Effects of aspirin and caffeine on the acoustic reflex threshold in chinchilla

The primary means of data assembly was through audiological assessment of stapedial reflex thresholds by impedance audiometry. A stimulation tube was acoustically coupled to an American Electromedics impedance bridge to provide contralateral ear acoustic stimulation. Reflex thresholds were measured from the probe ear through readings of external ear canal air pressure change on the impedance bridge compliance change meter. Acoustic reflex thresholds were measured both prior to, and following administration of each experimental substance.

A paired-sample t-test for related measures was used to evaluate the data. Primary findings included significant differences between pretreatment and posttreatment thresholds for 1000 Hz and 4000 Hz in the aspirin/caffeine combination group at the left ear. Significant differences were also found at 1000 Hz in the control group at the right ear.

Impedance audiometry has been shown to be affected by certain substances which depress the acoustic reflex threshold. Aspirin and caffeine, substances commonly ingested in moderate amounts, have been shown to affect the hearing sensitivity threshold, however, have not been thoroughly investigated with regard to acoustic reflex threshold change. Findings of the study showed isolated significant differences. Reliability of the results was questioned because of the ipsilateral group and frequency differences, and the control group differences at the right ear.

Further investigation was recommended in which hearing sensitivity threshold shift, as a result of substance administration, could be determined, and correllative studies performed with related acoustic reflex threshold shift data. Once in possession of more reliable data, researchers could further investigate effects of substance ingestion on the acoustic reflex threshold.