PubMed Health⌕ Search

Biomedical subjects

D W Robinson

Publications and source records attributed to D W Robinson.

At least 19 recordsLinked to original sources
PubMed1992

Quantification of hearing disability for medicolegal purposes based on self-rating.

Current practice for medicolegal assessment of individuals entails the use of an impairment measure obtained from average hearing threshold levels as a surrogate for hearing disability, and conversion of the surrogate to disability via a formula. Several different formulae are in use, but none is based explicitly on experimental data. To address this lack of empirical foundation in the assessment process, numerical self-ratings of hearing ability by 2058 subjects with a wide range of hearing threshold levels who had taken part in the National Study of Hearing in the UK were analysed to examine their relation to average hearing threshold level. The relation between self-rated hearing disability (the complement of self-rated hearing ability) and hearing threshold level was found to be sigmoid in form, and could be closely modelled by a modified Gompertz function. Functions for the median, upper quartile and lower quartile disability ratings with hearing threshold level are presented in graphical, parametric and tabular form. The median function gives a quantitative foundation for medicolegal assessments.

Adolescent↗
PubMed1992

Background noise in rooms used for pure-tone audiometry in disability assessment.

Background noise limits for audiometry are determined by the effects of masking and are specified in international standards. The standards provide for audiometric testing over a range of audiometric frequencies extending down to 500 Hz or lower. The lowest frequency of testing is an important factor determining the admissible noise, and for certain applications it is appropriate to consider the limits applicable to testing over a more restricted range. Assessment of hearing disability in the UK is generally based on a consideration of pure-tone hearing threshold levels in the frequency range 1 kHz upwards. A modification of the standardized noise limits is proposed which allows some relaxation appropriate to this higher minimum frequency. For air-conduction audiometry, these modifications affect only the permissible background noise in the frequency range below 1 kHz. Where bone-conduction audiometry is required in order to quantify a conductive component of the hearing loss, the measurements need to be made on both ears with the non-test ear masked in both cases; the external background noise will thus only be heard monaurally and this justifies a correction to the noise limits compared with those appropriate to bone-conduction audiometry without masking.

Audiometry, Pure-Tone↗
PubMed1991

Development of the light response in neonatal mammalian rods.

The sensitivity to light is low in many neonatal mammals when compared with that in the adult. In human infants at one month of age, for example, the dark-adapted sensitivity for detection of large stimuli is 50 times lower than in the adult, and in rats the overall sensitivity of the neonatal retina is also low compared with the adult. This low sensitivity in the neonate has been attributed to a number of factors, but the possibility that the photoreceptors themselves might be an important limitation on the overall visual sensitivity has not so far been clearly established. Here we record the light response of single neonatal rat rods and find that the sensitivity is considerably lower than in the adult. The response to a single photoisomerization is normal in the neonate, and the sensitivity deficit can therefore be attributed to a low level of functional rhodopsin. Opsin, the protein component of rhodopsin, must be present in normal amounts, as the sensitivity can be restored to adult levels by treating the retina with 9-cis retinal, an active homologue of the native chromophore 11-cis retinal. The low sensitivity of photoreceptors in the neonate can therefore be attributed mainly to a low concentration of 11-cis retinal in the developing retina.

Aging↗
PubMed1991

The limited accuracy of bone-conduction audiometry: its significance in medicolegal assessments.

Accurate bone-conduction testing with masking is always difficult, but for clinical purposes limited accuracy suffices. However, when assessing claimants for compensation, extreme care is needed since even small apparent air-bone gaps are sometimes translated into financial abatement. This paper sets out the stringent test conditions required to achieve adequate precision. It also indicates the inaccuracies inherent in such tests, and recommends procedures for interpreting the significance of bone-conduction thresholds.

Audiometry↗
PubMed1991

Long-term repeatability of the pure-tone hearing threshold and its relation to noise exposure.

