Biomedical subjects

T M Velde

Publications and source records attributed to T M Velde.

5 recordsLinked to original sources

PubMed1998

Auditory brain stem response in young and old guinea pigs.

OBJECTIVE: To characterize age-related auditory changes in genetically similar guinea pigs. BACKGROUND: In humans and animals, changes in hearing are known to occur with age. METHODS: Brain stem-evoked responses were measured in genetically similar guinea pigs that ranged 6-36 months in age. Changes in hearing and the input/output function curve were determined. RESULTS: Threshold shift with increase in age was seen. Marked reduction in amplitude of response with increasing age was also demonstrated. No change was seen in latency or interpeak interval. CONCLUSIONS: In genetically similar guinea pigs, age-related changes in threshold occurred. Latency and interpeak intervals remained unchanged. Amplitude of response decreased substantially after 12 months of age to a greater extent than predicted by threshold shifts alone. This phenomenon appears important in understanding the pathophysiology of age-related hearing loss.

Age Factors↗

PubMed1983

Ophthalmic timolol treatment causing altered hypoglycemic response in a diabetic patient.

A diabetic patient experienced a dangerous alteration in hypoglycemic symptoms during treatment with ophthalmic timolol maleate. Before and after timolol therapy, hypoglycemic reactions were characterized by sweating, uneasiness, and prompt resolution with glucose treatment. During timolol therapy, reactions were characterized by a changed mental status (including seizures on occasion) and a relative resistance to glucose treatment. Caution must be exercised in the use of even topically applied beta-adrenergic blockers in diabetic patients who are prone to hypoglycemia.

Aged↗

PubMed1981

Aural acoustic-immittance measurements: inter-aural differences.

Bilateral measurements of the aural acoustic-immittance characteristics of the middle-ear transmission system of 48 subjects were made with an acoustic-admittance meter. The measurements, including static acoustic-immittance, acoustic-reflex thresholds, and acoustic-reflex growth functions, were made using a 220-Hz probe. The contralateral reflex data for three pure tones (500, 1000, and 2000 Hz) and for broadband noise were acquired in 2-dB steps at sound-pressure levels from 84-116 dB (tones) and 66-116 dB (noise) during ascending- and descending-intensity level runs. For all acoustic-immittance measurements, right ear and left ear comparisons were made and found not to be significantly different. The individual subject data then were expressed as the absolute differences between ears. In this manner normative inter-aural immittance differences were defined. The peak static immittance data were analyzed in terms of median inter-aural differences and upper 80% cut-off values. The 80% ranges for normal immittance values were smaller for a within subject versus an across subject comparison. For acoustic-reflex thresholds, a disparity between ears of greater than 10 dB was suggested as indicative of an abnormality in the auditory mechanism. Finally, the reflex-growth data indicated mean inter-aural absolute differences that ranged to .040-.043 acoustic mmhos (300-400 acoustic ohms) at the higher reflex activator sound-pressure levels.

Acoustic Impedance Tests↗

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↗

PubMed1981

Speech recognition performance at loudness discomfort level.

The purpose of this experiment was to determine the relationship between the loudness discomfort level (LDL) and maximum speech recognition performance for listeners with sensorineural hearing loss. Performance-intensity functions were obtained for 30 listeners with mild to moderate sensorineural hearing impairment at five speech levels from -18 to +4 dB re: the LDL. Recognition scores were obtained for three speech materials. For all speech materials, recognition scores at levels below the LDL were equivalent to or higher than scores obtained at and above the LDL. These results support the contention that the LDL represents a sound pressure level above which no improvement in speech recognition occurs, and thus, might reasonably be used as the appropriate level for the saturation sound pressure level of a hearing aid.

Amplifiers, Electronic↗