title: High-frequency oscillation and tracheal gas insufflation in patients with severe acute respiratory distress syndrome and traumatic brain injury: an interventional physiological study.
abstract: BACKGROUND
  In acute respiratory distress syndrome (ARDS), combined high-frequency oscillation (HFO) and tracheal gas insufflation (TGI) improves gas exchange compared with conventional mechanical ventilation (CMV). We evaluated the effect of HFO-TGI on PaO2/fractional inspired O2 (FiO2) and PaCO2, systemic hemodynamics, intracranial pressure (ICP), and cerebral perfusion pressure (CPP) in patients with traumatic brain injury (TBI) and concurrent severe ARDS.
  
  
  METHODS
  We studied 13 TBI/ARDS patients requiring anesthesia, hyperosmolar therapy, and ventilation with moderate-to-high CMV-tidal volumes for ICP control. Patients had PaO2/FiO2 <100 mm Hg at end-expiratory pressure ≥10 cm H2O. Patients received consecutive, daily, 12-hour rescue sessions of HFO-TGI interspersed with 12-hour periods of CMV. HFO-TGI was discontinued when the post-HFO-TGI PaO2/FiO2 exceeded 100 mm Hg for >12 hours. Arterial/central-venous blood gases, hemodynamics, and ICP were recorded before, during (every 4 hours), and after HFO-TGI, and were analyzed by using repeated measures analysis of variance. Respiratory mechanics were assessed before and after HFO-TGI.
  
  
  RESULTS
  Each patient received three to four HFO-TGI sessions (total sessions, n = 43). Pre-HFO-TGI PaO2/FiO2 (mean ± standard deviation (SD): 83.2 ± 15.5 mm Hg) increased on average by approximately 130% to163% during HFO-TGI (P < 0.01) and remained improved by approximately 73% after HFO-TGI (P < 0.01). Pre-HFO-TGI CMV plateau pressure (30.4 ± 4.5 cm H2O) and respiratory compliance (37.8 ± 9.2 ml/cm H2O), respectively, improved on average by approximately 7.5% and 20% after HFO-TGI (P < 0.01 for both). During HFO-TGI, systemic hemodynamics remained unchanged. Transient improvements were observed after 4 hours of HFO-TGI versus pre-HFO-TGI CMV in PaCO2 (37.7 ± 9.9 versus 41.2 ± 10.8 mm Hg; P < 0.01), ICP (17.2 ± 5.4 versus 19.7 ± 5.9 mm Hg; P < 0.05), and CPP (77.2 ± 14.6 versus 71.9 ± 14.8 mm Hg; P < 0.05).
  
  
  CONCLUSIONS
  In TBI/ARDS patients, HFO-TGI may improve oxygenation and respiratory mechanics, without adversely affecting PaCO2, hemodynamics, or ICP. These findings support the use of HFO-TGI as a rescue ventilatory strategy in patients with severe TBI and imminent oxygenation failure due to severe ARDS.
authors.forename: Charikleia S
authors.initials: CS
authors.lastname: Vrettou
authors.forename: Spyros G
authors.initials: SG
authors.lastname: Zakynthinos
authors.forename: Sotirios
authors.initials: S
authors.lastname: Malachias
authors.forename: Spyros D
authors.initials: SD
authors.lastname: Mentzelopoulos
mesh_terms: D000328:Adult; D001930:Brain Injuries / Q000150:complications* / Q000503:physiopathology / Q000628:therapy*; D002560:Cerebrovascular Circulation; D005260:Female; D006439:Hemodynamics; D006612:High-Frequency Ventilation; D006801:Humans; D007327:Insufflation; D007427:Intracranial Pressure; D008297:Male; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange; D012119:Respiration; D012128:Respiratory Distress Syndrome / Q000150:complications* / Q000503:physiopathology / Q000628:therapy*; D014132:Trachea; D055815:Young Adult
chemical_list: D010100:Oxygen