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PubMed2006

Airway disease in highway and tunnel construction workers exposed to silica.

BACKGROUND: Construction workers employed in a unique type of tunnel construction known as tunnel jacking were exposed over an 18-month period to respirable crystalline silica at concentrations that exceeded the OSHA permissible exposure limit. The present study examines workplace exposures and occurrence of airway disease in these workers. METHODS: Medical and occupational histories and chest radiographs were obtained on 343 active construction workers who had worked on the site during the period in question. Chest radiographs were interpreted according to the ILO-1980 system of classification. Standardized questions were used to develop an algorithm to define symptoms consistent with asthma (SCA) and to determine these respiratory outcomes: chronic bronchitis, shortness of breath (SOB), and physician-diagnosed asthma (current vs. not current). Relationships with each of three work activities were examined: slurry wall breakthrough (SWB), chipping caisson overpour, and tunneling/mining. RESULTS: Participants included laborers, carpenters, tunnel workers, ironworkers, operating engineers, and electricians. No cases of silicosis were found on chest X-ray. Overall prevalence of chronic bronchitis, SCA, SOB, and physician-diagnosed asthma was 10.7%, 25%, 29%, and 6.6%, respectively. Odds ratios (OR) for carpenters compared to laborers were significantly elevated for chronic bronchitis, SCA, and SOB. SWB was associated with chronic bronchitis and SCA (OR 4.93, 95% CI = 1.01, 24.17; OR 3.32, 95% CI = 1.25, 8.84, respectively). The interaction between SWB, SCA, and trade was significant for carpenters (OR 6.87, 95% CI = 1.66, 28.39). Inverse trends were observed for months on the site and chronic bronchitis, SCA, and SOB (P = 0.0374, 0.0006, and 0.0307, respectively). CONCLUSIONS: Tunnel construction workers exposed to respirable crystalline silica and cement dust are at increased risk for airway disease. Extent of risk varies by trade and work activity. Our data indicate the importance of bystander exposures and suggest that tunnel jacking may be associated with greater risk compared to more traditional methods of tunnel construction. A healthy worker effect is suggested.

Adult↗
PubMed2003

Right-to-left shunt and risk of decompression illness with cochleovestibular and cerebral symptoms in divers: case control study in 101 consecutive dive accidents.

OBJECTIVE: We investigated the role of right-to-left shunt with standardized transcranial Doppler ultrasonography in a large population of divers referred for symptoms of decompression illness. DESIGN: Case series compared with a control group. SETTING: Military teaching hospital, hyperbaric unit. PATIENTS: Patients were 101 consecutive divers with clinical evidence of decompression illness and a control group of 101 healthy divers. INTERVENTION: Specification of the type of decompression illness involved and detection/evaluation of right-to-left shunt by standardized transcranial Doppler. The degree of right-to-left shunt was defined as major if the number of high-intensity transient signals in the middle cerebral artery was >20. MEASUREMENTS AND MAIN RESULTS: We evaluated the odds ratios by logistic regression analysis with vs. without right-to-left shunt for subjects with cochleovestibular symptoms, cerebral decompression illness, spinal decompression illness, and Caisson sickness. Of the 101 divers presenting with decompression illness, transcranial Doppler detected a right-to-left shunt in 59 (58.4%), whereas control subjects demonstrated a right-to-left shunt in 25 cases (24.8%; odds ratio, 4.3; 95% confidence interval, 2.3-7.8; p=.09). When a right-to-left shunt was detected, the right-to-left shunt was major in 12 of 25 patients in the control group and in 49 of 59 patients in the decompression illness group (odds ratio, 8.7; 95% confidence interval, 4.2-18.0; p<.001). Within the decompression illness group, the proportion of major right-to-left shunt was 24 of 34 (odds ratio, 29.7; 95% confidence interval, 10.0-87.2; p<.0001) in the cochleovestibular subgroup, 13 of 21 (odds ratio, 24.1, 95% confidence interval, 6.8-86.0, p< 0.0001) in the cerebral decompression illness subgroup, ten of 31 (odds ratio, 3.9; 95% confidence interval, 1.5-10.3; p<.01) in the spinal decompression illness subgroup, and two of two (odds ratio, 1.1; 95% confidence interval, 0.2-5.7; p=.9) in the subgroup of divers with Caisson sickness. CONCLUSION: Based on our results, we conclude that major right-to-left shunt was associated with an increased incidence of cochleovestibular and cerebral decompression illness, suggesting paradoxical embolism as a potential mechanism.

Adult↗
PubMed1990

Does dysbaric osteonecrosis progress in the absence of further hyperbaric exposure? A 10-year radiologic follow-up of 15 patients.

