Physiological comparison of spontaneous and positive-pressure ventilation in laryngotracheal stenosis

Br J Anaesth. 2008 Sep;101(3):419-23. doi: 10.1093/bja/aen171. Epub 2008 Jun 24.


Background: We compared spontaneous and positive-pressure ventilation in patients undergoing general anaesthesia for the treatment of extrathoracic, intralumenal laryngotracheal stenosis to assess the best method of ventilation in this patient group.

Methods: Records of 30 patients with laryngotracheal stenosis, but not with a tracheostomy, undergoing lumen-restoring surgery were prospectively reviewed. Awake spirometry and flow-volume loops were recorded before the procedure. Patients received i.v. anaesthesia induction, muscle paralysis, and positive-pressure ventilation through a laryngeal mask airway (LMA). Anaesthetized tidal volume (TV) and flow-volume loop measurements were obtained.

Results: We studied 19 males and 11 females [mean age 47 (SD 19) yr], ASA Grade III or IV, with lesions at 31 (10) mm below the vocal cords. Peak inspiratory flow (PIF) and peak expiratory flow (PEF) rates were 2.0 (1.2) litre s(-1) and 3.2 (1.7) litre s(-1) when awake. Tidal volumes were 657 (193) ml [9.2 (3.6) ml kg(-1)] and 586 (158) ml [8.3 (3.1) ml kg(-1)], respectively, when anaesthetized. There was a significant reduction in the PEF/PIF ratio, from a mean of 2.4 (1.3) awake to 1.0 (0.1) when anaesthetized (P<0.0001). A significant correlation was noted between awake PEF and anaesthetized expiratory TV (r=0.57; P<0.001) but not between awake PIF and anaesthetized inspiratory TV.

Discussion: Positive-pressure ventilation through an LMA is an effective method of ventilating patients with laryngotracheal stenosis. Spontaneous ventilation creates negative inspiratory intratracheal pressure that exacerbates an extrathoracic lesion, whereas positive-pressure ventilation generates positive intratracheal pressure that improves ventilation. This helps explain the apparent resolution of airway obstruction after positive-pressure ventilation.

Publication types

  • Comparative Study

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Anesthesia, Intravenous / methods
  • Female
  • Humans
  • Laryngeal Masks*
  • Laryngoscopy
  • Laryngostenosis / physiopathology
  • Laryngostenosis / surgery*
  • Male
  • Middle Aged
  • Peak Expiratory Flow Rate
  • Positive-Pressure Respiration*
  • Prospective Studies
  • Spirometry
  • Tidal Volume
  • Tracheal Stenosis / physiopathology
  • Tracheal Stenosis / surgery*