Principles involved in weaning a patient from ventilatory support in an ICU
Weaning procedures are usually started only after
the underlying disease process that necessitated mechanical ventilation has
significantly improved or is resolved. The patient should also have an adequate
gas exchange , appropriate neurological and muscular status, and stable
cardiovascular function.
Weaning indices are
objective criteria that are used to predict the readiness of patients to maintain
spontaneous ventilation.
The rapid shallow
breathing index (f/VT,
where 'f' is the respiratory rate and 'VT' is the tidal volume measured during the first minute
of a T-piece trial) is superior to conventional parameters in predicting the
outcome of weaning while arterial blood gases and respiratory rate.
The intact airway reflexes and a cooperative patient
are mandatory prior to completion of the weaning process unless the patient has
a cuffed tracheostomy tube.
Mechanical
Criteria for weaning/extubation
Criteria measurement
|
Inspiratory
pressure
<-25cmH2O
|
Tidal
Volume >5ml/kg
|
Vital
Capacity
>10ml/Kg
|
Minute
Ventilation
<10ml
|
Rapid
Shallow Breathing Index
<100
|
With the patient breathing spontaneously
Adequate
oxygenation should be maintained that is the arterial haemoglobin saturation of >90% at FiO2 of 0.4-0.5 with less
than 5cm of H2O of PEEP
RSBI = f(breaths/min) /VT(L)
Patients with RSBI of 100 or less can be
successfully extubated
The most common techniques to wean a patient from
the ventilator include SIMV, PRESSURE SUPPORT VENTILATION, low levels of CPAP,
spontaneous breathing short periods on T-piece.
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