Following insertion of a pulmonary artery catheter
a) list 3 tests which suggest appropriate Zone 3 positioning
b) list 2 conditions where PAWP will read higher than LVEDP
c) list 3 causes of inaccurate cold thermodilution cardiac output measurements
d) Is the pulmonary capillary hydrostatic pressure normally higher or lower than the pulmonary artery wedge pressure ?
Following insertion of a pulmonary artery catheter
a) list 3 tests which suggest appropriate Zone 3 positioning
PAWP < PADP
PAWP alters by < 50% of applied PEEP
PAWP increases by < 50% of changes in alveolar pressure
O2 satn in the wedged position greater than unwedged position
On the CXR, tip of catheter below level of LA.
b) list 2 conditions where PAWP will read higher than LVEDP
Mitral stenosis
Atrial myxoma
Pulm venous obstruction – fibrosis, vasculitis
MR
non-zone 3 catheter placement
L to R shunt
COPD
IPPV+/-PEEP
c) list 3 causes of inaccurate cold thermodilution cardiac output measurements
1) catheter malposition,
2) injection mistakes (volume, injection speed, injectate temperature)
3) inaccurate thermistor
4) Tricuspid regurgitation
5) Intra-cardiac shunts
6) Wrong computation constant
d) Is the pulmonary capillary hydrostatic pressure normally higher or lower than the pulmonary artery wedge pressure ?
Higher
The PA catheter receives a thorough treatment in a series of chapters dedicated all to itself, somewhere deep in the Haemodynamic Monitoring section. . Appropriate zone positioning is also discussed.
The tip should be in West's 3rd Zone.
The following features confirm this position:
Situations where the wedge pressure is higher than the LV end-diastolic pressure:
Causes of inaccurate cold thermodilution cardiac output measurements:
Finally, pulmonary capillary hydrostatic pressure is usually higher than the wedge pressure. Normally, because of the venous resistance, Pcap will be higher than PAWP; in situations when this resistance is zero (i.e never) the two values might be equal.
An excellent online resource is available, which treats this subject with a massive amount of detail.
Also, the PA catheter section from The ICU Book by Paul L Marino (3rd edition, 2007) is a good source for most of this information.
Finally, Edwards Life Sciences has a booklet on invasive haemodynamic monitoring, which is a good solid overview.