A comparison between sniffing and blowing for olfactory testing before and after laryngectomy.

Abstract

Olfactory dysfunction occurs after laryngectomy due to the loss of nasal airflow and inability to sniff. However, the reason for the loss of olfactory function after laryngectomy is unclear on evaluation with sniffing type tests performed individually. It is expected that the sensorineural olfaction remains, and the results of the sniffing test would be negative, while that of the odour-blowing test would be positive. Therefore, the aim of this study was to investigate both tests and prove normal olfaction in the patients. Patients who had undergone laryngectomy were evaluated using the T&T olfactometer for odour-sniffing tests, Jet Stream Olfactometer (JSO) for odour-blowing tests, and visual analogue scale (VAS). Evaluations were performed pre-operatively, and 1month, 6months, and 1-year post-laryngectomy. Thirty-two patients were included in the study. The median recognition thresholds using the T&T and JSO were 1.4 and 2.2 before surgery, 5.8 and 5.4 at 1month, 5.8 and 5.2 at 6months, and 5.8 and 5.0 at 1 year after surgery, respectively. Results of the olfactory threshold test in both T&T and JSO and VAS score were significantly worse after surgery compared to that before laryngectomy (p < 0.05). The degree of increase was significantly smaller with JSO than with T&T (p < 0.05). While we could not prove normal olfaction in patients after laryngectomy, the odour-blowing test was superior to the odour-sniffing test in detecting patients with residual olfaction. Simply blowing a scent is insufficient to obtain good olfaction; active airflow is crucial for recognizing odours.