The lung curtain does get in the way here, so run M-mode low down to catch the diaphragm.
We use the vital organ (liver or spleen) as our scan window and discriminator between chest cavity and abdominal cavity👍
Speaking of M-mode, it is sensitive for movement / gaging distance. So after you get the B-mode view, run it through the diaphragm👍
⭐️ We can measure the diaphragm’s EXCURSION.
>1cm indicates good spontaneous effort and should mean ‘weanability’, from the ventilator.
Next, position 2:
Place the probe mid clav/SC/marker to 12 O’clock.
Here, we see the muscle bulk to the diaphragm and can appreciate its layers + thickening.
Inspiration -> it thickens
Expiration -> it thins
⭐️ This is diaphragm thickening index or Tdi:
Thin/thick x 100
Run your m-mode through now, we can really appreciate this.
Here we see this respiratory muscle thicken on a spont breath in and thin down on passive recoil expiration.
Tdi >30% = no sonographic diaphragmatic dysfunction. It is 71% specific for extubation success 👏
Finally, position 3:
Probe mid ax/SC /marker to 9 O’clock.
Just another view and not a million miles from a cardiac subcostal. We can see the heart, part of the IVC and there’s minimal lung curtain interference.
Yup, run that M-mode through to appreciate movement and measure it again.
There isn’t heaps of outcome data, but assessment to note extreme wasting, poor excursion and poor Tdi certainly predict success or failure of SBT and liberation from the vent!
Where do we scan then?? Linear/curvilinear or phased probe positions shown👍👇
We don’t tend to use linear for the basal sections, as you need depth for the PLAPS points. To see the pleura clearly, minimise depth and drop gain down, you get a real concept of sliding on the screen.
Pleural slide disappears as the parietal and visceral pleura separate. So, a static washing line is seen between the rib pillars 👇. The more you see, the more you recognise. Decompress IF your patient is compromised. It’s more sensitive than CXR!
Probe position shown with marker to right shoulder, left Parasternal edge; roughly at intercostal spaces 2-3/3-4🤷♂️
2/13
What should you see on ultrasound, and the associated sono anatomy🤔
BTW, this is the only basic position you need for this. Dipping the tail or lifting the tail then get you inflow and outflow views. This is more advanced. #FUSIC
3/13
Next, the Parasternal short axis (PSAX) - Mitral view
If you’ve lined up the aortic and mitral valves in the centre of the image on PLAX, a simple rotation of the probe through 90 degrees gives you your view🤛👍
Apply careful firm pressure to displace pesky bowel gas. I start at the umbilicus; you can find the vertebral body easily here. You can then move up or down, tracing the vessel. The aim is to see as much of the vessel as you can. Marker - right (SAX) or to the head (LAX).
3/7
High Subxiphoid SAX
Find that vertebral body shadow again, you will see the aorta and IVC just above this. We are looking for the classic ‘seagull’ sign -
Here we slide the probe along a slug trail of gel, quite crudely, across a wide area of the body. This is often used to ‘window shop’, for structures we can’t see at first. When they snap into view, we can fine-tune movements 👍 Also allows view of larger organs.
3/7
ROCKING
Classic example here is when we get an apical view of the heart. At first, the heart may not be in line with the scan field. We can ‘swing’ it into view, so it appears more square on the screen. Makes parallel measurements more accurate and things less off-axis🤷♂️