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Biomedical subjects

D E Morgan

Publications and source records attributed to D E Morgan.

At least 55 records · Page 3Linked to original sources
PubMed1990

Infective endocarditis, 1983-1988: echocardiographic findings and factors influencing morbidity and mortality.

The echocardiograms and clinical records of 70 patients with infective endocarditis seen between 1983 and 1988 were examined to evaluate the role of two-dimensional and Doppler echocardiography in the diagnosis of infective endocarditis and identify risk factors for morbidity and mortality. A blinded observer reviewed the echocardiograms for the presence and size of vegetations and the severity of the valvular regurgitation. Vegetations were identified in 54 (78%) of 69 technically satisfactory echocardiograms. In 38 patients whose heart was examined at surgery or autopsy, all vegetations diagnosed by echocardiography were confirmed, but six additional vegetations were found. Abnormal (greater than or equal to 2+) valvular regurgitation was present in 88% of patients. No patient with less than or equal to 1+ regurgitation (n = 8) died or required valve surgery for heart failure, but three of the eight patients did undergo surgery for mycotic aneurysm, recurrent embolism or paravalvular abscess. In patients without embolism before echocardiography, there was a trend toward a greater incidence of subsequent embolism in those with vegetations greater than 10 mm in size (26% [8 of 31] compared with 11% [2 of 18] with vegetations less than or equal to 10 mm) (p = 0.19). By multivariate analysis, risk factors for in-hospital death (n = 7) were an infected prosthetic valve (p less than 0.007), systemic embolism (p less than 0.02) and infection with Staphylococcus aureus (p = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Abscess↗
PubMed1989

Evaluation of ventricular contractility indexes in the dog with left ventricular dysfunction induced by rapid atrial pacing.

Eight dogs were studied by simultaneous invasive hemodynamic and two-dimensional echocardiographic methods to determine whether left ventricular contractility is altered by 2 weeks of rapid atrial pacing. Additionally, this study evaluated the response of three ventricular contractility indexes to both the pacing intervention and acute load alteration. The indexes compared were ejection fraction, peak systolic pressure to end-systolic volume index ratio (SBP/ESVI) and end-systolic wall stress to end-systolic volume index ratio (ESWS/ESVI). After 2 weeks of pacing at 265 +/- 20 min-1 (mean +/- SD), cardiac index and ejection fraction were reduced to 73 +/- 38 ml/kg per min and 22 +/- 6%, respectively, from 161 +/- 22 and 46 +/- 7 before pacing (both p less than 0.001). Concomitantly, SBP/ESVI and ESWS/ESVI were reduced to 34 +/- 10 mm Hg/ml per kg and 54 +/- 19 g/cm2 per ml per kg, respectively, from 84 +/- 29 and 121 +/- 36 before pacing (both p less than 0.005). There were high correlations for the changes in SBP/ESVI and ejection fraction (r = 0.94, p less than 0.001) and ESWS/ESVI and ejection fraction (r = 0.89, p less than 0.003). Acute afterload alteration with phenylephrine depressed ejection fraction but not SBP/ESVI or ESWS/ESVI. Therefore, this study demonstrates 1) that left ventricular contractility is markedly depressed in the dog by 2 weeks of rapid atrial pacing, and 2) that SBP/ESVI and ESWS/ESVI are superior to ejection fraction as ventricular contractility indexes because these ratios accurately measure contractility changes but are influenced less by after-load conditions.

Animals↗
PubMed1987

Blood coagulation abnormalities in Fischer strain rats bearing tumors.

This study reports an unusual subpopulation of rats bearing transplanted tumors approximately 50% of the total and apparently unrelated to the presence of metastases, that exhibited shortened bleeding times despite reduced platelet numbers and/or fibrinogen levels. The remaining rats exhibited the expected inverse relationships between bleeding time and platelet numbers and/or fibrinogen level. Tumors were hepatomas and squamous cell carcinomas initially induced in the Fischer strain of rats and carried by passage through tissue culture or syngenic recipient animals.

Animals↗
PubMed1986

Echocardiographic assessment of tricuspid regurgitation during ventricular demand pacing.

