, using four mesh electrodes positioned to approximate a true orthogonal system around the heart, was compared with a single pulse system using two of these same electrodes, which were located in positions that would be used for an automatic implantable defibrillator. The influence of electrode size was also assessed. The minimal energy necessary for defibrillation (defibrillation threshold) was determined intraoperatively in 21 volunteer patients undergoing accessory pathway ablation of Wolff-Parkinson-White syndrome. Ventricular fibrillation was induced with alternating current. Ten seconds after fibrillation onset defibrillation shocks were begun using either the single or the sequential pulse technique with stored voltage incremented until defibrillation was accomplished (defibrillation threshold). Selection of the use of a single or sequential pulse technique for the initial attempt was randomized. Defibrillation thresholds were determined in three groups of patients: 1) those with four small mesh electrodes (6 cm2), 2) those with two small and two large (13 cm2) mesh electrodes, and 3) those with four large mesh electrodes. In all cases, the average minimal energy needed for sequential pulse defibrillation was less than that required for single pulse defibrillation in the same patients with the same electrodes (four small, 24.8 +/- 24.7 J single versus 6.7 +/- 8.3 J sequential; two small plus two large, 11.4 +/- 15.0 J single versus 2.7 +/- 1.4 J sequential; four large, 8.1 +/- 5.3 J single versus 3.9 +/- 2.6 J sequential). Using the 6 cm2 electrodes for single pulse defibrillation energies delivered at greater than 45 J in two patients failed to defibrillate the heart.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Flecainide acetate does not alter the energy requirements for direct ventricular defibrillation using sequential pulse defibrillation in pigs.

Flecainide acetate is a recently approved class 1c antiarrhythmic agent indicated for patients with serious ventricular arrhythmias. Because flecainide may be used in patients with automatic implantable defibrillators, we assessed the effect of flecainide on ventricular defibrillation energy requirements in a pig model. Different doses of flecainide maintaining plasma levels in the "subtherapeutic" (six pigs), "therapeutic" (eight pigs), and "supratherapeutic" (eight pigs) range were administered to three groups of pigs. A fourth group (six pigs) served as a time control and was given normal saline only. Episodes of ventricular fibrillation were induced and then terminated using sequential truncated trapezoidal direct current shocks delivered by a tripolar internal defibrillator system. Energy requirements for defibrillation were assessed by measuring defibrillation threshold and also by comparing shifts in the curves relating energy with percent successful defibrillation. Flecainide failed to alter defibrillation requirements at any dose. We conclude that ventricular defibrillation energy requirements are not affected by flecainide in our pig model. Both the defibrillation threshold technique and the comparison of curves relating success of defibrillation to energy yielded similar results suggesting that either can be used to assess energy requirements for defibrillation.

Animals↗