A patient being ventilated with APRV has the following settings: Phigh = 24 cm H2O; Thigh = 5 sec; Plow = 4 cm H2O; Tlow = 1 second, FIO2 = 0.3
The patient's spontaneous respiratory rate is 10 breaths/min. The current arterial blood gas values are: PaO2 = 91 mm Hg; PaCO2 = 62 mm Hg. What should the respiratory therapist recommend for this patient?
a. Increase the Plow to 5.5 cm H2O.
b. Decrease the Tlow to 0.5 sec.
c. Increase the Phigh to 40 cm H2O.
d. Decrease the Plow to 0 cm H2O.
ANS: D
To decrease the PaCO2, the Phigh/Plow gradient needs to be increased without increasing the Phigh above 35 cm H2O. Decreasing the Plow to 0 cm H2O is one way to increase that gradient. Increas-ing the Plow would decrease the gradient and therefore the VT. Although raising the Phigh would increase the pressure gradient and therefore the VT, pressures above 35 cm H2O increase the risk of overdistention injury.
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