VPOCUS: Introduction to Pleura and Lung Ultrasound, and Diagnosing Wet Lung
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Disclaimer..
- We are NOT Radiologists or Cardiologists
- We did not grew up with ultrasound probe in our hands
- Extent of our skill prior to our residencies was finding a bladder for cysto!!!p.1 -
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Evaluation of a focused assessment with sonography for trauma protocol to detect free abdominal fluid in dogs in motor vehicle accidents
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UNIVERSITY OF SASKATCHEWAN
Western College of Veterinary Medicine
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Universite de Montreal
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I want to be an ECC specialist!!!
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Disclaimer..
- We are NOT Radiologists or Cardiologists
- We did not grew up with ultrasound probe in our hands
- Extent of our skill prior to our residencies was finding a bladder for cysto!!!p.14 -
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VPCOS: Important points to remember
Not a formal radiographic or sonographic investigation (this takes years!)
- You don’t have to be a specialist to answer sonographically important clinically relevant questions that will help guide diagnostic tests and direct therapy!!!p.15 -
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VPOCUS: Important points to remember
Not a formal radiographic or sonographic investigation (this takes years!)
- You don’t have to be a specialist to answer sonographically important clinically relevant questions that will help guide diagnostic tests and direct therapy!!!Adjunct to triage examination: does not replace it!
- Triage dictates stabilization and order of VPOCUS:
- Answer the most urgent life-saving when stable
- Complete the remaining VPOCUS when stablep.16 -
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Formal ultrasound vs. point of care ultrasound
- Formal ultrasound
- Often consultative assessing all organs, anatomy and structures
- Often takes > 30- 60 minutes
- Requires years of training
- Often performed by specialists
- Cardiologists, radiologists
- Patients often stable
- Performed in radiology or cardiology
- Often placed in dorsal
- Often shaved
- Often uses gel- Point of care of ultrasound
- Assess key structures to answer specific closed or binary questions
- Performed in < 5 minutes
- Requires minimal experience
- Performed by non specialists
- ER doctors, general practitioners
- Patients often unstable
- Cage side exams in the ER/ICU
- Rarely if ever dorsal,
- Not shaved
- Often just alcoholp.17 -
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The value of asking binary questions…
What are all the sonographic diagnosis for vomiting in this hypotensive dogs
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Does this hypotensive vomiting dog have free abdominal fluid Y/N?- Human studies shows the likelihood of false negative and false positive results are markedly decreased when asking binary questions (avoid “fishing” expeditions)!
- Binary questions help you build confidence and expand your sonographic skill set
- Make sure each binary question asked is thoroughly investigated
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The value of asking binary questions…
-Why is this cat dyspneic
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In this cat that is dyspneic, does it have an enlarged left atrium Y/N?p.19 -
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General VPOCUS details
- CONTINUED STABILIZATION, TRIAGE
- To clip or not to clip?
- Alcohol vs. gel?
- Probe selection, frequency, depth?
- Right or left lateral vs. sternal vs. standing?
- Does anything change?
- ALWAYS CONSIDER WHERE PYTHOLOGY ACCUMULATES!!!!!Microconvex/curvilinear
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Avoid Dorsal
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Veterinary Point of Care Ultrasound
Applying binary questions to get raid simple answersGeneral Overview
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On the menu: Thoracic VPOCUS
- General technique, evolution and normal findings
1. Pleural space and lung pathology: is there …
a) Alveolar Interstitial Syndrome Y/N
b) Pleural effusion Y/N
c) Pneumothorax Y/N- KNOW YOUR BORDERS!
1. Caudal: Curtain sign
2. Cranial: Triceps/ scapula, thoracic inlet
3. Dorsal: Hypaxial Muscles
4. Ventral: Sternal (pectoral) MusclesNORMAL FINDINGS
1. Bat sign
2. Glide sign
3. A lines
4. B lines
5. Dry lung
6. Curtain signp.23 -
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Know your sonographically definable borders!
