Which of the following explains the basis for permissive hypercapnia as a ventilator strategy for ARDS?

a. Introduction of CO2 into the breathing circuit to stimulate spontaneous breaths.
b. Use of lower tidal volumes and accepting a gradual rise in PCO2 to avoid associated hazards of high Paw.
c. Allow patients with ARDS to breathe spontaneously to build their respiratory muscular endurance.
d. To use exhaled CO2 to increase residual volume and improve gas exchange.

ANS: B
Thus, in managing patients with ARDS, the clinician must resist the urge to correct the PaCO2 value to normal. Instead, in the absence of a contraindication to hypercapnia (e.g., elevated intra-cranial pressure), we allow hypercapnia ("permissive hypercapnia") with a goal to maintain the arterial pH at no less than 7.15 to 7.20. Even when PaCO2 rises to a point during which pH may become dangerously low (e.g., pH <7.15), the absolute need to keep the VT at 6 ml/kg IBW re-mains.