Who Becomes Difficult to Wean

Chronic conditions (e.g., cancer, chronic lung disease, immunocompromised host) 

Imbalance between work of breathing and respiratory muscle capacity Critical illness polyneuropathy or myopathy Upper airway obstraction (e.g., tracheal stenosis) 

Failure to recognize readiness for spontaneous breathing Inappropriate ventilator settings Imposed work of breathing from tracheostomy Psychological factors Excess sedation Delirium, depression or anxiety Sleep deprivation Process of care factors 

Absence of protocols for weaning and sedative administration Inadequate nursing staffing Physician experience 

Abbreviations. APACHE II, acute physiology and chronic health evaluation II SAPS, simplified acute physiology score. 

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