Amount of airflow required for olfactory perception in laryngectomees: a prospective interventional study.

OBJECTIVES

To determine minimum airflow rate required for olfactory stimulation in successfully rehabilitated laryngectomised patients after learning the polite yawning technique (PYT) and to confirm the hypothesis that sense of smell is rehabilitated once the nasal airflow is re-established.

DESIGN

Prospective open interventional trial.

SETTING

Tertiary academic hospital.

PARTICIPANTS

The study population comprised 100 laryngectomised patients. The control group consisted of 100 non-laryngectomised patients of similar age and sex. Rhinomanometry was used to measure air flow in the right and left nostrils, respectively, while the Smell Diskettes Olfaction test (SDOT) was used to test each individual's sense of smell.

MAIN OUTCOME MEASURES

The primary endpoint was increasing the airflow, while the secondary endpoint was improvement in the Smell Diskettes Olfaction test score after learning the polite yawning technique.

RESULTS

The difference in the Smell Diskettes Olfaction test results before and after introducing the polite yawning technique was statistically significant (F = 53.077; P < 0.001). The number of accurately identified odours increased with each measurement. There was a significant difference among rhinomanometric measurements of airflow through the right (F = 65.002; P < 0.001) and left nostrils (F = 75.465; P < 0.001). Nasal airflow improved with each measurement. The minimum airflow required for olfactory stimulation in successfully rehabilitated patients was approximately 60 cm(3) /s. The control group had considerably better airflow in both nostrils than the laryngectomised group. The difference between the total number of rehabilitated (normosmic) patients (48%) in the laringectomised group and normosmic participants (56%) in the control group (z = 1.132; P = 0.129) was not statistically significant.

CONCLUSION

The number of odours identified by laryngectomised patients increased with the volume of nasal airflow. The number of patients with rehabilitated olfactory function approximated the percentage of normosmic individuals in the non-laryngectomised population. These findings confirm the hypothesis that sense of smell is rehabilitated once the nasal airflow is re-established.