A patient is being evaluated for readiness to wean from mechanical ventilation. The values of which of the following mechanical factors would tend to predict successful liberation from the ventilator? I. minute ventilation:greater than 10 L/minute II. vital capacity:greater than 5 ml/kg III. maximum inspiratory pressure: less than 25 cm H2O IV. RSBI: less than 105

A. II, III only
B. III, IV only
C. I, II, IV only
D. II, III, IV only

ANS: B
A. Incorrect response: See explanation B.
B. Correct response: The following mechanical factors and their recommended values used to predict success for the discontinuation of mechanical ventilation include:
• ? Minute ventilation: less than 15 L/minute
• ? Maximum inspiratory pressure: less than –25 cm H2O
• ? Vital capacity: greater than 10 ml/kg
• ? Rapid shallow breathing index (f/Vt): less than 105
• ? Work: less than 5 joules/minute (exclusive of ETT work)
• ? Pressure-time index: less than 0.15
C. Incorrect response: See explanation B.
D. Incorrect response: See explanation B