Effect of PEEP and jugular venous compression on canine cerebral blood flow and oxygen consumption in the head elevated position

Cerebral blood flow (CBF) (radiolabelled microspheres) and oxygen consumption (CMRO₂) were studied in nine dogs during 30 min of either neck vein compression or application of positive end-expiratory pressure (PEEP) ventilation. With the animal in the prone position, elevation of the head from horizontal to 30 cm above the heart markedly decreased cisterna magna (P(CSF)) and dorsal sagittal sinus pressure (P(CV)). With the head elevated, compression of neck veins using neck tourniquet (pressure 40 mmHg) increased P(CSF) and P(CV) from 3.6 ± 2.2 to 6.8 ± 4.8 and -2.5 ± 2.7 to 2.3 ± 2.3 mmHg (mean ± SE, P < 0.05), respectively, while total or regional CBF and CMRO₂ remained unchanged. Application of PEEP (15 cm H₂O) increased right atrial pressure (-4.7 ± 1.7 to -0.1 ± 3.4 mmHg, P < 0.05), but did not affect P(CSF) or P(CV) (3.4 ± 3.3 to 3.3 ± 3.7 and -3.5 ± 2.6 to -4.1 ± 2.4 mmHg, respectively, P < 0.05). Total or regional CBF and CMRO₂ were also unaffected. These data demonstrate that, although neither maneuver affects CBF or CMRO₂ neck vein compression elevates P(CV) above atmospheric pressure, but PEEP does not. In patients at risk for cerebral venous embolism, intermittent neck vein compression should be used as a prophylactic measure to prevent air embolism.