Hyperbaric oxygen therapy seems to enhance recovery from acute acoustic trauma.

CONCLUSION: The average recovery of hearing and cessation of tinnitus was significantly better after hyperbaric oxygen therapy (HBOT) than after normobaric oxygen therapy (NBOT). HBOT can be valuable adjuvant therapy for patients with acute acoustic trauma (AAT). OBJECTIVES: AAT was one of the early indications for the use of HBOT. The rationale of administering oxygen to patients with AAT is based on experimental studies showing that noise exposure results in cochlear hypoxia, which could be compensated by HBOT. The aim of this study was to investigate the efficacy of HBOT in patients with AAT. PATIENTS AND METHODS: We compared the recovery from hearing impairment and tinnitus in 60 ears treated with HBOT with 60 ears treated with NBOT. The HBOT was given daily for 1-8 days. There were no significant differences in clinical or audiological data between HBOT and NBOT groups. RESULTS: The average recovery of hearing both at high and speech frequencies was significantly better and tinnitus persisted less commonly after the HBOT than after the NBOT. Normal hearing at the end of the follow-up period was regained in 42 ears in the HBOT group and in 24 ears in the NBOT group (p<0.01).

Efficiency of hyperbaric oxygen therapy in experimental acute acoustic trauma from firearms.

In acute acoustic trauma (AAT), excessive noise exposure causes rupture of cell membranes and decreased cochlear blood flow. This leads to decreased oxygen tension in inner ear fluids and reduction of a variety of different oxygen-dependent cellular activities. Hyperbaric oxygen treatment (HBO) may help the cells suffering from hypoxia to survive. We exposed male Wistar rats to 60 impulses of 162-dB SPL from a 7.62-mm assault rifle equipped with a blank adaptor. After the exposure, 15 animals were given HBO treatment for 90 min daily for 10 consecutive days at 0.25 MPa. After a survival time of 4 weeks, auditory brainstem responses were measured and the left cochleae processed for light microscopy. The impulse noise caused permanent damage to the cochlea of all animals, with the most severe lesions in the lower middle coil, where a significantly smaller number of hair cells was missing in the HBO-treated group. The morphological damage was also reflected in function, as measured by auditory brainstem responses, which showed the greatest threshold shifts at 6.0, 8.0 and 10.0 kHz.

Influence of strict regulations on the use of hearing protectors in the Finnish Defence Forces.

The regulations concerning hearing protection during military training in the Finnish Defence Forces were renewed in 1989. The material of this prospective study concerns 912 consecutive conscripts (463 before and 449 after the new regulations) who were referred to the Central Military Hospital for acute acoustic trauma (AAT). We focused on three issues: (1) general habits regarding the use of hearing protection during shooting drills and combat training; (2) hearing protection at the moment of AAT; and (3) the cause of AAT. In combat training, the use of any hearing protectors was only 50% before the new regulations, but after they came into force the proportion was greater than 90%, and more effective protectors were used. However, at the time of AAT the hearing protection was absent in more than 80% of cases in both groups. The most common cause of AAT was small arms in both groups (83%).

Effect of hyperbaric oxygen treatment on permanent threshold shift in acoustic trauma among rats.

Impulse noise from firearms is a common cause of acute acoustic trauma (AAT). Recently hyperbaric oxygen treatment has become available in many hospitals treating AAT. We exposed 39 Wistar rats to intense impulse noise of 60 shots from the assault rifle (162 dB SPL). After the exposure 15 animals were given hyperbaric oxygen treatment (HBO) by 10 treatment cycles of 90 minutes 100% oxygen in 0.25 MPa, one treatment cycle per day. Four weeks after the exposure the hearing thresholds were measured with auditory brainstem response audiometry at frequencies of 1.0, 2.0, 4.0, 6.0, 8.0 and 10.0 kHz. Characteristics for the resulting noise-induced hearing loss were large variations in its severity not only between animals, but also between the ears of a single animal. The largest permanent threshold shifts were found at 6.0, 8.0 and 10.0 kHz. Most of the HBO-treated animals showed less threshold shift than the non-treated animals. The difference between the HBO group and the control group was only slightly statistically significant (p = 0.067).

Adrenaline and nebulized salbutamol in acute asthma.

The effects of injected adrenaline and nebulized salbutamol on acute asthma were compared in 46 children. The results showed that salbutamol had a significantly better bronchodilatory effect than adrenaline. Nebulized salbutamol is recommended as a primary method of treatment of asthmatic attacks in childhood.