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Pulmonary Artery Flotation Catheter (PAFC)

Pulmonary Artery Flotation Catheter (PAFC)

PAFC catheters used to be the main method of assessing cardiac output in ICU. Now, they are used less frequently as other less invasive methods of assessing cardiac output are introduced. However, cardiac output measured by the PAFC remains the gold standard to which all other monitors are compared.

Monitoring PAC kit

Figure 1. Pulmonary artery floatation catheter

Insertion

Initially, a relatively wide bore introducer is inserted into the jugular or subclavian vein. The PA catheter is then passed into this in a sterile fashion. Once the catheter tip is in the superior vena cava, a balloon near its tip is inflated and the catheter is advanced under direct pressure waveform guidance Fig 2. The inflated balloon allows the catheter to be directed by the blood flow into the pulmonary vasculature. The decreasing diameter of the pulmonary artery means that the inflated balloon becomes ‘wedged’, normally at about 55 cm from insertion point. At this point the transduced pressure from the distal lumen of the catheter shows a much flatter trace than the previous PA artery trace. This ‘wedged’ trace is the Pulmonary artery occlusion pressure (PAOP) and is taken to indicate the left atrial pressure, which gives an indication of the filling pressures and thus preload on the left side of the heart. The balloon should then be deflated and only inflated when used to measure the PAOP. Leaving the balloon wedged might lead to pulmonary infarction.

Monitoring PAC waveform

Figure 2. Pressure is measured directly during the insertion of a PAFC. RA = right atrium, RV = right ventricle, PA = pulmonary artery, PAOP = pulmonary artery occlusion pressure.

Normal pressure values (mmHg)

RA

0-8

RV

15-30/0

PA

15-30/8

PAOP

5-15

Measurements

In addition to the PAOP, the catheter is used to measure cardiac output. A temperature change of blood is induced at a proximal part of the catheter and a temperature probe on the distal end of the catheter picks up this temperature change. This temperature change is induced either by a bolus of a cold glucose solution, or pulses of heat from a wire around the catheter. The temperature change detected at the tip is plotted against time, this is called the thermodilution curve, figure 3. The cardiac output is inversely related to the area under the thermodilution curve.

Monitoring washout

Figure 3. Thermodilution curve. AUC = area under the curve

 

With the measured values HR, MAP, CVP, PAOP, Cardiac output, and body surface area (BSA), a number of other values can be derived. These include stroke volume (SV), systemic vascular resistance (SVR), pulmonary vascular resistance (PVR) and left ventricular stroke work index (LVSWI).

The Oxygen saturation of the mixed venous blood (SvO2) passing the distal end of the catheter can be measured (normally about 75%); this gives an indication of the overall Oxygen consumption by the body. This is particularly useful in management of cardiogenic shock.

Complications of pulmonary artery floatation catheters

All the complications of central venous access
Right atrial or ventricular rupture
Arrhythmias
Knotting of catheter
Pulmonary artery rupture
Pulmonary artery occlusion leading to pulmonary infarction

Further reading

http://www.anaesthesiauk.com
http://www.edwards.com

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