The Catheter
Proximal lumen: 25 cm from tip, lies in right atrium, measures central venous pressure (CVP).
Distal lumen: at tip of catheter, lies in a branch of the pulmonary artery, connected to a pressure transducer.
Balloon lumen: permits introduction of 1.5 ml of air into the balloon at the distal tip.
Thermistor lumen: bead situated 4 cm from the tip of the catheter and measures temperature.
Use of the pulmonary artery catheter
- Assessment of volume status where CVP unreliable.
- Sampling of mixed venous blood to calculate shunt fraction.
- Measurement of cardiac output using thermodilution.
- Derivation of other cardiovascular indices, such as the pulmonary vascular resistance, oxygen delivery and uptake
Indications for insertion
In normal individuals, CVP correlates with filling pressures of both right and left atria, this is not true in the following disease states:
Left ventricular failure with pulmonary oedema
Interstitial pulmonary oedema
Chronic pulmonary disease
Valvular heart disease
Method of insertion
 Via a central vein (internal jugular/subclavian)
A dilator is necessary for the vein
Distal lumen is connected to a transducer and the waveform displayed
When the right atrial trace is seen, then the balloon is inflated and the catheter slowly advanced, the balloon will help to direct movement to the right atrium then wedge in a branch of the pulmonary artery.
Mixed venous oxygen (SvO2)
% of mixed venous blood that is oxygenated, measured photometrically at the end of the PA catheter
SvO2 is decreased with: anaemia, low CO, arterial oxygen desaturation, increased O2 consumption
Measured Values
CVP: Central Venous Pressure 1-6 mm Hg (reflects right atrial pressure).
PAP: Mean Pulmonary Artery Pressure Systolic 15-30mm Hg, Diastolic 6-12mm Hg.
PCWP: Pulmonary Capillary Wedge Pressure 6 - 12mm Hg. Estimates left atrial heart pressure and left ventricular end diastolic pressure.
CO: Cardiac Output 3.5 - 7.5 L/min
Sv02: Mixed venous partial pressure of oxygen (70 - 75%). Drawn from the end of the pulmonary artery catheter. Used to calculate how well oxygen is extracted by the tissues.
Complications
Arrhythmias on insertion
Knotting of catheter in right ventricle
Balloon rupture
Pulmonary infarction
Infection
ArticleDate:20050814
SiteSection: Article
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