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Effects of positive end-expiratory pressure on liver function and splanchnic microcirculation


The effects of positive end-expiratory pressure (PEEP) on liver function and blood flow in experimental and clinical studies revealed non-uniform results. In this clinical study, we investigated the effects of PEEP on liver function (indocyanine green plasma disappearance rate [ICG-PDR]) and splanchnic microcirculation as estimated by regional PCO2 (PRCO2) using gastric tonometry.


With approval by our local ethics committee and written consent, we studied 14 patients after elective coronary bypass surgery using extracorporal circulation (13 males, one female; age 48–74, mean 63 ± 7 years). All patients underwent extended hemodynamic monitoring by a pulmonary artery catheter for clinical indication. ICG-PDR and gastric mucosal PRCO2 were assessed on ICU admission (PEEP 5 mbar), 2 hours after increasing PEEP to 10 mbar and again after 2 hours at PEEP 5 mbar. In addition, the cardiac index, central venous pressure (CVP) and left atrial pressure (LAP) were measured. All patients were on pressure-controlled ventilation and the inspiratory peak pressure was adapted to maintain PaCO2 constant. Vasoactive drugs, blood pressure, minute volume and sedation were kept constant.


The cardiac index significantly increased during the study. However, there was a trend for ICG-PDR to change between the different time points (P = 0.05). However, the difference between regional and arterial PCO2 (PCO2-gap) significantly increased following PEEP5 (1) and remained higher at PEEP5 (2) than at PEEP5 (1) (Table 1).

Table 1


Increasing PEEP from 5 to 10 mbar was accompanied with a trend towards a decrease in liver function and blood flow (ICG-PDR). The changes in PCO2-gap were within the physiological range and of no clinical relevance. An increase in PEEP from 5 to 10 mbar can be applied without compromising liver blood flow and function and splanchnic microcirculation.

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Holland, A., Thuemer, O., Schelenz, C. et al. Effects of positive end-expiratory pressure on liver function and splanchnic microcirculation. Crit Care 9, P100 (2005).

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  • Cardiac Index
  • Central Venous Pressure
  • Indocyanine Green
  • Pulmonary Artery Catheter
  • Liver Blood Flow