Our study aims to assess the open-fitting capabilities and vent properties of traditional open-fitting behind-the-ear (open BTE) hearing aids to instant-fit open-fitting completely-in-the-canal (open CIC) systems.

The study analysed data from 40 patients grouped in two groups based on the used hearing aids. Free field pure tone and speech audiometry were performed to obtain the free-field pure tone average and free-field word recognition score (WRS). The matrix sentence test was employed to evaluate the auditory performance and functional outcomes of patients. The Satisfaction with Amplification in Daily Life (SADL) and the Abbreviated Profile of Hearing Aid Benefit (APHAB) questionnaire were used to assess the personal satisfaction and benefit provided by the hearing aid. Real ear measurements were conducted to objectively evaluate the Real-Ear Unaided Gain (REUG) and Real-Ear Occluded Gain (REOG) of the two groups. For this purpose, six frequency bands (band 1 from 125 to 200 Hz, band 2 from 250 to 400 Hz, band 3 from 500 to 800 Hz, band 4 from 1000 to 1600 Hz, band 5 from 2000 to 3150 Hz, and band 6 from 4000 to 6300 Hz) were defined and compared.

Free-field WRS exhibited a significant difference (p-value = 0.004) between open BTE and open CIC, with better results for the open BTE. Matrix test speech reception threshold scores did not differ significantly between groups. No statistical significant difference were observed between APHAB and SADL total scores. Correlation tests revealed a negative correlation between SRT and APHAB scores in the open BTE group, not seen in the open CIC. No statistically significant difference was observed for all bands of REUG values, demonstrating comparability in terms of acoustic resonance of the external auditory canal. Comparing the REOG recorded in the two groups a significant difference was observed for bands 2 through 6. While the average REOG values for bands 5 and 6 were higher in patients with traditional open BTE aids, in contrast, for bands 2, 3, and 4, the REOG values for the open CIC group were higher and statistically significant compared to patients wearing traditional open-fitting BTE hearing aids.

Patients with open CIC seem to perform worse in quiet environments compared to noisy ones, as indicated by the free field WRS score. However, the absence of differences in functional performance assessed with the matrix sentence test, and in the psychosocial aspects, makes these devices a good solution for individuals who reject hearing aids due to aesthetic concerns. The differences in terms of real ear measurements, while statistically significant, do not negatively impact overall performance.