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You are in Home >> Resources >> Clinical anaesthesia >> Cardiac Output

Pulmonary artery catheters

Created: 14/8/2005

 

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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