Chest CT scan for the screening of air anomalies at risk of pulmonary barotrauma for the initial medical assessment of fitness to dive in a military population

Abstract

Introduction: The presence of intra-pulmonary air lesions such as cysts, blebs and emphysema bullae, predisposes to pulmonary barotrauma during pressure variations, especially during underwater diving activities. These rare accidents can have dramatic consequences. Chest radiography has long been the baseline examination for the detection of respiratory pathologies in occupational medicine. It has been replaced since 2018 by the thoracic CT scan for military diving fitness in France. The objective of this work was to evaluate the prevalence of the pulmonary abnormalities of the thoracic CT scan, and to relate them to the characteristics of this population and the results of the spirometry.Methods: 330 records of military diving candidates who underwent an initial assessment between October 2018 and March 2021 were analyzed, in a single-center retrospective analysis. The following data were collected: sex, age, BMI, history of respiratory pathologies and smoking, treatments, allergies, diving practice, results of spirometry, reports of thoracic CT scans, as well as fitness decision.Results: The study included 307 candidates, mostly male, with a median age of 25 years. 19% of the subjects had abnormal spirometry. We identified 25% of divers with CT scan abnormalities. 76% of the abnormal scans were benign nodules, 26% of which measured 6 mm or more. Abnormalities with an aerial component accounted for 13% of the abnormal scans with six emphysema bullae, three bronchial dilatations and one cystic lesion. No association was found between the presence of nodules and the general characteristics of the population, whereas in six subjects emphysema bullae were found statistically associated with active smoking or abnormal spirometry results.Conclusion: The systematic performance of thoracic CT scan in a young population free of pulmonary pathology revealed a majority of benign nodules. Abnormalities with an aerial component are much less frequent, but their presence generally leads to a decision of unfitness. These results argue in favor of a systematic screening of aeric pleuro-pulmonary lesions during the initial assessment for professional divers.

An observational study ascertaining the prevalence of bullae and blebs in young, healthy adults and its possible implications for scuba diving

“…Therefore, previous investigations into the prevalence of bullae mainly originate from the field of diving medicine ( de Bakker et al, 2020a ; Bonnemaison et al, 2022 ; Weaver et al, 2022 ). Given their potential connection to PBT, the interest of the field of diving medicine in this topic is no surprise ( Germonpré et al, 2008 ; Goffinet and Simpson, 2019 ; de Bakker et al, 2020b ).…”

“…In numerous standards, chest X-ray is still mentioned to exclude clinically relevant pulmonary pathology, but computed tomography (CT) for structural analysis of the pulmonary system has been shown a highly superior imaging technique ( Health and Safety Executive, 2023 ). However, higher-resolution CT scans in healthy individuals can uncover incidental findings of unknown clinical significance, raising concerns for its routine use in fitness to dive assessments in the general population ( Wingelaar et al, 2020 ; Bonnemaison et al, 2022 ). A forensic ( post mortem ) CT study in 130 adults without pulmonary injuries revealed that 33.8% of subjects had bullae/blebs ( de Bakker et al, 2020a ).…”

“…A forensic ( post mortem ) CT study in 130 adults without pulmonary injuries revealed that 33.8% of subjects had bullae/blebs ( de Bakker et al, 2020a ). Bonnemaison et al reported a 2.3% prevalence of bullae and cysts in 307 (96% male) young military diving candidates ( Bonnemaison et al, 2022 ). Recently, Weaver et al reported a 4.7% prevalence pulmonary cysts, emphysema and/or bronchiectasis, based upon the analysis of the reports of almost 80,000 chest CT scans using text mining techniques ( Weaver et al, 2022 ).…”

Recommendations on scuba diving in Birt-Hogg-Dubé syndrome

“…In line with these observations, in a recent study, chest CT scans were performed in 76 young (median age 25 years) military diving candidates with no known lung pathology. An isolated pulmonary cyst was identified in one individual, and that person was subsequently deemed unfit to dive [ 17 ]. Nonetheless, the high frequency of pulmonary cysts in the general population combined with the large number of scuba divers and the limited number of fatal accidents indicates that the absolute risk of fatality due to lung cysts is likely to be low.…”

“…However, since pulmonary lesions have been associated with an increased risk of pulmonary barotrauma, one of the major causes of scuba diving-related fatalities, caution is in our opinion still warranted in patients with BHD until larger cohort studies are available. Based on the risks associated with lung lesions during scuba diving, it has been previously discussed to perform a chest CT as part of the medical certification of divers [ 17 ], because lung cysts are usually asymptomatic and will not be detected during routine medical diving screening. However, screening of all divers by chest CT was considered to be impractical and not cost-effective and therefore suggested as an option for professional divers [ 16 , 17 ].…”