Confused with different ventilators in NICU/PHDU?

Posted: January 2, 2012 by kiamseong in Paediatrics

Let’s understand the basic principal of functioning of ventilators in your NICU/PHDU.

Assist-control ventilation (Maquet ventilator/ IPPV – Drager ventilator)

  • Regardless ventilator/patient initiates breath, every breath the same (operator set tidal volume and minimal ventilator rate)
  • Ventilator just functions to compensate patient’s effort
    • Time cycled ventilator
      • Tidal volume and Resp rate set + Time set
      • Maquet (Siemen)/ Drager ventilator
    • Volume cycled ventilator
      • Tidal volume and Resp rate set + Flow set
      • Puritan-Vennett Bear ventilator
Advantage Disadvantage
  • Relative simple to set
  • Guarantee minimum ventilation


  • No synchrony between patient-ventilator, ventilator initiate come on top
  • Patient may lead ventilator
  • Inappropriate trigger è hiccough
  • Fall in lung compliance => risk of barotrauma
  • Require sedation to achieve synchrony

Pressure control ventilation

  • Time cycled assisted control ventilation in which inspiratory pressure is set instead of tidal volume
  • High initial flow => fall to zero by end of inspiration
  • Inspiratory pause is effectively built into the breath
  • Tidal volume not set if inspiratory time short then tidal volume lower

Synchronized Intermittent Mandatory Ventilation (SIMV)

  • Patient receives a set number of mandatory breaths, synchronized with any attempts by the patient to breath
  • Patient can take additional breath between mandatory breaths (pressure supported)
  • For improve patient-ventilator synchrony

Advantage Disadvantage
  • Better patient-ventilator synchrony
  • Guarantee minimum minute ventilation

Continuous Positive Airway Pressure (CPAP)

  • Constant pressure both inspiratory and expiratory phase -> splint open alveoli, therefore to decrease shunting
  • Inspiration initiate from baseline pressure and airway pressure decrease to baseline at the end of respiration
  • Patient controls rate and tidal volume himself (totally dependent on patient’s inspiration effort)
  • Allow spontaneous breathing at an elevated baseline pressure

Non-invasive PPV – without invasive artificial airway (Endotracheal tube/ETT)

  • Due to face mask seal not perfect, usually use with ventilator (BiPAP) to provide some degree of compensation for leaks around the mask
  • Require patient to be alert, cooperate, able to protect his airway, haemodynamically stable
  • Low level of support initially then gradually increase to improve patient tolerance
  • BiPAP = pressure support + PEEP
    • Inspiratory pressure = 8-10 cmH2O
    • Expiratory pressure = 4-6 cmH2O
  • Effective for patient with chronic obstructive airway diseases/ cardiogenic pulmonary oedema
  • Less effective for pneumonia/ARDS

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