Intra- and inter-rater reliability of the manual method of measuring respiratory muscle coordination

Introduction: Impaired muscle coordination is associated with fatigue and may contribute to respiratory muscle dysfunction, dyspnea and respiratory failure if affecting the respiratory muscles. We aimed to determine the inter- and intra-rater reliability of manually measuring the coordination of respiratory muscle activation. Methods: Electromyography (EMG) of the diaphragm, sternomastoid, scalene and parasternal intercostal were recorded during inspiratory threshold loading (ITL) at 50% of the maximal inspiratory pressure in 7 healthy adults (age 24±1, yrs; 5 ♂) until task failure (Tlim). The phase angle (θ) was used to quantify the timing coordination between respiratory muscle activation (EMGonset) and inspiratory flow onset relative to the duration of the respiratory cycle (Ttot). Phase angle was expressed in degrees as calculated by θ=([EMGonset–flowonset]/Ttot)×360. Two investigators evaluated the θ during the 1st minute of ITL and at Tlim; one of the investigators evaluated the θ twice so we could determine the inter- and intra-rater reliability of measures. Results: Inter- and intra-rater reliability (Intraclass Correlation Coefficient) ranged from 0.700 to 0.990 (p Conclusion: A manual method of measuring respiratory muscle coordination has good to excellent inter- and intra-rater reliabilities.