Relationship between sniff nasal inspiratory pressure and BODE index in patients with COPD

The aims of this study were to investigate the relationship between sniff nasal inspiratory pressure (SNIP) and severity of chronic obstructive pulmonary disease (COPD) as defined by the BODE index, and to investigate the capacity of different SNIP cutoffs to predict a BODE index score ≥5 (i.e., worse disease severity).

Thirty-eight subjects with COPD (21 men, 66 ± 8 years, forced expiratory volume in the first second (FEV(1)) 42 ± 16 % predicted) underwent assessments of SNIP, airflow limitation, body mass index (BMI), dyspnea (Medical Research Council scale), and exercise capacity (6-min walking test, 6MWT). The BODE index was calculated, and patients were separated into two groups according to the BODE quartiles (1 and 2, or 3 and 4).

Patients from quartiles 3 and 4 presented lower values of SNIP than patients from quartiles 1 and 2 (73 ± 18 vs 56 ± 21 cmH(2)O, respectively; p = 0.01). There was significant and inverse correlation between SNIP and the BODE index (r = -0.62; p<0.001). A logistic regression model revealed that a SNIP value below 63 cmH(2)O presented higher sensitivity and specificity (70 and 67 %, respectively) for predicting a BODE score equivalent to quartiles 3 or 4.

SNIP is moderately and significantly related to COPD severity as assessed by the BODE index. Moreover, the cutoff point of 63 cmH2O showed the best combination of sensitivity and specificity for predicting worse scores in the BODE index.