Nasal inspiratory pressure: an alternative for the assessment of inspiratory muscle strength?

INTRODUCTION Inspiratory muscle strength is usually assessed thorough the determination of static mouth pressure (PImax). However, since this manoeuvre presents certain problems, alternative techniques have been developed over the last few years. One of the most promising is determination of sniff nasal inspiratory pressure (SNIP). AIM To evaluate SNIP assessment as an alternative for the evaluation of the inspiratory muscle strength. METHODS Subjects were consecutively included and assigned to one of three different groups: control (8), COPD patients (23) and patients with neuromuscular disorders (21). Different maximal inspiratory pressures were determined: (a) dynamic in the esophagus (maximal sniff Pes, reference variable), (b) PImax, and (c) SNIP. RESULTS Both SNIP and MIP showed an excellent correlation with Pes (r=0.835 and 0.752, respectively, P<0.05 for both). SNIP/Pes intra-class correlation coefficients were 0.585 (CI 95%: −0.097 to 0.901) in controls, 0.569 (CI 95%: −0.048 to 0.836) in COPD patients, and 0.840 (CI 95%: 0.459 to 0.943) in neuromuscular disorders, respectively. For PImax/Pes, these values were 0.602 CI 95%: −0.108 to 0.933), 0.418 (CI 95%: −0.108 to 0.761), and 0.712 (CI 95%: 0.378 a 0.882). Moreover, both SNIP and PImax showed 100% sensitivity in the three groups of subjects, although specificities were 100%, 69% and 75% for SNIP, and 83%, 54% and 75% for PImax, respectively. CONCLUSIONS SNIP is a good physiological marker of inspiratory muscle strength. Its role is likely to complement that of PImax.