Resting limb muscle perfusion during inspiratory muscle loading in hypoxia and normoxia

Abstract Introduction Fatiguing of respiratory muscles reduces peripheral muscle perfusion. Further, acute hypoxia enhances respiratory muscle fatigue. This study investigated the effects of inspiratory muscle loading (IML) on resting locomotor muscle perfusion in hypoxia compared to normoxia. Methods Ten subjects completed two study days of fatiguing IML (blinded, randomized) in normobaric hypoxia (targeted oxygen saturation 80%) and normoxia, respectively. Contrast-enhanced ultrasound (CEUS) of the gastrocnemius muscle and popliteal doppler ultrasonography were used to monitor muscle perfusion. Based on CEUS and monitored cardiac output, perfusion surrogate parameters (CLP aer and CLP ap ) were established. Results Muscle perfusion declines early during IML in normoxia (CLP aer : −54 ± 25%, p  ap : −58 ± 32%, p  aer : −43 ± 23%, p  ap : −41 ± 20%, p  aer : p = 0.41 ANOVA; CLP ap : p = 0.29 ANOVA). Conclusion Acute hypoxia compared to normoxia does not affect locomotor muscle perfusion during fatiguing IML.