Assessing inspiratory muscle strength by sniff nasal inspiratory pressure

The sniff nasal inspiratory pressure (SNIP) consists in the measurement of pressure through an occluded nostril during sniffs performed through the controlateral nostril. It is an accurate and noninvasive approximation of esophageal pressure swing during sniff maneuvers. However SNIP can underestimate esophageal pressure swing in subjects with nasal obstruction, patients with chronic obstructive pulmonary disease and severe neuromuscular patients. Nevertheless, since SNIP maneuver has predicted normal values, is noninvasive and is easier to perform than maximal inspiratory pressure (MIP) maneuver, it could be considered as the first simple test to use in order to assess inspiratory muscle weakness. In addition, because it is as reproducible as MIP, it can be suitable to follow inspiratory muscle function in chronic neuromuscular patients. Because, of the important limit of agreement between SNIP and MIP, these two methods are not interchangeable but complementary.