SBT failure after prolonged mechanical ventilation: tracheostomy timing and weaning approach?
67M on mechanical ventilation for 14 days following ARDS from COVID pneumonia. Lung mechanics have improved (compliance 45, P/F 280 on PEEP 5, FiO2 0.3). However, he has failed three consecutive spontaneous breathing trials (SBTs) on pressure support 5/PEEP 5.
Each SBT fails at 20 to 30 minutes with tachypnea (RR > 35), diaphoresis, and accessory muscle use. RSBI during SBT ranges from 110 to 130.
Considerations:
- When do you recommend tracheostomy: early (day 7 to 10) vs late (after day 14)?
- For ICU-acquired weakness contributing to weaning failure, any specific rehab protocol?
- Do you change the SBT technique (PSV vs T-piece vs ATC)?
- Role of inspiratory muscle training?
1 Answer
My approach to difficult weaning:
Tracheostomy timing: At day 14 with 3 failed SBTs, I proceed with percutaneous tracheostomy. The TracMan trial did not show mortality benefit for early vs late tracheostomy, but the practical benefits are clear: improved patient comfort, reduced sedation requirements, better oral care, and earlier mobilization. For this patient, the decision is straightforward.
ICU-acquired weakness: This is likely the primary barrier. ICU-acquired weakness affects 25 to 50% of patients ventilated > 7 days. My protocol:
- MRC sum score assessment (if cooperative enough)
- Early mobilization: in-bed cycling by day 3, passive/active ROM exercises, dangling at bedside, standing with assist
- Protein-enhanced nutrition (1.5 to 2 g/kg/day protein)
- Minimize sedation (target RASS 0 to -1)
- Avoid neuromuscular blocking agents beyond the first 48 hours
SBT technique: I use pressure support 5 to 8 cmH2O for SBTs rather than T-piece. The landmark trial by Brochard et al. (1994) showed that pressure support weaning was faster than T-piece or SIMV weaning. I also use automatic tube compensation (ATC) to eliminate the resistance imposed by the endotracheal tube.
Inspiratory muscle training: Evidence is still evolving, but I use threshold IMT devices (starting at 30% of maximal inspiratory pressure, progressing by 10% every 3 days) in patients with weaning failure attributed to diaphragmatic weakness. The study by Martin et al. (2011) showed that IMT reduced ventilator days.