Noise exposure levels in stock car auto racing.

Noise-induced hearing loss associated with the workplace has been well described. Far less is known, however, about the risks to hearing from recreational sources of noise. We investigated the popular sport of stock car racing as a potentially significant source of noise exposure, and we conducted a sound-level survey at a National Association for Stock Car Auto Racing (NASCAR) event. Noise levels measured during the race ranged from 96.5 to 104 dB(A) at 46 meters ( approximately 150 feet) from the track and 99 to 109 dB(A) at 6 meters ( approximately 20 feet) from the track. The peak sound pressure level at 6 meters was 109 dB(A). Although significantly less than that associated with an immediate permanent threshold shift, such an exposure could cause a temporary threshold shift. Alhough hearing protection is recommended, particularly for track employees with longer periods of exposure, racing fans with only occasional exposure to such noise levels are unlikely to develop a permanent noise-induced hearing loss.

Nitric oxide in glutamate-induced compound action potential threshold shifts.

OBJECTIVE: Investigate the role of NO as a neurotransmitter in the gerbil cochlea and the effects of (7-NI) on compound action potential (CAP) threshold elevations induced by l-glutamate, an agonist at the NMDA glutamate receptor subtype, to further elucidate the role of NO in cochlear excitotoxicity. METHOD: In anesthetized gerbils, CAP thresholds were recorded before and after cochlear perfusions with a control solution of artificial perilymph (APS) and a test solution of L-glutamate (GA) in three experimental groups. RESULTS: The control group showed no CAP threshold elevations (p<0.05) when APS was perfused after systemic pre-treatment with 7-NI. GA perfusion alone caused significant elevation (p<0.05) of the mean cochlear CAP threshold (25 dB SPL+/-5.8 dB to 78 dB SPL+/-19.5 dB). The CAP threshold elevation was prevented (p<0.05) when the animals were pretreated with 7-NI before GA perfusion (24 dB SPL+/-4.2dB to 27 dB SPL+/-6.7 dB). CONCLUSION: NO mediates excitotoxicity when the cochlea is perfused with L-glutamate.

Immune modulatory oligonucleotides in prevention of nasal allergen-induced Eustachian tube dysfunction in rats.

OBJECTIVES: Develop a model of nasal allergen-induced Eustachian tube dysfunction (ETD) in a rat and investigate the role of immune modulatory oligonucleotides (IMOs) in the prevention of nasal allergen-induced ETD. STUDY DESIGN AND SETTING: Prospective, randomized study. Brown Norway rats were sensitized to ova albumin (OVA) and randomized to receive pretreatment with IMOs or phosphate-buffered saline. All animals were challenged intranasally with aerosolized OVA. Dynamic measures of Eustachian tube (ET) function were analyzed. RESULTS: Animals that were OVA-sensitized and IMO-pretreated had significantly lower mean passive opening (95% confidence interval [95% CI] 15.0,19.4) and closing (95% CI 4.8,7.8) ET pressures compared with those of (95% CI 24.1,32.7) and (95% CI 12.1,18.8) OVA-sensitized untreated rats, respectively. In addition, the IMO-pretreated animals demonstrated the ability to actively clear a significantly higher proportion of negative pressure (95% CI 0.64,0.96) compared with the untreated animals (95% CI 0.09,0.39). IMO-pretreated animals also demonstrated significantly improved mean mucociliary clearance times in seconds (95% CI 115,195) than those in untreated animals (95% CI 308,668). CONCLUSIONS: Pretreatment with IMOs prevented allergen-induced allergic inflammation around the Eustachian tube (ET) and resulted in improved ventilatory function of the ET compared with sensitized untreated animals. IMOs offer considerable promise in the management of nasal allergic disease as well as otitis media with effusion.

Immune modulatory oligonucleotides in the prevention and treatment of OVA-induced eustachian tube dysfunction in rats.

BACKGROUND: Otitis media with effusion (OME) is often associated with allergies. Immune modulatory oligonucleotides (IMO) mediate allergic inflammation and may therefore be efficacious in the treatment of airway inflammation. OBJECTIVE: To evaluate the role of an IMO via transtympanic mucosal application in prevention and treatment of ovalbumin-induced OME. DESIGN: Forty brown Norway rats were divided into control and treatment groups. Eustachian tube dysfunction was evaluated by passive opening pressures, passive closing pressures, active clearance of negative pressure, and mucociliary clearance transit time. RESULTS: Rats who underwent IMO treatment required 50% less pressure to open and close the eustachian tube (P < 0.05) and were able to actively clear 50% more negative pressure than the ovalbumin-control rats (P < 0.001). The treatment rats' mucociliary clearance time was half that of the control group (P < 0.001). CONCLUSION: IMO via transtympanic application can prevent and treat allergy-induced eustachian tube dysfunction in rats. IMO may offer substantial promise in the future management of OME.

The role of immunomodulatory oligonucleotides in prevention of OVA-induced Eustachian tube dysfunction.

OBJECTIVE: To evaluate the potential role of immunomodulatory oligonucleotides (IMO) in the prevention of OVA-induced Eustachian tube dysfunction (ETD) in a rat model. METHODS: Brown-Norway rats were sensitized to ovalbumin (OVA) and randomized to receive pre-treatment with IMO or phosphate buffered saline (PBS). After systemic sensitization, subjects received a transtympanic OVA challenge followed by evaluation of the Eustachian tube's dynamic function. RESULTS: Pre-treatment of OVA sensitized animals with IMO normalized passive opening and closing Eustachian tube pressures, improved active clearance of negative pressure in the middle ear, and resulted in reduced mean mucociliary transit times compared to untreated OVA-sensitized animals (P<0.001). CONCLUSION: These data demonstrate that pre-treatment with IMO prevent OVA-induced ETD in the rat. IMO treatment in the future may offer considerable promise in the management of OME in children.

