Sniff nasal inspiratory pressure. Reference values in Caucasian children

Like in adults, normal values of maximal inspiratory pressure (PImax) and maximal expiratory pressure (PEmax) span a large range in children, making interpretation of low values difficult. Recently, sniff nasal inspiratory pressure (Pnsn) was developed as a new noninvasive test of inspiratory muscle strength. In healthy adults, Pnsn is most often higher than PImax. The aim of this study was to establish reference values of Pnsn in children and to compare them with PImax. A group of 180 unselected healthy children age 6 to 17 yr was studied in a school setting. All had a forced vital capacity (FVC) > 80% of predicted and a ratio of forced expiratory volume in one second/forced vital capacity (FEV1/ FVC) > 85% of predicted. All maneuvers were performed in the sitting position. The Pnsn was measured using a catheter occluding one nostril during maximal sniffs performed through the contralateral nostril from FRC. The PImax was measured from FRC and residual volume, and PEmax from FRC and total lung capacity. All children were able to perform the Pnsn maneuver easily. Pnsn was 104 +/- 26 cm H2O in boys and 93 +/- 23 cm H2O in girls (p < 0.005). These values were similar to those previously measured in healthy adults. Pnsn correlated with age, weight, and height in boys, but not in girls. In both sexes, Pnsn was higher than PImax measured at the same lung volume (FRC) (p < 0. 0001). Pnsn was >= PImaxFRC in 73 of 93 boys and 79 of 87 girls. We conclude that Pnsn can be easily used to assess inspiratory muscle strength in children age 6 yr or more, providing values higher than PImax. Normal values are independent of age in girls, and can be predicted from age by a first-degree equation in boys. Being easy and noninvasive, Pnsn may prove useful to assess inspiratory muscle strength in children with neuromuscular disorders.