Site of Airway Collapse in Obstructive Sleep Apnea after Uvulopalatopharyngoplasty

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Abstract
The objective of this prospective study was to determine the site and pattern of upper airway collapse by a multiple-catheter technique in subjects demonstrated to have obstructive sleep apnea (OSA) after uvulopalatopharyngoplasty (UPPP). Standard diagnostic nocturnal polysomnography (PSG) was done on all subjects. The PSG recordings included electroencephalogram, electro-oculogram, electrocardiogram, chin and leg electromyograms, nasal and oral airflow, and abdominal effort. Polysomnography with a multiport flexible airway Gaeltec catheter was performed in 22 subjects. The Gaeltec flexible airway catheter has 4 high-fidelity pressure sensors to aid in determining the primary site of airway collapse. The primary site of airway collapse was determined by differential pressure gradients between pressure ports and by visual inspection of the pressure tracings. Forty-two subjects with prior UPPP from a total of 60 (39 men and 3 women, ages 33 to 61) agreed to be to studied by the standard PSG technique. Thirty-five subjects complained of excessive daytime sleepiness. Ten had mild OSA, 10 had moderate OSA, 12 had severe OSA, and 10 were “normal.” Of the 22 subjects who had airway catheter monitoring, 3 of the normals were reclassified as having upper airway resistance (mean peak negative esophageal pressure of —28 cm H2O); 2 patients demonstrated airway obstruction in the nasopharynx, 2 at the oropharynx, and 11 at the level of the hypopharynx. Postoperative nocturnal PSG data were compared to data gathered prior to UPPP. The mean respiratory disturbance index (RDI) for the catheter group was 54 events per hour prior to UPPP, and the mean RDI after surgery was 44. There was no correlation between the severity of OSA and the stage of sleep. We conclude that the majority of patients who complain of excessive daytime sleepiness following UPPP have OSA with the primary site of obstruction at the level of the hypopharynx. The severity of airway collapse is variable during each stage of sleep. Esophageal pressure monitoring during sleep should be considered when evaluating symptoms of persistent OSA in patients who have had UPPP.