Ventilator Weaning in Prolonged Mechanical Ventilation-A Narrative Review

Abstract

Patients requiring mechanical ventilation (MV) beyond 21 days, usually referred to as prolonged MV, represent a unique group with significant medical needs and a generally poor prognosis. Research suggests that approximately 10% of all MV patients will need prolonged ventilatory care, and that number will continue to rise. Although we have extensive knowledge of MV in the acute care setting, less is known about care in the post-ICU setting. More than 50% of patients who were deemed unweanable in the ICU will be liberated from MV in the post-acute setting. Prolonged MV also presents a challenge in care for medically complex, elderly, socioeconomically disadvantaged and marginalized individuals, usually at the end of their life. Patients and their families often rely on ventilator weaning facilities and skilled nursing homes for the continuation of care, but home ventilation is becoming more common. The focus of this review is to discuss recent advances in the weaning strategies in prolonged MV, present their outcomes and provide insight into the complexity of care.

Keywords: prolonged mechanical ventilation; specialized weaning units; tracheostomy.

Figure 1

Mechanical ventilator weaning strategies in prolonged mechanical ventilation. Prolonged mechanical ventilation (MV) is defined by at least 6 h of daily ventilation beyond 21 days. Weaning ability should be assessed by spontaneous breathing trials (SBTs) as long as the patient’s hemodynamical and respiratory status is stable. SBTs can be performed by unassisted breathing via a T-piece with oxygen blowby, low pressure support (PS) or automatic tube compensation (ATC) support below 8 cmH₂O for up to 12 h. If a patient passes the SBT, the patient is usually challenged with zero positive end expiratory pressure (PEEP) using unassisted breathing through a humidified oxygen delivery device connected to the tracheostomy tube (tracheostomy collar, TC) or ATC with zero PEEP for up to 3 to 5 days. A patient is considered weaned from the ventilator after 7 days of unassisted breathing. If a patient fails the zero PEEP challenge but remains in stable condition, they can be reassessed with repeated TC or zero PEEP ATC trials. For patients who fail the initial SBT, multiple approaches to weaning have been described: (1) TC weaning. In this mode, patients are challenged with unassisted breathing for up to 12 h, sometimes with a daily extension of TC time, and rested on assist control ventilation. (2) Pressure support (PS) ventilation (PSV) weaning. In PSV, patients are challenged daily with a sequentially reduced PS from 20 cmH₂O to 8 cmH₂O for up to 12 h. Patients are rested on assist control ventilation. (3) The Therapist-Implemented Patient-Specific (TIPS) weaning protocol is a combination of the Synchronized Intermittent Mandatory Ventilation (SIMV) mode, continued by PSV weaning and followed by TC weaning in a stepwise fashion. The PSV and TIPS modes may be preferred in patients with a marginal performance status. Following ventilator weaning, patients who can tolerate speaking valves (SV) and tracheostomy cannula downsizing and are able to swallow can be considered for tracheostomy capping. Patients who can continuously wear tracheostomy caps for 1 to 3 days can be safely decannulated. Tracheostomy cannulas are kept long-term for patients who failed multiple weaning attempts or cannot tolerate capping trials. Patients who fail weaning attempts transition to the home or subacute care level with the continuation of MV. Multiple failed weaning attempts necessitate the re-evaluation of goals of care. Abbreviations: MV = mechanical ventilation, SBT = spontaneous breathing trial, pass = pass SBT, fail = failed SBT, PS = pressure support, ATC = automatic tube compensation, PEEP = positive end expiratory pressure, TC = tracheostomy collar, PSV = pressure support ventilation, TIPS = Therapist-Implemented Patient-Specific weaning, SV = speaking valve, hrs = hours, d=days.