Clinical Progress Note: Point-of-Care Ultrasound in the Evaluation of the Dyspneic Adult

Point-of-care ultrasound (POCUS) continues to gain traction in contemporary clinical practice both as a diagnostic tool and as an extension of the physical examination. Hospital Medicine (HM) lags behind Emergency Medicine (EM) and Critical Care (CC) in our uptake of such technology, although momentum is gaining. Leaders in HM have published frameworks for competency and credentialing, and the Society for Hospital Medicine has created a pathway for certification.¹ POCUS use is the standard of care for several bedside procedures, but evidence for diagnostic applications is changing rapidly as the literature expands. However, the applicability of this evidence to HM patients can be challenging as most published studies are still from EM and CC settings. This Progress Note focuses on how a hospitalist might incorporate POCUS in the evaluation of adult patients with dyspnea. This topic was chosen after reviewing several relevant studies published in the past five years and recognizing the importance of dyspnea in HM. The Progress Note begins with a review of POCUS for undifferentiated dyspnea before exploring studies of common diagnoses that present with dyspnea, including pneumonia, pleural effusion, and acute decompensated heart failure (ADHF), aiming to update the knowledge of HM providers regarding this technology as well as to stimulate further study in this field.

In collaboration with an academic librarian in March 2019, PubMed was searched for studies published within the past five years using several MESH search terms for POCUS. The search was originally focused to the field of HM using specific search terms, but this yielded a very limited number of studies. Therefore, the search strategy was expanded to include EM and CC studies. This final search generated 346 papers that were supplemented with additional literature searches using references from studies found in the initial search.

Dyspnea is common in HM, both as the reason for a patient’s admission and as a symptom that develops during hospitalization such as after intravenous fluid resuscitation, a possible aspiration event, or central line placement. The differential diagnosis is broad, and multiple studies suggest that POCUS can aid in the evaluation of undifferentiated dyspnea while also being cost effective and avoiding the potential radiation of other testing modalities. The pulmonary POCUS evaluation incorporates a combination of several findings, including “A-lines” or horizontal artifacts from normal aerated lung; “B-lines”, vertical artifacts generated by extra-alveolar fluid, consolidation or “tissue-like pattern”; air bronchograms, consolidated lung surrounding airways; anechoic or hypoechoic areas in dependent zones of the lung; and the presence or absence of pleural sliding.²

In one prospective observational study of five internal medicine residents with no prior POCUS experience and three hours of training, the addition of handheld POCUS devices to usual clinical information improved the diagnostic accuracy for pneumonia, pulmonary edema, pleural effusion, and obstructive lung disease when evaluating patients with a primary complaint of dyspnea (area under the curve [AUC] 0.81 vs 0.87, P < .01).² However, the largest improvements in the operating characteristics were observed with the two residents who received an extended two-week elective of training.

In another study of 383 consecutive patients presenting to the ED with dyspnea, physicians with basic and advanced POCUS training were blinded to all clinical information and recorded a diagnosis after performing a lung POCUS examination. The “ultrasound physician’s” diagnosis was then compared to the treating emergency department (ED) physician’s diagnosis using history, physical, and other diagnostic data. Lung POCUS had a sensitivity and a specificity of 87.6% and 96.2% for pulmonary edema, 85.7% and 99% for pneumonia, 98.2% and 67.3% for asthma/chronic obstructive pulmonary disease (COPD), 46.2% and 100% for pulmonary embolus (PE), and 71.4% and 100% for pneumothorax, respectively.³ The scanning protocol used, the BLUE (Bedside Lung Ultrasound Examination) protocol, was focused on ruling out significant pulmonary etiologies of dyspnea. The protocol classified the finding of normal lung ultrasound (A-line profile) as COPD or asthma since these conditions will have a normal sonographic appearance. This approach could lead to incorrect labeling of other extrapulmonary causes of dyspnea as COPD or asthma. The findings of this study suggest that POCUS is most effective at ruling in pulmonary edema and pneumonia while being most effective at ruling out asthma or COPD as causes of dyspnea. It is both sensitive and specific for pneumothorax. However, as other studies have found, the sensitivity of POCUS for COPD, asthma, and PE was inferior to traditional clinical evaluation.⁴ One of the few studies looking specifically at hospitalized ward patients compared a blinded lung POCUS diagnosis and a discharge clinical diagnosis classified as cardiac, pulmonary, or mixed dyspnea. The authors of that study found an “interstitial pattern” (two areas with more than two B-lines) in 94% of those classified as cardiac on discharge, but POCUS findings were less precise for those discharged with a pulmonary etiology of dyspnea.⁵ Identifying B-lines on lung POCUS appears to be helpful in rapidly differentiating cardiac from pulmonary etiologies of dyspnea.

An additional advantage of POCUS is that multiple organ systems can be evaluated in rapid succession when the etiology of dyspnea is unknown. In a smaller ED study of patients presenting with undifferentiated dyspnea, a diagnosis was recorded after history-taking and physical examination and then recorded again after lung, cardiac, and inferior vena cava POCUS. Clinician diagnostic accuracy improved from 53% to 77% with the use of POCUS (P = .003) compared with the final diagnosis.⁶ The treating physician’s primary impression changed in almost 50% of cases after using POCUS, most of which was driven by improved sensitivity and specificity of ADHF. In another study of 2,700 patients presenting to the ED with dyspnea, cardiopulmonary POCUS shortened the time to diagnosis (186 ± 72 minutes vs 24 ± 10 minutes, P = .025).⁴ These studies suggest that the use of POCUS in the initial evaluation of patients with undifferentiated dyspnea is a valuable tool with respect to diagnostic accuracy and timeliness.