title: Different ventilatory approaches to keep the lung open.
abstract: OBJECTIVE
  To study the ability of different ventilatory approaches to keep the lung open.
  
  
  METHODS
  Different ventilatory patterns were applied in surfactant deficient lungs with PEEP set to achieve pre-lavage PaO2.
  
  
  METHODS
  Experimental laboratory of a University Department of Anaesthesiology and Intensive Care.
  
  
  METHODS
  15 anaesthetised piglets.
  
  
  METHODS
  One volume-controlled mode (L-IPPV201:1.5) and two pressure-controlled modes at 20 breaths per minute (bpm) and I:E ratios of 2:1 and 1.5:1 (L-PRVC202:1 and L-PRVC201.5:1), and two pressure-controlled modes at 60 bpm and I:E of 1:1 and 1:1.5 (L-PRVC601:1 and L-PRVC601:1.5) were investigated. The pressure-controlled modes were applied using "Pressure-Regulated Volume-Controlled Ventilation" (PRVC).
  
  
  RESULTS
  Gas exchange, airway pressures, hemodynamics, FRC and intrathoracic fluid volumes were measured. Gas exchange was the same for all modes. FRC was 30% higher with all post-lavage settings. By reducing inspiratory time MPAW decreased from 25 cmH2O by 3 cmH2O with L-PRVC201.5:1 and L-PRVC601:1.5. End-inspiratory airway pressure was 29 cmH2O with L-PRVC201.5:1 and 40 cmH2O with L-IPPV201:1.5, while the other modes displayed intermediate values. End-inspiratory lung volume was 65 ml/kg with L-IPPV201:1.5, but it was reduced to 50 and 49 ml/kg with L-PRVC601:1 and L-PRVC601:1.5. Compliance was 16 and 18 ml/cmH2O with L-PRVC202:1 and L-PRVC201.5:1, while it was lower with L-IPPV201:1.5, L-PRVC601:1 and L-PRVC601:1.5. Oxygen delivery was maintained at pre-lavage level with L-PRVC201.5:1 (657 ml/min.m2), the other modes displayed reduced oxygen delivery compared with pre-lavage.
  
  
  CONCLUSIONS
  Neither the rapid frequency modes nor the low frequency volume-controlled mode kept the surfactant deficient lungs open. Pressure-controlled inverse ratio ventilation (20 bpm) kept the lungs open at reduced end-inspiratory airway pressures and hence reduced risk of barotrauma. Reducing I:E ratio in this latter modality from 2:1 to 1.5:1 further improved oxygen delivery.
authors.affiliation: Department of Anesthesiology and Intensive Care, University Hospital, Uppsala, Sweden.
authors.forename: U H
authors.initials: UH
authors.lastname: Sjöstrand
authors.forename: M
authors.initials: M
authors.lastname: Lichtwarck-Aschoff
authors.forename: J B
authors.initials: JB
authors.lastname: Nielsen
authors.forename: A
authors.initials: A
authors.lastname: Markström
authors.forename: A
authors.initials: A
authors.lastname: Larsson
authors.forename: B A
authors.initials: BA
authors.lastname: Svensson
authors.forename: G A
authors.initials: GA
authors.lastname: Wegenius
authors.forename: K A
authors.initials: KA
authors.lastname: Nordgren
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D005652:Functional Residual Capacity; D006612:High-Frequency Ventilation; D008855:Microscopy, Electron, Scanning; D011175:Positive-Pressure Respiration / Q000379:methods*; D011650:Pulmonary Alveoli / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000648:ultrastructure; D011663:Pulmonary Surfactants / Q000172:deficiency; D011859:Radiography; D012129:Respiratory Function Tests; D012131:Respiratory Insufficiency / Q000628:therapy*; D013552:Swine
chemical_list: D011663:Pulmonary Surfactants