Table 4—

Common pathophysiologies and their incidence, which may impact on the ability to wean a patient from mechanical ventilation

Respiratory loadIncreased work of breathing: inappropriate ventilator settings
Reduced compliance: pneumonia (ventilator-acquired); cardiogenic or noncardiogenic oedema; pulmonary fibrosis; pulmonary haemorrhage; diffuse pulmonary infiltrates
Airway bronchoconstriction
Increased resistive load
 During SBT: endotracheal tube
 Post-extubation: glottic oedema; increased airway secretions; sputum retention
Cardiac loadCardiac dysfunction prior to critical illness
Increased cardiac workload leading to myocardial dysfunction: dynamic hyperinflation; increased metabolic demand; unresolved sepsis
NeuromuscularDepressed central drive: metabolic alkalosis; mechanical ventilation; sedative/hynotic medications
Central ventilatory command: failure of the neuromuscular respiratory system
Peripheral dysfunction: primary causes of neuromuscular weakness; CINMA
Anxiety, depression
MetabolicMetabolic disturbances
Role of corticosteroids
Ventilator-induced diaphragm dysfunction
  • SBT: spontaneous breathing trial; CINMA: critical illness neuromuscular abnormalities.