https://orcid.org/0000-0001-9094-1602
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Abstract
Background
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.
Ethics Statement
The procedures and experiment protocols were performed in accordance with the National Institute of Health Guide for Care and Use of Laboratory Animals, and were approved by the animal Ethics and Use Committee of the First Hospital of China Medical University.
Author Contributions
All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising, or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.
Disclosure
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest and report no conflicts of interest for this work.