A potential clinical method for calculating transmural left ventricular filling pressure during positive end-expiratory pressure ventilation: an intraoperative study in humans.
OBJECTIVE
This study sought to investigate whether right atrial pressure could be used to estimate pericardial pressure during positive end-expiratory pressure (PEEP).


BACKGROUND
Because of elevated intrathoracic pressure during PEEP, pulmonary capillary wedge pressure may not accurately reflect left ventricular preload. An estimate of pericardial pressure during PEEP would allow assessment of transmural filling pressure.


METHODS
In eight patients, at the start of cardiac surgery, pericardial and pleural pressures were recorded by balloon transducers placed over the anterolateral left ventricular wall. We also recorded intravascular pressures and left ventricular short-axis area by transesophageal echocardiography.


RESULTS
A stepwise increase in PEEP from 0 to 15 cm H2O caused a linear increase in pleural pressure from 0.3 +/- 0.6 (mean +/- SEM) to 6.1 +/- 0.8 mm Hg (p < 0.01). Pericardial pressure increased from 2.3 +/- 0.5 to 5.9 +/- 0.6 mm Hg (p < 0.01). The correlation between right atrial (Pra) and pericardial pressure (Pperic) was good: Pra = 0.85 x Pperic + 1.8, r = 0.77. The correlation between changes in right atrial pressure and in pericardial pressure was better: delta Pra = 0.96 x delta Pperic -0.2, r = 0.97. Pulmonary capillary wedge pressure increased with PEEP (p < 0.05), whereas left ventricular area decreased (p < 0.05). However, there was a progressive reduction in transmural pressure, calculated as wedge pressure minus pericardial pressure (p < 0.05), and in transmural pressure, estimated as wedge pressure minus right atrial pressure (p < 0.05). The estimated transmural filling pressure correlated (r = 0.86) with end-diastolic area.


CONCLUSIONS
The present observations suggest that right atrial pressure may be used to estimate changes in pericardial pressure with PEEP and that pulmonary capillary wedge pressure minus right atrial pressure is a potentially clinically useful approximation of transmural filling pressure.
Smiseth
O A
OA
Division of Cardiology, St. Paul's Hospital, University of British Columbia, Vancouver, Canada.
Thompson
C R
CR
Ling
H
H
Robinson
M
M
Miyagishima
R T
RT
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D016275:Atrial Function; D001794:Blood Pressure; D001026:Coronary Artery Bypass; D017548:Echocardiography, Transesophageal; D005260:Female; D006352:Heart Ventricles / Q000000981:diagnostic imaging; D006801:Humans; D007432:Intraoperative Period; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000379:methods*; D011669:Pulmonary Wedge Pressure; D012044:Regression Analysis; D016277:Ventricular Function, Left / Q000502:physiology*; D017725:Ventricular Pressure