title: Application of mid-frequency ventilation in an animal model of lung injury: a pilot study.
abstract: BACKGROUND
  Mid-frequency ventilation (MFV) is a mode of pressure control ventilation based on an optimal targeting scheme that maximizes alveolar ventilation and minimizes tidal volume (VT). This study was designed to compare the effects of conventional mechanical ventilation using a lung-protective strategy with MFV in a porcine model of lung injury. Our hypothesis was that MFV can maximize ventilation at higher frequencies without adverse consequences. We compared ventilation and hemodynamic outcomes between conventional ventilation and MFV.
  
  
  METHODS
  This was a prospective study of 6 live Yorkshire pigs (10 ± 0.5 kg). The animals were subjected to lung injury induced by saline lavage and injurious conventional mechanical ventilation. Baseline conventional pressure control continuous mandatory ventilation was applied with V(T) = 6 mL/kg and PEEP determined using a decremental PEEP trial. A manual decision support algorithm was used to implement MFV using the same conventional ventilator. We measured P(aCO2), P(aO2), end-tidal carbon dioxide, cardiac output, arterial and venous blood oxygen saturation, pulmonary and systemic vascular pressures, and lactic acid.
  
  
  RESULTS
  The MFV algorithm produced the same minute ventilation as conventional ventilation but with lower V(T) (-1 ± 0.7 mL/kg) and higher frequency (32.1 ± 6.8 vs 55.7 ± 15.8 breaths/min, P < .002). There were no differences between conventional ventilation and MFV for mean airway pressures (16.1 ± 1.3 vs 16.4 ± 2 cm H2O, P = .75) even when auto-PEEP was higher (0.6 ± 0.9 vs 2.4 ± 1.1 cm H2O, P = .02). There were no significant differences in any hemodynamic measurements, although heart rate was higher during MFV.
  
  
  CONCLUSIONS
  In this pilot study, we demonstrate that MFV allows the use of higher breathing frequencies and lower V(T) than conventional ventilation to maximize alveolar ventilation. We describe the ventilatory or hemodynamic effects of MFV. We also demonstrate that the application of a decision support algorithm to manage MFV is feasible.
authors: Respiratory Institute, Cleveland Clinic, Cleveland, Ohio. University of Arkansas for Medical Sciences, Little Rock, Arkansas. mirelee@ccf.org.
authors: Eduardo
authors: E
authors: Mireles-Cabodevila
authors: Respiratory Institute, Cleveland Clinic, Cleveland, Ohio.
authors: Robert L
authors: RL
authors: Chatburn
authors: Section of Pediatric Critical Care Medicine, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas.
authors: Tracy L
authors: TL
authors: Thurman
authors: Department of Anesthesiology, University of Texas Southwestern Medical Center at Dallas, and the Children's Medical Center of Dallas, Dallas, Texas.
authors: Luis M
authors: LM
authors: Zabala
authors: Department of Respiratory Care, Arkansas Children's Hospital, Little Rock, Arkansas.
authors: Shirley J
authors: SJ
authors: Holt
authors: Biostatistics Program, Department of Pediatrics, College of Medicine, University of Arkansas for Medical Sciences, and the Arkansas Children's Hospital, Little Rock, Arkansas.
authors: Christopher J
authors: CJ
authors: Swearingen
authors: Section of Pediatric Critical Care Medicine, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas.
authors: Mark J
authors: MJ
authors: Heulitt
mesh_terms: D055371:Acute Lung Injury / Q000503:physiopathology / Q000628:therapy*; D000818:Animals; D004195:Disease Models, Animal; D008168:Lung / Q000503:physiopathology*; D008297:Male; D010865:Pilot Projects; D011175:Positive-Pressure Respiration / Q000379:methods*; D015656:Respiratory Mechanics; D013552:Swine; D013990:Tidal Volume
keywords: algorithms; auto-PEEP; decision support; hemodynamic; lung injury; mechanical ventilation; optimum ventilation; pulmonary gas exchange; targeting scheme; ventilation protocol