Lung ultrasound in internal medicine: A bedside help to increase accuracy in the diagnosis of dyspnea

Abstract

Background: Dyspnea is one of the most frequent causes of admission in Internal Medicine wards, leading to a sizeable utilization of medical resources.

Study design and methods: The role of bedside lung ultrasound (LUS) was evaluated in 130 consecutive patients (age: 81±9years), in whom blindly collected LUS results were compared with data obtained by clinical examination, medical history, blood analysis, and chest X-ray. Dyspnea etiology was classified as "cardiac" (n=80), "respiratory" (n=36) or "mixed" (n=14), according to the discharge diagnosis (congestive heart failure either alone [n=80] or associated with pneumonia [n=14], pneumonia [n=24], and obstructive disventilatory syndrome [n=12]). An 8-window LUS protocol was applied to evaluate B-line distribution, "interstitial syndrome" pattern, pleural effusion and images of static or dynamic air bronchogram/focal parenchymal consolidation.

Results: The presence of a generalized "interstitial syndrome" at the initial LUS evaluation allowed to discriminate "cardiac" from "pulmonary" Dyspnea with high sensitivity (93.75%; confidence intervals: 86.01%-97.94%) and specificity (86.11%; 70.50%-95.33%). Positive and negative predictive values were 93.76% (86.03%-97.94%) and 86.09% (70.47%-95.32%), respectively. Moreover, LUS diagnostic accuracy for the diagnosis of pneumonia was not inferior to that of chest X-ray.

Conclusions: Bedside LUS evaluation contributes with high sensitivity and specificity to the differential diagnosis of Dyspnea. This holds true not only in the emergency setting, but also in the sub-acute Internal Medicine arena. A wider use of this portable technique in our wards is warranted.

Keywords: Bedside ultrasound; Diagnosis; Internal medicine; Lung congestion; Lung ultrasound; Pneumonia.