MECHANICAL VENTILATION IN ACUTE ASTHMA

INDICATIONS

  • Progressive drowsiness/fatigue
  • Moribund patients
  • Progressive hypercarbia
  • Cardio/Respiratory arrest

RAPID SEQUENCE INDUCTION

  • Ketamine (bronchodilator)
  • Suxamethonium

VENTILATOR SETTINGS

  • Minute ventilation of < 10 L/min

  • VT < 8 ml/kg

  • respiratory rate < 14 breaths/min

  • Inspiratory flow rate >  80 L/min

PRINCIPLES

  • Keep peak airway pressure < 40cmH2O
  • Maintain oxygenation
  • Do not attempt to normalize hypercarbia
  • Small tidal volumes
  • Low respiratory rate
  • Low inspiratory : expiratory (I : E) ratio or Low inspiratory time
  • No PEEP (use of PEEP is controversial)

COMPLICATIONS

  • Barotrauma (pneumothorax can be rapidly fatal in asthma)
  • Hypotension (due to raised intrathoracic pressure and decreased venous return)

OTHER TREATMENT

  • Nebs can be given via ETT
  • Inhalational halothane (bronchodilator)
  • Heliox (reduces ventilatory pressures)