Sniff nasal inspiratory pressure in healthy Japanese subjects: mean values and lower limits of normal.

BACKGROUND

When assessing respiratory muscle strength using sniff nasal inspiratory pressure (SNIP), it is important to consider ethnic differences. Therefore, it is necessary to determine the mean values and lower limits of normal for SNIP in the Japanese population.

OBJECTIVE

To determine the mean values and lower limits of normal for SNIP, which is used as an assessment of inspiratory muscle strength, in healthy Japanese subjects.

METHODS

A total of 223 healthy Japanese volunteers (112 men, 111 women), aged 18-69 years, were studied; none had a history of pulmonary disease, heart disease, neuromuscular disease or sinusitis. To measure SNIP, a nasal plug was inserted into one nostril and the mouth was kept closed. Each subject was asked to take short, sharp sniffs with maximal effort from functional residual volume.

RESULTS

Based on the intraclass correlation coefficient, SNIP measurements showed good reproducibility in both men and women. The mean SNIP values were 76.8 +/- 28.9 cm H(2)O in men and 60.0 +/- 20.0 cm H(2)O in women; the values were significantly higher in men than in women (p < 0.01). On stepwise multiple linear regression analysis, the SNIP values were negatively related to age in men and positively related to body mass index (BMI) in women. The lower limits of normal for SNIP were 32.9 cm H(2)O in men and 28.8 cm H(2)O in women.

CONCLUSIONS

In healthy Japanese subjects, the mean SNIP value was higher in men than in women. In Japanese subjects, SNIP values appear to be related to age in men and BMI in women.