Emergency
The subcostal 4-chamber view – tips and tricks
Tips and tricks
In order to obtain the subcostal acoustic window, sufficient pressure needs to be applied to the transducer so the ultrasound waves can travel under the rib cage as seen in the image below.
Asking the patient to bend his legs often helps as this causes relaxation of the abdominal muscles allowing for correct transducer placement.
Asking the patient to take a deep inspiration often improves image quality because the heart is displaced towards the abdomen and the transducer (remember to tilt the tail of the transducer upwards).
Once you have found an acoustic window, try optimizing the image (tilting and rotating) so the cavities are fully open. Often, a 10 degree counter-clockwise rotation is necessary.
If you get a lung-shadow across the apex, try sliding the transducer a little towards the patient’s right side.
RA: Right atrium
RV: Right ventricle
LA: Left atrium
LV: Left ventricle
PF – curtain sign
Where air is present, the image is obscured
In the normal aerated lung without pleural fluid, the lung is expanding in caudal direction with deep inspiration. The expanded lung interspaces between the transducer and the diaphragm making the diaphragm disappear in the ultrasound screen – this is called the ‘curtain sign’.
The curtain sign rules out significant amounts of pleural fluid in the phrenicocostal sinus.
With pleural fluid collection the consolidation of the lung and the fluid between the lung and the diaphragm prevent the lung curtain.
Not even in healthy patients can the curtain sign always be seen if the breathing is shallow.
Asking the patient to take a deep breath is often necessary when assessing for curtain sign.
PF – Summary
Rule in
Pleural fluid collection can be ruled in by ‘spine sign’ or visible fluid.
Rule out
Significant amounts of fluid in the pleura can be ruled out by ‘lung curtain’ and absence of ‘spine sign’, when the patient is positioned correctly.
Remember that fluid is dependent upon gravity and is found at the lowest point accessible.
In a patient in the Trendelenburg position, the fluid is found in the apical part of the pleural cavity and not in the basal part above the diaphragm.
PF – Visible fluid
Visualising pleural fluid
In most cases, a pleural fluid collection is clearly visible as a black border just above the diaphragm, often with consolidation of the basal part of the lung.
Positioning is key
Remember that fluid follows gravity.
If no fluid is seen in a patient in the Trendelenburg position, fluid can still be hidden in the apical part of the pleural cavity – try repositioning the patient to a horizontal or semi-upright position.
PF – Spine sign
Normal ultrasonographic image
The medial border of the pleural cavity being the thoracic spine and mediastinum is normally not seen with ultrasonography because the ultrasound waves do not travel through the aerated lung tissue.
When fluid is present
With pleural fluid replacing aerated lung tissue in the phrenicomediastinal recess, the mediastinum and the thoracic spine become visible and can be seen as a medial border of the cavity – above the diaphragm.
This is called the ‘spine sign’.
PF – The focused question
Can pleural fluid be confirmed or excluded?
The following signs confirm a pleural fluid collection:
Summary – focused ultrasonography of the lungs
You have now learned how to:
Obtain the:
Pulmonary edema (PE)
Pulmonary edema is fluid accumulation in the air spaces and parenchyma of the lungs.
“Cardiogenic pulmonary edema” is caused by failure of the left ventricle of the heart.
“Noncardiogenic pulmonary edema” is due to a number of other causes than left ventricular failure, including toxic lung damage and fluid overload.