Repeated Atmospheric Pressure Alteration Effect on the Cochlea in Rats: Experimental Animal Study.

OBJECTIVE: This study aimed to evaluate the effects of repeated pressure alterations on cochlear structures in rats in an attempt to understand indirectly the inner ear status of flight crew who are repeatedly exposed to pressure alterations.METHODS: There were 12 adult Wistar albino rats equally divided into 2 groups: Group 1 (controls) and Group 2 (study group). The animals in Group 2 were exposed to repeated pressure changes in a pressure cabin which is regulated by manometers. The animals in Group 1 were placed in the cabin without being exposed to pressure changes. Auditory brainstem response (ABR) testing was performed in all animals at the beginning and at the end of the study. After 12 wk the animals were sacrificed and their cochleas were investigated using scanning electron microscopy (SEM).RESULTS: In the study group, hearing decreases at 2 kHz, 4 kHz, 6 dB at 8 kHz, and 32 kHz were encountered at the end of 3 mo. On SEM evaluation of the control group, the outer hair cells (OHC) and stereocilia were normal throughout the cochlea. In the study group, there were irregularities in lateral surface connections and separations, collapse, and adhesions in the basal segment of the cochlea and partial loss of stereocilia throughout the cochlea.CONCLUSION: Repeated alterations in the atmospheric pressure can lead to damage in the inner ear with subtle or evident hearing loss. Frequent flyers like air workers may be at risk of inner ear damage, which may be considered an occupational health problem.Eroglu S, Dizdar HT, Cevizci R, Cengiz AB, Ogreden S, Bulut E, Ilgezdi S, Dilci A, Ustun S, Sirvanci S, Kaya OT, Bayazit D, Caki BO, Oktay MF, Bayazit Y. Repeated atmospheric pressure alteration effect on the cochlea in rats: experimental animal study. Aerosp Med Hum Perform. 2021; 92(7):550555.

The effect of hyperbaric oxygen therapy on fracture healing in nicotinized rats.

BACKGROUND: The aim of the present study was to investigate the effect of hyperbaric oxygen therapy on fracture healing in nicotinized rats. METHODS: Thirty-two rats were divided as follows: nicotinized group (1), hyperbaric oxygen group (2), nicotinized + hyperbaric oxygen group (3), and control group (4). For 28 days, nicotine was administered in Groups 1 and 3. Then, a standard shaft fracture was induced in the left femur of rats. Groups 2 and 3 underwent hyperbaric oxygen therapy for 21 days. At the end of the experiment, fracture site, left femur and whole body bone mineral content and density were measured. RESULTS: The radiological and histopathological scores of Group 1 were statistically significantly lower compared to Groups 2, 3 and 4, and there was no statistically significant difference between the Groups 2, 3 and 4. In a comparison between the groups, no statistically significant difference was found in terms of bone mineral content and density values measured at the fracture site, left femur and whole body. CONCLUSION: The negative effects of nicotine on fracture healing are eliminated with hyperbaric oxygen therapy, but hyperbaric oxygen alone does not cause significant changes in healing (radiologically and histopathologically).

The effect of hyperbaric oxygen treatment on the healing of burn wounds in nicotinized and nonnicotinized rats.

The importance of oxygen in wound healing and the negative effects of cigarette smoking have been demonstrated in various studies. In this study, our aim was to investigate the effect of hyperbaric oxygen (HBO2) treatment on wound healing in nicotinized and nonnicotinized rats. The study was conducted on 32 Sprague Dawley rats. The rats were divided into four groups, with eight rats in each: group 1, nonnicotinized rats; group 2, nonnicotinized rats treated with HBO2; group 3, nicotinized rats; and group 4, nicotinized rats treated with HBO2. To prepare the nicotinized groups, the rats were given nicotine for 28 days. At the end of day 28, standard, deep, second-degree to third-degree burns were created on the rats. The HBO2-treated groups underwent HBO2 treatment once a day for 7 days after the creation of the burn damage. All rats were killed 21 days after injury, and the burns were subjected to macroscopic, histopathological, and microbiological evaluation. During this evaluation, the smallest necrotic areas and the lowest rate of fibrosis were observed in group 2. The largest necrotic areas and the highest inflammation and fibrosis rates were observed in the nicotine-treated group 3. When the nicotinized and nonnicotinized groups were compared separately, there was a significant difference in favor of the groups treated with HBO2. Bacterial growth was the highest in the nicotinized group 3, whereas no statistically significant difference was observed among the other groups. We conclude that HBO treatment accelerates the recovery of burn wounds and provides more effective healing by reducing the development of scars both in nicotinized and nonnicotinized rats.

