Relationship between mastoid pneumatization and middle ear barotrauma in divers

OBJECTIVES/HYPOTHESIS: Previous studies have shown a relationship between eustachian tube function and size of mastoid pneumatization, as well as eustachian tube function and middle ear (ME) barotrauma. The purpose of this study is to investigate a possible relationship between size of mastoid pneumatization and ME barotrauma in sports scuba (self-contained underwater breathing apparatus) divers. STUDY DESIGN: Prospective, blinded. MATERIAL AND METHODS: Twenty-four sports scuba divers (48 ears), who were fit to dive in the predive and otolaryngologic examination, were included in the study. Size of mastoid pneumatization was measured by simplified rectangular dimension method on a mastoid x-ray taken at Schüller's view. Divers were counseled to refer to the investigators if any symptoms occurred during and/or after diving. All symptomatic ears were examined within 24 hours of diving by the same investigator, who was blinded to the degree of pneumatization. RESULTS: ME barotrauma occurred in 15 ears (31%) of 11 divers (46%) at one time or another. The median degree of pneumatization in ears with barotrauma (22.9 cm2) was significantly smaller than that in unaffected ears (34.1 cm2; (P <.001). Furthermore, findings showed that with increasing degree of pneumatization, there was a decreasing risk of symptomatic barotrauma (P <.001). No barotrauma occurred in ears with a pneumatization greater than 34.7 cm2. However, barotrauma occurred in all 3 ears with a pneumatization degree smaller than 13.6 cm2. CONCLUSION: Our findings indicate an inverse relationship between size of pneumatization and risk of symptomatic ME barotrauma in sport scuba divers.