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Biomedical subjects

D W Robinson

Publications and source records attributed to D W Robinson.

At least 37 records · Page 2Linked to original sources
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

Microvascular free jejunum transfer.

A series of 37 microvascular free jejunal transfers for reconstruction of the pharyngolaryngeal region using a conduit or oropharynx using a patch of jejunum is reported. The technique results in a high success rate with only two failures in the series. Post-operative recovery is rapid with low morbidity and many patients are able to go home after seven to ten days. Radiotherapy, either pre-operatively affecting the recipient vessels or post-operatively affecting the transferred jejunal segment, has not been found to affect adversely the outcome of the reconstructive procedure.

Aged↗
PubMed1982

House dust mites in Bristol.

A survey of bedding in Bristol revealed reducing mite concentrations on children's toys, mattresses, overblankets and pillows. Dermatophagoides pteronyssinus was the commonest mite found. A vacuuming schedule was devised for removing mites so that a double blind trial could be carried out. Investigation suggests that even with expert utilization of efficient vacuum cleaners the clinical efficacy would be limited as the mites appear to rapidly migrate back into the bedding.

Allergens↗
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↗
PubMed1981

Audiometric zero for air conduction. A verification and critique of international standards.

The international standard of audiometric zero for normal hearing by air conduction was originally given only for laboratory reference earphones. Subsequently, it has been extended to cover earphones in general audiometric use, and in other ways. A new determination is described in which these derived standards are tested by comparison with the measured thresholds of hearing of 108 subjects in the age range 18-30 years. Particular attention is paid to the otological classification of the subjects and its relation to the description of otological normality in the ISO standards. Suggestions for adjustment of the standards at certain frequencies are made.

Adolescent↗
PubMed1980

Air-radiated sound from bone vibration transducers and its implications for bone conduction audiometry.

The effect of air-borne sound radiated from transducers used in bone conduction audiometry has been known for many years. This paper seeks to quantify this effect for the vibrator types (B70A, B71, and B72. Using three examples of each vibrator sound pressure levels were measured at the entrance to the external ear canal on four human heads. Values obtained have been related to hearing theshold levels for otologically normal young persons using two different methods: firstly using international standard values of open-ear free-field theshold with corrections for monaural listening and for diffraction, and secondly by direct measurement of the subjects' monaural open-ear thresholds. None of the vibrators tested meets international standard requirements for air-borne sound radiation at all frequencies, but in practics, provided a high quality ear plug is fitted to the test ear at 3 and 4 kHz large errors are unlikely to be recorded for any of the vibrator types tested.

Audiometry↗