Nature and Science of Sleep (Oct 2020)

How Does Chronic Intermittent Hypoxia Influence Upper Airway Stability in Rats?

  • Meng Y,
  • Li W,
  • Zou Y,
  • Yao Y,
  • Huang H,
  • Sun J,
  • Li X,
  • Guo S,
  • Zhang X,
  • Wang W

Journal volume & issue
Vol. Volume 12
pp. 749 – 758

Abstract

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Yanling Meng,1 Wenyang Li,1 Ying Zou,1 Ye Yao,1 Hong Huang,1 Jianjun Sun,1 Xiaomeng Li,1 Shu Guo,2 Xilong Zhang,3 Wei Wang1 1Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, People’s Republic of China; 2Department of Plastic Surgery, The First Hospital of China Medical University, Shenyang, People’s Republic of China; 3Department of Respiratory and Critical Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, People’s Republic of China C orrespondence: Wei Wang Email [email protected]: Obstructive sleep apnea (OSA) is characterized by repetitive episodes of upper airway collapse during sleep. The contraction of upper airway dilator muscles plays a crucial role in maintaining UA patency. Chronic intermittent hypoxia (CIH) is the most important pathophysiological process of OSA. Exposure to CIH induced not only the damage of dilator muscles but also the plasticity of the muscles. This study aimed to dynamically assess the influence of CIH on the upper airway.Methods: The experiments were performed on 44 rats. They were randomly divided into a normoxia (NO) group (n=22) and CIH group (n=22). In each group (n=6, respectively), EMG, transcranial magnetic stimulation (TMS) response, and critical pressure (Pcrit) value were recorded on day 0 (the day before exposure), and the 7th, 14th, 21st, and 28th day of air/CIH exposure. For each group, 16 rats were used for transmission electron microscopy observations on day 0, and the 7th, 14th and 28th day of air/CIH exposure (n=4 for every time point).Results: Compared to the NO group at the same point, the CIH group showed a damaged ultrastructure of genioglossus, increased activity of genioglossus corticomotor area, and increased Pcrit of the upper airway from the 7th to the 28th day of CIH. Increased EMG activity occurred at the 14th day of CIH and lasted for 2 weeks.Conclusion: The elevated genioglossus corticomotor excitability in response to the CIH could not counterbalance the damage effect of CIH on upper airway dilator muscles, which ultimately increased the collapsibility of the upper airway.Keywords: chronic intermittent hypoxia, ultrastructure, transcranial magnetic stimulation, upper airway critical pressure, electromyogram

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