rupture causing air embolism, and this might be the cause of the more serious type 2 decompression sickness (Walder, 1963). For this reason routine chest radiographs are advised on all hospital personnel before working in a hyperbaric environment. It is suggested that the examination should include radiographs on expiration and full inspiration to see if any localized overinflation could be found. Patients who were seen to have cysts or bullae of their lungs should be excluded from work in compressed air. Where routine chest radiographs were carried out in tunnel workers on the Clyde and such cases were excluded, there was apparently no reduction in the incidence of type 1 or type 2 decompression sickness (Davidson, 1964).No abnormalities were noted on the chest radiographs of the Glasgow staff other than small calcified foci on two occasions. In these two subjects no change in the appearance of the chest radiograph was noted after frequent exposures to hyperbaric pressure. Moreover, in another series of studies more than 50 patients with advanced chronic respiratory disease were decompressed from pressures not exceeding 2 atmospheres without untoward consequences-one such patient had 26 compressions over a period of three years (Ledingham et al., 1968).Aseptic necrosis of bone is a late sequel of working in compressed air, and radiographic changes may not appear until 6, 12, or 18 months after the causative episode. When the bone lesion is next to a joint surface, as in the head of the femur or the head of the humerus, permanent disability may result. An extensive study of 241 tunnel workers at the Clyde Tunnel showed that 19% of the men had one or more bone lesions and that in 10% lesions were juxta-articular and so potentially disabling.Among hospital personnel and those responsible for their safety there was concern that disabling bone lesions might develop. It is true that compared with tunnel workers the number of staff involved in medical hyperbaric environments is small, and the duration and number of exposures much less. In 21 of the 36 members of the staff examined radiologically, however, sufficient time has now elapsed for a bone lesion to have appeared; fortunately no radiological indication of any such lesion has emerged. So far as we are aware no comparable radiographic study at other hospital hyperbaric units has been reported.These data at present support the claim that pressures of air in the range 1-3 atmospheres are relatively safe for use in a specialized medical hyperbaric environment. It , 1969, 3, 327-330 Summary: Lung scans with the use of macroaggregated human serum albumin labelled with technetium-99m were carried out in 52 patients before thoracotomy.Forty-three patients had carcinoma of the bronchus. Tumours less than 2 cm. in diameter on the chest radiograph were not detected. Larger tumours showed defects in perfusion, ranging in size from the mass seen on the chest radiograph to almost absent perfusion of the entire lung. The extent of the defect in perfusion was closely rel...
The lung scans of 101 patients with carcinoma of the bronchus have been compared with the bronchoscopic and radiographic findings. As the tumour approaches the hilum as judged by bronchoscopy or the chest radiograph the relative perfusion of the affected lung decreases. When the relative perfusion of the affected lung is less than one third of the total the tumour is likely to be inoperable. The reduction in perfusion is related to involvement of the vessels in the hilum by tumour and to a lesser extent to bronchial obstruction.Defects in perfusion in the unaffected lung were seen in 53 patients and were usually due to chronic bronchitis and emphysema or inactive pulmonary tuberculosis.In the management of patients with carcinoma of the bronchus lung scans are of value in predicting when a tumour is likely to be inoperable and also in giving an indication as to whether a pneumonectomy or lobectomy will be possible. In addition, defects in the contralateral lung may be sufficiently large to contraindicate surgery.Lung scanning is a safe and effective way of demonstrating the relative pulmonary arterial blood flow to each lung (Sabiston and Wagner, 1964;Tauxe, Burchell, and Black, 1967) and has been used in this way to assess lung function in patients with carcinoma of the bronchus (Hatch, Maxfield, and Ochsner, 1965;Garnett, Goddard, Fraser, and Macleod, 1968). Defects in perfusion vary in size from those corresponding to the lesion visible on the chest radiograph to absent perfusion of an entire lung, while minor abnormalities are commonly seen in the opposite lung. This paper compares the lung scan findings with the bronchoscopic and radiographic appearances in patients with carcinoma of the bronchus seen between 1967 and 1969, and discusses the practical value of this technique. PATIENTS AND METHODSThe patients studied all had untreated carcinoma of the bronchus at the time of their lung scan. The relative pulmonary arterial blood flow (relative perfusion) of each lung has been determined from the colour dot scans by expressing the counts of radioactivity in the affected lung as a percentage of the total counts in the scan. This method correlates well with differential bronchospirometry as a measure of relative pulmonary blood flow (Chemick, LopezMajano, Wagner and Dutton, 1965;Rogers, Kuhl, Hyde, and Mayock, 1967; Gamett, Goddard, Machell, and Macleod, 1969).In addition a semiquantitative method, also based on the colour dot scans, has been used to assess the size of the defects in perfusion in the unaffected lung.
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