Twenty patients from our pacemaker clinic population were assessed clinically and by saline contrast echocardiography (subxiphoid view) to determine the prevalence of tricuspid regurgitation (TR) and, if TR was present, its mechanism. The patients had no known TR before lead placement, a single transvenous right ventricular pacing lead present more than 6 months (mean 52, range 7 to 138), ventricular demand pacing alternating with sinus rhythm and rate programmability. Each patient was studied in sinus rhythm and during ventricular pacing. Using the criterion of inferior vena cava (IVC) contrast reflux during ventricular systole to diagnose TR, no patient had evidence of TR in sinus rhythm, consistent with clinical examination. During ventricular demand pacing, jugular venous pulse cannon A waves developed in 10 patients, and 18 patients (including these 10) had IVC contrast reflux during ventricular systole. Analysis of the timing of IVC reflux revealed its close temporal relation to the timing of atrial systole rather than a fixed timing during ventricular systole. This reflux occurred with loss of normal atrioventricular (AV) synchrony and the underlying mechanism in all cases was shown to be right atrial contraction against a closed tricuspid valve. Two patients who did not have such a pattern with pacing maintained normal AV synchrony. These observations indicate that: TR is an uncommon accompaniment of ventricular demand pacing; the jugular venous pulse and IVC echocardiographic contrast patterns during ventricular demand pacing simulate TR when AV asynchrony [corrected] occurs; and the IVC contrast pattern of pacing induced AV asynchrony [corrected] is best termed the cannon A wave synchronous pattern.

Aged↗
PubMed1984

Effects of age and mild hearing loss on speech recognition in noise.

Using an adaptive strategy, the effects of mild sensorineural hearing loss and adult listeners' chronological age on speech recognition in babble were evaluated. The signal-to-babble ratio required to achieve 50% recognition was measured for three speech materials presented at soft to loud conversational speech levels. Four groups of subjects were tested: (1) normal-hearing listeners less than 44 years of age, (2) subjects less than 44 years old with mild sensorineural hearing loss and excellent speech recognition in quiet, (3) normal-hearing listeners greater than 65 with normal hearing, and (4) subjects greater than 65 years old with mild hearing loss and excellent performance in quiet. Groups 1 and 3, and groups 2 and 4 were matched on the basis of pure-tone thresholds, and thresholds for each of the three speech materials presented in quiet. In addition, groups 1 and 2 were similar in terms of mean age and age range, as were groups 3 and 4. Differences in performance in noise as a function of age were observed for both normal-hearing and hearing-impaired listeners despite equivalent performance in quiet. Subjects with mild hearing loss performed significantly worse than their normal-hearing counterparts. These results and their implications are discussed.

Adult↗
PubMed1983

Accuracy of adaptive procedure estimates of PF-max level.

A measure of maximum speech recognition ability (PB max) is often obtained in the clinical audiologic evaluation of patients. However, without developing a complete performance-intensity function (PIF), it is often difficult to determine an appropriate intensity level for measuring PB max. Levitt (1978) has described an adaptive procedure designed to estimate an intensity level at which maximum speech recognition performance could be measured. We have investigated the accuracy of this procedure by comparing speech recognition performance on a CNC word list presented at the level estimated by the adaptive procedure with maximum performance as measured on the listener's performance-intensity function. Using the presentation level indicated by the adaptive procedure, PB max scores were obtained for 12 of 16 normally hearing subjects and 19 of 25 listeners with mild-to-moderate sensorineural hearing loss. Similar accuracy was obtained for the hearing-impaired subjects using a single presentation level of 95 dB SPL, while use of a 40 dB SL speech level would have resulted in a lower proportion of PB-max measurements. Although PB max is most accurately estimated by delineating the entire performance-intensity function, the current results suggest that, if speech recognition is to be measured only at a single level, scores obtained at the level estimated by the adaptive procedure or at 95 dB SPL may serve as reasonable estimates of PB max for listeners with primarily cochlear hearing losses of less than or equal to 50 dB.

Adolescent↗
PubMed1982

Treatment of unipolar depression accompanied by delusions. ECT versus tricyclic antidepressant--antipsychotic combinations.

A retrospective chart study conducted to compare the effectiveness of ECT to tricyclic antidepressant--antipsychotic combination therapy in the treatment of psychotic major depressive disorder. A favorable treatment response occurred in 86% of the ECT-treated patients and 42% of the antidepressant--antipsychotic-treated patients. Depressive symptoms showed improvement in all ECT-treated patients but only 50% of the tricyclic antidepressant--antipsychotic-treated patients. It was concluded that a significantly better treatment response can be expected in delusional depressed patients if treated with ECT rather than a tricyclic antidepressant--antipsychotic drug combination.

Adult↗
PubMed1982

A procedure for quantifying the effects of noise on speech recognition.

This paper describes the results of two experiments in which speech recognition performance was determined for listeners with sensorineural hearing loss, while listening in babble. Adaptive strategies were used in both experiments to measure the signal-to-babble ratio required to achieve a preselected level of performance at several speech presentation levels encountered in normal conversation or when listening through an amplification system. The results suggest that the proposed adaptive strategy may provide a practical method by which the relative effects of competition on speech recognition may be quantified in an individual listener.

Adolescent↗
PubMed1981

Form equivalence of the speech perception in noise (SPIN) test.

