Characteristics of collapse of upper airway in patients with obstructive sleep apnea-hypopnea syndrome when muscle is fully relaxed / 中华麻醉学杂志

ABSTRACT

Objective To investigate the characteristics of upper airway collapse in patients with obstructive slcep apnea hypopnea syndrome (OSAHS) when muscle is fully relaxed.Methods Thirty male ASA Ⅱ or Ⅲ patients with OSAHS aged 20-59 yr with body mass index 21-36 kg/m2 and apnea-hypopnea index (AHI) of 28-102times/h were studied.The patients were sedated with iv midazolam 1 mg and sufentanil 5 μg.Nasotracheal intubation was then performed under topical anesthesia with 1％ dicaine.After confirmation of correct position of nasotracheal tube,anesthesia was induced with propofol 0.5 mg/kg and vecuronium 0.08 mg/kg and maintained with target-controlled infusion of propofol and remifentanil.BIS was maintained at 40-60.Fiberopticnasopharyngoscope and pressure transducer were inserted via contralateral nasal cavity and connected with imaging workstation.The site and length of the obstruction were measured and calibrated.Positive pressure was applied to the pharyngeal cavity and gradually increased in increments of 1 cm H2O until 20 cm H2O.The change in cross-section area and critical opening pressure at different planes in pharyngeal cavity were recorded.Results Complete obstruction occurred at the plane of hard palate in one patient (3％).The soft palate and uvula completely collapsed in all 30 patients (100 ％).The collapse occurred at tongue level in 23 patients (77 ％).Every 1 cm H2O increase in pressure produced increase in cross-section area by (10 ± 4)mm2 at the level of hard palate and by(28 ± 18) mm2 at the level of soft palate and uvula.The critical opening pressure ranged from 3 to 18 cm H2O and was≤ 15 cm H2O in 90％ patients.Conclusion Soft palate and uvula collapse in all patients with OSAHS when muscle is fully relaxed.The critical opening pressure is ≤ 15 cm H2O in 90％ patients.