Biomedical subjects

Chris James

Publications and source records attributed to Chris James.

7 recordsLinked to original sources

PubMed2006

The size of the cochlea and predictions of insertion depth angles for cochlear implant electrodes.

AIMS: To establish normative data on the size of the basal turn of the cochlea using high-resolution computed tomography of the temporal bone in adults and children. To determine whether final insertion depth angle for a perimodiolar cochlear implant electrode varies according to cochlear size. METHODS: Forty-two patients screened for cochlear anomaly using computed tomography were randomly selected from patients with otologic disease. Reconstruction of the full basal turn was performed for both ears using a 1.0-mm layer, minimum intensity projection. The largest distance from the round window to the lateral wall (distance A) and the perpendicular distance (B) were measured. Distances were averaged between ears for each individual. In addition, 15 patients were implanted with the Nucleus 24 Contour Advance electrode array using a linear insertion depth of either 17 mm (n = 9) or 19 mm (n = 6). Postoperative X-rays were analyzed using the method of Xu et al. [Am J Otol 2000;21:49-56] to obtain the insertion depth angles for individual electrodes. RESULTS: Mean distance A was 9.23 mm (SD = 0.53, range 7.9-10.8 mm). Perpendicular distance B was significantly correlated with distance A (r2 = 0.57, p < 0.001). The mean difference in insertion depth angle between the 17 and 19 mm groups was 80 degrees . A statistically significant correlation (r2 = 0.51) was found between distance A and the insertion depth angle for the 17 mm group. CONCLUSIONS: The cochlear size measure distance A was repeatable to within the resolution of the high-resolution computed tomography image data. The basal turn of the normally formed cochlea is variable in size. These variations in size would produce >5.0 mm variation in the length of the lateral wall to the point consistent with an insertion depth angle of 360 degrees . Cochlear size influenced final insertion depth angles obtained for the perimodiolar Nucleus 24 Contour Advance electrode.

Adolescent↗

PubMed2006

Residual hearing conservation and electroacoustic stimulation with the nucleus 24 contour advance cochlear implant.

OBJECTIVE: To assess the conservation of residual hearing in recipients of the Nucleus 24 Contour Advance cochlear implant (CI) and the benefits of combined electrical and acoustic stimulation. STUDY DESIGN: Prospective multicenter study. SETTING: CI clinics in Western Europe. PATIENTS: Adult candidates for conventional cochlear implantation with a minimum preoperative word recognition score of 10% in the ear to be implanted. INTERVENTION: "Soft-surgery" protocol, including a 1- to 1.2-mm anterior and inferior cochleostomy hole with the electrode array, inserted 17 mm using the "advance-off-stylet" technique. Patients with postoperative pure-tone hearing threshold levels (HTLs) of 80 dB hearing loss or less at 125 and 250 Hz and 90 dB hearing loss or less at 500 Hz were refitted with an in-the-ear hearing aid for combined ipsilateral electrical and acoustic (El-Ac) stimulation. MAIN OUTCOME MEASURES: A questionnaire to collect information regarding surgery. Pure-tone HTLs measured at intervals. Word recognition tested in quiet and sentence recognition tested in noise at 10 and 5 dB signal-to-noise ratio (SNR). HEARING CONSERVATION RESULTS: HTL data were available for 27 patients. HTLs were conserved within 20 dB of preoperative levels for 33, 26, and 19% of patients for 125, 250, and 500 Hz, respectively. However, the recommended soft-surgery protocol was strictly followed in only 12 of 27 patients. For these 12 patients, hearing thresholds were conserved within 20 dB for 50, 50, and 33% of patients. Median threshold increases were 40 dB (range, 250-500 Hz) for the whole group and 23 dB for the strict surgery group. Ten patients retained sufficient HTLs to enter the El-Ac user group. SPEECH RECOGNITION RESULTS: Group mean recognition scores for nine El-Ac users for words presented at 65 dB sound pressure level were 45% for CI alone and 55% for CI + ipsilateral hearing aid (p < 0.05, paired t). For sentences presented in noise at 5 dB SNR, mean word scores were 46% CI alone and 56% CI + ipsilateral hearing aid (p < 0.01, paired t). CONCLUSION: Hearing was conserved for conventional candidates for cochlear implantation where the recommended soft-surgery protocol was strictly adhered. Combined ipsilateral electrical and acoustic stimulation provided considerable benefits for speech recognition in noise, equivalent to between 3 and 5 dB SNR, compared with CI alone.