The role of soluble interleukin-4 receptor and interleukin-5 antibody in preventing late-phase allergy-induced eustachian tube dysfunction.

OBJECTIVES: We investigated the role of soluble interleukin (IL)-4 receptors (sIL-4R) and IL-5 antibodies (IL-5Ab) in preventing allergic eustachian tube dysfunction (ETD) and middle ear effusion (MEE). STUDY DESIGN: Brown-Norway rats were sensitized to ovalbumin (OVA) and challenged transtympanically. Two groups of rats received either IL-4R or IL-5Ab transtympanically 1 hour before challenge. Three additional groups were used as controls. Following the second transtympanic challenge, the ventilatory and clearance functions of the eustachian tube (ET) were assessed at 0, 2, and 8 hours. Histology was prepared using cut paraffin sections stained with hematoxylin and eosin. RESULTS: sIL-4R-pretreated rats showed no significant changes in ventilatory or clearance functions of the ET or inflammatory changes in ET mucosa, whereas IL-5Ab pretreatment showed significant late ventilatory and clearance dysfunction as well as inflammatory mucosal changes. CONCLUSION: These data demonstrate that the late-phase allergic inflammatory response that leads to subsequent formation of ETD and MEE is prevented by pretreatment with sIL-4R and, more modestly, with IL-5Ab.

Gastroesophageal reflux and eustachian tube dysfunction in an animal model.

OBJECTIVE: To explore the possible relationship between gastroesophageal reflux and eustachian tube dysfunction in an animal model. STUDY DESIGN: Randomized trial. METHODS: Twenty Sprague-Dawley rats were randomly assigned into two groups, the control (phosphate-buffered saline, n = 10) and experimental (hydrochloric acid [HCl]/pepsin, n = 10) groups. All rats underwent an operation to implant a polyethylene tube into the posterior nasopharynx, through which phosphate-buffered solution or simulated gastric juice (0.5 mg/mL pepsin in 0.01 HCl) was infused at a rate of 0.1 mL/h for 2 0 minutes three times a day for 7 days. Passive opening pressure (POP), passive closing pressure (PCP), active clearance of positive pressure (ACPP) and active clearance of negative pressure (ACNP) were measured before catheter implantation, on postoperative day 5, and after days 1, 3, 5, and 7 of infusion. Mucociliary clearance time (MCCT) was measured after day 7 of infusion. Statistical analysis used a two-way analysis of variance (POP, PCP, ACPP, and ACNP) and Mann-Whitney rank sum test (MCCT). RESULTS: Significant increases in POP (P = .004), PCP (P <.001), ACPP (P <.001), ACNP (P <.001), and MCCT (P <.001) were demonstrated in the HCl/pepsin group compared with the control group. No significant difference was seen between preoperative and postoperative values. CONCLUSIONS: Nasopharyngeal exposure to simulated gastric juice causes eustachian tube dysfunction in rats. Specifically, middle ear pressure regulation and mucociliary clearance of middle ear contents were disabled. These results support recent reports in the literature linking nasopharyngeal reflux to eustachian tube dysfunction and secondary development of otitis media.

Effect of intranasal histamine challenge on Eustachian tube function.

OBJECTIVE: To show a relationship between intranasal histamine challenge, the development of middle ear effusion and Eustachian tube (ET) dysfunction in a rat model. METHODS: Non-allergic Sprague-Dawley rats weighing between 450-600 g were randomly assigned to receive an intranasal infusion of 16 microl of 10% histamine or normal saline. ET function was assessed by using the forced-response test to measure passive and active opening and closing pressures at time intervals of 6, 10, 14, 18, 22, and 26 min and 24 h post-infusion. Mucociliary clearance times (MCCTs) of the tubotympanum at 18 min post-infusion were measured by timing the transit of dye from the middle ear to the nasopharynx. Outcome measures were ET dysfunction and evidence of clinical effusion. RESULTS: Intranasal histamine caused acute ET dysfunction when introduced into the nasopharynx demonstrated by significant elevations in passive and active opening and closing pressures (P < or = 0.001) compared to controls. The largest difference was seen at 26 min post-infusion. Furthermore, MCCTs were 2.4 times longer after infusing intranasal histamine than after saline infusion. No clinically significant effusions were evident in either group at any time interval. CONCLUSION: These data demonstrate a successful development of an intranasal histamine rat model, in addition to a relationship between intranasal histamine challenge and development of acute ET dysfunction.

Eustachian tube dysfunction after tobacco smoke exposure.

OBJECTIVE: To examine the effects of tobacco smoke exposure on eustachian tube (ET) function. STUDY DESIGN: ET pressures of Sprague Dawley Rats (n = 16) were measured after 1, 7, and 15 exposures and in control animals. Passive opening pressure, passive closing pressure, active clearance of positive pressure, and active clearance of negative pressure were measured. Mucociliary clearance times were also quantified (n = 32). RESULTS: Passive opening and passive closing pressures of smoke-exposed animals were greater than controls (P < 0.05). Passive opening pressure in smoke-exposed animals increased with increasing exposure (P < 0.001). Animals with 1 exposure had an active clearance of positive pressure higher than controls (P = 0.005) and those with 7 and 15 exposures had more negative active clearance of negative pressure than controls (P = 0.002, 0.03) Mucociliary clearance time was significantly elevated in experimental animals with 7 exposures (P = 0.006). CONCLUSIONS: Alterations in ET function exist in animals exposed to tobacco smoke. SIGNIFICANCE: ET dysfunction after tobacco smoke exposure may predispose children to the development of otitis media.