As we have discussed in previous pearls, the ARDSnet trial forms the basis for ventilatory management in the ICU. A primary component to current ventilatory management is the focus on maintaining lower and safer distending pressures through the use of lower tidal volumes.
Similar to last week's pearl on the obstetric patient, these ventilatory settings may not be applicable to all patients.
Recall that the use lower tidal volumes results in lower minute ventilation. This leads to the accumulation of CO2, termed permissive hypercapnia. In general, we tolerate higher levels of CO2 in favor of lower plateau pressures.
For the brain-injured patient, however, increases in CO2 may increase intracranial pressure (ICP) causing adverse effects.
Current recommendations for mechanical ventilation in the brain-injured patient include maintaining a PaCO2 between 35 - 40 mm Hg. Thus, you need to be more vigilant at following PaCO2 in this patient population.
Lapinsky SE, Posadas-Calleja JG, Mcullagh I. Clinical review: Ventilatory strategies for obstetric, brain-injured, and obese patients. Crit Care 2009;13:206-13.