Biomedical subjects

K T Kavanagh

Publications and source records attributed to K T Kavanagh.

40 records · Page 3Linked to original sources

PubMedDate not supplied

Endoscopic surgical management for laryngomalacia. Case report and review of the literature.

Laryngomalacia is the most common of the many causes of respiratory stridor in the newborn. It may be identified by fiberoptic nasopharyngoscopy in the nursery or office. Several anatomic mechanisms of supraglottic collapse have been reported in the literature. The most common is a narrowing of the supraglottic airway with blockage of the glottic opening by the redundant tissue of the aryepiglottic folds. Although surgery rarely is indicated, severe airway obstruction, necessitating surgical intervention, can occur. Resection of supraglottic tissue should be performed only as an alternative to tracheotomy. Surgical procedures ranging from tracheotomy to epiglottidectomy have been advocated. Direct visualization of the obstructing tissue by nasopharyngoscopy allows the planning of an appropriate surgical procedure. In a patient with lateral supraglottic collapse, deep resection of the epiglottis would be expected to weaken the support of the aryepiglottic folds and aggravate the airway condition. Similarly, resection of tissue along the aryepiglottic folds will be useful only if preoperative evaluation demonstrates the obstruction to be at this location.

Airway Obstruction↗

PubMedDate not supplied

Comparison of the intrasubject repeatability of auditory brain stem and middle latency responses elicited in young children.

The auditory brain stem response (ABR) and middle latency response (MLR) were studied in 48 young children (96 ears). The responses were elicited using low intensity stimuli (30-dB nHL clicks) and simultaneously were recorded on a dual time base. Both the ABR and MLR were elicited in 70 ears. In 12 ears, just one response was recorded (ABR in eight ears and the MLR in four ears). In 14 ears, neither response was recorded. Test-retest analysis on the same subject demonstrated that the ABR was more repeatable and easier to identify than the MLR. The test-retest difference was determined for the amplitude and latency of the ABR and MLR waveforms. The test-retest latency difference for wave Pa was found to be 3.6 times larger than for wave V. The normalized test-retest amplitude difference for P phi-Na, Na-Pa, and Pa-Nb was found to be two to three times larger than for wave V. These data support the conclusion that the ABR, rather than the MLR, should be used to measure hearing in young children. The authors also advocate using minimal high pass (HP) filtering when recording the ABR in a sedated or sleeping child. Muscle artifact was not found to be a problem. The authors suggest the use of minimal HP filtering so that phase-shift distortion is minimized and a larger response amplitude can be recorded.

Audiometry, Evoked Response↗

PubMedDate not supplied

Evaluation of hearing handicaps and presbyacusis using World Wide Web-based calculators.

This article is a clinical report on the applicability of computer software in determining hearing handicaps and presbyacusis. The software is now World Wide Web based and can be implemented in a clinical setting by using JavaScript calculators housed on the World Wide Web at . Added features consist of calculating the maximum recommended allowable noise exposure using the National Institute of Occupational Safety and Health 1997 frequencies in handicap determination and the projection of future audiometric thresholds using the International Standards Organization 1999 compression factor. A review of the literature and the theoretical and clinical applications of these new features are discussed. A guide in the selection of Web-based development software is also presented in the hope of encouraging other researchers to develop Web-based versions of their software applications.

Audiometry↗

PubMedDate not supplied

Auditory brainstem and middle latency responses. I. Effect of response filtering and waveform identification. II. Threshold responses to a 500-HZ tone pip.

Auditory brainstem (ABR) and middle latency responses (MLR) were recorded for ten normal subjects. Changes in wave latency were recorded with high- and low-pass filtering using Butterworth filters with standard phase-shift characteristics. When an open filter (15-3,000 HZ) was used, waves IV, V and VI of the ABR were superimposed on wave P phi of the MLR. A positive (P) wave was recorded in the trough of wave Na as the high-frequency cutoff of the recording bandpass (15-100 Hz) was raised above 100 Hz. Wave P divided Na into two parts. The first trough was the slow-negative response and the second was Na2. The origin of the P wave is unclear but may represent a muscle potential. Because of previous inconsistencies in the waveform identification used with these recording techniques, the authors present a modified method of classification which accommodates changes in waveform appearance that occur with different response filtering. The thresholds for various waves of the auditory brainstem (ABR) or middle latency response (MLR) were determined to a 500-Hz tone pip in ten normal listeners in a variety of recording filter bandwidths. Wave V (recording filters 100-3,000 Hz) had a threshold of 26 dB nHL. Wave SN (30-3,000 Hz) had a threshold of 18 dB nHL. Waves Na, Pa and Nb had thresholds of 10 to 11 dB nHL. The threshold for waves Na, Pa and Nb were unaffected by changing the recording bandpass from 15-3,000 Hz. The ABR amplitude increased when the recording filter's low-frequency cutoff was lowered from 100 to 15 Hz (high frequency cutoff, 3,000 Hz). This augmentation is probably due to the inclusion of the lower frequency energy of wave P phi. Lowering the recording filters high-frequency cutoff from 3,000 to 100 Hz (low-frequency cutoff, 15 Hz) resulted in exclusion of the higher frequency ABR but did not elevate response threshold. In all listeners tested, the MLR had a lower threshold than the ABR to a 500-Hz tone pip. It is suggested that the MLR has good potential for use in evaluation of low-frequency threshold.

Acoustic Stimulation↗