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Biomedical subjects

D Byrne

Publications and source records attributed to D Byrne.

At least 19 recordsLinked to original sources
PubMed1999

An efficient, adaptive method of measuring loudness growth functions.

This paper presents a new categorical loudness scaling procedure that differs from previously published loudness scaling procedures by (i) adaptively selecting a new set of levels for each new sequence, (ii) deriving levels that are equispaced on the loudness scale, and (iii) using a continuous scale with few labels. A major advantage of the adaptive procedure is that the individual dynamic range need not be measured prior to loudness testing. The adaptive procedure proved to be time efficient and to produce complete loudness functions from Not heard to Uncomfortably loud for normal hearing and hearing impaired subjects. The pattern of short-term and long-term reliability was similar to that reported for non-adaptive loudness scaling procedures. Three presentations produced a stable loudness function. Normative curves for one octave babble-noise at six test frequencies are presented and compared to normative data obtained with a selection of published categorical scaling procedures.

Adolescent↗
PubMed1998

Cost-saving implant training aids.

This article describes a simple step-by-step procedure that uses inexpensive materials to enable those who wish to learn procedures used in the construction of a screw-type implant overdenture to practice these procedures before they use expensive precious metal components. The use of this procedure will result in considerable savings in training costs and affords a greater opportunity to provide practical experience before making this type of an overdenture for patients. It could also provide for a rapid expansion in the number of trained personnel who could make this form of treatment available to a larger number of patients.

Dental Alloys↗
PubMed1998

The fit of cast and premachined implant abutments.

STATEMENT OF PROBLEM: There is insufficient information regarding the adaptation of abutments to implants. PURPOSE: This study assessed the adaptation of premachined, cast, and laboratory modified premachined abutments to implants at two sites: abutment/implant interface and screw to screw seat. MATERIAL AND METHODS: Six combinations of abutments and implants were studied: CeraOne abutments joined to Nobel Biocare implants; STR (Implant Innovations Inc.) abutments joined to 31 implants; Cast UCLA (31) abutments subjected to porcelain firing cycles and joined to 31 implants; Cast UCLA abutments subjected to porcelain firing cycles and joined to Nobel Biocare implants; UCLA premachined abutments cast with gold palladium alloy and subjected to porcelain firing cycles (later joined to 31 implants); and UCLA premachined abutments joined to 31 implants. Each group contained five assemblies. RESULTS: The adaptation of abutments to implants was closer and the amounts of contact larger for assemblies with premachined and laboratory modified premachined abutments than for those with cast abutments. CONCLUSION: The finishing of custom-made abutments requires further refinement.

Analysis of Variance↗
PubMed1998

Open earmold fittings for improving aided auditory localization for sensorineural hearing losses with good high-frequency hearing.

OBJECTIVE: We tested the hypothesis that the use of nonoccluding earmolds for hearing aid fittings could optimize auditory localization in the vertical plane for people with moderate, low-frequency hearing losses and good hearing at frequencies above 4000 Hz. This benefit was expected to arise from leaving the pinna unobstructed and by optimizing hearing (unaided) for frequencies above the hearing aid's limit. DESIGN: Twenty-two participants had hearing losses greater than 30 dB over the range 250 to 2000 Hz and had minimal losses (< 30 dB) at 6000 Hz and 8000 Hz. Their auditory localization was tested, using a horizontal arc and a vertical arc of loudspeakers, when listening unaided and when fitted bilaterally with Behind The Ear hearing aids with three earmold types--closed (occluded), open (partly occluded), sleeve (nonoccluded). RESULTS: Localization of vertical plane sound sources was significantly poorer for the closed earmold condition than for unaided. The open and sleeve conditions were better than the closed condition, and, for the sleeve earmold, vertical localization was almost equal to that unaided. The capacity to benefit from using open rather than closed earmolds was related to hearing level; people with the best hearing at 4000, 6000, and 8000 Hz received the most benefit. There was limited evidence that open earmolds also can be advantageous for some aspects of horizontal plane localization. CONCLUSIONS: Nonoccluding earmolds optimize aided vertical localization for hearing aid users with good high-frequency hearing. The "sleeve" earmold, so far used only in research, may be a useful clinical option.