Audiometric repeatability is examined for a population of 356 male and female industrial employees (712 ears), sub-divided according to the amount of previous noise exposure. Re-tests were carried out after an interval averaging 13 months. After a similar interval, 150 of the subjects gave a third audiogram. Fixed-frequency self-recording audiometry was employed, using common equipment and procedures throughout. Results are presented as distributions of the algebraic test-re-test differences for each frequency and for the frequency combination 1-2-3 kHz. Repeatability was best at 1 and 2 kHz and substantially poorer at 6 kHz. Cumulative distributions of the signless differences show that more than 50% of initial hearing threshold levels repeated to better than 5 dB. For all frequencies except 6 kHz the mean values of signless test-re-test differences for the various sub-groups were between 3.4 and 5.6 dB; at 6 kHz the values were between 5.8 and 7.8 dB. In the case of the three-frequency average, the mean differences were reduced to between 2.8 and 3.8 dB. A few repeats (about one in 200) stand out as clearly anomalous; these occur only in isolation and mainly at the higher frequencies. The performance of groups classified by the amount of their previous noise exposure did not differ significantly. In the case of those tested three times, the repeatability over the second inter-test interval showed at most a marginal improvement compared with the first interval.

Acoustic Stimulation↗
PubMed1991

Relation between hearing threshold level and its component parts.

A model is presented showing how different components of threshold shift combine. It has long been evident that simple arithmetical addition cannot apply, but it is only recently that experimental data have been shown to validate a simple interaction between age- and noise-related components. The combination formula extends to sensory loss from other causes. Used in conjunction with growth functions for the age and noise components, it facilitates both the prediction of future hearing loss and the 'retrodiction' of past hearing threshold levels at any point in the life of the average person, given the present age and the noise exposure history. By reconstructing the hearing thresholds for a notional 'life' in which an episode of noise exposure is eliminated, the formula enables the specific effect of that episode to be evaluated at later times. As with any such system, uncertainties arise in the application to individuals. Possible ways forward are discussed.

Auditory Threshold↗
PubMed1989

Extrusion of calcium from rod outer segments is driven by both sodium and potassium gradients.

Calcium is transported across the surface membrane of both nerve and muscle by a Na+-dependent mechanism, usually termed the Na:Ca exchange. It is well established from experiments on rod outer segments that one net positive charge enters the cell for every Ca2+ ion extruded by the exchange, which is generally interpreted to imply an exchange stoichiometry of 3 Na+:1 Ca2+. We have measured the currents associated with the operation of the exchange in both forward and reversed modes in isolated rod outer segments and we find that the reversed mode, in which Ca2+ enters the cell in exchange for Na+, depends strongly on the presence of external K+. The ability of changes in external K+ concentration ([K+]o) to perturb the equilibrium level of [Ca2+]i indicates that K+ is co-transported with calcium. From an examination of the relative changes of [Ca2+]o, [Na+]o, [K+]o and membrane potential required to maintain the exchange at equilibrium, we conclude that the exchange stoichiometry is 4 Na+:1 Ca2+, 1 K+ and we propose that the exchange should be renamed the Na:Ca, K exchange. Harnessing the outward K+ gradient should allow the exchange to maintain a Ca2+ efflux down to levels of internal [Ca2+] that are considerably lower than would be possible with a 3 Na+:1 Ca2+ exchange.

Algorithms↗
PubMed1988

Threshold of hearing as a function of age and sex for the typical unscreened population.

Thresholds of hearing as a function of age and sex for screened, or 'otologically normal', persons have been standardised (ISO 7029) on the basis of a study by Robinson and Sutton (1978). For purposes such as the evaluation of hearing loss due to noise exposure in industrial populations, it is not generally realistic to compare the hearing thresholds to an age-matched 'otologically normal' baseline, since the difference will include adventitious hearing loss as well as the noise-related components. This paper presents typical data for an unscreened population, in a companion form to ISO 7029. The results are derived from a critical analysis of published material and are shown to converge closely to ISO 7029 at the extremity of the distributions. Striking uniformity in the form of the distributions is revealed among apparently discordant data from different studies, showing that the adventitious hearing loss, or so-called 'pathological overlay', is essentially equivalent to accelerated ageing.

Adolescent↗
PubMed1987

Microvascular salvage for failed colonic interposition.

Free revascularized jejunal grafts have been used in three patients to restore alimentary tract continuity after ischaemic failure of pedicled colonic graft replacements of the oesophagus. In all three patients colon had been placed retrosternally. In one patient immediate replacement of a totally necrotic colon interposition was undertaken. In two patients, late long strictures were replaced by jejunal segments. Access to the retrosternal colon was gained in each case by neck and median sternotomy incisions. Revascularization of the jejunal segments was from the facial artery and external jugular vein in two patients and from the internal mammary vessels in one. Satisfactory swallowing of solids and liquids has been achieved and sustained.

