Sniff nasal inspiratory pressure (SNIP) in amyotrophic lateral sclerosis: Relevance of the methodology for respiratory function evaluation

Abstract

ObjectivesWe investigated two different methodological approaches for determining nasal inspiratory pressure during a sniff (SNIP) in patients with Amyotrophic Lateral Sclerosis (ALS). Patients and MethodsWe included 37 ALS patients and 11 controls. SNIP was measured in the sitting position, performed in each nostril with (SNIPocclud) and without (SNIPopen) closing the contralateral nostril. The best of 3 consistent results was considered for analyses. Patients were also assessed with MIP and the revised functional ALS rating scale (ALSFRS-R). Mann-Whitney U test, Wilcoxon test and Spearman's rank correlation coefficient with Bonferroni correction were applied. Coefficient of variation (CV) was calculated. ResultsSNIP was significantly lower in patients than controls, either for SNIPopen (p = 0.011) or SNIPocclud (p = 0.002). SNIPopen values were significantly lower both in ALS patients and controls than SNIPocclud (p < 0.001 and p = 0.007, respectively). SNIPopen CV was 8.14% and 8.51%, while SNIPocclud CV was 4.98% and 6.37%, respectively for controls and patients. SNIPopen and SNIPocclud were strongly correlated in both groups (r = 0.761 for controls; r = 0.768 for patients). In ALS, both methods were moderately correlated with MIP (respectively r = 0.525, p = 0.006 and r = 0.685, p < 0.001) and the respiratory subscore of ALSFRS-R (respectively r = 0.525, p = 0.001 and r = 0.64, p < 0.001). Although bulbar and spinal onset patients presented no differences for SNIPopen (p = 0.157), significant differences were found for SNIPocclud (p = 0.018). ConclusionSNIPocclud should be considered when evaluating ALS patients as its values present lower variability and favor longer follow-up.