Reduced pharyngeal muscle tone can cause trapping of the upper airway during inspiration. It can be seen in respiratory sleep apnea, etc. Reduced pharyngeal muscle tone can cause trapping of the upper airway during inspiration. Normal breathing requires a high degree of coordination of respiratory muscle contraction. The upper airway muscles have some basic tone to keep the airway open. Each diaphragm contraction is preceded by a nerve discharge that causes the upper airway muscles to contract. The contraction of the chin-lingual muscle pulls the tongue forward to fix the pharyngeal wall, further keeping the upper airway open and resisting the trapping effect of negative pressure in the pharyngeal cavity on the upper airway during inspiration. Hypotonia of the base of the chin-lingual muscle can cause posterior displacement of the tongue root and narrowing of the airway, and hypotonia of the intercostal muscles can cause instability of the chest wall during inspiration, resulting in paradoxical thoracoabdominal movements. During the REM sleep phase, the inspiratory phase firing of the upper airway and intercostal muscles can also be inhibited, and the tendency of the upper airway to trap and close and chest wall instability is exacerbated when the negative thoracic pressure increases after diaphragm contraction. In normal NREM sleep, the basal tone of upper airway muscles decreases, the caliber of upper airway decreases, and airway resistance increases, but the firing phase of upper airway muscles and the rhythmic contraction of intercostal muscles remain intact. during REM sleep, the basal tone of upper airway muscles, intercostal muscles, and most skeletal muscles are further suppressed. If airway trapping is detected, prompt examination and treatment should be performed.