title: Transtracheal high-flow insufflation supports spontaneous respiration in chronic respiratory failure.
abstract: OBJECTIVE
  Transtracheal insufflation of oxygen-enriched air at a high flow rate has been proposed to support ventilation. The purpose of this study was to investigate the physiologic effects of high-flow insufflation unobtrusively with a respiratory inductive plethysmograph in patients with chronic respiratory failure. Using a respiratory inductive plethysmograph also permitted monitoring of end-expiratory lung volume, and respiratory variables could be quantified independently of the tracheal bias flow.
  
  
  METHODS
  Prospective randomized comparison of low-flow vs high-flow transtracheal insufflation.
  
  
  METHODS
  Pulmonary division of a tertiary teaching hospital.
  
  
  METHODS
  Fourteen spontaneously breathing outpatients with chronic hypoxemic respiratory failure carrying a transtracheal catheter for long-term oxygen therapy.
  
  
  METHODS
  Oxygen-enriched air (fraction of inspired oxygen, 0.37) at 15 L/min and oxygen at 1.5 L/min were transtracheally administered for 1 h each. The breathing pattern and the end-expiratory lung volume were monitored by inductive plethysmography along with pulse oximetry and transcutaneous PCO2. Arterial blood gases were also analyzed at the end of the hour of both low-flow and high-flow insufflation.
  
  
  RESULTS
  High-flow insufflation decreased the mean (+/- SEM) minute ventilation (Ve) by 20% from 8.37 +/- 0.49 to 6.66 +/- 0.57 L/min, the mean respiratory rate from 19.2 +/- 0.9 to 15.7 +/- 1.0 breaths/min, while mean expiratory time increased from 2.0 +/- 0.1 to 2.8 +/- 0.2 s, and end-expiratory lung volume decreased by 0.55 +/- 0.15 L compared to low-flow oxygen insufflation (p < 0.05 for all comparisons). Mean arterial and transcutaneous PCO2 decreased from 45 +/- 1 to 43 +/- 1 mm Hg and from 54 +/- 2 to 53 +/- 2 mm Hg, respectively (p < 0.05 in both instances), while arterial PaO2 and oxygen saturation did not change.
  
  
  CONCLUSIONS
  High-flow transtracheal insufflation of oxygen-enriched air assists ventilation by reducing Ve without compromising gas exchange and by reducing end-expiratory lung volume, possibly through the reversal of dynamic hyperinflation.
authors.affiliation: Division of Pulmonary Medicine, University Hospital, Zürich, Switzerland. thomas.brack@usz.ch
authors.forename: Thomas
authors.initials: T
authors.lastname: Brack
authors.forename: Olivier
authors.initials: O
authors.lastname: Senn
authors.forename: Erich W
authors.initials: EW
authors.lastname: Russi
authors.forename: Konrad E
authors.initials: KE
authors.lastname: Bloch
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007327:Insufflation / Q000379:methods; D008297:Male; D008875:Middle Aged; D010991:Plethysmography; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000628:therapy*; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial