Table 3.

Pathophysiologic factors associated with weaning failure.

Neurological factors	Decreased respiratory center output, electrolyte disorders, sedation, and sleep apnea
	Phrenic nerve dysfunction
Muscle pump dysfunction	Hyperinflation, acidosis-electrolyte disorders, malnutrition, and critical ilness neuromyopathy Diaphragmatic dysfunction
Increased ventilation demands	Increased CO2 production Dead-space ventilation
Increased mechanical load	Increased airway resistance (tube, central, or smaller airways)
	Reduced lung compliance (alveolar filling, atelectasis, and fibrosis)
	Increased chest wall elastance
	Reduced lung elastic recoil (COPD)
	Intrinsic PEEP
Cardiovascular	Increased metabolic demand Increased venous return Increased left ventricular afterload
Endocrine dysfunction	Hypothyroidism and myxedema
Psychological factors	Anxiety, delirium, and sleep deprivation