<prompt> A 60-year-old man is being weaned from a ventilator in the ICU. The likelihood that weaning is going to fail is suggested by the presence of which of the following?A respiratory rate of 24 breathsminA PaO2 of 80 mm Hg on FiO2 of 40A vital capacity VC of 5 mLkg body weightA minute ventilation of 8 Lmin  <response>: Vital capacity VC of 5 mLkg body weight.Successful weaning from the ventilator is suggested by the presence ofa PaO2 of 70 mm Hg or more with an FiO2 of0.35 or lessb An alveolar arterial gradient of 350 mm Hgc A PaO2 -to-FiO2 ratio of 200d A PaCO2 of over 30 mm Hg and 55 mm Hge A VC of more than 10-15 mLkgf A maximum negative inspiratory force of more than -25 cm H2 Og A minute ventilation of 10 Lminh A tidal volume of over 5 mLkgi A respiratory rate of 30 breathsmin 