An evaluation was conducted of the equivalence of the ten forms of the Speech Perception in Noise (SPIN) Test with normal hearing subjects. Each subject was tested monaurally on all ten forms. Twenty-five subjects were presented the materials at 80 dB SPL at a signal-to-babble ratio of - 1 dB. An additional 25 subjects heard the materials at 30 dB SPL, at a signal-to-babble ratio of + 3 dB. The data were analyzed for equivalence using a parallel tests model. A detailed rationale for the application of this model to the equivalence of the SPIN test is presented. The results indicated that a subset of seven lists fits the equivalence model for PH, PL, and difference (PH - PL) scores. Additionally, analysis of list-pair data (combination of companion forms) suggested that all five list-pairs resulted in equivalent performance.

Adult↗
PubMed1980

Use of digitized speech materials in audiological research.

Computer methods, based on the theory and application of signal processing, combined with numerical methods for simulating mathematical processes, facilitate greater objectivity in most aspects of speech intelligibility testing, including specification of the stimuli, control of the tests, evaluation of the responses, corrective feedback, and automatic interpretation. This paper discusses several basic issues in digital signal processing, and also describes the application of computer-aided procedures for recording and delivery of speech materials for audiologic research. Examples of the use of computer procedures for manipulation of digitized stimuli demonstrate the increased efficiency and versatility of these procedures compared to more conventional tape recording methods. In addition, the use of digitized recordings allows more reliable specification of speech levels than conventional calibration methods involving observations of signal peaks on a VU-meter.

Audiology↗
PubMed1980

Intact acoustic reflexes in the presence of ossicular disruption.

The potential usefulness of impedance studies is reviewed and a case of osteogenesis imperfecta, having bilateral ossicular discontinuity and intact acoustic reflexes, is presented. This seeming paradox was explainable on the basis of surgically confirmed, bilateral disruption of the stapes crura, central to the stapedial tendon insertion.

Acoustic Impedance Tests↗
PubMed1980

Subclinical effects of chronic increased lead absorption--a prospective study. III. Neurologic findings at follow-up examination.

Neurologic examination, nerve conduction testing and electro-oculographic testing have been performed at a baseline examination and a follow-up examination in a group of lead workers with blood lead levels predominantly between 60 and 80 micrograms/dl and in a group of control workers. A statistically significant decreased saccade accuracy measurement in the lead workers compared to the controls was found at both examinations. No other simple test or pattern of findings differentiated between the lead workers and the controls, and the biological significance of the lower saccade accuracy is not clear. Nerve conduction measurements do not appear to be a satisfactory method of detecting subclinical neurologic effects of lead exposure.

Humans↗
PubMed1979

Suggested threshold sound pressure levels for frequency-modulated (warble) tones in the sound field.

The problems inherent in using frequency-specific stimuli in the sound field to determine threshold sensitivity are reviewed, including a discussion of some of the specific problems encountered when introducing pure tones, narrow bands of noise, and frequency-modulated (FM) tones. The results of two experiments are reported. In Experiment I, the relationship between pure tones and frequency-modulated tones is developed under earphones in an anechoic chamber, and in two sound-isolated auditory test rooms (not anechoic). Experiment I resulted in the development of a reference threshold sound pressure level for frequency-modulated signals in the sound field. In Experiment II the reference level was applied to a clinical test facility and evaluated with a group of hearing-impaired individuals. The results suggest that the sound-field reference levels accurately reflect monaural threshold under earphones, when the earphone is calibrated to the ANSI, 1969 standard, and the sound field is calibrated to the suggested standard.

Acoustic Stimulation↗
PubMed1979

Loudness discomfort level and acoustic reflex threshold for speech stimuli.

Loudness discomfort level (LDL) and acoustic reflex threshold (ART) measurements were obtained from subjects with normal hearing using several speech stimuli, as well as broad-band and speech-spectrum noise. The purpose of the investigation was to determine the LDL for a variety of representative speech samples, and to determine the relationship between the LDL and ART for selected speech and noise stimuli. For all stimuli, LDL measurements were relatively constant, but ART measurements decreased significantly for wide-band noise stimuli as compared with the speech stimuli. Mean differences between the two measures were consistent, but individual subject data were characterized by wide variability precluding accurate prediction of the LDL from ART measurements.

Acoustic Stimulation↗
PubMed1978

Recovery of eighth nerve function after cerebellopontine angle surgery.

Retrocochlear lesions cause typical patterns of hearing loss as detailed in special audiometric tests. Such losses, however, may be temporary deficits. Indeed, return to near normalcy following severely depressed auditory function is documented in this article. Conservative surgery on lesions influencing eighth nerve function should be considered. This is not to say that neoplasia can be partially removed, but rather that when tumors can be resected while preserving the cochlear nerve, this should be done inasmuch as good hearing levels may be restored.

Auditory Threshold↗