The lungs have traditionally been considered a barrier to ultrasound imaging because large changes in acoustic impedance result in ultrasound reflection and the acoustic impedance of air is extremely low compared with anatomic tissues. It was not until 1986 that the diagnosis of pneumothorax with ultrasound was reported in veterinary medicine.1 In 1995, Lichtenstein published his landmark paper describing the most fundamental element of pulmonary ultrasound, the lung sliding sign.2
Lichtenstein opened the door for a large body of research based on the analysis of artifacts generated by the nearly complete reflection of the ultrasound beam when it encounters the interface between soft tissue and aerated parenchyma of the lung. What was initially seen as “noise” became useful information. The tissues and interfaces reflect the sound waves exhibiting notably different kinds of “noise” artifacts in several normal and pathologic conditions.
In 2011, the International Liaison Committee for the International Consensus Conference on Lung Ultrasound (ICC-LUS) critically evaluated the literature regarding point-of-care lung ultrasound. Over 300 publications were reviewed. From this, a consensus statement was written.3 Overwhelmingly, the recommendations support the use of ultrasound to evaluate the lungs in critically ill and injured patients.4–6
The chest radiograph historically is one of the most iconic elements of the practice of medicine. It is understandable that many physicians resist ultrasound for lung pathology given the ingrained role of radiography. The advantages of lung ultrasound, however, outweigh the challenges of learning a new practice.
Sonography has many advantages over plain films and cross-sectional imaging. It is highly portable allowing its use in situations of limited resources as well as austere conditions. Ultrasound is feasible at the bedside and improves interaction during clinical interview increasing patient satisfaction.7 Furthermore, the pulmonary applications of ultrasound consistently present levels of accuracy superior to plain films and comparable to CT scans, without exposing the patient to radiation.8–10
Point-of-care ultrasound provides an immediate diagnostic answer without the delays of media processing, transport, and consultative interpretation. This is particularly important in the critically ill.
Ultrasound plays a critical role for diagnosing lung pathology, including pneumothorax, hemothorax, interstitial syndromes, pneumonia, pulmonary edema, and contusion.3 Point-of-care ultrasound provides the clinician with immediate, accurate data regarding lung pathology.
Pulmonary ultrasound should be considered a first-line diagnostic modality for critically ill patients.3 Point-of-care ultrasound, particularly lung ultrasound, is widely referred to as “the new stethoscope.”
Clinical scenarios for performing lung ultrasound include
- Evaluation of acute dyspnea
- Airway management
- Alveolar-interstitial syndromes: cardiogenic pulmonary edema, acute respiratory distress syndrome (ARDS), pulmonary contusion, and other interstitial syndromes
- Consolidations: pneumonia, atelectasis, other nonpneumonic consolidations
- Neonatal applications
- Pleural effusions
Evaluation of Acute Dyspnea
Critical ultrasound achieves its prime role in the hands of the emergency and critical care physicians when ...