Assessment of cardiac preload and left ventricular function under increasing levels of positive end-expiratory pressure.
OBJECTIVE
(1) To assess the impact of high intrathoracic pressure on left ventricular volume and function. (2) To test the hypothesis that right ventricular end-diastolic volume (RVEDV) and intrathoracic blood volume (ITBV) represent cardiac preload and are superior to central venous pressure (CVP) or pulmonary capillary wedge pressure (PCWP). The validity of these parameters was tested by means of correlation with left ventricular end-diastolic volume (LVEDV), the true cardiac preload.


METHODS
Prospective animal study.


METHODS
Fifteen adult sheep.


METHODS
All animals were studied before and after saline washout-induced lung injury, undergoing volume-controlled ventilation with increasing levels of PEEP (0, 7, 14 and 21 cmH2O, respectively).


RESULTS
Left ventricular ejection fraction (LVEF), stroke volume (LVSV) and LVEDV were measured using computed tomography. ITBV and RVEDV were obtained by the thermal dye dilution technique. At PEEP 21 cmH2O, LVSV significantly decreased compared to baseline, PEEP 0 and PEEP 7 cmH2O. LVEDV was maintained except for the highest level of PEEP, while LVEF remained unchanged. RVEDV and RVEF also remained unchanged. The overall correlation of RVEDV and ITBV with LVEDV was satisfactory ( r=0.56 and r=0.62, respectively) and clearly superior to cardiac filling pressures.


CONCLUSIONS
In the present study, (1) ventilation with increasing levels of PEEP did not alter RV function, while LV function was impaired at the highest level of PEEP; (2) unlike cardiac filling pressures, ITBV and RVEDV both provide valid estimates of cardiac preload even at high intrathoracic pressures.
Luecke
Thomas
T
Department of Anesthesiology and Intensive Care Medicine, Faculty of Clinical Medicine, University Hospital of Mannheim, Mannheim, Germany. thomas.luecke@anaes.ma.uni-heidelberg.de
Roth
Harry
H
Herrmann
Peter
P
Joachim
Alf
A
Weisser
Gerald
G
Pelosi
Paolo
P
Quintel
Michael
M
D000818:Animals; D001810:Blood Volume; D002306:Cardiac Volume; D002496:Central Venous Pressure; D004195:Disease Models, Animal; D008991:Monitoring, Physiologic / Q000379:methods / Q000592:standards; D011175:Positive-Pressure Respiration / Q000009:adverse effects / Q000379:methods; D011446:Prospective Studies; D011669:Pulmonary Wedge Pressure; D012128:Respiratory Distress Syndrome / Q000139:chemically induced / Q000503:physiopathology* / Q000628:therapy*; D012756:Sheep; D012965:Sodium Chloride; D013318:Stroke Volume; D013815:Thermodilution; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D016277:Ventricular Function, Left; D016278:Ventricular Function, Right
D012965:Sodium Chloride