Carbon Monoxide Headquarters
Chronic CO Poisoning:
Lumio Chronic Carbon Monoxide Study (Cont.):
Hearing disturbances were noted in 78.3% of the patients suffering from chronic CO poisoning. A smaller number of hearing disturbances (26.7%) were found in patients exposed to CO in their work places, but in whom chronic CO poisoning could not be confirmed. Thus, hearing disturbances were present in approx. 3X as many patients suffering chronic CO poisoning than in patients not affected.
The majority of patients had similar "typical" hearing deficiencies, ie. threshold of hearing was about normal (frequencies up to 1000 Hz). Loss occurred above that frequency. The typical hearing deficiency was noted in 67.7% of patients who suffered chronic CO poisoning, and in only 14% of patients not so affected. Thus, the typical hearing disturbance was 5X more likely in patients suffering chronic CO poisoning.
Generally the patients themselves were not aware of the presence of a hearing deficiency. Of the patients suffering from chronic CO poisoning, 47.9% complained of impairment of hearing during the time they were exposed to the CO. The audiogram, however, showed changes in 78.3% of the patients with CO poisoning.
After excluding all patients who suffered CO poisoning but in who were suspected of having another cause for hearing impairment, there still remained 66.3% for which nothing but chronic CO poisoning can account for the hearing deficiency.
Follow-up examinations revealed that typical hearing losses improved only slightly, or not at all. An improvement of hearing was found in only 26.7% of the cases, and it was always slight.
The deficiency is of the inner ear type and bilateral, improves slightly or not at all, and involves chiefly the upper frequencies.
The data suggest that typical hearing deficiency may appear during the initial stage of chronic CO poisoning, when vestibular symptoms are not yet present.
From: Lumio, J.S. (1948) Hearing deficiencies caused by carbon monoxide (generator gas). Acta Otolaryngol., Suppl. 71, 1-112.
...... last changed 03/20/02
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