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Biomedical subjects

I M Calder

Publications and source records attributed to I M Calder.

At least 19 recordsLinked to original sources
PubMed1992

Cerebral vasculopathy in divers.

Brains from 12 amateur and 13 professional divers, all but one of whom died accidentally, were examined neuropathologically. Grossly distended, empty vessels (presumably caused by gas bubbles) were found in the brains of 15 out of 22 divers who died from diving accidents. Perivascular lacuna formation was found in cerebral and/or cerebellar white matter in three amateurs and in five professionals. In addition to lacuna formation, hyalinization of vessel walls was present in the brains of three amateurs and five professionals. Necrotic foci in grey matter occurred in seven cases and perivascular vacuolation of white matter occurred in seven cases. The vascular changes probably arose from intravascular gas bubble formation. In one professional diver, there was also unilateral necrosis of the head of the caudate nucleus.

Adult↗
PubMed1991

Anoxic asphyxia--a cause of industrial fatalities: a review.

The investigation of commercial diving accidents has indicated that the danger of anoxia, from the inhalation of gases not containing oxygen, is not fully recognized. The problem is more common in a variety of general industrial situations and is an occasional cause of death in anaesthesia. It is a particular hazard with inert gases, which, because they are recognized to be non-toxic, give a false sense of security. The pathological findings consist of pulmonary oedema and petechial haemorrhages, mainly in the brain, lungs and myocardium. Whenever possible, a minimum oxygen content should be included in all gases liable to be respired, but where this is not possible, oxygen analysers and alarms should be provided. Where a general hazard exists, personnel must be warned of the danger.

Acute Disease↗
PubMed1989

Spinal cord degeneration associated with type II decompression sickness: case report.

The medical history, clinical and neuropathological findings at necropsy are described in a 50-year-old male amateur diver who suffered from Type II decompression sickness, a spinal 'bend'. He survived as a paraplegic for 4 years. In the spinal cord upward Wallerian degeneration in the posterior columns and downward degeneration in the corticospinal tracts was explained by multiple small and medium sized infarcts affecting the centripetal blood supply to the cord. There was preservation of a rim of subpial fibres on the surface of the posterior and lateral columns. The grey matter and nearby white matter (supplied by the centrifugal arterial supply) was unaffected.

Decompression Sickness↗
PubMed1989

Cochlear degeneration in minipigs after repeated hyperbaric exposures.

Auditory function and cochlear pathology were investigated in 4 minipigs subjected to compression to 4 ATA, held for 1 h, and decompressed using a standard schedule (Blackpool Tables) on 21 occasions. Three minipigs were used as controls. Brainstem auditory evoked response testing was carried out after the last hyperbaric exposure and showed no response bilaterally in 3 and unilaterally in 1 of the test animals. Light microscopy demonstrated a loss of hair cells throughout the cochlea in all the compressed animals; in one the tectorial membrane was detached and adherent to Reissner's membrane. Vestibular changes were confined to the saccule. Hemorrhage was not a prominent feature. On scanning electron microscopy the pathologic changes included missing hair cells and fused and giant stereocilia. Possible causes of the pathology include barotrauma or direct effects of repeated compression and decompression on the inner ear, or both. The compression-decompression profile used was one that is thought to be safe for compressed air workers who are repeatedly exposed to hyperbaric conditions.

Animals↗
PubMed1987

Spinal cord degeneration in divers.

Spinal cords from 8 professional and 3 amateur divers who died accidentally were examined histopathologically. Marchi-positive degeneration was found in the cords of 3 professional divers, variously affecting the posterior, lateral, and to a lesser extent the anterior columns. In 1 there was degeneration of afferent fibres within the posterior columns.

Accidents, Occupational↗
PubMed1987

Relation of alveolar size to forced vital capacity in professional divers.

Eight cases have been studied in which both lung function and histological morphometric data was available on divers' lungs. A correlation was found between the increase in forced vital capacity measured at routine annual medical examination and the morphometric measurement of alveoli by mean cord length. The results suggest that reduction of forced expiratory volume in one second may be due to narrowing of small airways by distention of the alveoli.

Adult↗
PubMed1987

Mushroom compost worker's lung.

