Page 315 - Clinical Application of Mechanical Ventilation

Hemodynamic Monitoring 281

TABLE 10-5 Potential Problems with Arterial Catheter

Factors Problem

Air bubbles in tubing Dampens the pressure signal
Loose tubing connections
Transducer and catheter placed higher than Measurement lower than actual
measurement site

Transducer and catheter placed lower than Measurement higher than actual
measurement site

Inadequate pressure applied to the flush Backup of blood in the tubing
solution bag

Blood clot at catheter tip, catheter tip blocked Inaccurate reading, signal interference
by wall of artery
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Potential Problems with Arterial Catheter

Air bubbles and loose tubing connections can “dampen” the pressure signal.
Improper leveling of the transducer and catheter can cause false high or false
low readings. Inadequate pressure applied to the heparin solution bag can result
in backup of blood in the tubing when the arterial pressure becomes higher than
the heparin line pressure. Clotting of blood at the catheter tip or blockage of the
catheter tip by the wall of the artery can interfere with the hemodynamic signal. The
potential problems that are related to the arterial catheter are shown in Table 10-5.
Most intensive care units have standard procedures in place to minimize such
problems. Careful adherence to proper setup and calibration of hemodynamic
monitoring equipment are essential.

CENTRAL VENOUS CATHETER

The central venous pressure (CVP) can be monitored through a central venous
catheter placed either in the superior vena cava near the right atrium or in the right
atrium. The pressure measured in the right atrium is right atrial pressure (RAP) but
it is commonly called CVP. The RAP can also be monitored via the proximal port
of a pulmonary artery catheter.
The primary use CVP in hemodynamic monitoring is to measure the filling pres-
CVP measures the filling
pressures in the right heart sures in the right heart. The CVP is helpful in assessing fluid status and right heart
and assesses the systemic function. However, it is often late to reflect changes in the left heart. The central
fluid status and right heart
function. venous catheter can also be used to collect “mixed” venous blood samples and for
administration of medications and fluids. (Note: A true mixed venous blood sample

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