Airbags and permanent auditory deficits. A real correlation?

Objectives: To evaluate the relationship between airbag-induced noise and individual metabolic risk factors in determining persistent hypoacusia in drivers after road accidents.

Methodology: We selected 22 patients previously involved in a car accident with deployment of airbags. Patients underwent general and audiological clinical history, tonal audiometric examination, vocal audiometric examination, impedance meter examination and blood tests.

Results: We divided patients, according to audiometric data, into 2 groups: group A with no residual otological disturbances (6 subjects) and group B with persistent hypoacusia (16 subjects). Blood parameters were into physiological levels in all group A patients; on the contrary 12 (subgroup B1) out of 16 group B patients had altered blood levels of glucose, urea and cholesterol, with mean values of 155.8 +/- 38.6 mg/dl, 48.2 +/- 8.3 mg/dl and 250.8 +/- 28.1 mg/dl, respectively, revealing statistically significant differences in these parameters when compared with the other 4 hypoacusic cases (Sub-group B2) and with the normal subjects (Group A) (p < 0.01 for glucose, p < 0.05 for urea and p < 0.001 for cholesterol).

Conclusions: Our findings confirm the transitory otological damage due to airbag deployment: the intensity of the acoustic wave hitting the ear after airbag deployment is responsible for a temporary rise in the acoustic threshold but the persistence of an auditory deficit can be due to co-factors able to interfere with the acute acoustic trauma recovery processes through a metabolic, angiopathic, neuropathic or unknown mechanism. Moreover, also the age of the patients could affect in a significant way the recovery from the acoustic trauma.