Pressure Support: Weaning
Advanced, Organ-Based and Clinical Sciences
In order to reduce the risk of complications from prolonged mechanical ventilation, patients should be weaned from mechanical ventilation as soon as it is clinically appropriate to do so. Criteria for extubation should include: resolution of the process that initially necessitated mechanical ventilation; hemodynamic stability (because weaning may increase the work of breathing and worsen cardiovascular strain); adequate oxygenation on minimal FiO2 (< 40-50%); maximum negative inspiratory force of at least -20 cmH2O, vital capacity > 10 mL/kg, or RSBI < 105 during normal tidal volume breathing; airway patency (cuff leak); and the ability to protect the airway (intact gag reflex) and clear pulmonary secretions (strong cough).
Methods of weaning may include intermittent mandatory ventilation (IMV), spontaneous breathing trials (SBTs), or pressure support ventilation (PSV). Of these methods, daily SBTs have been associated with earlier extubation and greater likelihood of success. However, SBTs may also be conducted with CPAP or low-level PSV in order to help overcome the additional airway resistance imposed by the endotracheal tube. SBTs should be conducted for at least 30 minutes but not longer than 120 minutes once daily during the weaning period, during which time the patient is assessed for extubation readiness. During PSV weaning, the quantity of pressure support is gradually reduced by 2-3 cm H20 as tolerated on a daily basis until criteria for extubation are met.
Failure to successfully wean from mechanical ventilation may be indicated by the presence of tachypnea or respiratory distress, respiratory acidosis, significant hemodynamic changes, hypoxemia, diaphoresis, or agitation, in additional to the clinical assessment performed by the physician. If a patient fails to meet extubation criteria he or she should be re-assessed in order to identify the reasons for continued respiratory failure. If a decision is made to extubate, the patient should be carefully assessed during the post-extubation period in order to identify any need for non-invasive respiratory support or re-intubation.