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Elevated imposed work of breathing masquerading as ventilator weaning intolerance
O C Kirton1, C B DeHaven, J P Morgan
1University of Miami School of Medicine, Department of Surgery, Fla., USA.
Chest
|October 1, 1995
Summary
Measuring the imposed work of breathing from the endotracheal tube (WOBImp) can help safely extubate patients. If physiological work of breathing (WOBPhys) is not excessive, patients can be extubated even with apparent ventilatory insufficiency.
Area of Science:
- Critical Care Medicine
- Respiratory Physiology
- Mechanical Ventilation
Background:
- Apparent ventilatory insufficiency during weaning can lead to prolonged intubation.
- The endotracheal tube and breathing apparatus can significantly increase the work of breathing.
Purpose of the Study:
- To test if patients with high total work of breathing (WOBTOT) due to high imposed work of breathing (WOBImp) can be safely extubated if their physiological work of breathing (WOBPhys) is not excessive.
Main Methods:
- Prospective study in a university hospital trauma ICU.
- Evaluated 28 adults intubated for >= 48 hours with tachypnea but acceptable blood gases.
- Measured WOBTOT, WOBImp, and calculated WOBPhys using a microprocessor-based monitor.
Main Results:
- Six patients (5%) with WOBTOT < 0.8 J/L were extubated successfully.
- Twenty-one patients had elevated WOBTOT; WOBImp was twice WOBPhys.
- Twenty of 21 patients with acceptable WOBPhys (< 0.8 J/L) were successfully extubated; overall reintubation rate was 4%.
Conclusions:
- Measuring WOBImp can differentiate between true ventilatory failure and failure due to equipment.
- This measurement allows safe extubation of patients whose apparent insufficiency is caused by WOBImp.
- Accurate assessment prevents unnecessary prolongation of mechanical ventilation.