Temporary threshold shift induced by physical exercise

Temporary threshold shift after noise exposure in hypobaric hypoxia at high altitude: results of the ADEMED expedition 2011

OBJECTIVES

To evaluate whether there is an increased risk for noise-induced hearing loss at high altitude rsp. in hypobaric hypoxia.

METHODS

Thirteen volunteers got standard audiometry at 125, 250, 500, 750, 1000, 1500, 2000, 3000, 4000, 6000, and 8000 Hz before and after 10 min of white noise at 90 dB. The system was calibrated for the respective altitude. Measurements were performed at Kathmandu (1400 m) and at Gorak Shep (5300 m) (Solo Khumbu/Nepal) after 10 days of acclimatization while on trek. Temporary threshold shift (TTS) was analyzed by descriptive statistics and by factor analysis.

RESULTS

TTS is significantly more pronounced at high altitudes. Acclimatization does not provide any protection of the inner ear, although it increases arterial oxygen saturation.

CONCLUSION

The thresholds beyond which noise protection is recommended (> 80 dB) or necessary (> 85 dB) are not sufficient at high altitudes. We suggest providing protective devices above an altitude of 1500 m ("ear threshold altitude") when noise level is higher than 75 dB and using them definitively above 80 dB. This takes the individual reaction on hypobaric hypoxia at high altitude into account.

An unusual case of sudden sensorineural hearing loss after cycling class

In this case report, our patient developed sudden sensorineural hearing loss (SSNHL) after loud noise exposure during a popular cardiovascular group exercise cycling class. To increase awareness among all healthcare professionals of the effects of these modern-day group fitness classes on hearing loss, we describe this case and review the current literature on SSNHL and its management. A 35-year old man developed SSNHL in the setting of loud noise exposure during a high intensity aerobic exercise class. After a short course of oral steroids with no improvement, intratympanic steroids were administered weekly for three weeks. The patient showed minimal improvement; thus, hyperbaric oxygen therapy was conducted. Serial audiograms continued to show severe to profound mixed hearing loss in the right ear. In conclusion, individuals who participate in loud, high-intensity aerobic group-exercise classes should be careful of the potential for noise-induced hearing loss. Aerobic exercise may make these individuals more susceptible to noise-induced hearing loss. Early intervention is critical for any chance of recovery.

Evaluation of auditory fatigue in combined noise, heat and workload exposure

This study was performed in a climatic chamber to evaluate the combined effects of noise intensity, heat stress, workload, and exposure duration on both noise-induced temporary threshold shift (TTS) and the recovery time by adopting Taguch's method. Fourteen subjects without previous significant noise exposure and smoking history were recruited to participate in this study. All hearing threshold levels at eight different frequencies (250 to 8,000 Hz) of better ear were measured in an audiometric booth by using the ascending method in 2 dB steps before each exposure condition. The test was also carried out after exposure to evaluate TTS at various times. The TTS recovery time was assessed using an audiometric test on all subjects at post-exposure times of 2, 20, 40, 60, 80 and 120 min, respectively. It was found that TTS depended mainly on the exposed noise dose and was enhanced by workload and heat stress. The TTS recovery time is dependent upon the magnitude of the initial hearing loss. In conclusion, TTS driven by noise exposure is enhanced by heat and workload. Further studies are required to evaluate the effects of workload with extreme temperature in a workplace environment.