A 60 year old patient  has been admitted to the ICU for 5 days with severe sepsis secondary to a perforated sigmoid colon. He had a sigmoid colectomy and washout of his peritoneum, and appropriate antibiotic therapy. His initial course was complicated  by severe septic shock that is now resolving and acute renal failure for which he is still receiving continuous  renal replacement therapy.  He is currently still ventilated  via an oral endotracheal tube, on SIMV with a rate of 16, TV of 700, PEEP of 5 and FiO2 of 0.45.

He is receiving a small dose of fentanyl and propofol, but is awake and co-operative although he has generalised weakness. His arterial blood gases are shown below:


pH            7.32

PaO2        85 mmHg         (11.3 Kpa)

PaCO2     45 mmHg             (6 Kpa)

HCO3      18 mmol/L

BE           -4.9 mmol/L

What criteria will you use to determine whether the patient  is ready to be extubated?

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College Answer

Usually based upon combination of factors rather than a single number.

•    Has the process that required intubation resolved?
o Sepsis and shock
o Abdominal pain
o Intra-abdominal complications that require further intervention

•    Airway?
o Cuff leak
o Difficult airway at time of intubation

•    Respiratory?
o Rapid shallow breathing index (80-110??, on a spontaneous breathing mode)
o Secretions (volume/character)
o Vital capacity (>8-12ml/kg) measured with 0 PS.
o Minute ventilation (<10l/min)
o Adequate gas exchange
o Negative inspiratory force (< -20cm H2O)

•    Neurological?
o Awake and co-operative
o General muscle strength

•    Cardiovascular?
o Low/stable dose of vasopressors and inotropes
o Stable cardiac rhythm

•    Other factors
• Need for more procedures

Discussion

Again, this is a question regarding the standard criteria for extubation.

The Standard Criteria for Extubation

  • Resolution of the condition which had required the intubation and ventilation
  • Patient-triggered mode of ventilation
  • Adequate oxygenation
  • Low PEEP: 5-8 cmH2O
  • Hemodynamic stability
  • Good cough reflex on tracheal suctioning
  • Good gag reflex on oropharyngeal suctioning
  • Adequate muscle strength
  • Satisfactory vital capacity
  • Normal acid base status (pH >7.25)
  • Adequate neurological performance (oriented and obeying commands)

The Specific criteria for this patient

  • The severity of abdominal pain, and the extent to which it influences the patients ability to cough and take deep breaths.
  • Any further planned surgical procedures

References

References

I tend to throw these references out whenever the question clearly refers to standard extubation criteria.

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