Caudal = curtain sign (red)
Dorsal = hypaxial/sublumbar (dark blue)
Cranial = 1) Shoulder flexor muscle (green)
2) Thoracic inlet (green)
Ventral = 1) Ventral pleural border (light blue)
2) Ventral lung border (pink)Lung shown in gray
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Normal Findings: Transthoracic
For orientation, start with the probe perpendicular to the ribs
Once you find the pleural line, probe orientation doesn’t matterWhat do we see when we place the probe perpendicular to the ribs?
Transthoracicp.25 -
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WHAAAAAATTTT?!?!?!
Transthoracic image
Remember that ultrasound has 2 key enemies in healthy animals:
1) Bone
2) Airp.26 -
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Normal Findings: Identifying the pleural line - the bat sign
Bat sign occurs because ultrasound waves can not travel through BONE or AIR when the probe is Transverse
Where the ultrasound beam can’t traverse:
bone = wings
air = body - pleural line!p.27 -
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Normal findings: Bat sign and the pleural line
- Pleural line: Bat Sign (gator sign)
- Ultrasound waves can’t go through bone!
- Rib shadows
- Ultrasound waves can’t go through air!
- 99.9% of the ultrasound beam is reflected at soft tissue air interface (e.g. at the plural line), rendering aerated lung impenetrable to ultrasound- All sonographic signs arise from the pleural line
LUS is a surface imaging techniquep.28 -
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Normal findings: identifying the glide sign
Parietal pleura (internal lining of the thorax)
Visceral pleura (outer lining of the lung)
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Parietal and visceral pleura can’t distinguished on ultrasound and form a single line: Pleural line
As they slide along each other motion is created = glide sign
Glide sign criteria:
1) Pleural must be in contact
2) Patient must breathe: dynamic finding!Rib Shadow
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- The bat sign, pleural line and glide sign
Pleural line
(parietal and visceral pleura)Rib Shadow
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Glide sign: Pearls and considerations …
- The glide sign is difficult to identify in patients that are panting or have rapid shallow breathing- Don’t move your hand! Only interpret the glide open sign when the patient is not moving (movement creates a false positive)
- Can change the probe/probe settings
- Check both sides of the thorax!
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Mechanism of A line formation
- A lines: Caused by reverberation artifact
- Beam bounces between two highly reflective surfaces
- A normal artifact of dry air- filled lung but also seen with pneumothorax
- Decay with depth- Ultrasound probe and pleura are highly reflective
- With every delay in the beam returning to the transducer an A line produced
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Key Point: A lines
- A stands for Air!!! Soft tissue air interface!
- A lines are present with aerated lung
- A lines are present with a pneumothoraxGlide sign criteria:
1) Pleural must be in control
Three main causes of separated pleura;
I. Pleural effusion
II. Pneumothorax
III. Pleural Space Masses*2) Patient must breathe: dynamic finding!
A lines do not help determine if pneumothorax is present or not!!Will you have a glide sign with pneumothorax?
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Normal findings: B lines
- B Lines (also called lung rockets, come tails, ring down artifacts)
- Occurs when fluid and air are next to each other at the lung surface
- Can occur naturally in 11 to 31 % of dogs and in 12 % of catsNORMAL FINDINGS
1. Bat sign
2. Glide sign
3. A lines
4. B lines
5. Dry lung
6. Curtain signp.35 -
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B line criteria for identification
- Occasional is normal
- *Vertical white lines
- *Originate at the lung surface
- *Moves with the pleura
- Usually extends to the far field
- Often obliterates A LinesB lines originating from the pleural line rule out pneumothorax at that probe!!!
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Normal findings: criteria of dry lungs
Glide sign: pleura are in contact + ? 3 B lines at the probe location, or only A lines = DRY LUNG
**The presence of 3 B lines or A-lines are in conjunction with a normal glide sign indicates “DRY LUNG” at that probe location
NORMAL FINDINGS
1. Bat sign
2. Glide sign
3. A lines
4. B lines
5. Dry lung
6. Curtain signp.37 -
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KNOW YOUR BORDERS!
