title: Intrapulmonary percussive ventilation superimposed on conventional mechanical ventilation: comparison of volume controlled and pressure controlled modes.
abstract: BACKGROUND
  Previous bench studies suggest that dynamic hyperinflation may occur if intrapulmonary percussive ventilation (IPV) is superimposed on mechanical ventilation in volume controlled continuous mandatory ventilation (VC-CMV) mode. We tested the hypothesis that pressure controlled continuous mandatory ventilation (PC-CMV) can protect against this risk.
  
  
  METHODS
  An ICU ventilator was connected to an IPV device cone adapter that was attached to a lung model (compliance 30 mL/cm H2O, resistance 20 cm H2O/L/s). We measured inspired tidal volume (VTI) and lung pressure (Plung). Measurements were first taken with IPV off and the ICU ventilator set to VC-CMV or PC-CMV mode with a targeted VTI of 500 mL. For each mode, an inspiratory time (TI) of 0.8 or 1.5 s and PEEP 7 or 15 cm H2O were selected. The experiments were repeated with the IPV set to either 20 or 30 psi. The dependent variables were differences in VTI (ΔVTI) and Plung with IPV off or on. The effect of VC-CMV or PC-CMV mode was tested with the ICU ventilators for TI, PEEP, and IPV working pressure using repeated measures of analysis of variance.
  
  
  RESULTS
  At TI 0.8 s and 20 psi, ΔVTI was significantly higher in VC-CMV than in PC-CMV. PEEP had no effect on ΔVTI. At TI 1.5 s and 20 psi and at both TI values at each psi, mode and PEEP had a significant effect on ΔVTI. With the ICU ventilators at TI 1.5 s, PEEP 7 cm H2O, and 30 psi, ΔVTI (mean ± SD) ranged from -27 ± 25 to -176 ± 6 mL in PC-CMV and from 258 ± 369 to 369 ± 16 mL in VC-CMV. The corresponding ranges were -15 ± 17 to -62 ± 68 mL in PC-CMV and 26 ± 21 to 102 ± 95 mL in VC-CMV at TI 0.8 s, PEEP 7 cm H2O, and 20 psi. Similar findings pertained to Plung.
  
  
  CONCLUSIONS
  When IPV is added to mechanical ventilation, the risk of hyperinflation is greater with VC-CMV than with PC-CMV. We recommend using PC-CMV to deliver IPV and adjusting the trigger variable to avoid autotriggering.
authors.affiliation: Service de Réanimation Polyvalente, Hôpital Nord, Centre Hospitalier Universitaire de Saint-Etienne, Saint-Etienne, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Riffard
authors.affiliation: Hautes Etudes d'Ingénieur de Lille, Lille, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Buzenet
authors.affiliation: Service de Réanimation Médicale, Groupement Hospitalier Nord, Centre Hospitalier Universitaire de Lyon, Lyon, France. claude.guerin@chu-lyon.fr.
authors.forename: Claude
authors.initials: C
authors.lastname: Guérin
mesh_terms: D003422:Critical Care; D006801:Humans; D008170:Lung Compliance / Q000502:physiology; D008954:Models, Biological; D010474:Percussion; D011175:Positive-Pressure Respiration / Q000009:adverse effects / Q000379:methods*; D018467:Positive-Pressure Respiration, Intrinsic / Q000209:etiology / Q000517:prevention & control*; D013990:Tidal Volume / Q000502:physiology
keywords: bench study; hyperinflation; intrapulmonary percussive ventilation; lung model; mechanical ventilation; pressure controlled continuous mandatory ventilation; volume controlled continuous mandatory ventilation