Adult↗
PubMed1986

Function of a free jejunal "conduit" graft in the cervical esophagus.

The function of an autotransplanted jejunal graft used to reconstruct the pharyngoesophagus was evaluated in 12 patients, 2-40 mo after surgery. On clinical assessment most patients swallowed liquids and solids with minimal difficulty, although several described a need for liquids to "flush" solids to the stomach. Radiologic studies demonstrated a delay in orogastric transit in some patients above the lower anastomosis. The mechanism was apparent on motility studies: swallows generally failed to induce contractions in the graft, although the esophagus below exhibited stripping peristaltic waves. Regular contractile activity, characteristic of phase III of the intestinal migrating motor complex, was identified in 11 grafts. There was no temporal association between migrating motor complexes in the graft and those recorded at the jejunal donor site. Instillation of nutrients into the gastric antrum induced a typical "fed" pattern of contractions in the intact jejunum but not in the extrinsically denervated graft. In conclusion, the graft provides a useful, though generally passive conduit. The graft maintains its intrinsic motor repertoire, which is asynchronous with that of the donor site. The findings also support the hypothesis that extrinsic nerves are required to induce a "fed" pattern of intestinal motility.

Aged↗
PubMed1986

Pharyngolaryngectomy reconstruction by revascularized free jejunal graft.

The results of reconstruction after total pharyngolaryngectomy using a free revascularized jejunal graft in 72 patients are presented. There was a low hospital mortality (2.8%), a short average time until swallowing (13 days) and a short average postoperative hospital stay (20 days). Twelve patients had resections more extensive than the standard total pharyngolaryngectomy. Sixteen patients (22.2%) suffered some graft complication, but only five (two early graft losses, one late graft loss, one fistula and one stricture) required further reconstructive surgery. Abdominal complications were minimal. There were no complications attributable to post-operative radiotherapy. Swallowing of solids and liquids is good and is maintained long-term. These results are compared with those reported for other methods of reconstruction. This comparison supports a contention that jejunal autograft is the reconstruction of choice after pharyngolaryngectomy.

Adult↗
PubMed1984

Deoxyribonucleic acid output in the sputum from cystic fibrosis patients.

The deoxyribonucleic acid (DNA) content of sputum from cystic fibrosis patients was examined to establish if it was likely to be a useful indicator of worsening clinical condition. The assay was reproducible (coefficient of variation 4.2%) and added DNA could be demonstrated. Added antibiotics did not influence the result. The daily DNA content in the sputum showed similar variations to the weight, but the DNA output (content X weight/24 h) was perhaps a more sensitive indicator of clinical status. There was a weak, negative correlation between DNA output and peak expiratory flow rate.

Cystic Fibrosis↗
PubMed1982

Reconstruction of defects involving the mandible and floor of mouth by free osteo-cutaneous flaps derived from the foot.

Microsurgical transfer of a compound osteo-cutaneous free flap derived from the dorsal foot skin and second ray can provide a satisfactory reconstruction for defects of the mandible and floor of the mouth. The procedure is particularly recommended for anterior segment losses where a thin flap and a curved skeleton is required. The flap can be prepared at the time of tumour resection without inconvenience to either surgical team and the surgery does not significantly affect either the operative or post-operative condition of the patient. No external bony fixation is required and no case of non-union has been encountered.

Adult↗
PubMed1982

A standard determination of paired air- and bone-conduction thresholds under different masking noise conditions.

Air-(ac) and bone-conduction (bc) thresholds were determined for 96 subjects in the age range 16-30 years. The bc tests were carried out using a B-71 vibrator applied to left and right mastoid under three conditions at the contralateral ear: unoccluded, masked at 25 dB and at 40 dB sensation level; ac audiometry and masking noise used a TDH-39 earphone. By a systematic process of otological classification of the subjects, the bc threshold for 'normal hearing' could be estimated with an uncertainty of less than 1 dB and interpolated for masking noise levels from zero to 40 dB sensation level. Results are expressed as alternating force levels in an artificial mastoid of current commercial design. Variance of the air-bone difference for individual ears is found to be less than the sum of ac and bc threshold variances calculated separately, implying strong air-bone correlation. Comparison is made with other recent studies using B-71 and KH-70-type vibrators, and average results are presented in the context of a proposed international standard for the normal threshold of hearing by bc.

Adolescent↗