Enhancement of self-sustained muscle activity through external dead space ventilation appears to be associated with hypercapnia

• Published in: Respiratory physiology & neurobiology 2022-01, Vol.295, p.103777-103777, Article 103777
• Main Authors: Hatano, Kei, Matsuura, Ryouta, Ohtsuka, Yoshinori, Yunoki, Takahiro
• Format: Article
• Language: English
• Subjects: Adult; Central chemoreceptors; Chemoreceptor Cells - physiology; Electric Stimulation; Electromyography; Humans; Hypercapnia; Hypercapnia - physiopathology; Hyperventilation - physiopathology; Hypoxia - physiopathology; Male; Motor Neurons - physiology; Muscle, Skeletal - physiology; Plateau potentials; Self-sustained muscle activity
• ISSN: 1569-9048; 1878-1519
• DOI: 10.1016/j.resp.2021.103777

•We recorded the self-sustained muscle activity (SSMA) from the human soleus muscle.•SSMA is an indirect observation of plateau potentials in spinal motoneurons.•External dead space ventilation (1500 mL) and normoxic hypercapnia (4 % CO2) enhanced SSMA.•SSMA did not significantly change during hypoxia (15.8 % O2) and voluntary hyperventilation.•Hypercapnia may be involved in the activation of plateau potentials underlying SSMA. We reported that external dead space ventilation (EDSV) enhanced self-sustained muscle activity (SSMA) of the human soleus muscle, which is an indirect observation of plateau potentials. However, the main factor for EDSV to enhance SSMA remains unclear. The purpose of the present study was to examine the effects of EDSV-induced hypercapnia, hypoxia, and hyperventilation on SSMA. In Experiment 1 (n = 11; normal breathing [NB], EDSV, hypoxia, and voluntary hyperventilation conditions) and Experiment 2 (n = 9; NB and normoxic hypercapnia [NH] conditions), SSMA was evoked by electrical train stimulations of the right tibial nerve and measured using surface electromyography under each respiratory condition. In Experiment 1, SSMA was significantly higher than that in the NB condition only in the EDSV condition (P < 0.05). In Experiment 2, SSMA was higher in the NH condition than in the NB condition (P < 0.05). These results suggest that the EDSV-enhanced SSMA is due to hypercapnia, not hypoxia or increased ventilation.