SOURCES OF VARIABILITY IN POSTERIOR RHINOMANOMETRY

Sources of variability in nasal airway resistance measured by posterio r rhinomanometry were studied in 5 subjects tested on 5 different days and 56 subjects tested on 2 different days. On each day, a questionna ire on upper airway health and nasal symptoms was completed. The mean individual difference in nasal airway resistance between the 2 test da ys in the group of 56 subjects was 5.3% (SD 52.7%). Between-subject va riability accounted for 74.9% and 72.5% of the total variability in th e group of 5 and the group of 56 subjects, respectively. For the 5 sub jects, by accounting for a change in upper airway symptoms or upper re spiratory tract infection that occurred over the 5 test days, there wa s a significant decrease in the between-subject variability. The diffe rence in sources of variation due to a change in upper airway symptoms was not seen in the group of 56 subjects. We conclude that the larges t source of variability in nasal airway resistance is due to between-s ubject differences.