Abstract
The use of the pulmonary artery (PA) catheter has become a central part of the management
of critically ill patients in modern intensive care units. The PA catheter provides
a remarkable amount of information that continues to increase with ongoing technological
advances. In modern intensive care units, measurement of the pulmonary arterial wedge
pressure (PAWP) is perhaps the most common and most important indication for inserting
PA catheters in critically ill patients. The interpretation of the measured PAWP in
such patients is also the most controversial aspect of the use of PA catheters, however.
The most important use of PAWP is to estimate (not measure) two parameters: (1) the hydrostatic pressure gradient for pulmonary
edema formation and (2) the left ventricular end-diastolic volume (LVEDV) or preload.
PAWP does not directly measure either of these two parameters. When properly acquired, mean PAWP, taken
at end-expiration, generally provides a reliable measure (a minimum estimate) of the
pulmonary microvascular hydrostatic pressure, which is the major determinant of fluid
flux from the pulmonary microvasculature. Similarly, when properly acquired, end-diastolic
PAWP, taken at end-expiration, generally provides a reliable estimate of left ventricular
end-diastolic pressure (LVEDP), but importantly this value may not reliably reflect
LVEDV, or preload, if left ventricular (LV) compliance or juxtacardiac pressure are
abnormal.
Key Words:
Pulmonary artery wedge pressure - left ventricular end-diastolic pressure - pulmonary
edema - adult respiratory distress syndrome
