Chapter 7: Thorax

INTRODUCTION

Thoracic ultrasound is increasingly recognized as a valuable tool for evaluating the critically ill, injured, or dyspneic patient. The use of thoracic ultrasound was first reported in veterinary medicine in 1986 when diagnosing a pneumothorax.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 traditionally seen as “noise” became useful information. The tissues and interfaces reflect the sound waves exhibiting different types of reliable and reproducible 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 pulmonary point-of-care ultrasound (POCUS). Over 300 publications were reviewed. From this, a consensus statement was written.³ The statement reflects the strong evidence and overwhelming expert support for the use of ultrasound to evaluate the lungs in critically ill and injured patients.⁴⁻⁶

CLINICAL CONSIDERATIONS

The chest radiograph is one of the most iconic elements of medical practice. It is understandable that many providers resist utilizing ultrasound for lung pathology given the ingrained role of radiography. The advantages of lung ultrasound, however, outweigh the challenges of learning a new practice.

POCUS 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. POCUS increases patient–provider interaction during clinical encounters, which improves patient satisfaction.⁷ Furthermore, the pulmonary applications of ultrasound provide accuracy superior to plain films and comparable to computed tomography (CT), without exposing the patient to ionizing radiation.⁸⁻¹⁰

POCUS provides an immediate diagnostic answer without the delays of media processing, transport, and consultative interpretation. This is particularly invaluable in critically ill and injured patients.

Ultrasound plays a critical role in diagnosing a wide variety of lung pathology, including pneumothorax, hemothorax, interstitial syndromes, pleural effusions, pneumonia, pulmonary edema, and pulmonary contusions.³ Ultrasound has been found to be helpful in identifying pulmonary emboli as well.¹¹ POCUS provides the clinician with immediate and accurate data regarding lung pathology.

CLINICAL INDICATIONS

Consider thoracic ultrasound a first-line diagnostic modality for critically ill patients.³ POCUS, particularly lung ultrasound, is widely referred to as “the new stethoscope,” but this is a misconception. POCUS is a diagnostic test, which demonstrates its maximal value when combined with a thoughtful history and physical examination.

Clinical scenarios for performing thoracic ultrasound include the following:

• Acute dyspnea

• Chest wall trauma

• Pneumothorax

• Alveolar-interstitial syndromes: cardiogenic pulmonary edema, acute respiratory distress ...