Lung US Flashcards
Indications
- known or suspected blunt chest trauma
- penetrating chest trauma
- eval* of haemothorax (more sensitive & faster
- determination of urgent chest tube placement
- eval* pneumothorax (=/more sensitive to CXR)
- rule in occult pneumothorax; esp Pts req PPV or Helo Tx
- when no CT is avail*/quickly accessible
- guide fluid pleural aspirations
- closed intercostal tube drainage place selection
- guide biopsy of peripheral lesions
Contraindications
Diagnostic quality may be limited on the background of pre-existing chronic lung path* eg; pul* fibrosis
Transducer selection
- req generous field of depth for recognition & interp* of artefacts (use to identify pathology)
- lower frequency Td (</= 5 MHz) will give good penetration without excessive loss of image quality due to attenuation
- general curvilinear Tds apply here: rounded face may be more comfortable for scanning as ribs may be painful
- microconvex Tds (paed probes) have add* advantages of a small foot print for better IC imaging & application in younger Pts
- high Freq* TDS may be helpful for the search of lung comets & detailed visualisation of pleural layers & small subpleural lesions
- phased-array Tds for Echocardiographic applications could be used (provide diff you visualisation of the near field tho, limiting Dx capacity; eg; consolidation/atelectasis)
Exam Prep, Positioning & Limitations
Exam:
- LUS setting built in
Positioning:
- supine, seated, reclined, lateral decubitus pos* etc
Limitations:
- Pts w Dyspnoea
- limited Pt positioning; supine Only
- Pt interventions: ETT/drains
- Pt access in smaller rooms or emergency sites
A-lines
Horizontal lines (roughly parallel to the chest wall) that are brightly echogenic & located between the rib shadows when the probe is position longitudinally
- normal lung will have A-lines
B-lines
Vertical echogenic lines extending from the pleural line to the lower edge of the screen without fading
- B-lines tend to erase A-lines
- move synchronously w lung during respiration & show ‘lung sliding’
- comets Vs long B-lines
E-lines
Caused by subcutaneous emphysema
- appear similar to B-lines BUT start superficial to the pleural line
Z-lines
Found in normal lung, as well as those w pneumothorax
- less echogenic than the pleural line
- usually taper off after 2-4cms
- do not erase A-lines
- do not move w lung sliding
Lung sliding
Created by movement of lung visceral pleura moving relative to the parietal pleura during resp*
M-mode assists in clarifying lung sliding
May disappear if air, blood, pus or other fluid fill the potential space between the pleura
Lung pulse
Vertical movement of the pleural line synchronous to the cardiac rhythm
- more commonly seen on L hemithorax
- caused by transmission of heart motion thru consolidated/motionless lung
Lung point
Area where normal lung sliding is seen in an otherwise non-sliding lung
- presence of lung sliding in one area (the long point) & not another is a strong indicator of a pneumothorax
- a large pneumothorax may Not exhibit this sign
Regions to scan
6 regions to be systematically examined:
- upper & lower costophrenic recesses of the anterior, lateral & posterior chest wall bilaterally
Regions of interest
Above pleural Line:
- air
- foreign bodies
Sub-pleural abnormalities:
- consolidation
Pleural line abnorm:
- thickening, nodularity, or irregularity of the pleural line increases suspicion of malig & inflamm*
Lung sliding:
Loss of lung sliding:
- occurs when there is no dynamic interaction of the visceral & parietal pleura
- best appreciated w careful visualisation of the pleural line
- M-mode used to document lung sliding: seashore sign Vs stratosphere sign
Poss causes:
- pleural separation; pneumothorax, pleural eff* or Dx
- pleural adhesions; pneumonia, acute lung inj, pleurodesis, pleural fibrosis, ILD, fibrotic lung Dx
- non-ventilation; apnoea, sever hyperinflation, asthma, COPD, ETT comps (R main bronchus), atelectasis
Below pleural line:
- A-lines
- B-lines
Lung US Dx signs
Pleural fluid:
- usually appears as anechoic or hypoechoic compared to the liver, area surrounded by typical anatomic boundaries
- margins may be angular, in keeping w the fluid filled spaces
Fluid is defined by:
- finding a atomic boundaries that surround the effusion
- dynamic chats sticks typical of fluid; gravity dependant, movement of echogenic material within the fluid, changes in shape of pleural fluid w resps.
Atypical fluid:
- morbid obesity & chest wall oedema may degrade US image quality
- complex loculated effusions may be hyperechoic & located in a non-dependentpart of the thorax
Haemothorax/Empyema:
- may be isoechoic w the liver & have No dynamic changes w resps
Malignant pleural effusion:
- presence of pleural or diaphragmatic thickening/nodularity, or an echogenic swirling pattern, is suggestive of same
Air & fluid together:
- may present a complex image - consult radiology (eg; haemopneumothorax)
