Evaluation of the importance of head and probe stabilisation in acoustic rhinometry

As yet there is no established procedure to ensure the repeatability of acoustic rhinometry measurements although anecdotal evidence suggests that instrument fixation improves repeatability. The aim of this study is to validate the methodology of acoustic rhinometry and determine whether instrument fixation and head stabilisation is necessary. Four methods were compared in fifteen healthy volunteers, after nasal decongestion: A) Patient holding the probe (patient-held), B) Probe fixed in a probe stand (probe-stand), C) Probe fixed in stand and head stabilised in head rest (head-rest), D) Examiner holding the probe (examiner-performed). The two minimum cross-sectional areas and volume between 0 and 5 cm were recorded. The examiner-performed and probe-stand methods were consistently less variable than the other methods. With examiner-performed method, this was significant (p < 0.05) versus head-rest and patient-held methods for both measures of minimum cross-sectional area. For nasal volume the examiner-performed method was significantly (p < 0.05) less variable than the head-rest method. In conclusion, examiner-performed acoustic rhinometry is more repeatable than combined head stabilisation and instrument fixation and therefore the use of a head-rest may be unnecessary. Instrument fixation or examiner performed test is also preferable to allowing the patient to position the probe. The repeatability of the probe-stand method was similar to the examiner-performed method.