N. Brienza et al., EFFECTS OF PEEP ON LIVER ARTERIAL AND VENOUS-BLOOD FLOWS, American journal of respiratory and critical care medicine, 152(2), 1995, pp. 504-510
Citations number
32
Categorie Soggetti
Emergency Medicine & Critical Care","Respiratory System
Total venous return decreases with positive end-expiratory pressure (P
EEP). It is likely that the liver plays an important role in this resp
onse, either through the development of an increase in venous resistan
ce or through an increase in the venous backpressure at the outflow en
d of the liver. In addition, hepatic arterial flow is reported to be s
electively decreased by the application of PEEP. Therefore, to clarify
the effects of PEEP on liver hemodynamics, we generated pressure-flow
(P-Q) relationships in both liver vascular beds of anesthetized, mech
anically ventilated pigs at PEEP of 0, 5, 10, and 15 cm H2O to obtain
values of backpressure (Pback, mm Hg) from linear extrapolation of the
P-Q relationships and resistance (mm Hg/ml/min/kg) from its slope. PE
EP decreased portal vein flow (Qpv) and caused an increase in the live
r venous resistance (from 0.08 rt 0.01 to 0.16 +/- 0.02 mm Hg/ml/min/k
g; p < 0.05). Ppvback and right atrial pressure (Pm) increased equally
(from 5.1 +/- 0.3 to 9.9 +/- 0.4 mm Hg, p < 0.05, and from 4.0 +/- 0.
2 to 8.6 +/- 0.5 mm Hg, p < 0.05, respectively, at PEEP 15). The reduc
tion in portal venous flow was related to an increase in the backpress
ure to flow (as a result of an increase in Pra) and to an increase in
liver venous resistances that may cause blood pooling in the splanchni
c compartment and decrease venous return through the liver. PEEP incre
ased Phaback (from 11.2 +/- 0.9 to 14.5 +/- 0.7 mm Hg at PEEP 15, p <
0.05) but did not change hepatic arterial resistance. Because a devrea
se in Qpv, without PEEP, decreases hepatic arterial resistance via the
hepatic artery buffer response, opposing constricting and dilating ef
fects appear to occur with the application of PEEP.