title: The effect of rapid maxillary expansion on pharyngeal airway pressure during inspiration evaluated using computational fluid dynamics.
abstract: BACKGROUND
  Recent evidence suggests that rapid maxillary expansion (RME) is an effective treatment of obstructive sleep apnea syndrome (OSAS) in children with maxillary constriction. Nonetheless, the effect of RME on pharyngeal airway pressure during inspiration is not clear. The purpose of this retrospective study was to evaluate changes induced by the RME in ventilation conditions using computational fluid dynamics.
  
  
  METHODS
  Twenty-five subjects (14 boys, 11 girls; mean age 9.7 years) who required RME had cone-beam computed tomography (CBCT) images taken before and after the RME. The CBCT data were used to reconstruct 3-dimensional shapes of nasal and pharyngeal airways. Measurement of airflow pressure was simulated using computational fluid dynamics for calculating nasal resistance during exhalation. This value was used to assess maximal negative pressure in the pharyngeal airway during inspiration.
  
  
  RESULTS
  Nasal resistance after RME, 0.137 Pa/(cm(3)/s), was significantly lower than that before RME, 0.496 Pa/(cm(3)/s), and the maximal negative pressure in the pharyngeal airway during inspiration was smaller after RME (-48.66 Pa) than before (-124.96 Pa).
  
  
  CONCLUSIONS
  Pharyngeal airway pressure during inspiration is decreased with the reduction of nasal resistance by the RME. This mechanism may contribute to the alleviation of OSAS in children.
authors.affiliation: Field of Developmental Medicine, Health Research Course, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan. Electronic address: yamame@dent.kagoshima-u.ac.jp.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Iwasaki
authors.affiliation: Field of Developmental Medicine, Health Research Course, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan.
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Takemoto
authors.affiliation: Field of Developmental Medicine, Health Research Course, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan.
authors.forename: Emi
authors.initials: E
authors.lastname: Inada
authors.affiliation: Field of Developmental Medicine, Health Research Course, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Sato
authors.affiliation: Field of Developmental Medicine, Health Research Course, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan.
authors.forename: Hokuto
authors.initials: H
authors.lastname: Suga
authors.affiliation: Division of Pediatric Dentistry, Department of Oral Health Science, Course of Oral Life Science, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan.
authors.forename: Issei
authors.initials: I
authors.lastname: Saitoh
authors.affiliation: Kanomi Orthodontic Office, Himeji, Hyogo, Japan.
authors.forename: Eriko
authors.initials: E
authors.lastname: Kakuno
authors.affiliation: Kanomi Orthodontic Office, Himeji, Hyogo, Japan.
authors.forename: Ryuzo
authors.initials: R
authors.lastname: Kanomi
authors.affiliation: Field of Developmental Medicine, Health Research Course, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan.
authors.forename: Youichi
authors.initials: Y
authors.lastname: Yamasaki
mesh_terms: D002648:Child; D019295:Computational Biology; D054893:Cone-Beam Computed Tomography; D045853:Exhalation / Q000502:physiology; D005260:Female; D006801:Humans; D057446:Hydrodynamics; D021621:Imaging, Three-Dimensional; D001239:Inhalation / Q000502:physiology*; D008137:Longitudinal Studies; D008297:Male; D009296:Nasal Cavity / Q000000981:diagnostic imaging / Q000503:physiopathology; D010155:Palatal Expansion Technique; D010614:Pharynx / Q000000981:diagnostic imaging / Q000503:physiopathology*; D012123:Pulmonary Ventilation / Q000502:physiology*; D012189:Retrospective Studies; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology* / Q000628:therapy
keywords: CBCT; Computational fluid dynamics; OSAS; Pharyngeal airway pressure; Rapid maxillary expansion