title: Sniff nasal inspiratory pressure in patients with moderate-to-severe chronic obstructive pulmonary disease: learning effect and short-term between-session repeatability.
abstract: BACKGROUND
  Sniff nasal inspiratory pressure (SNIP) is a non-invasive measure of inspiratory muscle function often used as an outcome measure in clinical studies. An initial period of familiarisation with the test is recommended to minimise the learning effect. The repeatability of SNIP in patients with chronic obstructive pulmonary disease (COPD) is currently unknown.
  
  
  OBJECTIVE
  The aim of this study was to assess the between-session repeatability of SNIP over a 3-week period in moderate-to-severe COPD patients and compare it with that of maximal inspiratory (PI max) and expiratory pressure (PE max).
  
  
  METHODS
  Twenty-one patients (13 males) with a mean forced expiratory volume in 1 s (FEV1) of 38% of predicted (SD: 15) and FEV1/forced vital capacity of 34.3% (SD: 10.4) performed SNIP and PI max and PE max manoeuvres on 3 different sessions (S1, S2 and S3) 3-7 days apart. SNIP was performed at functional residual capacity (FRC), and PI max was performed at FRC and at residual volume (RV) to explore volume-dependent differences in the learning effect between sessions and PE max from total lung capacity.
  
  
  RESULTS
  The intra-class correlation coefficient (ICC) for SNIP was the highest of the three measures: S1-S3 ICC (95% CI) SNIP: 0.96 (0.88-0.94); PI max at FRC 0.82 (0.63-0.92); PI max at RV: 0.89 (0.78-0.95), and PE max: 0.96 (0.92-0.98), and had the lowest mean change between sessions [mean S2 - S1: 2.1(p = 0.4) and S3 - S2: -0.3 (p = 0.9)].
  
  
  CONCLUSIONS
  SNIP is repeatable over a period of 3 weeks in medically stable, moderate-to-severe COPD patients. In our study, 2 sessions were adequate to learn how to perform the test.
authors.affiliation: Division of Asthma, Allergy and Lung Biology, Dental Institute, King's College London, London, UK.
authors.forename: Dimitra
authors.initials: D
authors.lastname: Nikoletou
authors.forename: Gerrard
authors.initials: G
authors.lastname: Rafferty
authors.forename: William D-C
authors.initials: WD
authors.lastname: Man
authors.forename: Naveed
authors.initials: N
authors.lastname: Mustfa
authors.forename: Nora
authors.initials: N
authors.lastname: Donaldson
authors.forename: Robert L
authors.initials: RL
authors.lastname: Grant
authors.forename: Lorna
authors.initials: L
authors.lastname: Johnson
authors.forename: John
authors.initials: J
authors.lastname: Moxham
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D007320:Inspiratory Capacity / Q000502:physiology; D059032:Learning Curve; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D011214:Practice, Psychological; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012123:Pulmonary Ventilation / Q000502:physiology*; D015203:Reproducibility of Results; D012132:Respiratory Muscles / Q000503:physiopathology*; D013997:Time Factors