Acoustic Stimulation↗

PubMed2005

Impact on child mortality of removing user fees: simulation model.

OBJECTIVE: To estimate how many child deaths might be prevented if user fees were removed in 20 African countries DESIGN: Simulation model combining evidence on key health interventions' impacts on reducing child mortality with analysis of the effect of fee abolition on access to healthcare services. RESULTS: Elimination of user fees could prevent approximately 233,000 (estimate range 153,000-305,000) deaths annually in children aged under 5 in 20 African countries. CONCLUSION: Given the relatively low cost of abolition, replacing user fees with alternative financing mechanisms should be seen as an effective first step towards improving households' access to health care and achieving the millennium development goals for health.

Africa↗

PubMed2005

Clarifying efficiency-equity tradeoffs through explicit criteria, with a focus on developing countries.

Expenditures on health in many developing countries are being disproportionately spent on health services that have a low overall health impact, and that disproportionately benefit the rich. Without explicit consideration of priority setting, this situation is likely to remain unchanged: resource allocation is too often dictated by historical patterns, and maintains vested interests. This paper explores how prioritization between different health interventions can be rationalised by the use of clearly defined criteria. A number of key efficiency and equity criteria are examined, in particular analysing how potential tradeoffs could be incorporated into the decision making process.

Cost-Benefit Analysis↗

PubMed2005

Preservation of residual hearing with cochlear implantation: how and why.

CONCLUSIONS: Hearing may be conserved in adults after implantation with the Nucleus Contour Advance perimodiolar electrode array. The degree of hearing preservation and the maximum insertion depth of the electrode array can vary considerably despite a defined surgical protocol. Residual hearing combined with electrical stimulation in the same ear can provide additional benefits even for conventional candidates for cochlear implantation. OBJECTIVES: We present preliminary results from a prospective multicentre study investigating the conservation of residual hearing after implantation with a standard-length Nucleus Contour Advance perimodiolar electrode array and the benefits of combined electrical and acoustic stimulation. MATERIAL AND METHODS: The subjects were 12 adult candidates for cochlear implantation recruited according to national selection criteria. A "soft" surgery protocol was defined, as follows: 1-1.2-mm cochleostomy hole anterior and inferior to the round window; Nucleus Contour Advance electrode array inserted using the "Advance-off-stylet" technique; and insertion depth controlled by means of three square marker ribs left outside the cochleostomy hole. These procedures had been shown to reduce insertion forces in temporal bone preparations. Variations in surgical techniques were monitored using a questionnaire. Pure-tone thresholds were measured pre- and postoperatively. Patients who still retained thresholds <90 dB HL for frequencies up to 500 Hz were re-fitted with an in-the-ear (ITE) hearing aid. Word recognition was tested in quiet and sentence perception in noise for the cochlear implant alone and in combination with an ipsilateral hearing aid. RESULTS: Hearing threshold level data were available for 12 patients recruited from 6 of the centres. Median increases in hearing threshold levels were 23, 27 and 33 dB for the frequencies 125, 250 and 500 Hz, respectively. These median increases include the data for two patients who had total loss of residual hearing due to difficulties encountered during surgery. "Cochlear view" X-ray images indicated that the depth of insertion varied between 300 and 430 degrees, despite modest variations in the length of the electrode inserted (17-19 mm). The insertion angle had some influence on the preservation of residual hearing at frequencies of 250-500 Hz. Six of the 12 patients retained sufficient hearing for effective use of an ipsilateral ITE hearing aid (< or = 80 dB HL at 125 and 250 Hz; < or = 90 dB HL at 500 Hz). Word recognition scores in quiet were improved from 10% to 30% with the cochlear implant plus ipsilateral hearing aid in 3 patients who had at least 3 months postoperative experience. Signal:noise ratio thresholds for sentence recognition were improved by up to 3 dB. Patients reported that they experienced greatly improved sound quality and preferred to use the two devices together.