Adolescent↗
PubMed1998

Speech recognition of hearing-impaired listeners: predictions from audibility and the limited role of high-frequency amplification.

Two experiments were conducted to examine the relationship between audibility and speech recognition for individuals with sensorineural hearing losses ranging from mild to profound degrees. Speech scores measured using filtered sentences were compared to predictions based on the Speech Intelligibility Index (SII). The SII greatly overpredicted performance at high sensation levels, and for many listeners, it underpredicted performance at low sensation levels. To improve predictive accuracy, the SII needed to be modified. Scaling the index by a multiplicative proficiency factor was found to be inappropriate, and alternative modifications were explored. The data were best fitted using a method that combined the standard level distortion factor (which accounted for decrease in speech intelligibility at high presentation levels based on measurements of normal-hearing people) with individual frequency-dependent proficiency. This method was evaluated using broadband sentences and nonsense syllables tests. Results indicate that audibility cannot adequately explain speech recognition of many hearing-impaired listeners. Considerable variations from audibility-based predictions remained, especially for people with severe losses listening at high sensation levels. The data suggest that, contrary to the basis of the SII, information contained in each frequency band is not strictly additive. The data also suggest that for people with severe or profound losses at the high frequencies, amplification should only achieve a low or zero sensation level at this region, contrary to the implications of the unmodified SII.

Adult↗
PubMed1998

General practice and the new science emerging from the theories of 'chaos' and complexity.

This paper outlines the general practice world view and introduces the main features of the theories of 'chaos' and complexity. From this, analogies are drawn between general practice and the theories, which suggest a different way of understanding general practice and point to future developments in general practice research. A conceptual and practical link between qualitative and quantitative methods of research is suggested. Methods of combining data about social context with data about individuals and about biomedical factors are discussed. The paper emphasizes the importance of data collected over time and of considering the multiplicative interactions between variables. Finally, the paper suggests that to develop this type of research, general practice many need to reassess systems of categorizing and recording appropriate data.

Data Collection↗
PubMed1998

Improvement in aided sound localization with open earmolds: observations in people with high-frequency hearing loss.

Sound localization ability was tested in nine people with marked, bilateral, high-frequency hearing loss and little or no low-frequency loss. They had previously been fitted bilaterally with behind-the-ear hearing aids and closed earmolds and showed poorer aided than unaided localization performance. Further testing was conducted in unaided and aided conditions, with the aids coupled to closed, open, and "sleeve" (extra-open) earmolds. Closed earmolds affected localization, particularly in the frontal horizontal plane, but performance was restored to unaided levels in both of the open earmold conditions. In the lateral vertical plane, localization was found to correlate with the extent of difference between low- and high-frequency hearing levels. That result is discussed in terms of a dynamic, low-frequency localization cue. Open earmolds are argued to improve aided sound localization for the present sample by permitting undistorted access to low-frequency interaural time/phase differences.

Aged↗
PubMed1997

Bond strengths of maxillary anterior base metal resin-bonded retainers with different thicknesses.

PURPOSE: This study evaluated the effect of three different thicknesses of base metal resin-bonded retainers on retention/resistance. MATERIAL AND METHODS: Three ivorine teeth, a central incisor, lateral incisor, and canine, were prepared to receive resin bonded retainers. Fifteen metal replicas of prepared teeth were made (five for each tooth morphotype). A total of 45 metal retainers were cast in three different thicknesses, 0.3, 0.5, and 0.7 mm, with 15 for each thickness. Retainers were cemented to metal die replicas with Panavia EX luting agent. After 24 hours, forces to dislodge the retainers were applied at 45 degrees to the vertical mesiodistal plane at the proximolingual line angle. RESULTS: An increase in thicknesses resulted in elevation of dislodging forces that were almost linear for the three thicknesses of canine retainers. The central incisor exhibited the greatest increase in resistance to dislodgment between retainers that were 0.3 and 0.5 mm thick, whereas increased thickness for the lateral incisor retainer resulted in minimal or no benefit.

Analysis of Variance↗
PubMed1997

A comparison of the dimensional accuracy of the splinted and unsplinted impression techniques for the Bone-Lock implant system.

