Full BSE guide for pulmonary hypertension is extensive and takes time.
Many critical care interventions can increase pulmonary pressures e.g. IPPV and pulmonary vascular resistance.
PVR increased by:
- Extremes of lung volume (lowest around FRC)
- Decreased pulmonary blood flow – increased flow and pressure will recruit closed vessels.
- Haematocrit & blood viscosity.
- Vasoconstrictors, 5HT, histamine.
- Alpha stimulation – e.g. noradrenaline. Consider using vasopressin first line if pre-existing pulmonary hypertension (increases smooth muscle tone and BP but causes pulmonary vasodilatation).
- Local/regional PVR increased by PE, compression (pleural effusion/atelectasis).
PVR decreased by:
- Low TV and pressures.
- Improving cardiac output (dopamine, dobutamine, milrinone etc).
- Reducing blood viscosity.
- Avoidance of acidosis.
- Vasodilators (sildenafil, prostacyclin, inhaled nitric oxide).
Remember RV and PA must be considered a coupled unit.
All measures estimating pressure are intrinsically linked to R heart system and valves. Presence of pulmonary stenosis or severe TR will render calculations inaccurate.
Includes following assessments:
- Pulmonary artery systolic pressure (PASP)
- Pulmonary artery diastolic pressure (PADP)
- Mean pulmonary artery pressure (MPAP)
A comprehensive pulmonary hypertension assessment includes:
- RV/LV diastolic ratio
- RVOT acceleration time.
- Eccentricity index.
- TR Vmax.
- RV dimensions. S & D areas.
- IVRT measured with PW TDI.
- RA volume.
- RV MPI (Tei index).
Pulmonary artery systolic pressure:
Measure TR Vmax.
Bernoulli equation is automatically applied by machine to turn the Vmax into a pressure gradient.
Gradient = 4 x V^2
This value is the gradient between the RVSP and RAP
Gradient = RVSP – RAP
Therefore: RVSP = gradient + RAP
This relies on there being no pulmonary stenosis which would produce a gradient between RV and PA. If no PS can assume that PASP = RVSP.
RA pressure is estimated using techniques in described in relevant section. If CVP then obviously this is more accurate.
If PS – peak gradient across the valve will be difference between RVSP and PASP.
PASP = RVSP – PS gradient
Normal PASP is 15-30mmHg.
Pulmonary artery diastolic pressure:
Relies on presence of pulmonary regurgitation.
Use CW to measure PR Vmax in either parasternal RV outflow view or PSAX view.
Again machine will use Bernoulli to calculate pressure gradient between PA and RV.
Gradient = PADP – RVDP
PADP = gradient + RVDP
RV is assumed to be the same as RAP
PADP = gradient + RAP
Normal PADP is 5-15mmHg
Mean pulmonary artery pressure:
Calculate based on above:
MPAP = ((PASP = PADP) / 3) + PADP
Normal is 15mmHg
Pulmonary hypertension when MPAP >25.
Usually means PASP of >40.
Additional features of pulmonary hypertension from full protocol:
Toggle for images/info.
- PLAX – evidence of RV dilation and hypertrophy.
- PLAX RV inflow – dilation and hypertrophy. TV annular dilation. Vmax/PG in eccentric jets.
- PLAX RV outflow – PV annular dimension. PV assessment. MPA dilation (though not diagnostic/sensitive as standalone feature).
- PSAX – similar info to what is seen in PLAX views.
- Eccentricity index in systole and diastole. Right Ventricular Size and Function
- PSAX for pressure/volume overloading
- RVOT acceleration time – PW at PV leaflets. AT shortens with pulmonary hypertension Normally >140ms. Colebourn book uses normal as >110ms and <105ms as abnormal.
- Pulmonary regurgitation CW to measure PR end diastolic velocity (PAEDP) and PR Vmax (MPAP):
- Measurement of PVR.
- A4C – visual assessment.
- CW of TR.
- Severity of TR
- Measure RA area and volume
- TDI of tricuspid annulus – RVS’
- MPI (Tei index) Right Ventricular Size and Function
- Subcostal view for measurement of RV free (inferior) wall.
- IVC dilation & estimation of RA pressure. Right Atrium
V good youtube playlist showing the pulmonary hypertension protocol.