Neural Respiratory Drive During CO₂ Rebreathing And Sleep In Normal Subjects

Background:The diaphragm is the most important respiratory muscle, whilst the genioglossus plays an important role in maintaining upper airway patency. Accurate assessment of neural respiratory drive to both the diaphragm and genioglossus during sleep, would be helpful for better understanding pathophysiological mechanism leading to sleep disordered breathing. The purposes of the present study were 1) to establish a technique to accurately record genioglossus electromyogram during overnight poysomnography, 2) to investigate the changes of neural drive to the diaphragm and the genioglossus during CO2 rebreathing, 3) to compare neural drive to the diaphragm and to the genioglossus in different sleep stages..Methods:8 male volunteers without sleep disordered breathing participated in this study. A multi-diaphragmatic function catheter was used to measure EMGdi, Pes, Pga and transdiaphragmatic pressure. A pair of custom-make fine-wire electrodes were inserted percutaneously into the genioglossus to record the genioglossus EMG. All subjects were asked to undertake CO2 rebreathing before sleep. A series of volitional maneuvers including Sniff, TLC, MIP, MVV and Swallow were performed to record the maximal EMG. Polysomnography including EEG, EOG genioglossus EMGs recorded from fine-wire and surface electrodes, diaphragm EMG, airflow measured from a pneumotach and SpO2 was recorded. Results:The signal-to-noise ratio from fine-wire electrodes was much better than that from surface electrodes. Inter-subject variability of the EMGgg measured from Sniff maneuver was less than other maneuvers. Both EMGdi and EMGgg from fine-wire electrode increased during CO2 rebreathing, whilst EMGgg from surface electrodes show no difference throughout rebreathing process. Both the diaphragm and genioglossus activaties significantly correlated with ETCO2 level. EMGgg could be recorded reliably during overnight polysomnography. EMGdi , EMGgg, Pes and Pdi decreased in REM sleep compared with NREM stages.Conclusion:EMGgg can be reliably measured by fine-wire electrodes during CO2 rebreathing and overnight polysomnography. Neural drive to the genioglossus and the diaphragm increased with increasing inhaled CO2 level. Neural respiratory drive to the both genioglossus and diaphragm was weaker during REM than NREM..