Insertion of the pulmonary artery catheter

This chapter is not relevant to any specific Section of the 2017 CICM Primary Syllabus, which makes it completely pointless for the purpose of any sort of exam revision. However, things which do not appear in the syllabus do ocasionally appear in the exam, and highly practical topics like this make a very attractive target for CICM Second Part equipment vivas. 

The best resource for this would probably have to be the 2013 article by Kelly & Rabbani, and it accompanies a very nice video, but these resources are only available to the paying customers of NEJM. Similarly, money will buy you the UpToDate article on PA catheter insertion.  A free alternative is available (Summerhill & Baram, 2005) which covers all the important points. The definitive resource for all PA catheter insertion waveforms and their permutations would have to be Chapter Three, "Pulmonary Artery Pressure" (p. 27) of Jonathan B. Mark's Atlas of Cardiovascular Monitoring (1998). 

How far to the right atrium?

As one shoves the catheter deeper and deeper, the distal lumen is transduced, and so the resulting pressure waveforms are one's guide to the catheter's position. However, there is a certain predictability in human anatomy, and so one can list the depths of insertion along with the expected structures encountered at those depths, at least for a normal sized person:

Distances and Destinations of the PA Catheter

Site	Depth (i.e. catheter insertion depth for the tip to reach this site)
Right atrium	20cm
Right ventricle	30-35cm
Pulmonary artery	40-45 cm
Wedge position	50cm
Site-dependent modifiers of these expected depths
Subclavian veins	0 cm
Left IJ	+ 5 cm
Right EJ	+ 5 cm
Left EJ	+ 10 cm
Femoral veins	+ 15cm
Right cubital fossa	+ 30 cm
Left cubital fossa	+ 35 cm

However, the waveforms are the real means of determining correct placement.

In the Superior Vena Cava and the right atrium

The introducer sheath goes in first. Before the PA catheter is threaded in, the distal lumen is connected to a CVP transducer, so the pressure wave can be observed. The pressure here will be 1-6mmHg in a normal person, but realistically it will probably be higher because this is probably an unstable patient with a complex mixed shock state (otherwise why the PA catheter?)

Atrial fibrillation may be encountered at this stage as the catheter tip tickles the atrium. Not always is the waveform so pretty; tricuspid regurgitation may give a large v-wave, which may be confused for a pulmonary atrial wave. Additionally, a normal RV waveform may come and go, as the catheter tip flicks in and out of the ventricle. 

In the right ventricle

Once you are past the tricuspid valve, you suddenly get a nice pulsatile waveform, which is the right ventricular contraction.

The systolic pressure here should be between 15 and 30mmHg. The diastolic should be same as right atrial pressure, about 1-6mmHg (makes sense given that the right ventricle fills from the right atrium).

Its not a common place occurrence, but ventricular arrhythmias may be expected to happen here. As soon as you are in the RV, and are seeing the pulse waveform, you can inflate the balloon with air. The volume is 1.5ml.

In the pulmonary artery

Past the pulmonary valve, one can now see the PA waveform, which resembles the waveform of any other artery. At this stage the diastolic pressure rises to about 6-12mmHg (due to flow resistance in the pulmonary arterial network) This is the fabled PA diastolic pressure, the PADP, which maintains a supposedly stable and reliable relationship with the PAWP.

Now, we wedge the catheter

The catheter with the inflated balloon is advanced further, until the PA waveform disappears, and a venous-looking waveform appears. This is the wedge waveform. It indicates that the pulmonary artery is occluded.

The pressure here should also be 6-12 mmHg, like the PA diastolic pressure. If it is different, it shouldn't be far off ( about 5mmHg) and this relationship should persists for some hours, so you can just use the PADP (this way you don't have to wedge repeatedly). Once you have found this wedging point, deflate the balloon passively, and fix the catheter in position.

Do not keep it inflated. Bad things will happen.