Test–retest reliability of skeletal muscle oxygenation measurements during submaximal cycling exercise in patients with chronic heart failure

<jats:title>Summary</jats:title><jats:p>The potential purpose of near‐infrared spectroscopy (<jats:styled-content style="fixed-case">NIRS</jats:styled-content>) as a clinical application in patients with chronic heart failure (<jats:styled-content style="fixed-case">CHF</jats:styled-content>) is the identification of limitations in O<jats:sub>2</jats:sub> delivery or utilization during exercise. The objective of this study was to evaluate absolute and relative test–retest reliability of skeletal muscle oxygenation measurements in patients with <jats:styled-content style="fixed-case">CHF</jats:styled-content>. Thirty patients with systolic heart failure (left ventricular ejection fraction 31 ± 8%) performed 6‐min constant‐load cycling tests at 80% of the anaerobic threshold (AT) with tissue saturation index (<jats:styled-content style="fixed-case">TSI</jats:styled-content>) measurement at the vastus lateralis. Tests were repeated after 10 ± 5 days to evaluate reliability. Absolute reliability was assessed with limits of agreement (LoA, expressed as bias ± random error) and coefficients of variation (<jats:styled-content style="fixed-case">CV</jats:styled-content>) for absolute values (LoA range: 0·4 ± 6·2% to 0·6 ± 7·9%; <jats:styled-content style="fixed-case">CV</jats:styled-content> range: 4·7–7·1%), amplitudes (LoA range −0·5 ± 5·8% to −0·7 ± 6·8%; <jats:styled-content style="fixed-case">CV</jats:styled-content> range: 26·2–42·1%), onset and recovery kinetics (mean response times; LoA 0·4 ± 9·5 s, <jats:styled-content style="fixed-case">CV</jats:styled-content> 23·5% and LoA −5·8 ± 50·8 s, <jats:styled-content style="fixed-case">CV</jats:styled-content> 67·4% respectively) and overshoot characteristics (<jats:styled-content style="fixed-case">CV</jats:styled-content> range 45·7–208·6%). Relative reliability was assessed with intraclass correlation coefficients for absolute values (range 0·74–0·90), amplitudes (range 0·85–0·92), onset and recovery kinetics (0·53 and 0·51, respectively) and overshoot characteristics (range 0·17–0·74). In conclusion, absolute reliability of absolute values and onset kinetics seems acceptable for serial within‐subject comparison, and as such, for evaluation of treatment effects. Absolute reliability of amplitudes and recovery kinetics is considered unsatisfactory. Relative reliability of absolute values and amplitudes is sufficient for purposes of physiological distinction between patients with <jats:styled-content style="fixed-case">CHF</jats:styled-content>. Despite lower relative reliability, kinetics may still be useful for clinical application.</jats:p>