Year : 2014 | Volume
: 9 | Issue : 4 | Page : 185--186
Thoracic ultrasound: Picture worth a thousand sounds
Ajit Moghekar, Atul Mehta
Associate Staff, Department of Critical Care, Respiratory Institute, Cleveland Clinic, Cleveland, Ohio 44195, USA
Staff Physician, Respiratory Institute, Cleveland Clinic, Cleveland, Ohio 44195
|How to cite this article:|
Moghekar A, Mehta A. Thoracic ultrasound: Picture worth a thousand sounds.Ann Thorac Med 2014;9:185-186
|How to cite this URL:|
Moghekar A, Mehta A. Thoracic ultrasound: Picture worth a thousand sounds. Ann Thorac Med [serial online] 2014 [cited 2020 Sep 25 ];9:185-186
Available from: http://www.thoracicmedicine.org/text.asp?2014/9/4/185/140118
"I take an active role in my imaging and how I look."
Pulmonologists have traditionally relied on their lung auscultation and percussion skills at the bedside to evaluate various lung pathologies. Although useful, these skills have been associated with interexaminer variability and inaccuracies. ,,, To avoid these issues, imaging modalities such as chest radiographs, computed tomography (CT) scans, and ultrasound are used. Chest radiography provides limited information and can be particularly challenging in a critically ill patient.  On the other hand, imaging by CT can be time consuming, involves significant exposure to radiation,  poses a risk of transportation of a critically ill patient, and its inappropriate use increases healthcare costs. Despite these limitations, radiographs and CT scans are invaluable for evaluating lung pathology. However, there remains a need for an imaging technology that not only provide useful and accurate information but is also cost effective and free of risk to the patient. With significant improvements in image quality and ease of use, ultrasound has the ability to address some of the limitations of chest radiographs and CT scans. Thoracic ultrasound provides a dynamic evaluation of the pleural space and the lung, without radiation and therefore is considered safe. This is especially useful for repeat evaluations after therapeutic interventions. Additionally, compact and easily portable machines have now enabled physicians to themselves perform the exam and interpret the images in real time to make instant clinical decisions at the bedside. Thus the 'point of care' ultrasonography is now a powerful tool for the intensivist and the pulmonologist, which has the potential to improve clinical decisions and consequent patient outcomes.
While the use of ultrasound to evaluate pleural effusion and guide thoracentesis was first described in 1967,  ultrasound was deemed useless for the evaluation of lungs due to the presence of air and surrounding bony chest wall. Studies by Daniel Lichtenstein during the 1990s and early 2000 have revolutionized the use of ultrasound to assess lung parenchyma and have demonstrated its utility in the evaluation of pneumothorax, alveolar consolidations, alveolar interstitial syndromes, and rapid assessment of acute respiratory failure. ,,,, Thus, while these newer applications are still gaining widespread acceptance, the role of ultrasound in evaluating pleural space diseases is widely recognized. Ultrasound has greater sensitivity than chest X-ray including lateral decubitus film to detect pleural effusions.  Ultrasound also provides a dynamic image of the pleural fluid with underlying moving lung as compared to a static CT scan image. Ultrasound thus provides greater clarity than CT scans in defining underlying septations and debris within the fluid,  which when present on an ultrasound exam are always exudates.  The use of ultrasound to guide thoracentesis has shown to reduce the rates of pneumothorax and increase success of the procedure. , Additionally, ultrasound is useful in guiding chest drainage for parapneumonic effusions and empyema.  In the critical care setting, ultrasound can be safely used to drain pleural effusions in patients on mechanical ventilation thereby highlighting its use in this patient population where any complications can be catastrophic. , To that end, the British Thoracic Society recommends routine use of ultrasound for pleural procedures in the critical care setting.  As such, today in the developed countries thoracentesis is seldom performed without ultrasound guidance.
Numerous studies to date have demonstrated utility of ultrasound to rapidly detect or exclude the presence of pneumothorax, particularly in a setting of chest trauma. Interestingly, ultrasound was first used to diagnose pneumothorax in a horse in 1986.  A recent meta-analysis concluded that bedside ultrasonography performed by clinicians has higher sensitivity and similar specificity compared with chest radiographs for the diagnosis of pneumothorax. This analysis also showed that operator experience critically impacts the use of ultrasonography in pneumothorax.  In this regard thoracic ultrasound can eliminate need for fluoroscopic examination or the chest X-ray which are frequently performed following bronchoscopic lung biopsy.
Lung ultrasonography if applied in a stepwise manner can help a clinician make a rapid and accurate diagnosis in patients with acute respiratory failure. , The literature on lung ultrasound continues to expand rapidly with novel applications. Recently, it was reported that ultrasound can be used as an aid to titrate positive end-expiratory pressure (PEEP) in patients with ARDS (acute respiratory distress syndrome) at the bedside. At our institution we are exploring the use of ultrasound in early detection of subclinical rejection following lung transplantation. Given the accumulating evidence in support for lung ultrasonography, the first International evidence-based recommendations for point of care lung ultrasound have recently been published in an attempt to standardize its application. 
Similar to bronchoscopy, thoracic ultrasonography (including pleural and lung ultrasound), though operator dependent has a potential to become a ubiquitous tool in the armamentarium of the practicing pulmonary and critical care physicians. With an increased number of trained physicians, it is expected that thoracic ultrasound will reduce the need for chest radiographs and CT scans, thereby decreasing radiation exposure and associated healthcare costs. However, due to substantial dependence on the operator for its use, adequate training and standardization for prudent use are urgently required. In the United States, training for point of care ultrasound is therefore becoming an essential component of most pulmonary and critical care fellowships. Going a step further, some medical schools are providing their students with hand-carried ultrasound equipment.  As noted in the 2004 conference, on compact ultrasonography by the American Institute of Ultrasound Medicine, the concept of 'ultrasound stethoscope' may soon be a reality  wherein rather than listening to breath sounds with a stethoscope, we will be visualizing them with an ultrasound. Hence, in this context, 'a picture will be worth a thousand sounds and a movie worth a million.'
We thank Nirupama Mulherkar, PhD for writing assistance.
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