Answer
Numerous weaning parameters can be used to help predict successful extubation. However, no weaning protocol is 100% accurate in predicting successful weaning and extubation. These weaning parameters must be tailored for each clinical scenario.
For instance, if the rapid, shallow breathing index (the respiratory rate/tidal volume, or frequency/tidal volume [f/Vt]) is less than 105, the patient is likely to be weaned from mechanical ventilation. The investigators who derived this number examined primarily middle-aged patients. However, data from follow-up studies of patients older than 70 years suggest that a slightly higher rapid, shallow breathing index of less than 130 may be acceptable.
These parameters give no insight into whether a patient can protect his or her airway or clear secretions. Clinical judgment and experience play a large role in the physician's decision to withdraw mechanical ventilatory support. If a patient cannot be extubated and/or if the results of the rapid, swallow breathing test are not satisfactory, the reason for the failure must be evaluated and treated.
Parameters commonly used to assess a patient's readiness to be weaned from mechanical ventilatory support include the following:
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Respiratory rate less than 25 breaths per minute
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Tidal volume greater than 5 mL/kg
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Vital capacity greater than 10 mL/k
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Minute ventilation less than 10 L/min
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PaO2/FIO2 greater than 200
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Shunt (Qs/Qt) less than 20%
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Negative inspiratory force (NIF) less than (more negative) -25 cm water
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f/Vt less than 105, or less than 130 in elderly patients
Additionally, it has been reported that intercostal retraction after adding dead space may help in the detection of susceptibility to extubation failure. [5]
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An example of the Drinker and Shaw negative-pressure ventilator (iron lung).
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The pressure, volume, and flow to time waveforms for assist-control ventilation.
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The pressure, volume, and flow to time waveforms for controlled ventilation.
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The components of mechanical ventilation inflation pressures. Paw is airway pressure, PIP is peak airway pressure, Pplat is plateau pressure.
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The effects of decreased respiratory system compliance (A) and increased airway resistance (B) on the pressure-time waveform.
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Determination of the lower inflection point to estimate the best (optimal) positive end-expiratory pressure (PEEP) from the pressure-volume hysteresis curve.
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The effect of positive end-expiratory pressure (PEEP) on the pressure-time inflation curve.
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The pressure, volume, and flow to time waveforms for synchronized intermittent mandatory ventilation (SIMV).
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The pressure, volume, and flow to time waveforms for synchronized intermittent mandatory ventilation (SIMV) with pressure-support ventilation.
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The flow to time waveform demonstrating auto–positive end-expiratory pressure (auto-PEEP).
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The pressure, volume, and flow to time waveforms for pressure-regulated volume-controlled ventilation.
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The pressure, volume, and flow to time waveforms for proportional-assist ventilation.
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The pressure, volume, and flow to time waveforms for airway pressure–release ventilation.
