title: Choke point physiology in airway stenting: A case presentation and discussion.
abstract: BACKGROUND
  The point in the airway that allows the smallest maximal flow is known as the "choke point". The tube law describes the velocity of the expired air, which cannot exceed the wave-speed. Flow limitation during forced expiration is affected by the relationship between the transmural pressure (Ptm) and cross-sectional area (A) of the airway. Wave speed is dependent on the stiffness of the airway wall, as well as on the cross-section of the airway itself (dA/dPtm).
  
  
  METHODS
  Airway stenting at the wave-speed, flow-limiting segment (choke point) is assessed by using a catheter, via the working channel of a stereoscopic bronchoscope, to measure the difference between lateral pressure and pleural pressure.
  
  
  RESULTS
  Based on the wave-speed concept of maximal expiratory flow limitation, stenting at the choke point increased the cross-sectional area and supported the weakened airway wall, thus improving expiratory flow limitation and relieving dyspnea.
  
  
  CONCLUSIONS
  To ensure correct stent positioning and thus optimal functional benefit, it is important to locate the exact position of tracheobronchial stenosis.
authors.affiliation: Division of Respiratory Medicine, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa 216-8511, Japan. Electronic address: miyazawat@marianna-u.ac.jp.
authors.forename: Teruomi
authors.initials: T
authors.lastname: Miyazawa
authors.affiliation: Department of Respiratory Medicine, International University of Health and Welfare Atami Hospital, 13-1 Higashikaigan-cho, Atami-City, Shizuoka 413-0012, Japan.
authors.forename: Seiichi
authors.initials: S
authors.lastname: Nobuyama
authors.affiliation: Division of Respiratory Medicine, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa 216-8511, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Nishine
authors.affiliation: Division of Respiratory Medicine, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa 216-8511, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Handa
authors.affiliation: Division of Respiratory Medicine, Department of Internal Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa 216-8511, Japan.
authors.forename: Masamichi
authors.initials: M
authors.lastname: Mineshita
mesh_terms: D012143:Respiratory Physiological Phenomena; D015607:Stents
keywords: Flow-limiting segment; Lateral pressure; Stent; Tracheobronchial stenosis