title: How does open-mouth breathing influence upper airway anatomy?
abstract: OBJECTIVE
  Open-mouth breathing during sleep may increase the severity of obstructive sleep apnea (OSA) and complicate nasal continuous positive airway pressure (CPAP) therapy in patients with OSA. The aim of this study was to assess the effect of open-mouth breathing on upper airway anatomy using lateral cephalometry and fiberoptic nasopharyngoscopy.
  
  
  METHODS
  This was a cross-sectional study.
  
  
  METHODS
  Lateral cephalometry and fiberoptic nasopharyngoscopy were carried out on 28 subjects with a mean age of 36.7 years. We compared the effect of the mouth being open or closed on the results in lateral cephalometry (pharyngeal length, distance between the mandible and hyoid bone [MP-H], angles from the sella-nasion to mandibular points A and B [SNA, SNB, respectively], retropalatal, retroglossal, and hypopharyngeal distance) and fiberoptic nasopharyngoscopy (retropalatal and retroglossal cross-sectional area).
  
  
  RESULTS
  On lateral cephalometric measurements, retropalatal distance (P = .000), retroglossal distance (P = .000), and MP-H (P = .002) were lower with mouth open, and pharyngeal length (P = .000) was greater. However, there were no significant differences in SNA and hypopharyngeal distance. On fiberoptic nasopharyngoscopy, retropalatal (P = .005) and retroglossal (P = .000) cross-sectional areas were significantly reduced with the mouth open.
  
  
  CONCLUSIONS
  Open-mouth breathing is associated with reduction of the retropalatal and retroglossal areas, lengthening of the pharynx and shortening of the MP-H in the upper airway. We suggest that knowledge of these anatomic changes improves our understanding of the increase of OSA severity and the low adherence to nasal CPAP therapy in mouth breathers.
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, College of Medicine, Korea University, Seoul, South Korea. shleeent@kumc.or.kr
authors.forename: Seung Hoon
authors.initials: SH
authors.lastname: Lee
authors.forename: Ji Ho
authors.initials: JH
authors.lastname: Choi
authors.forename: Chol
authors.initials: C
authors.lastname: Shin
authors.forename: Heung Man
authors.initials: HM
authors.lastname: Lee
authors.forename: Soon Young
authors.initials: SY
authors.lastname: Kwon
authors.forename: Sang Hag
authors.initials: SH
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015992:Body Mass Index; D002508:Cephalometry; D045422:Continuous Positive Airway Pressure / Q000379:methods*; D003430:Cross-Sectional Studies; D018450:Disease Progression; D004724:Endoscopy / Q000379:methods; D005260:Female; D005336:Fiber Optic Technology / Q000295:instrumentation; D006801:Humans; D007013:Hypopharynx / Q000033:anatomy & histology*; D008297:Male; D008875:Middle Aged; D009058:Mouth Breathing / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology*; D009296:Nasal Cavity / Q000033:anatomy & histology*; D010256:Paranasal Sinuses / Q000033:anatomy & histology*; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000453:epidemiology* / Q000628:therapy*