Assessing the reproducibility of nasal spirometry parameters in the measurement of nasal patency.

The reproducibility of nasal spirometry was assessed in ten subjects at two visits. Topical nasal decongestion was applied to minimise mucosal variation. Eleven parameters of flow volume were measured. Data analysis using Spearman's rank correlation coefficients revealed peak inspiratory flow rate (PIFR) followed by forced expiratory volume in first one second (FEV1) to be the most reproducible measures, yielding significance values of < 0.05. For all other spirometric parameters significance was not reached. Analysis revealed that using a naso-pulmonary index (a ratio of nasal to pulmonary flow) was detrimental to reproducibility. We conclude that future nasal spirometric studies should use PIFR and FEV1 as their derived variables of flow-volume loops in the assessment of nasal patency, and the naso-pulmonary index is of no value.