Sniff nasal inspiratory pressure in children

Maximal static inspiratory pressure (P(IMAX)) generated at the mouth is one of the tests of inspiratory muscle strength in children. In adults, inspiratory muscle strength has also been assessed using sniff nasal inspiratory pressure (SNIP). This test is easier to perform than P(IMAX) and might therefore be applicable to children. To test this hypothesis, we measured P(IMAX) and SNIP in 116 children aged 4 to 11 years (54 girls, 62 boys). P(IMAX) was measured using a tube mouthpiece and SNIP using a tightly fitting plug in one nostril, while a sniff was performed through the other nostril. Both tests were performed from functional residual capacity (FRC). Pressure was measured with a differential pressure transducer and displayed in real time on a computer screen. Weight, standing height, sitting height, gender, and age were recorded. There was a significant difference (P < 0.01) in group mean (SD) data between SNIP (81.3 (27.4) cmH(2)O) and P(IMAX) (67.9 (28.1) cmH(2)O). Bland/Altman analysis demonstrated a mean difference of -13.5 cmH(2)O (SD 21.4) between the techniques. Regression analysis indicated highly significant relations (P < 0.01) between SNIP and P(IMAX), and between weight, standing and sitting height, and age for SNIP, and between weight, standing height, and age for P(IMAX). SNIP and P(IMAX) were greater in boys than girls (83.2 vs. 79.2 cmH(2)O SNIP; 72.9 vs. 62.0 cmH(2)O P(IMAX)), but this difference was only significant for P(IMAX) (P < 0.05). SNIP was significantly greater than P(IMAX) (P < 0.01) in both boys and girls. These data suggest that SNIP provides a simple, noninvasive additional test to P(IMAX) for assessing inspiratory muscle strength in children.