STATEMENT OF PROBLEM: The precise transfer of intraoral relationships of implants to laboratory working models is central to the success of implant prostheses. PURPOSE: In this study a stone master model incorporating five implants (Bone-Lock) was used to compare the dimensional accuracy of a splinted impression technique with an unsplinted impression technique. METHODS: A three-factor analysis of variance was used to examine the effect of technique, relative position of the implant on the cast, and plane of measurement. RESULTS: All three factors had a significant effect on dimensional accuracy. CONCLUSIONS: The splinted technique exhibited more deviation from the master model than the unsplinted technique did. This was primarily associated with rotational discrepancies around the long axes of the implants for the splinted technique.

Analysis of Variance↗
PubMed1997

Auditory localization, detection of spatial separateness, and speech hearing in noise by hearing impaired listeners.

In two groups, one with sensorineural and the other with conductive-mixed hearing loss, measures were made of single-source localization and speech intelligibility in both spatially separate and nonseparate noise. There was also a test for detecting when two sounds came from the same location or from separate ones. Localization test results confirmed earlier findings, namely, disruption of vertical plane ability generally, and a further, particular disturbance to horizontal plane localization in the conductive-mixed group. Compared with a normal control group, there were only slight signs of benefit from separation of speech and noise in the region lateral to the listener, and virtually none in the frontal region. The new test, spatial separateness, had elements in common with both of the other tests, and links were observed from localization to separateness detection, and from separateness to benefit from separation of speech and noise. Localization was also related to speech hearing in nonspatially separated noise.

Aged↗
PubMed1997

Urokinase thrombolysis as initial therapy for acute and non-acute ischemic extremities.

Limb ischemia, both acute and chronic, presents a risk to life and limb with mortality rates from 3% to 37% and amputation rates of the same range. Our experience with urokinase thrombolysis as the initial therapy for acute and non-acute ischemic extremities over 57 consecutive cases of native arterial occlusion by either thrombus or embolus has resulted in no mortality and only 3.5% requiring amputation (2 of 57). In 74% of cases initial thrombolytic therapy was followed by either balloon angioplasty (35 patients) or surgery (7 patients) to relieve the underlying cause of obstruction (i.e., stenosis, occlusion or aneurysm). Thrombolysis alone was sufficient and effective treatment in the remaining 26% (15 patients).

Adult↗
PubMed1997

Consonant perception in quiet: effect of increasing the consonant-vowel ratio with compression amplification.

Single-channel syllabic compression amplification may increase the consonant-vowel ratio (CVR). This study was conducted to investigate the effect of CVR increases, associated with syllabic compression, on consonant perception in quiet for people with normal hearing and those with sensorineural hearing impairment. Fifteen hearing-impaired and 15 normal-hearing older people were assessed with different versions of the Nonsense Syllable Test, which had been recorded with linear and compression amplification (compression ratio = infinity). Overall scores did not differ significantly with type of amplification for both subject groups. Analysis of classes of sounds revealed the differential effect of type of amplification for the subject groups. This study highlights the need for audiologists to be aware that applying amplification that raises the level of consonants in relation to vowels is not always beneficial for people with hearing impairment, as the evidence indicates that CVR may be a cue to the perception of some consonants.

Adult↗
PubMed1996

Effects of earmold type on ability to locate sounds when wearing hearing aids.

OBJECTIVE: To determine whether the choice of earmold type can affect aided auditory localization. HYPOTHESES: 1) for sensorineural hearing losses with good low-frequency hearing (Low group, n = 10), the use of open earmolds could avoid decrements in horizontal plane localization found with closed (occluding) earmolds; 2) for sensorineural losses with good high-frequency hearing (High group, n = 12), the use of open earmolds could result in better vertical plane localization than could the use of closed earmolds; and 3) for conductive/mixed hearing losses (CM group, n = 19), the choice of earmold type-hard short, soft short, or soft long-could affect aided localization. DESIGN: Aided and unaided auditory localization was tested for the above three groups of hearing-impaired listeners when wearing bilaterally fitted hearing aids. RESULTS: For the Low group, results were inconclusive because nine listeners showed virtually perfect horizontal localization with both closed and open earmolds. For the High group, two listeners showed improved vertical plane localization with open earmolds. These were the only listeners with HTLs of 30 dB or better at 6000 Hz and 8000 Hz. For the CM group, aided horizontal plane localization was significantly better than unaided localization for about half of the listeners and was similar for the other half. There was no significant group difference for the three earmold types. For some individuals, one earmold type was better than the others. CONCLUSIONS: The choice of earmold can effect aided localization, but the specific effects need further elucidation. Audiologists should be aware that people with conductive or mixed hearing losses may have poor auditory localization and that this may be improved by the fitting of hearing aids.

