POINT: Should Point-of-Care Ultrasound Examination Be Routine Practice in the Evaluation of the Acutely Breathless Patient? Yes
POINT: Should Point-of-Care Ultrasound Examination Be Routine Practice in the Evaluation of the Acutely Breathless Patient? Yes
The acutely breathless patient likely elicits almost as much discomfort for the physician as the patient feels. The time to an initial differential diagnosis, and hopefully an accurate singular diagnosis, may prove lifesaving. While the art and science of the time-honored tradition of the history and physical examination will not be disputed, rapid blood work analysis, radiologic assessment, and echocardiographic assessment have become paramount in solidifying a diagnosis. For the purpose of this debate we will assume that the acutely breathless patient has some degree of hypoxemia, presuming that breathlessness in the absence of hypoxemia will move the physician away from the pulmonary system in order to focus on nonpulmonary causes such as cardiac dysfunction and metabolic, neurologic, and psychological conditions.
To help elucidate what is causing the patient’s breathlessness, we ask ourselves a series of questions. Are the lungs “wet”? If so, is it unilateral or bilateral wetness? Is there alveolar consolidation, or are there pleural effusions? Is there airway disease or pulmonary vascular disease? With this in mind we can now turn to our methods of diagnosis, and review these methods regarding accuracy, sensitivity, specificity, ease of performance of the diagnostic test both for the patient and the provider, and whether or not there is clinical and time dissociation inherent with each diagnostic modality.
While the authors of this manuscript proudly declare that we each own a stethoscope, and on occasion use it either to detect airway disease, such as wheezing, or to pretend to hear the various cardiac murmurs, several studies declare that the stethoscope is essentially “dead.”1 Many colleagues may disagree with this statement, but then again these are likely clinicians not learned in the ways of thoracic ultrasound. If we accept that while we will use our stethoscope in the initial physical examination, we would also agree that an imaging modality is necessary. Chest radiographs will of course be taken, and an obvious abnormality will be picked up easily; however, the diagnostic accuracy is not great. For instance, pulmonary edema may be cardiogenic or noncardiogenic, a hazy basilar opacity may be a pleural effusion and/or a consolidation, and an overpenetrated radiograph may not pick up early edema of the lung. Chest CT imaging, especially with intravenous contrast, is considered by many to be the gold standard for thoracic imaging and is used as the comparator for many studies to decide the accuracy, sensitivity, and specificity of the studied imaging modality. We think that all would agree that too many chest CT scans are produced each year, especially to rule out a pulmonary embolus. While the chest CT scan will provide us with accurate details of both the pulmonary parenchyma and pleural space, overreliance on this test leads to overexposure to ionizing radiation, contrast, and the need to transport patients with potentially life-threatening diagnoses. So, what are we left with?
Thoracic ultrasound, of course. We consider thoracic ultrasound to encompass lung and pleural ultrasound, echocardiography, and lower extremity compression ultrasound of the deep veins. There is no other imaging modality that can be performed at the bedside by the treating physician without any clinical and time dissociation inherent to consultative radiology and echocardiography, where an immediate diagnosis and therapeutic plan may be rendered. Consider a real case we recently encountered: a young man with sickle cell S disease who was seen in the ED with acute breathlessness and hypoxemia. His history included asthma, acute chest syndrome, and avascular necrosis of the left hip. Physical examination revealed crackles at the lung bases and some expiratory wheezes diffusely. He had clear laboratory evidence of hemolysis. The emergency room and hematology physicians were worried about an asthma exacerbation, acute chest syndrome, pneumonia, or a pulmonary embolus. A chest radiograph was read as indicating potential early pulmonary edema. A CT angiogram of the chest was ordered, along with a lower extremity venous compression study. ICU consultation was requested because of his increased work of breathing.
Point-of-care ultrasound (POCUS) is easy to learn, highly sensitive, and specific for diagnosing the etiology of acute respiratory failure. In addition, it is performed at the bedside by the treating physician, who has firsthand knowledge of the presenting history and physical examination. POCUS is now widely available throughout most health systems. Daniel Lichtenstein, considered by most to be the father of POCUS, has published scores of articles dating back decades on the usefulness of bedside ultrasonography. In his landmark study, the BLUE protocol, a correct diagnosis of acute respiratory failure was made in over 90% of cases.2 There is overwhelming support in the medical literature for the use of POCUS in every patient who presents acutely breathless, as well as any patient in cardiopulmonary failure.3, 4
Let us remember the patient above and illustrate how we used POCUS to help make a diagnosis at the bedside and begin immediate treatment. First, lung ultrasonography was performed and revealed bilateral anterior and lateral “B lines,” or comet tail artifacts. This means with high accuracy that the patient had a pulmonary edema pattern, bilaterally.5 Further, the pleural line was “lumpy bumpy,” or not smooth, indicative of an inflammatory or infectious process.6 There were no pleural effusions or alveolar consolidations. His goal-directed echocardiogram showed a large right ventricle with decreased function, and preserved and slightly hyperdynamic left ventricular function. There was evidence of pressure overload imposed on the right ventricle, as evidenced by interventricular septal flattening. His lower extremity deep venous compression study did not reveal a thrombus. Putting it all together, we decided that this patient had acute chest syndrome and red cell exchange was performed with dramatic improvement in his clinical condition. This POCUS examination was performed at the bedside, by our fellow in under 10 min. There was no need for patient transport.
Clinical dissociation, where one physician orders a test, someone else performs the test, and yet another clinician interprets the test, does not occur with POCUS. With POCUS, the physician performs image acquisition, image interpretation, and most importantly integrates these findings with the history and physical examination results to render a differential diagnosis. This concept is not new. The medical literature is replete with studies showing that nonradiologists and noncardiologists can become proficient in POCUS. As course leaders in POCUS, we have taught thousands of clinical providers through the American College of Chest Physicians since 2006. Both the young and not-so-young, “set in their ways” clinicians are astounded at the amount of information learned at the bedside with a “high-frequency” stethoscope.7 POCUS is an extension of the physical examination, many times answering the questions we all ask regarding the breathless patient. Does the patient have pulmonary edema? (a B-line pattern on ultrasound). Does the patient have pneumonia plus-or-minus a parapneumonic effusion, and if so, is the effusion complex? (alveolar consolidation pattern, simple or complex pleural effusion on ultrasound). Does the patient have airway disease, such as COPD or asthma? (a line pattern, or normal aeration pattern, on lung ultrasound with wheezing heard with a stethoscope: “very low-frequency ultrasound”). Does the patient have a pulmonary embolus? (a line pattern with or without a DVT, and a large dilated right ventricle). This patient may actually need to undergo CT pulmonary angiography. For these reasons, we believe that all patients who present with acute breathlessness should undergo POCUS. Not only do we believe that all patients who are acutely breathless deserve point-of-care ultrasonography, but we believe that its omission is cause for great concern.