Question 2a

College Answer

(a)        Describe how you would assess him for extubation.

Readiness for extubation requires an assessment of factors that necessitated intubation in the first place, and standard criteria. Standard criteria would include:
·           adequacy of oxygenation (usually on low level of FIO2 [eg. 0.4] and PEEP [eg. 5]),
·           ventilation (minimal respiratory supports eg. low level of pressure support [eg. :: 10]
or tube compensation; some other ventilatory indices may be used [eg. VE < 10
L/min, tidal volume :respiratory rate ratio, maximal inspiratory force [negative pressure]),
·           protection of airway (adequate cough ± gag),
·           ability to clear secretions (sputum production and cough), and
·           appropriate neurological state (usually/preferably obeys command, orientated). Specifics for this man would also include:
·           an assessment of the airway swelling (supraglottic) via direct questioning (limited) and direct or indirect visualisation(laryngoscopy, endoscopy). Discussion with treating surgical team critical, especially with regard to timing, as swelling likely to increase over the first 48 hours. Uncommonly need more formal imaging.
·           acceptable neurological state given his intellectual handicap (limited ability to understand and/or co-operate may alter threshold for the previously mentioned criteria).

Discussion

This question closely resembles Question 11 from the second paper of 2011. In order to simplify revision, the answer to that question is duplicated below.

The normal criteria for extubation readiness are as follows:

... in the model answer, one may also want to mention that 30% of patients who DONT satisfy these criteria can still be successfully extubated.

The Specific criteria for this patient

• Direct laryngoscopy to visually assess airway oedema should reveal an improvement in the swelling and predict the difficulty of reintubation laryngoscopy.
• There should be a surgical plan for ongoing management of swelling
• The neurological criteria for extubation should be adjusted (one cannot expect everybody to obey commands and be orientated)

Things to consider before a difficult extubation:

• Perform a cuff leak test. The cuff leak is a good indicator: if it is present, there is little likelihood of post-extubation stridor . Sure, the patient may fail for a hundred other reasons, but at least they will not br stridorous. In fact, failing the cuff leak test does not preclude a successful extubation (Kriner et al, 2006), but in a patient with a difficult airway one would want to be extra careful.
• See the airway before extubation. This is particularly important in cases where some sort of primary airway problem was the main reason for intubation. An excellent example of such a scenario is the a 45 year old "intellectually handicapped man" from the college SAQs (Question 11  from the second paper of 2011 and Question 2a from the second paper of 2004). The man had a large dental abscess which affected his airway. Before extubating him, the wise candidate would ask for direct laryngoscopy in order to
• Scan the airway before extubation. This is an extension of direct laryngoscopy, which can only ever show you the intubated larynx. If there is some sort of sublaryngeal pathology (eg. subglottic stenosis) a CT would reveal it, whereas laryngoscopy or bronchoscopy would not.
• Prepare for management of post-extubation stridor: these techniques are discussed in greater detail elsewhere, but briefly listed they consist of the following:
  • Dexamethasone
  • Adrenaline nebs
  • Extubation on to NIV
  • Extubation on to heliox
  • Extubation in the operating theatre with ENT on standby
• Extubate over an airway exchange catheter. These are long hollow polyurethane tubes. You can extubate the patient, leaving one in situ (or just the guidewire from one, sitting above the carina). If the patient gets into respiratory trouble, the end of the catheter can be attached to a standard 15mm conector, and the patient may be ventilated by this method while a definitive airway is beign established. Historically, they seem to improve reintubation success rates in cohorts of difficult airway patients. For example, Loudermilk et al (1997) reported a high rate of successful first-time reintubation with these devices.
• Postpone extubation. Extubation, as the DAS point out, is an entirely elective procedure. There is no such thing as a "crash extubation". There is never any rush. A delay may improve the degree of airway oedema, or allow for expert staff to assemble so that the best chance of reintubation is afforded.
• Electively convert to tracheostomy. In some circumstance, it is clear that the upper airway problem is persisting and is unlikely to resolve of the medium-term. Prolonged intubation has its own numerous disadvantages and will cause vocal cord oedema eventually, so to keep the patient intubated for an excessively long time is not an option either. In some cases, extubation to you own airway will be impossible and a tracheostomy is inevitable.

Andrew D Bersen wrote chapter 27 of the Oh's Manual, which regards mechanical ventilation.

Table 27.3 on page 363 of the 6th edition of Ohs Manual is a nice list of the various indices meantioned above (eg. the rapid shallow breathing index).

On page 362, Bersen references this Chest article from 2001, where the evidence for extubation criteria is summarised.
MacIntyre NR (chairman), Evidence-based guidelines for weaning and discontinuing ventilatory support: a collective task force facilitated by the American College of Chest Physicians; the American Association for Respiratory Care; and the American College of Critical Care Medicine. CHEST December 2001 vol. 120 no. 6 suppl 375S-396S.

Recommendations regarding which conditions favour extubation has been put forward in a 2007 practice guidelines statement by the AARC:
AARC GUIDELINE: REMOVAL OF THE ENDOTRACHEAL TUBE; RESPIRATORY CARE •JANUARY 2007 VOL 52 NO 1