Optimization of sniff nasal inspiratory pressure (SNIP) measurement methodology in healthy subjects

R J Wilding; M Thynne; M M F Subhan

doi:10.1186/s12890-023-02348-0

Optimization of sniff nasal inspiratory pressure (SNIP) measurement methodology in healthy subjects

BMC Pulm Med. 2023 Feb 15;23(1):66. doi: 10.1186/s12890-023-02348-0.

Authors

R J Wilding¹, M Thynne², M M F Subhan³

Affiliations

¹ University Hospitals Plymouth NHS Trust, Plymouth, PL6 8DH, UK.
² Chest Clinic, University Hospitals Plymouth NHS Trust, Plymouth, PL6 8DH, UK.
³ School of Biomedical Sciences, Faculty of Health, University of Plymouth, C507, Portland Square, Drake Circus, Plymouth, PL4 8AA, UK. feisal.subhan@plymouth.ac.uk.

Abstract

Background: Maximal inspiratory pressure (MIP) is currently the most commonly used measure for respiratory muscle strength (RMS) estimation, however, requires significant effort. Falsely low values are therefore common, especially in fatigue-prone subjects, such as neuromuscular disorder patients. In contrast, sniff nasal inspiratory pressure (SNIP) requires a short, sharp sniff; this is a natural manoeuvre, decreasing required effort. Consequently, it has been suggested that use of SNIP could confirm the accuracy of MIP measurements. However, no recent guidelines regarding the optimal method of SNIP measurement exist, and varied approaches have been described.

Objectives: We compared SNIP values from three conditions, namely with 30, 60 or 90 s time intervals between repeats, the right (SNIP_R) and left (SNIP_L) nostril, and the contralateral nostril occluded (SNIP_O) or non-occluded (SNIP_NO). Additionally, we determined the optimal number of repeats for accurate SNIP measurement.

Method: 52 healthy subjects (23 males) were recruited for this study, of which a subset of 10 subjects (5 males) completed tests comparing the time interval between repeats. SNIP was measured from functional residual capacity via a probe in one nostril, while MIP was measured from residual volume.

Results: There was no significant difference in SNIP depending on the interval between repeats (P = 0.98); subjects preferred the 30 s. SNIP_O was significantly higher than SNIP_NO (P < 0.00001) but SNIP_L and SNIP_R did not significantly differ (P = 0.60). There was an initial learning effect for the first SNIP test; SNIP did not decline during 80 repeats (P = 0.64).

Conclusions: We conclude that SNIP_O is a more reliable RMS indicator than SNIP_NO, as there is reduced risk of RMS underestimation. Allowing subjects to choose which nostril to use is appropriate, as this did not significantly affect SNIP, but may increase ease of performance. We suggest that twenty repeats is sufficient to overcome any learning effect and that fatigue is unlikely after this number of repeats. We believe these results are important in aiding the accurate collection of SNIP reference value data in the healthy population.

Keywords: Healthy subjects; Reproducibility; Respiratory muscle strength; SNIP.

MeSH terms

Functional Residual Capacity
Healthy Volunteers
Humans
Male
Nasal Cavity*
Pressure
Respiratory Function Tests