Point-Of-Care Ultrasound In the Evaluation of Acute Respiratory Distress Syndrome

Introduction:

Point-of-care ultrasound (POCUS) is a valuable tool in emergencies that provides a quick diagnosis. It is a test performed at the bedside to diagnose the abdomen. These POCUS machines are ultrasound machines that use sound waves, and these are affordable, movable, and can also be used by radiologists who are less trained. The article talks in detail about the point-of-care ultrasound in the evaluation of acute respiratory distress syndrome (ARDS).

What Is Point of Care Ultrasound (POCUS)?

Point-of-care ultrasound is a type of ultrasound examination that makes decisions on the spot and is performed at the bedside by a physician as a part of a clinical examination. It can demonstrate blood flow and bowel movements. POCUS gives better diagnosis and, therefore, better patient care. The images that are produced are different due to the different densities. Black images demonstrate fluids such as urine or blood. Gray images demonstrate soft tissues such as the liver. White images without a shadow demonstrate fibrous tissues, and white images with a shadow demonstrate stones and bones.

What Is Acute Respiratory Distress Syndrome (ARDS)?

ARDS is a severe inflammatory condition of the lung that occurs suddenly and causes respiratory failure and impaired oxygenation. It can be caused by a direct source such as pneumonia (infection of the alveoli or air sacs of the lungs) and toxic gas inhalation or an indirect cause such as trauma and sepsis (a condition in which due to an infection, the body responds improperly and in severe cases causes organ dysfunction). The use of lung ultrasound (LUS), which is non-invasive, can diagnose rapidly without any involvement of radiation and is more efficient than conventional X-rays.

How Is Point-Of-Care Ultrasound (POCUS) Used in the Evaluation of Acute Respiratory Distress Syndrome (ARDS)?

POCUS is an efficient tool that can help in the evaluation of ARDS and can provide real-time imaging at the bedside. Apart from this, it can also help in evaluating the pathology of the lung, and cardiac function, along with complications of blood vessels that are associated with ARDS. It can also help in differentiating noncardiogenic pulmonary edema (swelling) and cardiogenic pulmonary edema. Some of the ways that POCUS can be used are:

Lung Ultrasonography: Heath providers can use POCUS, which can provide a picture of lung pathologies and their surfaces. The ultrasound findings include:

• Loss of lung sliding, which is the movement between the pleural lines during respiration, is absent. This occurs due to lung stiffness.

• Presence of B lines which are vertical artifacts that are produced from the pleural lines. These B lines indicate interstitial lung edema (swelling due to the presence of fluid). One of the common features of ARDS is lung edema (too much fluid accumulation in the lungs).

• The presence of areas of consolidation is seen as hypoechoic (appears darker) and echogenic (appears bright) regions. Lung consolidation is when the small sacs of the airways are inflamed and contain fluid such as blood or pus.

• The alveolar interstitial syndrome is characterized by the presence of lung rockets bilaterally, which contain more than two B-lines.

• Heterogenous distribution is more commonly seen in the anterior area.

• The visceral-parietal pleural (membranes that cover the lungs) interface looks irregular or thickened.

• The absence of pleural effusions (fluid in the pleural space) is commonly seen in cardiogenic pulmonary edema.

• There is an absence of high levels of cardiac filling pressure.

• In the case of mild ARDS, the A-lines (a type of ultrasonic artifact that occurs in an aerated lung) are seen in the front portion.

• In the case of severe ARDS, the BB lines are increased, and the A lines and B lines are decreased.

Echocardiography: POCUS not only helps in the examination of the ARDS but also can help in evaluating the cardiac function and hemodynamic (flow of blood) status of the individual. Therefore, this helps in the evaluation of the right ventricular function, which is mostly affected in the case of ARDS. ARDS causes right heart strain leading to right ventricular dilation (enlargement of the right ventricle) and decreased systolic function (inability to pump efficiently).

Vascular Ultrasound: POCUS also helps in the evaluation of complications that arise in ARDS patients called deep vein thrombosis (DVT, a condition in which there is a formation of blood clots in the deep veins) in the lower extremities. Therefore, POCUS can help in anticoagulation treatment.

Others: POCUS helps in visualizing blood vessels and guiding needle placement for fluid replacement or drug delivery and, therefore, can assist in the identification of veins for IV (intravenous) cannulation, central venous catheter (CVC) insertion, intraosseous access (placement of the needle into the bone), and arterial cannulation. It also helps guide thoracentesis (removal of fluid from the outer membrane of the lungs). Apart from these, it can be helpful in difficult cases such as obese patients or scarring for vascular access. It can help avoid complications such as pneumothorax (air collection outside the lungs but confined to the pleural cavity) due to procedural complications, accidental puncture of adjacent structures, nerve injury, or hematoma (collection of blood outside large blood vessels due to injury or trauma).

What Are the Limitations of Point-Of-Care Ultrasound?

The limitations include:

• The use of POCUS requires sufficient training and expectation to interpret the images properly. Therefore, operator skill is important while performing the procedure.

• Limited image quality can interfere with the interpretation. Factors that can affect the patient include the thickness of the chest wall, the patient’s body status, the position of the patient, and the presence of air.

• A limited view of the field can limit the ability to identify less common causes of ARDS.

• POCUS cannot provide information on gas exchange. Therefore additional tools such as blood gas analysis are required.

• In some situations, X-rays or CT (computed tomography) scans may be required to evaluate the lung pathology.

Conclusion:

POCUS is an important diagnostic tool that should be used by all primary healthcare sectors. It can help in the examination of not only ARDS but also other emergency cases such as cardiac, obstetric, trauma, and abdominal evaluations. It also provides real-time visualization to treat emergencies such as needle placements for fluid replacement or delivering drugs, enhancing patient safety. However, this requires appropriate training by the health sector staff.