[Purpose] Measurements of inspiratory strength are critical for detecting inspiratory
muscle weakness. Sniff nasal inspiratory pressure (SNIP) is a quick, noninvasive
measurement of global inspiratory strength; however, it is not clear how many trials are
needed for reliable measurements. [Subjects and Methods] One hundred and nineteen subjects
(age 39.9±16.5, range 18–69 yrs) completed the study. They were divided into subgroups of
different ages and gender. Subjects were asked to take 20 maximal sniffs after normal
expiration, with 30 seconds rest in-between. The highest values among the first 10 and
last 10 SNIP maneuvers were recorded as SNIP1-10, and SNIP11-20, respectively. The paired
t-test was used to compare the differences. Two-way measures ANOVA was used to compare the
effects of age and gender on SNIP. [Results] SNIP 11–20 was significantly greater than
SNIP1–10, suggesting that 10 trials is not enough to eliminate learning effects. Age did
not affect SNIP in either gender, suggesting SNIP is preserved. In stepwise multiple
linear regression analysis, the SNIP values were positively related with body mass index
in women and positively related with weight in men. [Conclusion] The results suggest that
twenty trials are needed for reliable SNIP measurements. The mean value and lower limits
of normal SNIP are provided for clinical comparison.