Emergency lung ultrasound for the diagnosis of pulmonary edema
Background:
Acute dyspnea is one of the most common presentations to the emergency
departments (ED). Pulmonary edema is a common cause for acute dyspnea,
however, can be sometimes difficult to diagnose in ED if patient has co-existing
respiratory disease such as COPD. Traditionally, chest x-ray and clinical
examination is used to diagnose pulmonary edema. However, most of the times
patients are treated for both fluid overload and underlying infection as the
definitive diagnosis is difficult in the emergency department. Ultrasound is being
used currently in the ED routinely and its application is expanding beyond FAST.
Lichtenstein et al in 2008, introduced a BLUE (Bedside Lung Ultrasound in
Emergency) protocol for differentiating different lung pathologies with bedside
ultrasound.
Objective:
To evaluate the role of bedside ultrasound, in diagnosing pulmonary edema, in
patients presenting with acute dyspnea in the ED.
Method:
We designed a prospective observational study at the emergency department of
an urban tertiary hospital. A convenience sample of patients presenting to the ED
with acute dyspnea were included from January 2014 to end of March 2014. A
total of 22 patients were included for this pilot study. All patients presenting to
the ED with acute dyspnea were included
Senior emergency physicians (consultants and registrars) with level 1
emergency ultrasound experience were trained in lung ultrasound by the
department ultrasound lead. A phased array probe (5-1MHz) was used at a
depth setting of 16-18cms. US was performed as per protocol described in
previous studies and literature i.e., eight zones were scanned (four on each side).
The criterion for the US diagnosis of pulmonary edema was the presence of all
three of the following: (1) multiple B-lines (three or more) on a single scan image
in one zone (2) at least two positive zones on one side (3) bilateral positive scan.
The EP performing the US was blinded to the history, examination and clinical
impression of the attending EP. Findings of the US were recorded on a proforma
and were kept blinded to the attending EP. All patients had a routine chest x-ray
and were treated accordingly by the attending EP and later by the admitting
medical team who were also blinded to the US findings. All chest x-rays were
later reported by an independent radiologist blinded to the US findings. Findings
of the US were retrospectively compared with chest x-ray reports and the final
diagnosis by the admitting medical team. Chest x-ray was considered the
criterion standard in the first instance, however, where there was not a clear
report or confusion, the findings were co-related with the final diagnosis of the
admitting medical team (only two such cases in this pilot study).
Results:
Our study has clearly proven the diagnostic ability of bedside US in patients with
pulmonary edema. The study showed that for diagnosing pulmonary edema, the
bedside lung ultrasound has 100% (95% CI: 71.33 % to 100.00 %) sensitivity,
90.91% (95% CI: 58.67 % to 98.49 %)specificity, 91.67% (95% CI: 61.46 % to 98.61
%)positive predictive value and100% (95% CI: 68.97 % to 100.00 %)negative
predictive value.
Conclusion:
Although this is a small pilot study but the results showed that bedside lung
ultrasound can aid in the diagnosis of pulmonary edema in patients with acute
dyspnea. We propose to extend this study with larger sample size in order to
validate our current results from this pilot. Add some reference…. Previous study
which supports this in the beginning of conclusion.