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managing ventilator problems


  • ventilator alarms deserve immediate attention
  • look at the patient:
    • assess ABC:
      • is the airway in place?
      • is tubing connected?
      • is the chest rising and falling regularly?
      • is the patient a good colour?
      • check SaO2 and end-tidal PCO2 if available
  • check ventilator alarm message
  • if patient is hypoxic, distressed, sweaty, or not obviously ventilating, and solution is not immediately obvious, disconnect ventilator and commence manual ventilation with 100% oxygen.
  • ventilator pressure = resistive pressure + elastic pressure + PEEP
    • resistive pressure = airway flow x airway resistance
    • elastic pressure (alveolar pressure) = lung volume / lung compliance
    • airway flow = volume of air delivered / time
    • “plateau” pressure = pressure at end-inspiration hold (0.3-0.5sec) maneuver (when flow = zero and PEEP = zero) = elastic pressure
    • resistive pressure = peak inspiratory pressure - plateau pressure
    • elastic (alveolar) pressure = plateau pressure

causes of high pressure alarm

by pathophysiology

  • associated with a high end-inspiratory pressure (plateau pressure):
    • asynchronous breathing
    • a fall in lung compliance
      • endobronchial intubation
      • pneumothorax
      • abdominal distension
    • increased lung volume and raised intrinsic PEEP
      • air trapping due to inadequate expiratory time due to:
        • expiratory airflow obstruction eg. bronchospasm
        • high minute volume
        • fast respiratory rate
  • associated with a normal or unchanged end-inspiratory pressure:
    • increased airway resistance
      • partially blocked ETT
      • bronchospasm

by site

airway resistance

  • ETT kinking
  • ETT migrated to right main bronchus
  • cuff herniation over end of ETT
  • small airway size for ventilation required


  • reduced lung compliance
  • increased bronchial airway resistance (eg. bronchospasm)
  • auto PEEP
  • change in patient position


  • water in circuit
  • tubing kinked
  • malfunctioning exhalation valve (nebulized medication can accumulate and block the valve)


  • check ventilator fow setting in volume cycled modes - ? too high

low pressure alarm

  • most likely cause is disconnection of circuit from patient or ventilator
  • circuit leaks
  • leak through chest tube
  • cuff leak

high tidal volume alarm

  • tidal volume has exceeded alarm limit
  • check pressures

ventilator and circuit

  • extra flow added to circuit
  • check todal volume or Pinsp setting
  • flow sensor malfunction
  • is the alarm set properly?


  • patient has taken a large breath

low tidal volume alarm

  • find and fix cause immediately
  • pressure has been reached and volume lost
  • Pinsp setting in PCV is too low
  • disconnection of circuit
  • leaks in circuit
  • Vt not achieved in the time allocated in time cycled ventilation
  • flow sensor malfunction
  • is alarm set appropriately?


  • patient taking small tdal volume:
    • patient lung compliance change - loss of Vt in PC mode
    • increased patient airway resistance - reaching high pressure limit and volume dumped
    • drowsy or sedated
    • exhaustion with respiratory failure
    • change in patient position
  • patient being suctioned


  • ETT position or obstruction
  • ETT cuff complication

low oxygen

  • usually oxygen cylinder has ran out or oxygen tubing has disconnected
  • defective oxygen mixer
  • defective oxygen sensor
ventproblems.txt · Last modified: 2014/09/29 17:05 (external edit)