Definition
Pleural fluid collection refers to any accumulation of liquid in the pleural cavity.

Causes
Pleural fluid collection can arise from multiple conditions, including hydrothorax (effusion/transudate), hemothorax (blood), pyothorax (pus), etc.

The most frequent causes are pleural effusion and hemothorax.

Hemothorax is predominantly caused by trauma to the thorax, whereas the causes of pleural effusion are multiple – including heart failure, infection, and malignancies.

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.

Are signs of pulmonary edema present or can pulmonary edema be excluded?

The following ultrasonographic signs are suggestive of pulmonary edema:
• Multiple B-lines (>2) between two costae in more than one view bilaterally

The following ultrasonographic signs rule out pulmonary edema:
• Absence of multiple B-lines between two costae in more than one view bilaterally

Definition
Pneumothorax is the presence of air in the pleural space.

Facts
Loss of contact between the visceral pleura and the parietal pleura and a gradual collapse of the affected lung can result from a continuous leak of air into the pleural space.

The application of ultrasonography allows rapid evaluation for pneumothorax and the sensitivity and specificity are higher than for conventional x-ray.

Can pneumothorax be confirmed or excluded?

The lung ultrasound signs Lung sliding/lung pulse, B-lines and Lung point are used in diagnosing or excluding pneumothorax. These signs are explained in the following topics.

Use the signs:
Ruling out pneumothorax:
• Presence of lung sliding/pulse or B-lines on the anterior part of the thorax

Suspicion of possible pneumothorax:
• Absence of both lung sliding/pulse and B-lines

Diagnostic of pneumothorax:
• Absence of lung sliding/pulse and B-lines on the anterior part of the thorax
• AND Presence of a “lung point”

Lung sliding
Lung sliding is a horizontal movement of the bright pleural line in synchrony with the respiratory cycle indicating sliding movement of the visceral pleura against the parietal pleura.

Lung pulse
Lung pulse is a variation of the same phenomenon, but is caused by projection of the heart beats through the lung tissue, causing small frequent movements of the pleural blades.
Lung pulse is only clearly seen when there is no respiration/ventilation.

Pathologies
Absence of lung sliding and lung pulse is seen in any condition causing the visceral and the parietal pleura to be either separated (e.g. pneumothorax) or joined (e.g. pleurodesis).

Presence of lung sliding or lung pulse is 100% specific and rules out pneumothorax at the location of the transducer.

What are B-lines?
B-lines are hyperechoic, laser-like, vertical artefacts that visually originate from the pleural line and continue to the bottom edge of the screen without fading in intensity.

B-lines and pneumothorax
Visualisation of the B-line artefact is only possible when there is no air between the two pleural blades and they are in contact with each other.

The finding of one or more B-lines can be used to rule out pneumothorax.

B-lines also play a role in diagnosing pulmonary edema (discussed later).

What is a lung point?
In pneumothorax, the edge of the collapsed lung will appear as a “lung point”.

The lung point represents the transition zone between the area of air-filled pleura and the reunion of the pleural blades.

The lung point moves back and forth in synchrony with the patient’s breathing.

Anterior to the lung point, with air-filled pleura, no lung sliding is seen.

Posterior to the lung point, with contacting pleural blades, normal lung sliding is seen.

Right at the lung point both can be observed as seen on the image to the right.

Lung point and pneumothorax
Lung point is diagnostic of pneumothorax.