Objective:The variability of the apnea-hypopnea index（AHI） measured in the first and second halves of the night is significant in patients with obstructive sleep apnea hypopnea syndrome（OSAHS）. This variation may be related to fluid redistribution caused by the supine position during sleep. Methods:Eighty-nine adult subjects were enrolled. Circumferences（neck, chest, waist, and calf） were measured before sleep onset and upon awakening. Polysomnography（PSG） was performed, and the night was divided into two halves based on the midpoint of total sleep time to calculate AHI for each half. The correlation between changes in AHI and changes in circumferences was analyzed. Results:Twenty simple snorers and sixty-nine OSAHS patients were included, with a median AHI of 22.6（11.8, 47.3） events/hour. Compared to pre-sleep measurements, there was no significant change in neck circumference upon awakening in the control group（P=0.073）, while reductions were observed in the other three measurements（P=0.006, P=0.038, P<0.001）. In the OSAHS group, neck circumference increased（P<0.001）, and reductions were noted in the other three measurements（P<0.001 for all）, with the most significant change observed in calf circumference 40.0（37.1, 42.0） cm to 38.0（35.8, 40.5） cm. Compared to the first half of the night, total AHI, supine AHI, and NREM AHI significantly decreased in the second half（P=0.010, P=0.031, P=0.001）, while no significant changes were observed in lateral AHI and REM AHI（P=0.988, P=0.530）. Further analysis revealed a significant relationship between increased chest circumference and decreases in NREM AHI, supine AHI, and supine NREM AHI（P=0.036, P=0.072, P=0.034）, as well as between decreased lateral position AHI and increased waist circumference（P=0.048）. Additionally, this study found a negative correlation between changes in calf circumference and changes in AHI（R=-0.24, P=0.048）, while neck circumference changes positively correlated with changes in AHI（R=0.26, P=0.03）. Conclusion:In OSAHS patients during the second half of sleep compared to before sleeping, chest circumference, waist circumference, and calf circumference decrease while neck circumference increases; total AHI, supine position AHI, and NREM period AHI decrease; increases in chest circumference are associated with decreases in NREM period AHI, supine position AHI, supine position NREM period AHI. There is nocturnal variability in AHI among OSAHS patients that may be associated with fluid shifts during sleep.
Humans ; Sleep Apnea, Obstructive/physiopathology* ; Male ; Female ; Polysomnography ; Fluid Shifts/physiology* ; Adult ; Middle Aged ; Neck ; Severity of Illness Index ; Sleep/physiology* ; Snoring/physiopathology*

Objective:To compare the changes of morphology of pharynx in patients with obstructive sleep apnea hypopnea syndrome （OSAHS） and healthy individuals during oral or nasal breathing, and explore the relevant influencing factors. Methods:Twenty-nine adult patients with OSAHS and 20 non-snoring controls underwent MRI to obtain upper airway structural measurements while the subjects were awake and during mouth breathing with a nasal clip.The following were analyzed. ①The changes of upper airway structure of oral and nasal respiration in non-snoring control/OSAHS patients were observed; ②The differences and influencing factors of upper airway structure changes between OSAHS patients and controls were compared during breathing. Results:The control group consisted of 15 males and 5 females, with an apnea-hypopnea index （AHI）<5 events/h, while the OSAHS group comprised 26 males and 3 females with an AHI of 40.4±23.1 events/h and the mean lowest arterial oxygen saturation （LSaO2） was 79.5% ±10.0%. In the both groups, the vertical distance between the mandible and the posterior pharyngeal wall decreased （P<0.05）; The long axis of tongue body decreased （P<0.05）, and the contact area between tongue and palate decreased. There was no significant change in the total volume of the retropalatine（RP） and retroglossal（RG） airway in the control group （P>0.05）. However, the minimum cross-sectional area and volume of the RP airway in OSAHS decreased （P<0.001）. The lateral diameters of uvula plane in OSAHS decreased during mouth breathing, which was contrary to the trend in the control group （P=0.017）. The AHI of patients was positively correlated with the reduction of the volume of the RP airway during oral breathing （P=0.001）; The reduction of the distance between the mandible and the posterior pharyngeal wall was positively correlated with the length of the airway （P<0.001）. Conclusion:Mouth breathing leads to the shortening of the long axis of the tongue, the reduction of the contact area between the soft palate and the tongue, vertical distance between the mandible and the posterior pharyngeal wall, and the cross-sectional area of the epiglottis plane. These changes vary between OSAHS patients and controls. During mouth breathing, the diameters, areas and volumes of the RP area decreased, and were more significant in severe cases.
Male ; Adult ; Female ; Humans ; Mouth Breathing ; Sleep Apnea, Obstructive/surgery* ; Pharynx/surgery* ; Palate, Soft ; Uvula/surgery* ; Syndrome