4 Mechanical Ventilation, part 4 (Extubation)

Question 1

Empirical criteria to determine if the patient is ready to start to be tested for discontinuation of MV

Answer 1

Reversal/correction of the reason for which the patient required mechanical ventilation
Spontaneous respiratory efforts
Adequate oxygen uptake
–PaO2 >70 mmHg when receiving FiO2 ≤0.5 AND PEEP 5 or less
Conscious and cooperative (receiving no or minimal sedation)
Hemodynamic stability (HR <140, SBP 90-160, with low-dose or off intropes or vasodilators)

approximately 80% will successfully complete SBT

approx 80% will successfully complete SBT

Question 2

types of spontaneous breathing trial

Answer 2

Pressure support trial
CPAP trial
T-piece trial

Question 3

Remarks on pressure support trial

Answer 3

PS of 5-8 cm H20 is provided
duration: 30 minutes up to 2 hours are equivalent
Terminate as soon as clinical signs of failure occur
Once or twice daily trials are recommended

(more frequent trials may increase weaning duration)

Question 4

CPAP trial

Answer 4

5 cm H2O is commonly used
duration and termination as for PS trial

Question 5

indicators of failed SBT

Answer 5

Immediate: f/Vt ≥105

subsequent:
Sustained RR >35

Arterial O2 sat <90%
pH <7.2 OR dec >0.1 pH unit
Increase in PaCO2 of >8 mmHg

SBP >200 mmHg or <90 mmHg OR up/down >20%
Severe agitation, acute confusion, sweating, or new arrhythmias

need to re-institute previous level of ventilation

Question 6

remarks on respiratory muscle fatigue after failed SBT

Answer 6

Can be avoided by termination and reinstitution of MV as soon as clinical signs of SBT failure occur (not longer than 1 h delay)

If diaphragmatic muscle fatigue is allowed to occur, it requires 24 hours for recovery and allowing sufficient recovery time when this is suspected is essential

Question 7

Cuff leak test

Answer 7

1. Deflate cuff, controlled breaths, get the lowest of 3 expired VTs of 6 breaths, and substract from inspiratory VT
2. Leak should exceed 100 mL or 15-20% of delivered VT

Question 8

Remarks on extubation process

Answer 8

1. Patient should be adequately fasted - at least 6 hours prior to extubation (with gastric contents aspirated if NGT is present)
2. Place the patient in sitting position, receiving FiO2 1.0
3. Ensure adequate monitoring (as for intubation)
4. Deflate the cuff and extubate during exhalation

Question 9

Prevention of post-extubaiton stridor

Answer 9

Methylprednisone 20 mg every 4 hours for 4 doses
or single dose methylprednisolone 40 mg 4 hours prior to extubation