Progression of dysbaric osteonecrosis of the femoral and humeral heads was evaluated in 15 caisson workers. All patients had dysbaric osteonecrosis but had had no further exposure to hyperbaric pressures for a minimum of 10 years. The original and follow-up radiographs were compared in each case. Of 24 normal articular heads (nine humeral and 15 femoral), one (4%) humeral head developed new subcortical sclerosis. Of the 36 juxta-articular lesions, seven (four humeral and three femoral) showed major changes in the 10-year interval. Of these seven, two (one humeral and one femoral) had new articular fractures and three (two humeral and one femoral) with articular fractures showed progressive osteoarthritis. We conclude that caisson workers can develop lesions in previously normal areas and experience worsening of previously known lesions in the absence of further exposure to hyperbaric pressures.

Aged↗
PubMed1977

Treatment of gas gangrene. Interest of hyperbaric oxygen therapy.

We report 27 cases of gas gangrene treated at the University Hospital of Liège since the Anesthesiology Department has been using a caisson for hyperbaric oxygen therapy. Frequency of gas gangrene does not appear to have decreased during recent years. The etiologies now encountered are mainly of post-traumatic and post-operative origin (especially surgery on the digestive tract); arterial insufficiency is a predisposing factor. The prognosis depends on the speed with which an effectual treatment is started; the latter consists in intensive hyperbaric oxygen therapy, antibiotic therapy and resuscitation. Surgery should be as conservative as possible and is undertaken only when progress of the disease has been checked by hyperbaric oxygen therapy. The association of these various modes of treatment proves effectual despite a still significant mortality.

Adolescent↗
PubMed2006

Mortality from non-malignant respiratory diseases among people with silicosis in Hong Kong: exposure-response analyses for exposure to silica dust.

OBJECTIVES: To examine the exposure-response relationships between various indices of exposure to silica dust and the mortality from non-malignant respiratory diseases (NMRDs) or chronic obstructive pulmonary diseases (COPDs) among a cohort of workers with silicosis in Hong Kong. METHODS: The concentrations of respirable silica dust were assigned to each industry and job task according to historical industrial hygiene measurements documented previously in Hong Kong. Exposure indices included cumulative dust exposure (CDE) and mean dust concentration (MDC). Penalised smoothing spline models were used as a preliminary step to detect outliers and guide further analyses. Multiple Cox's proportional hazard models were used to estimate the dust effects on the risk of mortality from NMRDs or COPDs after truncating the highest exposures. RESULTS: 371 of the 853 (43.49%) deaths occurring among 2789 workers with silicosis during 1981-99 were from NMRDs, and 101 (27.22%) NMRDs were COPDs. Multiple Cox's proportional hazard models showed that CDE (p = 0.009) and MDC (p<0.001) were significantly associated only with NMRD mortality. Subgroup analysis showed that deaths from NMRDs (p<0.01) and COPDs (p<0.05) were significantly associated with both CDE and MDC among underground caisson workers and among those ever employed in other occupations with high exposure to silica dust. No exposure-response relationship was observed for surface construction workers with low exposures. A clear upward trend for both NMRDs and COPDs mortality was found with increasing severity of radiological silicosis. CONCLUSION: This study documented an exposure-response relationship between exposure to silica dust and the risk of death from NMRDs or COPDs among workers with silicosis, except for surface construction workers with low exposures. The risk of mortality from NMRDs increased significantly with the progression of International Labor Organization categories, independent of dust effects.

Adult↗
PubMed1988

[Characteristics of various indicators of the rheological properties of the blood in patients with initial manifestations of cerebrovascular insufficiency and ischemic stroke].

The rheological properties of the blood and aggregation of erythrocytes and platelets were studied in 30 apparently healthy subjects and in 220 patients with impaired blood supply to the brain. The results have confirmed a high informative value of the complex of parameters of rotational viscosimetry: the limit of blood fluidity, apparent blood viscosity, caisson viscosity of the blood, and the coefficient of erythrocyte cohesion (A) and of the parameters of aggregation of the formed elements of the blood, this complex allowing an objective differentiation between microcirculatory peculiarities in patients with initial manifestations of cerebral blood supply insufficiency (IMCBSI) versus patients with ischemic stroke (IS). It has been elucidated for the first time that patients with IMCBSI secondary to atherosclerosis have a low A parameter confirming optimization of the microcirculation following elevation of the hematocrit. The alterations in the rheological properties of the blood were the greatest in patients with IS within the first three days after the onset of the disease. Elevated cohesion of erythrocytes persisted for one month after the onset of IS. It has been proved that repeated examinations are necessary for the individual and adequate correction of the blood rheology.

