Intermittent noise-induced hearing loss and the influence of carbon monoxide.
Chen GD; McWilliams ML; Fechter LD
Hear Res 1999 Dec; 138(1-2):181-191
Intermittent noise causes less hearing loss than continuous noise of equal intensity. The reduction in damage observed with intermittent noise may be explained by the fact that the auditory system has time to recover between the noise phases. Simultaneous carbon monoxide (CO) exposure produces greater noise-induced hearing loss than does noise alone (Chen and Fechter, 1999). In the present study, intermittent noise (octave-band with a center frequency of 13.6 kHz, 100 dB) of a 2 h total duration but with a different duty cycle (% of noise during exposure) was used. The intermittent exposure that had a shorter noise duty cycle induced a less permanent threshold shift (PTS) than those that had a longer noise duty cycle (or less rest periods). This relation between the loss in compound action potential (CAP) sensitivity and the noise duty cycle (or rest period) was abolished by the presence of CO. The cochlear microphonic (CM) amplitude revealed similar results to those seen using the CAP. While intermittent noise that had a short noise duty cycle did not cause hair cell loss by itself, the combined exposure to noise and CO (1200 ppm) caused remarkable OHC loss in the basal turn.
Hearing protection; Noise induced hearing loss; Synergistic effects; Ototoxicity; Statistical analysis; Analytical chemistry; Analytical methods; Chemical analysis; Exposure assessment; Hearing tests; Hearing disorders; Noise exposure; Noise frequencies; Noise levels;
Author Keywords: Intermittent noise; Noise-induced hearing loss; Carbon monoxide; Compound action potential; Surface preparation; Rat
University of Oklahoma, Health Sciences Center, College of Pharmacy, 1110 N. Stonewall, Oklahoma City, OK 73190
Disease and Injury: Hearing Loss
University of Oklahoma, Health Sciences Center, Oklahoma Center for Toxicology, Oklahoma City, Oklahoma