Introduction: A new instrument to measure breathing movements, Respiratory Movement Measuring Instrument (RMMI), has been developed. There is still a lack of knowledge about the reliability of the instrument.
Objectives: The aim was to investigate reliability of the RMMI.
Methods: In this trial, RMMI (ReMo Inc. Keldnaholt, Reykjavik, Iceland) was used. Inter- and intrarater reliability was performed on 30 volunteers who were tested three times in the supine position. Two of the tests were performed by one of the authors and the third test by the other. Intrasubject reliability was tested on 10 volunteers 12 times randomly during 1 h. Intra-instrument reliability was performed by measuring 12 solid surfaces where the instrument was placed horizontally against a couch or vertically against a chair.
Results: Intra-rater reliability: The correlations were moderate to strong (r = 0.54-0.94) except for the left lower thoracic position r = 0.35. Inter-rater reliability: The correlations were strong (r = 0.71-0.99) except for the left lower thoracic position r = 0.35. The strongest correlations were seen on the tests on abdominal breathing movements. Intra subject reliability: The over-all difference within and between the participants and test was non-significant (P = 0.98). The average difference between the tests was 1.4 mm. Intra instrument: The differences between the measurements were small (mean 0.15 mm). The over-all difference was non-significant (P = 0.79).
Conclusion: The RMMI is a reliable instrument and usable in both clinical practice and research.