Adult↗
PubMed2001

Tuberculosis risk factors in a silicotic cohort in Hong Kong.

SETTING: Hong Kong silicotic patients are followed regularly at the Pneumoconiosis Clinic. OBJECTIVE: To quantify the incidence of tuberculosis disease that occurs after the date of diagnosis of silicosis (DOD), and to identify the risk factors for its development. DESIGN: Retrospective analysis of a Hong Kong silicotic cohort with DOD from 1 January 1988 to 31 December 1993. RESULTS: Of 718 subjects whose records were identified, 11 were excluded from the study. The incidence of tuberculosis (TB) after DOD was 3019 patients per 100,000 population, approximately nine times that of the local population matched for age and sex. Twelve factors were subject to univariate analysis followed by logistic regression. Four TB risk factors were identified: 1) no anti-tuberculosis treatment before DOD (relative risk [RR] 4.51, 95% confidence interval [CI] 2.46-8.24), 2) progressive massive fibrosis (PMF) (RR 3.78, 95%CI 2.25-6.36), 3) small opacities exceeding 1.5 mm (RR 2.17, 95%CI 1.38-3.42), and 4) caisson work (RR 1.56, 95%CI 1.01-2.41). Relative risks were calculated for patient subgroups stratified according to TB risk factors. CONCLUSION: This study has reaffirmed the strong association of tuberculosis and silicosis, and has identified several TB risk factors with a logistic regression model.

Adult↗
PubMed1986

Aseptic necrosis in caisson workers: a new set of decompression tables.

There is a high incidence of aseptic necrosis and decompression sickness among caisson workers due to inadequate decompression using the current OSHA decompression tables (1-7). Because of this, a new set of tables--Autodec III-O2--was developed which more effectively eliminates nitrogen from the body and, therefore, should decrease the incidence of both bends and aseptic necrosis. The Autodec III-O2 schedule's superiority was statistically significant at a level of 0.08 compared to the OSHA table. It is our conclusion that OSHA should adopt the Autodec III-O2 schedule as a replacement for the current decompression tables.

Adult↗
PubMed2004

Prevention of work-related decompression illness events by detection of a cardiac right-to-left shunt.

A 44-year-old tunnel worker was studied who suffered from several unexplained decompression illness events for almost 15 years. This caisson worker was affected after standard pressure profiles that did not cause symptoms of decompression illness in his colleagues on the same shift. Transesophageal echocardiography revealed an atrial septal defect (grade II) in this otherwise healthy man. Cranial magnetic resonance imaging showed ischemic brain lesions. Among divers, patent foramen ovale, the most common cause of cardiac right-to-left shunts, was shown to increase the risk for decompression illness events by a factor of 4.5 and to double the risk of ischemic brain lesions. Hyperbaric workers with symptoms of unexplained decompression illness, even if they are only slight, should immediately be transferred to a cardiologist so that a cardiac right-to-left shunt will not be overlooked.

Adult↗
PubMed1997

Dysbaric osteonecrosis in divers and caisson workers. An animal model.

Dysbaric osteonecrosis was induced successfully in adult sheep after 12 to 13, 24-hour exposures to compressed air (2.6-2.9 atmospheres absolute) during a 2-month period. All exposed sheep had decompression sickness and extensive bone and marrow necrosis in their long bones. Radiographic analysis of these progressive lesions showed mottled to distinct medullary opacities and endosteal thickening characteristic of dysbaric osteonecrosis. Six months after the last hyperbaric exposure, neovascularization of once ischemic fatty marrow was centripetal from the diaphyseal cortex. Proliferating endosteal new bone, fatty marrow calcification, and appositional new bone formation were widespread. Juxtaarticular osteonecrosis involved marrow fibrosis and loss of osteocytes in subchondral cortical bone. Tidemark reduplication in juxtaarticular bone and cartilage thinning suggested possible early osteoarthritis induction by recurrent episodes of transient ischemia after multiple hyperbaric exposures. Dysbaric osteonecrosis appears to involve a bone compartment syndrome of elevated intramedullary pressure initiated by decompression induced N2 bubble formation in the fatty marrow of the long bones. An animal model that can be used to investigate the pathogenesis, diagnosis, and treatment of dysbaric osteonecrosis is discussed.

Animals↗
PubMed1988

[Neurologic symptoms in inhalation poisoning with metallic mercury].

