Novel techniques, standardization tools to enhance reliability of acoustic rhinometry measurements

Acoustic rhinometry measurements are influenced by factors related to subject posture, breathing, inclination and positioning of the wavetube, leaks and distortion at the nostril-nose adapter connection and ambient noise. We present simple techniques to control these errors. Thus, gel on contoured nose adapters, shadow tracing to maintain posture, laser homing for wavetube alignment, are all integrated into a practical scheme that is easy to implement and causes minimum discomfort to subjects. Repeatability improved to below 3% coefficient of variation (CV) in non decongested subjects when trained operators used all the techniques together viz. gel on nose adaptors, shadow tracing, laser homing. In a factorial experiment, repeated measurements were made on subjects over two consecutive days with operator training and standardization tools as variables. An analysis of variance identified the most important factors to be gel on contoured nose adapters, operator training and control of breathing. With gel, the mean CV between readings was 5.8%, measurement time 30.3 seconds. The tools, especially gel and shadow tracing, helped untrained operators achieve performance levels that were more comparable with trained operators. Reproducible curves could be taken rapidly. Thus a significant difference of 31.2 seconds between untrained and trained operators reduced to 12.6 seconds using tools. These techniques significantly improve the reliability, speed and ease of doing repeated acoustic rhinometry measurements and thus the quality of data generated in nasal studies.