Bowie et al, Anesthesia and Analgesia 2001;92:415-417

Reviewer: John F. Heath, M.D.

Conclusion:
Low levels of CPAP probably do not adversely affect cerebral hemodynamics in most patients but could adversely affect patients with already elevated ICP or decreased MAP.

Summary:
Transcranial doppler monitoring was used in 15 awake, healthy volunteers to assess middle cerebral artery flow velocity (FV) and pulsatility index (PI) during the application of 5 and 10 cm H20 CPAP.   A previous study had demonstrated a significant increase in mean FV and a decrease in PI during the application of 12 cm H20 CPAP (awake, spontaneously breathing pts).  This could indicate cerebral vasodilatation (distal to the MCA) with a subsequent increase in cerebral blood volume and increased ICP. Other studies demonstrated a decrease in FV and an increase in PI during the application of 5-15 cm H20 PEEP(anesthetized, ventilated pts,MAP decreased) or no change in FV or PI (anesthetized, ventilated pts, MAP no change).  This study demonstrated no signicant changes from baseline in FV or PI or MAP.