title: Influence of Tracheal Obstruction on the Efficacy of Superimposed High-frequency Jet Ventilation and Single-frequency Jet Ventilation.
abstract: BACKGROUND
  Both superimposed high-frequency jet ventilation (SHFJV) and single-frequency (high-frequency) jet ventilation (HFJV) have been used with success for airway surgery, but SHFJV has been found to provide higher lung volumes and better gas exchange than HFJV in unobstructed airways. The authors systematically compared the ventilation efficacy of SHFJV and HFJV at different ventilation frequencies in a model of tracheal obstruction and describe the frequency and obstruction dependence of SHFJV efficacy.
  
  
  METHODS
  Ten anesthetized animals (weight 25 to 31.5 kg) were alternately ventilated with SHFJV and HFJV at a set of different fHF from 50 to 600 min. Obstruction was created by insertion of interchangeable stents with ID 2 to 8 mm into the trachea. Chest wall volume was measured using optoelectronic plethysmography, airway pressures were recorded, and blood gases were analyzed repeatedly.
  
  
  RESULTS
  SHFJV provided greater than 1.6 times higher end-expiratory chest wall volume than HFJV, and tidal volume (VT) was always greater than 200 ml with SHFJV. Increase of fHF from 50 to 600 min during HFJV resulted in a more than 30-fold VT decrease from 112 ml (97 to 130 ml) to negligible values and resulted in severe hypoxia and hypercapnia. During SHFJV, stent ID reduction from 8 to 2 mm increased end-expiratory chest wall volume by up to 3 times from approximately 100 to 300 ml and decreased VT by up to 4.2 times from approximately 470 to 110 ml. Oxygenation and ventilation were acceptable for 4 mm ID or more, but hypercapnia occurred with the 2 mm stent.
  
  
  CONCLUSIONS
  In this in vivo porcine model of variable severe tracheal stenosis, SHFJV effectively increased lung volumes and maintained gas exchange and may be advantageous in severe airway obstruction.
authors.affiliation: From the Hedenstierna Laboratory, Anaesthesiology and Intensive Care, Department of Surgical Sciences, Uppsala University, Uppsala, Sweden (R.S., P.F., A. Larsson); and Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy (A. LoMauro, S.G., R.P., A.A.).
authors.forename: Robert
authors.initials: R
authors.lastname: Sütterlin
authors.forename: Antonella
authors.initials: A
authors.lastname: LoMauro
authors.forename: Stefano
authors.initials: S
authors.lastname: Gandolfi
authors.forename: Rita
authors.initials: R
authors.lastname: Priori
authors.forename: Andrea
authors.initials: A
authors.lastname: Aliverti
authors.forename: Peter
authors.initials: P
authors.lastname: Frykholm
authors.forename: Anders
authors.initials: A
authors.lastname: Larsson
mesh_terms: D000402:Airway Obstruction / Q000378:metabolism / Q000473:pathology* / Q000628:therapy*; D000818:Animals; D006611:High-Frequency Jet Ventilation / Q000379:methods*; D013552:Swine; D014135:Tracheal Stenosis / Q000378:metabolism / Q000473:pathology* / Q000628:therapy*; D016896:Treatment Outcome