title: Comparison of the effects of pressure support ventilation delivered by three different ventilators during weaning from mechanical ventilation.
abstract: OBJECTIVE
  To compare the effects of pressure support ventilation (PSV) delivered at the same level by three different ventilators on patients' work of breathing (WOB), breathing pattern and gas exchange.
  
  
  METHODS
  Prospective, self-controlled clinical study.
  
  
  METHODS
  Intensive care unit of a tertiary university hospital.
  
  
  METHODS
  Nine intubated adult patients during weaning from mechanical ventilation.
  
  
  METHODS
  Patients were randomly connected to one of three ventilators: the Siemens Servo 900 C (SC), the Ohmeda CPU 1 (CPU), and the Engström Erica (EE) during both zero cmH2O PSV and 15 cmH2O PSV.
  
  
  RESULTS
  During zero PSV, there was no significant difference in terms of WOB, VT, VE, or auto-PEEP among the three ventilators, although there was a trend towards higher levels of WOB with EE. During 15 cmH2O PSV, WOB was significantly less with SC than with EE or CPU (0.47 +/- 0.48 J/l for SC, 1.0 +/- 0.48 for EE and 0.78 +/- 0.51 for CPU1, p = 0.003). WOB was 64% less than at zero PSV with SC but only 38% less with EE. This was associated with a different pressurization shape, as assessed by the interior surface of Paw-VT loops (1.23 +/- 0.09 J/l for SC, 0.9 +/- 0.02 for EE, and 0.79 +/- 0.18 for CPU; p < 0.001). At 15 cmH2O PSV, auto-PEEP was significantly lower with SC than with EE (1.7 +/- 2.1 cmH2O for SC, 4.7 +/- 3.6 for EE, and 2.8 +/- 0.3 for CPU; p = 0.04). External expiratory resistances, in cmH2O/l/s, were significantly higher with EE than with CPU or SC (12.9 +/- 3.2 EE, 7.5 +/- 2.4 CPU, 5.9 +/- 0.5 SC; p < 0.001).
  
  
  CONCLUSIONS
  During PSV, the different working principles of different mechanical ventilators profoundly affect patient's WOB. Among the various factors, velocity of pressurization of PSV may play a role in its efficacy in unloading the respiratory muscles.
authors.affiliation: Service de Réanimation Médicale, Hôpital Henri Mondor, Créteil, France.
authors.forename: J
authors.initials: J
authors.lastname: Mancebo
authors.forename: P
authors.initials: P
authors.lastname: Amaro
authors.forename: J L
authors.initials: JL
authors.lastname: Mollo
authors.forename: H
authors.initials: H
authors.lastname: Lorino
authors.forename: F
authors.initials: F
authors.lastname: Lemaire
authors.forename: L
authors.initials: L
authors.lastname: Brochard
mesh_terms: D000208:Acute Disease; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000009:adverse effects / Q000379:methods*; D018467:Positive-Pressure Respiration, Intrinsic / Q000209:etiology; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange; D012131:Respiratory Insufficiency / Q000503:physiopathology / Q000628:therapy*; D013990:Tidal Volume; D015300:Ventilator Weaning / Q000009:adverse effects / Q000379:methods*; D014939:Work of Breathing