This study draws attention to difficulties in the diagnosis and the understanding of the mechanism of action of mushroom compost worker's lung. Descriptions are given of 4 workers in one factory who developed acute respiratory failure within a 6-month period; 13 others who were unaffected were also studied. Serological investigation appears to be largely unhelpful, and the evidence against the condition being included amongst the extrinsic allergic alveolitides is discussed. A detailed clinical and occupational history is essential for diagnosis.

Adolescent↗
PubMed1987

Use of postmortem radiographs for the investigation of underwater and hyperbaric deaths.

The use of postmortem radiographs as a useful adjunct in the investigation of hyperbaric and immersion deaths is discussed. This technique enables accurate identification of gas within cavities that otherwise could not be detected at routine autopsy, which may also be artifact. In addition it is possible to define bone lesions that need a histologic diagnosis.

Adult↗
PubMed1986

Dysbarism. A review.

This review of dysbarism outlines the development of the knowledge of the effects of pressure changes on tissues and organs, which is related to a complex of physical, physiological and pharmacological changes. It also shows that with the ever increasing pressures to which man is subject the effects can be regarded as total body rather than the traditional concept of a few target organs.

Acute Disease↗
PubMed1985

A method for investigating specialised accidents with special reference to diving.

This paper describes a format for the investigation of complicated accidents which result in diving deaths. It emphasises the necessity for communication between technical, medical and legal personnel to arrive at a reasoned appreciation of factors leading to an accident. Properly applied this can result in a meaningful accumulation of data, which can be periodically analysed and be used in formulating Regulations for prevention of further accidents.

Decompression Sickness↗
PubMed1985

The risk of leptospirosis in United Kingdom fish farm workers. Results from a 1981 serological survey.

Less than one per cent of serum samples taken from 257 fish farmers in 1981 had agglutinating antibodies to strains of Leptospira interrogans of serogroup Icterohaemorrhagiae at a titre of 30 or greater. Compared with the results from other serological surveys, this agglutinating antibody prevalence suggests that fish farming does not have a high occupational risk for leptospirosis. Between 1961 and 1981 the incidence in fish farmers was about 33 per 100000 person years at risk. During the same period the incidence in the general adult male population was 0.137 per 100000 person years at risk, so that fish farming had a moderately increased risk of Icterohaemorrhagiae serogroup infection (relative risk = 243). No one particular risk factor within fish farming could be reliably identified and therefore recommendations to reduce the risk can only be general.

Adult↗
PubMed1985

Damage to the middle ear and the inner ear in underwater divers.

Postmortem human tissue from recently deceased divers was processed histologically to assess any inner and middle ear damage that could have resulted from the effects of pressure during diving. The following new findings are particularly noteworthy. In one diver, ascent while breath holding resulted in the rupture of the ear drum and blood in the middle ear, in addition to pulmonary barotrauma. In a second diver, following inner ear decompression sickness, new bone growth, similar to that described earlier in experimental studies with the squirrel monkey, was observed in the arms of one of the semicircular canals. These observations are further confirmation that otologic disorders can be a serious threat to divers.

Barotrauma↗
PubMed1985

Autopsy and experimental observations on factors leading to barotrauma in man.

Morbid anatomical data have been examined in detail from 13 fatal diving accidents in which the primary cause of death was due to pulmonary damage. In addition, the observations on 6 cases of experimental barotrauma on cadavers are recorded. The information is supplemented by the incidental findings in the respiratory system of 19 professional divers killed by causes other than barotrauma, and 97 healthy, age-matched controls who died suddenly or unnaturally. In cases of pneumothorax resulting both from diving and experiment the constant feature was the presence of pleural adhesions and lung bullae, some of which were involved in causing tissue damage. A high proportion (up to 26%) of lungs not involved in barotrauma also showed pleural adhesions. In cases of barotrauma, the parenchymal damage is not consistently related to scars or fibrous tissue. The observations suggest that a high incidence of pleural lesions are not detected or detectable on routine medical examination which do not compromise the lung. However once a pneumothorax has occurred it is highly probable that a further incident may rupture another bulla and these appear to be multiple. The converse appears to be true with parenchymal barotrauma that is not consistently related to scar tissue. This would therefore suggest that in a proven and recovered case of barotrauma it should not necessarily debar further diving activity.

Adult↗