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Extubation and the Myth of “Minimal Ventilator Settings”..Part 1

In the Editorial of  February issue of
AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE Dr Tobin  stated the following:


"At the point of extubation, a clinician needs to ask him or herself two questions:
1) will the patient be able to sustain spontaneous ventilation following tube removal? and
2) will the patient be able to protect his or her airway after extubation?

My focus is solely on the first question.


A patient’s ability to successfully sustain spontaneous ventilation after extubation will depend on the mechanical load on the respiratory system secondary to resistance, elastance, and intrinsic PEEP, and how well a patient’s respiratory muscles can cope with the imposed load.

If there is any reason to fear that a patient might experience respiratory difficulties following extubation, it is incumbent on a physician to try and replicate the conditions that the patient will face after extubation— but to do so before removal of the endotracheal tube.



Some physicians claim that application of pressure support of 5 to 10 cm H2Osimply overcomes the resistance engendered by an endotracheal tube . Thus, if a patient is able to sustain ventilation at this ventilator setting, he or she should be able to breathe without difficulty following extubation.

This claim ignores the inflammation and edema that develops in the upper airways after an endotracheal tube has been in place for a day or more. On removal of the tube, the mucosal swelling produces an increase in upper airway resistance.

Straus and colleagues demonstrated experimentally that the respiratory work dissipated against the supraglottic airway after extubation is almost identicalto the work dissipated against an endotracheal tube before extubation. Thus, applying any level of pressure support causes physicians
to underestimate the respiratory resistance a patient will encounter after extubation.

The addition of a small amount of pressure support produces surprisingly large reductions in inspiratory work in ventilated patients: 5 cm H2O decreases inspiratory work by 31 to 38%, and 10 cm H2O decreases work by 46 to 60% . Nonetheless, most—but not all—patients can tolerate a 30 to 60% increase in inspiratory load at the point of extubation."




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