1. Caudal: Curtain signThe normal curtain sign
Curtain sign: Transition between thorax and abdomen
NORMAL FINDINGS
1. Bat sign
2. Glide sign
3. A lines
4. B lines
5. Dry lung
6. Curtain signUltrasound beam strikes lung surface/air: A lines
Ultrasound beam strikes soft tissue
You can’t see the diaphragm when air/lung separates it from the chest wall!
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How stable the patient need to be to perform VPOCUS?
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How stable the patient need to be to perform VPOCUS?
If you can auscultate you can probably do VPOCUS!!
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Can scan patient in the oxygen cage
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On the menu: Thoracic VPOCUS
3. Pleural space and lung pathology: is there …
a) Alveolar Interstitial syndrome Y/N
b) Pleural effusion Y/N
c) Pneumothorax Y/NNORMAL FINDINGS
1. Bat sign
2. Glide sign
3. A lines
4. B lines
5. Dry lung
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- Sonographically detecting alveolar interstitial pathology
Many lung ultrasound protocols: all have 2 things in common
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Abnormal findings - excessive B lines
- > 3 B lines in a single window is for increased increased lung fluid
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Abnormal findings - excessive B lines
- Must consider history and clinical findings
- Vomiting dog with dyspnea and B-lines: think aspiration pneumonia
- Dog hit by car with B-lines: think pulmonary contusionsp.45 -
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Lung Ultrasound
- Can only detect lung injury at the periphery
- 95 % of human pathology that causes alveolar interstitial disease reaches the lung surface
- Therefore it is detectable via lung ultrasound
- Likely similar in veterinary patientsLUS is a surface imaging technique
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B lines: interstitial alveolar syndrome and rules out pneumothorax:
- Number of B lines appears to correlate with the severity of alveolar interstitial pathology
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Dry lung vs. Wet Lung
A
One B-lineB
Multiple B-lineC
Coalescing B-lineSeverity
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Thoughts?
Pitfalls: confusing the abdomen for lung (esp. The stomach on the left)
Curtain sign: left side
Curtain sign: right side
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Thoughts?
Pitfalls: confusing the abdomen for lung (esp. The stomach on the left)
Mcmurray 2015
Curtain sign: left side
Curtain sign: right side
Make sure you start over lung and know how to identify the curtain sign!!
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Some artifacts to note:
- Z-Lines: seen in 100% of the healthy dogs
- Mandatory Features of Z-Lines
- Arise from the pleural line
- Do not erase the A-lines
- I11- defined
- Independent of lung sliding
- Vanish after a few centimeters (2-5 cm)- Clinical Correlate: Z-Lines have no pathologic significance
- Found in both normal patients and in pneumothoraxIncidence of Z, I and B lines detected with point of care ultrasound in healthy dogs.
Martin A., Gouveia D., Cardoso A., Viegas I., Busoni V., Gommeren K., Boysen S.
EVECCS congress, Tallinn, June 2019p.51 -
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B vs. Z lines
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B line Summary
- Occasional B lines are normal
- ? 3 per site at only 1-2 sites per side of the chest
- Increased B lines indicate alveolar interstitial syndrome
- ? 3 per site
- Need to consider with history/physical exam findings
- Congestive heart failure: diffuse bilateral
- Aspiration pneumonia: initially ventral
- Can be unilateral with some pathologies- Don’t confuse Z lines for B lines
- Stop and access if they move with the glide sign and accentuate and obliterate A linesp.53 -
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On the menu: Thoracic VPOCUS
3. Pleural space and lung pathology: is there …
- Alveolar Interstitial syndrome Y/N
- Pleural effusion Y/N
- Pneumothorax Y/Np.54