Abstract
Background: Noninvasive positive pressure ventilation（NPPV）mask-related pressure injuries occur due to improper fit of the mask. We developed a continuous multi-contact pressure measurement system between the NPPV mask and face to evaluate the mask fitting objectively. This study aimed to evaluate the reliability and validity of the measurement system.
Methods: This study involved 20 volunteers who could fit a medium-sized NPPV oronasal mask and 1 rater. For the assessment of intra-rater reliability, and agreement, the contact pressure was measured thrice for 1 min after fitting the NPPV mask and adjusting the leakage volume to approximately 50 L/min. For known-groups validity, we compared the contact pressures between masks with a lower strap tension of > 200 gf and those with a strap tension of approximately 0 gf, the contact pressures were measured once for 10 seconds. This study protocol was approved by an ethics committee.
Results: The intraclass correlation coefficient ranged from 0.79 to 0.99, standard error of measurement ranged from 0.3 to 5.6 mmHg, and small detectable change ranged from 0.9 to 15.6 mmHg. For known-groups validity, any contact pressure values of masks with a strap tension of > 200 gf were significantly higher than those with a strap tension of approximately 0 gf at all locations（P < 0.001）.
Conclusions: Our measurement system showed high intra-rater reliability and adequate agreement and knowngroups validity to evaluate the NPPV mask fitting in healthy adults with a medium-sized face.