The effect of hyperbaric oxygen therapy on the survival of random pattern skin flaps in nicotine-treated rats.

Previous studies have shown that nicotine increases the risk of necrosis in skin flaps. We investigated the effect of hyperbaric oxygen (HBO(2)) treatment on the survival of random skin flaps in nicotine-treated rats. Thirty-two Sprague-Dawley rats were divided into four groups with eight rats in each group. Group 1 (n=8) was the control, group 2 (n=8) received HBO(2) treatment without being exposed to nicotine, group 3 (n=8) received nicotine and group 4 (n=8) received HBO(2) treatment with exposure to nicotine. The rats in the nicotine-treated groups were prepared by treating them with nicotine for 28 days. At the end of the 28th day, standard McFarlane-type random skin flaps were lifted from the backs of all the rats. In groups 2 and 4, HBO(2) treatment started at the 30th min following the surgery and continued once a day for 7 days. The flap survival rates and histopathological evaluation results related to neovascularisation and granulation tissue formation were significantly better in the HBO(2)-treated groups (groups 2 and 4) than in the groups that did not receive HBO(2) treatment (groups 1 and 3) (p < 0.05). The flap survival rates, neovascularisation and granulation tissue formation were highest in group 2 and lowest in group 3 (p ≤ 0.001). No significant difference was observed between group 4, which received HBO(2) treatment with nicotine exposure, and the control group (group 1) (p > 0.05). In conclusion, our study demonstrates that HBO(2) treatment has a positive effect on flap survival in nicotine-treated rats.

Can hyperbaric oxygenation decrease doxorubicin hepatotoxicity and improve regeneration in the injured liver?

BACKGROUND/PURPOSE: Portal vein embolization is used in the treatment of hepatocellular cancer, with the purpose of enhancing resectability. However, regeneration is restricted due to hepatocellular injury following chemotherapeutics (e.g. doxorubicin). The aim of this study was to investigate whether hyperbaric oxygenation (HBO) can alleviate the hepatotoxicity of chemotherapy and improve regeneration in the injured liver. METHODS: Rats were allocated to four experimental groups. Group I rats were subjected to right portal vein ligation (RPVL); rats in groups II and III were administered doxorubicin prior to RPVL, with group III rats being additionally exposed to HBO sessions postoperatively; group IV rats was sham-operated. All rats were sacrificed on postoperative day 7, and liver injury was assessed by measuring alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. Protein synthetic ability was determined based albumin levels and liver regeneration by the mitotic index (MI). RESULTS: The AST and ALT values of group II rats were significantly higher than those of group I, but not those of group III. Rats treated with doxorubicin and HBO (groups II and III) showed slightly but not significant differences in albumin levels than those subjected to only RPVL or sham-operated. The MI was significantly increased in groups I, II, and III, with the MI of group III rats significantly higher than those of group I rats. CONCLUSIONS: Based on our results, we conclude that HBO treatment has the potential to diminish doxorubicin-related hepatotoxicity and improve regeneration in the injured liver.

Dysbaric osteonecrosis in experienced dive masters and instructors.

INTRODUCTION: Dysbaric osteonecrosis (DON) is a type of aseptic bone necrosis of long bones such as the humerus, femur, and tibia. It is observed in workers who perform in high-pressure environments. METHODS: There were 58 volunteer divers included in this study who had performed at least 500 dives, were working as a dive master or instructor, had never performed industrial and commercial dives, and did not have a diagnosis of osteonecrosis. Radiological evaluation was performed according to the guidelines suggested by The British Research Council Decompression Sickness Panel. A total of eight X-rays were taken per patient. When suspicious lesions were detected, MRI of the region was performed. RESULTS: Of the 58 divers, 2 were eliminated because of inadequate X-ray studies. A total of 18 DON lesions were detected in 14 of 56 (25%) divers. Age was the only variable independently associated with the development of DON (P < 0.05). DISCUSSION: The DON prevalence of 25% in this study is high considering the dive instructors had thorough diving training and strictly practiced the decompression rules. We believe this high prevalence is a result of frequent and sometimes deep dives for many years. Our findings raise the question of whether these divers can be seen as "sports divers" or should be seen as "occupational divers." If the latter description is approved, dive masters and instructors should be kept under periodic screening for DON lesions just like professional commercial divers to help reduce the morbidity associated with this disease.