A strategy for extubation success
Optimisation of conditions prior to the attempt
- The condition which the patient was intubated for has resolved.
- Otherwise, this is a "one way extubation" and you don't plan to reintubate the patient if they deteriorate.
- The mode of breathing is patient-triggered; eg. PSV
- The patient is able to initiate breaths; ideally this mode has been going on for some time and has been well-tolerated.
- FiO2 is reasonable: 40% or lower
- Obviously, you cant always get what you want. Oxygenation is a poor predictor of weaning success anyway.
- PEEP is reasonable: 5-8 cmH2O
- There is some argument that extubating from a higher PEEP might cause pulmonary oedema. Furthermore, the higher PEEP suggests that the patient is relying on positive pressure to maintain patency of lung units which would otherwise become atelectatic.
- In other words, if you cant wean the PEEP to 5-8, extubating the patient would cause their respiratory function to deteriorate.
- A way to get around this is to extubate onto CPAP.
- There is no reason to anticipate increased respiratory effort or increased respiratory difficulty
- i.e. there is no severe abdominal or chest wall pain (the flail chest and the laparotomy wound are well covered by regional anaesthesia, for example), no metabolic acidosis, no bronchospasm, and the patients respiratory rate is not too high.
- The sedation is minimised (or...can be safely minimised)
- One ought to give their patients the best chance of a good neurological performance at the extubation assessment.
- If the patient is in the grip of some sort of wild thrashing delirium, one can anticipate a rocky periextubation course. One may defer such an extubation until somebody elses shift. One may wish to tinker with the sedation and optimise whatever concurrent encephalopathy.
- The nasogastric feeds have been turned off for 6 hours or so
- Given that this airway manipulation is an elective procedure, one ought to treat the fasting status in the same way one would treat any elective airway procedure.
Assessment of extubation readiness
- The level of consciousness is satisfactory and the patient is cooperative
- There needs to be some minimum of patient cooperation, or at least the promise of adequate airway patency at extubation. You are not going to extubate somebody whose GCS would mandate intubation if they were found on the sidewalk.
- The patient can raise their head off the pillow, and their arms off the bed.
- This is a crude rapid test for muscle weakness. If the patient is able to do this, they probably don't have critical illness neuromyopathy.
- There is an adequate cough.
- If the tracheal suctioning results in a vigorous cough, one can expect secretions dribbling into the carina should do the same. One can rely on such a patient to clear their own sputum, instead of letting it fester in their airway.
- There is an adequate gag.
- If the oropharyngeal suctioning results in a vigorous gag, one can expect oral secretions will also be detected, and the patient will protect their lower airway from their upper airway secretions.
- The patient can generate a good tidal volume with zero pressure support.
- We are talking 10ml per kg of ideal body weight, at least.
- It means they probably have enough available lung tissue to support good ventilation post-extubation
- The patient can overcome a -20 cmH2O pressure trigger
- This is the pressure trigger of a patient-triggered mode of ventilation
- If they are able to generate such a negative pressure, one can make some assumption about the strength of their respiratory muscles.
- There is a satisfactory audible and/or measured cuff leak
- This is controversial. The audible cuff leak is the faint gurgle of escaping air one hears with the cuff down during mechanical inspiration; the measured cuff leak is the difference between the administered gas volume and the end-tidal gas volume (the end-tidal should be at least 15% less than the administered)
- Fisher and Raper from RNSH published a study which demonstrated that a failed cuff leak test does not predict a failed extubation. The presence of a cuff leak was still predictive of extubation success.
- Not everybody believes in cuff leaks. However, the coroner will be interested to know why you did not perform this simple bedside test.
A more complete summary of the AARC extubation assessment guidelines can be found here.