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

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

Author information

1
Department of Otolaryngology, National Centre for Airway Reconstruction, Charing Cross Hospital, London W6 8RF, UK. rn@cantab.net

Abstract

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.

PMID:
18577538
DOI:
10.1093/bja/aen171
[Indexed for MEDLINE]
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