Bone Conduction↗
PubMed1996

Effects of acclimatization and deprivation on non-speech auditory abilities.

This article reviews the evidence for acclimatization and deprivation with respect to non-speech auditory abilities. Although this subject has not been studied extensively, clear evidence exists for acclimatization and/or deprivation effects on intensity discrimination, binaural masking level difference, and auditory localization and lateralization. There is also some argument for such effects with regard to changes in tolerance for intense sounds or preferred levels of amplification. However, the main evidence for these effects, changes in loudness discomfort levels with repeated testing, may reasonably be explained as procedural or task-related effects rather than changes in auditory abilities. On the other hand, the successful use of tinnitus maskers to treat hyperacusis suggests that particularly low tolerance levels may be improved by exposure to certain types of auditory stimulation. Overall, this retrospective review of changes in non-speech auditory abilities, associated with the presence or absence of listening experience, indicates that acclimatization or deprivation effects may have influenced the results of some of the experiments reviewed. This suggests that experiments designed to study acclimatization or deprivation are timely and useful. In addition, acclimatization and deprivation are potential variables that should be considered, and preferably controlled, within experiments on auditory abilities. Clinically, the review adds weight to the argument for considering acclimatization and/or deprivation in hearing aid fitting and evaluation.

Functional Laterality↗
PubMed1996

Report of the Eriksholm Workshop on auditory deprivation and acclimatization.

The terminology used in studies documenting changes in auditory performance following fitting of hearing aids has been diverse. Definitions for the auditory deprivation effect and auditory acclimatization are offered as a first step in rationalization. Two statements summarize current knowledge concerning auditory deprivation effects and auditory acclimatization, as well as considering the potential implications for research, field trial and clinical practice applications. Potential areas for future research are identified.

Auditory Perception↗
PubMed1996

Operative laparoscopic management of adnexal cysts: initial experience at the Royal Women's Hospital 1991-1994.

The introduction of operative laparoscopic surgery for benign adnexal cysts had led to shorter postoperative hospitalization (mean stay of 2.0 days) in association with a low rate of major complications (1.6%). A planned laparoscopic approach was successful in 95.2% (179/188) of patients. The majority of women were premenopausal (93.6%) and the most common procedure performed was an ovarian cystectomy (73.5% of cysts). Three ovarian cysts that were thought to be benign by preoperative and intraoperative assessment were subsequently found to be ovarian tumours of low malignant potential after histological examination. Operative laparoscopy has become the preferred mode of treatment for benign adnexal cysts at the Royal Women's Hospital. It confers a wide range of benefits to patients, reduces health-care costs and appears to be a safe and effective treatment modality.

Adolescent↗
PubMed1996

Relationship of aided speech recognition to hearing thresholds and aided speech-peak sensation levels in severely and profoundly hearing-impaired adults.

The relationship of speech recognition to hearing threshold levels and to aided speech-peak sensation levels was examined in a group of severely and profoundly hearing-impaired adults. Closed-set vowel and consonant recognition tests were administered at the subjects' most comfortable levels. Both vowel and consonant recognition scores were relatively predictable from hearing threshold level at 2000 Hz, the correlations being -.84 and -.76, respectively. Recognition of most speech-feature contrasts was also predictable from hearing threshold levels, at one or two frequencies, always including 2000 Hz. The predictability of speech recognition was similar, but no better, from aided speech-peak sensation levels than from hearing threshold levels. Vowel and consonant scores were similar to or better than those reported in previous studies, possibly reflecting subject selection factors and/or extensive testing that was used to optimize hearing aid fittings. For the majority of subjects, altering the low-frequency response of the hearing aid did not significantly affect vowel or consonant recognition scores.

Adult↗