Weaning from respiratory support

Patients requiring extended periods of respiratory support may often present major problems as their requirement for positive-pressure ventilation reduces. The patient often needs to be sedated to tolerate an endotracheal tube. The transition from intermittent positive-pressure ventilation to extubation is often a calculated risk, and reintubation is frequently associated with cardiovascular instability. Extubation is often deferred because of this doubt. Modern modes of ventilatory support have reduced both doubt and risk, but have not removed them altogether.

EHFO does not require intubation and is often well tolerated by the awake patient, provided that the frequency is maintained around the patient's own respiratory rate and the span is no greater than 40 cmH2O. Therefore the decision to stop ventilation is easier as it can be restarted with minimal delay if respiratory embarrassment becomes evident. A further benefit is improvement in sputum clearance. A study of patients in acute respiratory failure showed reductions in both duration of ventilation and overall hospital stay (Gaitini eta.L 1991).

In our own practice, weaning problems were the original stimulus for assessing the Hayek oscillator. A familiar scenario is illustrated by a patient who, after presenting with staphylococcal pneumonia associated with renal failure, required a protracted period of intermittent positive-pressure ventilation from which he proved difficult to wean. Over a period of weeks ventilatory assistance was reduced to moderate levels of pressure support ventilation, but could not progress further without significant CO2 retention and associated hypoxemia. The introduction of EHFO was associated with rapid reductions in pressure support requirement and rapid extubation. After a further period of intermittent EHFO lasting for 6 to 18 h/day, the patient made a complete recovery. Subsequent to this case, we have documented five further cases of successful weaning from positive-pressure ventilation after failure of conventional techniques. Provided that the individual is able to tolerate EHFO, sedation can be stopped immediately. Again, this is likely to be associated with improved respiratory effort.

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