Nineteen caisson workers had been exposed to metallic mercury vapours while digging tubes underneath the first district of Vienna (exposure between 470 and 2440 min; mean 1621 min). The blood mercury values on admission were between 29 and 166 micrograms/l (mean 75 +/- 34 micrograms/l). The main findings reported are clinical neurologic symptoms, psychic complaints, neurographic results and autonomic parameters (cardiovascular reflexes): 47% complained of headache and tiredness, 37% showed tremor and suffered from sleep disturbances, 26% showed hypersalivation, 16% changes in handwriting, and 11% slight dysarthria. The cardiovascular reflexes (autonomic parameters) were abnormal in 7 of 12 patients. On neurography the distal latency (median nerve) was pathologic in 47%, the distal latency (peroneal nerve) was pathologic in 26%, the antidromic sensory nerve conduction velocity (median nerve) was abnormal in 10%, the motor nerve conduction velocity, compound amplitude and vibratory threshold were normal.

Adult↗
PubMed2003

Health outcome following multi-day occupational air diving.

Acclimatization to decompression stress has been reported in caisson workers and helium-oxygen divers; however the alternative notion that the risk of decompression sickness increases with successive days of diving is widespread. We examined 201 multi-day series of 2 to 29 diving days identified retrospectively in a database of occupational air dives for evidence of acclimatization or sensitization. Decompression related health status was measured using a self-administered diver health survey; resulting scores were analyzed by linear modelling. Daily diving consisted of 1-3 dives each to mean maximum depth of 17.2 (SD 3.9) meters seawater for a mean duration of 23 (SD 17) min. Daily diver health scores increased with calculated daily risk of decompression sickness but were not influenced by the order of dives in multi-day series. Poor health outcome indicated by treated decompression sickness and diver health scores > 8 occurred early in multi-day series. There was no evidence of sensitization to decompression stress whereas the timing of poor health outcomes suggests an element of acclimatization.

Analysis of Variance↗
PubMed1987

[Research on the incidence of decompression sickness in compressed air works. The development of its recent five years' study].

Compressed air works have been used as the safest construction work for the basic underground or underwater compressed shield or caisson works in Japan; however, the workers who were exposed to the compressed fields must have put themselves at risk of decompression sickness. Decompression sickness is generally considered to be due to the bubble effects and the bubbles originate from the supersaturated gas dissolved in the blood and other tissues. The standard decompression schedule by the Ministry of Labor has been practically applied at the end of compressed air works, and the laborers decompress slowly from the bottom pressure to the surface according to the schedule. It is difficult to completely prevent the sickness and the average percentage of contracting "bends," using the Japanese standard decompression schedule, is considered to be 0.54%. But previous papers reported higher incidences from 1.42 to 3.3% or more. We have continued an actual investigation on the incidence, and the number of the exposed trials amounted to nearly a hundred thousand. These data were compared between recent five years' group and before. Eventually, it was ascertained that the incidence has been significantly decreased in the recent five years; however, greater care in occupational safety control is still needed.

Adult↗
PubMed2001

Relationship between right-to-left shunts and cutaneous decompression illness.

The presence of a large right-to-left shunt is associated with neurological decompression illness after non-provocative dives, as a result of paradoxical gas embolism. A small number of observations suggest that cutaneous decompression illness is also associated with a right-to-left shunt, although an embolic aetiology of a diffuse rash is more difficult to explain. We performed a retrospective case--control comparison of the prevalence and sizes of right-to-left shunts determined by contrast echocardiography performed blind to history in 60 divers and one caisson worker with a history of cutaneous decompression illness, and 123 historical control divers. We found that 47 (77.0%) of the 61 cases with cutaneous decompression illness had a shunt, compared with 34 (27.6%) of 123 control divers (P<0.001). The size of the shunts in the divers with cutaneous decompression illness was significantly greater than in the controls. Thus 30 (49.2%) of the 61 cases with cutaneous decompression illness had a large shunt at rest, compared with six (4.9%) of the 123 controls (P<0.001). During closure procedures in 17 divers who had cutaneous decompression illness, the mean diameter of the foramen ovale was 10.9 mm. Cutaneous decompression illness occurred after dives that were provocative or deep in subjects without shunts, but after shallower and non-provocative dives in those with shunts. The latter individuals are at increased risk of neurological decompression illness. We conclude that cutaneous decompression illness has two pathophysiological mechanisms. It is usually associated with a large right-to-left shunt, when the mechanism is likely to be paradoxical gas embolism with peripheral amplification when bubble emboli invade tissues supersaturated with nitrogen. Cutaneous decompression illness can also occur in individuals without a shunt. In these subjects, the mechanism might be bubble emboli passing through an 'overloaded' lung filter or autochthonous bubble formation.

Case-Control Studies↗