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Mechanical ventilation

Complications of mechanical ventilation

Common ones are listed in the table below.


Common complications of mechanical ventilation


Haemodynamic instability

Ventilator associated pneumonia


We will now discuss two of these common complications.

Haemodynamic instability

Increasing intrathoracic pressure with positive pressure ventilation has haemodynamic consequences.

In general, it causes a reduction in cardiac preload with a corresponding decrease in cardiac output and organ perfusion. This may be masked by vasoconstriction, which will protect blood pressure.

The effect of an increase in intrathoracic pressure in an individual patient will depend upon:

  • Volume status: Hypovolaemic patients are very sensitive to this effect.
  • Lung compliance: patients with reduced compliance can tolerate higher intrathoracic pressures. Less of the airway pressure is transmitted to the blood vessels.

The precise effect in an individual patient is difficult to predict.

Ventilator associated pneumonia

Infection of the lungs that develops after 48 hours of ventilation.

The presence of an endotracheal tube bypassing natural defences against infection, drugs causing gastric stasis and incompetence of gastrointestinal sphincters, patient positioning, and the general hypoimmunity seen in many critically ill patients all predispose to the development of ventilator associated pneumonia.


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