Adult↗

PubMed2005

Binaurality in middle ear implant recipients using contralateral digital hearing AIDS.

OBJECTIVE: For some patients, conventional hearing aids might have disadvantages that clearly limit the benefit of using them. The middle ear implant, Vibrant Soundbridge hearing prosthesis offers an approach to help such patients. Our study's objective was to identify the binaurality in a well-fitted digital hearing aid worn in the contralateral ear in recipients experienced with use of the Vibrant Soundbridge middle ear implant device. STUDY DESIGN: In a prospective study, warble-tone thresholds and stereophony were evaluated for the following conditions: (1) binaural unaided-with the middle ear implant inactive and the behind-the-ear hearing aid removed; (2) middle ear implant alone-middle ear implant active, behind-the-ear hearing aid removed; (3) middle ear implant plus behind-the-ear omnidirectional-middle ear implant active, behind-the-ear active; and (4) behind-the-ear omnidirectional alone-middle ear implant inactive, behind-the-ear omnidirectional active. Behind-the-ear omnidirectional and behind-the-ear is defined as the behind-the-ear active in the omnidirectional or directional response, respectively. Behind-the-ear is a contralateral digital hearing aid to the middle ear implant. Benefits such as improved sound detection, speech perception in quiet and in noise, and sound quality were investigated. The evaluation of subjective hearing benefit was based on the Abbreviated Profile of Hearing Aid Benefit (APHAB) test. Paired t tests (subject) were used to analyze the differences between mean thresholds for the different test conditions. SETTING: Tertiary referral center. PATIENTS: Eight adults (aged 45-68 yr) had undergone implantation with a single Vibrant Soundbridge at least 12 months before starting the study. These eight subjects presented no contraindication for contralateral hearing aid use. Patients were fitted 5 weeks before testing with a Siemens Signia digital behind-the-ear hearing aid in the side contralateral to the Vibrant Soundbridge. RESULTS: Five weeks after use of the contralateral hearing aid together with the middle ear implant, mean differences in warble-tone thresholds between Conditions 2 and 3 and between Conditions 3 and 4 were both statistically significant. The mean differences in speech reception thresholds were in line with the mean differences in average warble-tone thresholds. The mean speech reception threshold for the middle ear implant plus behind-the-ear omnidirectional condition was slightly worse (3 dB) than that for the middle ear implant alone condition; however, this difference was not statistically significant. Whereas speech reception threshold difference between Condition 1 and Condition 4 was not statistically significant (60 dB and 61 dB, respectively). The mean difference for the 0-degree azimuth alone was statistically significant (p < 0.05) for the conditions middle ear implant alone and middle ear implant plus behind-the-ear omnidirectional. The middle ear implant alone appears to give good sensitivity at 2 kHz for any direction. Increasing scores indicate greater percentages of problems. Percentages of problems were on average lower for the middle ear implant when used with the contralateral digital hearing aid based on the global score. CONCLUSION: The use of a middle ear implant Vibrant Soundbridge together with a contralateral digital hearing aid improved functional gain and speech perception thresholds in quiet, especially for the sound coming from the front of the patient. The use of a middle ear implant together with a contralateral digital hearing did not significantly improve hearing in noise.

Acoustic Stimulation↗

PubMed2005

Key performance indicators for the implementation of social health insurance.

Several low- and middle-income countries are interested in extending their existing health insurance for specific groups to eventually cover their entire populations. For those countries interested in such an extension, it is important to understand what characterises a well performing social health insurance scheme. This article provides a simple framework to analyse key performance issues related to the functions of health financing within the context of social health insurance. The framework first illustrates how performance in the health financing functions of revenue collection, pooling and purchasing affects the realisation of health financing targets of resource generation, optimal resource use and financial accessibility of health services for all. Then, within each health financing function, key performance issues and associated measurable indicators are developed. The set of performance indicators provided in this article should help policy makers to monitor the development of social health insurance schemes and identify areas for improvement. In doing so, policy makers can come closer to achieving universal coverage -- access to appropriate healthcare for all at an affordable cost -- the ultimate goal of social health insurance.

Developing Countries↗