Acute dyspnea and bedside ultrasound

Source:  Acute dyspnea and bedside ultrasound    Tag:  pulmonary edema xray
Elderly gentleman seeks the emergency department because of sudden dyspnea. He has no previous diagnosis of relevance such as COPD or heart failure. EMS notices crepitations on lung auscultation and treats patient with diuretics and CPAP with some relief. In the ED patient is still dyspneic and using accessory muscles for breathing but no clear crepitations are to be heard on auscultation and patient is not obviously obstructive. Stable vital signs, systolic blood pressure of 160mmHg.
Bedside chest x-ray is ordered but image result is not expected for a while. The ultrasound machine is turned on and the cardiac probe put on patient's thorax, revealing...

1. Heart, subxiphoid view

# Left > right ventricle => right strain and pulmonary embolism very unlikekly
# No pericardial effusion anteriorly, 2-3mm black line seen and assumed to be physiologically normal fluid
# Visually, decreased contractibility of left ventricle

2. Right pleura

Pleural effusion and several B-lines are clearly seen as the base of the lung reaches down, indicating right sided pulmonary edema

3. Left pleura

Great amounts of pleural effusion. No clots seen and thus no suspicion of blood. Multiple B-lines indicating left sided lung edema.

4. Right lung, apex

'Lung sliding' exludes pneumothorax. Multiple B-lines => edema reaches apex, suggesting massive pulmonary edema.

5. Left lung, apex

Same as right side; thus patient has massive, bilateral pulmonary edema.

The investigation was done in about 2 minutes.

The X-ray image arrives 45mins later

It shows enlarged heart with widened pulmonary veins and interstitial fluid bilaterally. Bilateral pleural effusion, more on left side. ProBNP arrives at 2500 with minimal Troponin elevation. Patient is treated as acute left sided heart failure and treated with CPAP and nitro infusion (SCAPE).

Discussion
Previously, ultrasound has been said to be impossible to use for evaluating lungs, after all "air is ultrasound's greatest enemy". Experimenting with this has shown that indirect signs can be seen such as A- and B- lines and as air is replaced with consolidations and edema, ultrasound will immediately pick this up. For pneumothorax and pleural effusion, pulmonary edema and consolidations (pneumonia or ARDS), ultrasound is becoming a first choice for quick bedside evaluation. Increasing amount of data is supporting this and in some emergency departments, bedside chest x-ray has been replaced by ultrasound as only CT has better sensitivity for most conditions of relevance in the ED.

Pneumothorax:
Acad Emerg Med. 2005 Sep;12(9):844-9
“The sensitivity for chest radiography was 75.5% (95% CI = 61.7% to 86.2%) and the specificity was 100% (95% CI = 97.1% to 100%). The sensitivity for US was 98.1% (95% CI = 89.9% to 99.9%) and the specificity was 99.2% (95% CI = 95.6% to 99.9%)”

Pleural effusion, pulmonary edema, consolidation:
Anesthesiology. 2004 Jan;100(1):9-15
“Auscultation had a diagnostic accuracy of 61% for pleural effusion, 36% for alveolar consolidation, and 55% for alveolar-interstitial syndrome. Bedside chest radiography had a diagnostic accuracy of 47% for pleural effusion, 75% for alveolar consolidation, and 72% for alveolar-interstitial syndrome. Lung ultrasonography had a diagnostic accuracy of 93% for pleural effusion, 97% for alveolar consolidation, and 95% for alveolar-interstitial syndrome. “

Let's summarize the data above:
Auscultation Chest X-ray Ultrasound
Pleural effusion 61% 47% 93%
Consolidation 36% 75% 97%
Pulmonary edema 55% 72% 95%

Pulmonary embolism
The story of ultrasound becomes only better and better. Here, ultrasound is compared with CT for diagnosis of pulmonary embolism - the condition every physician fears to miss.
Chest. 2001 Dec;120(6):1977-83:
“The sensitivity of TS [transthoracic sonography] for detecting PEs was 80% (sensitivity of CT scanning, 82%), and the specificity of TS for detecting pulmonary lesions was 92%”


Volume status and heart - ultrasound for evaluation for shock
With ultrasound, a rough estimate of cardiac function and volume status (~vena cava status) can be done in instant. Together with above mentioned evaluation of thorax, ultrasound can in only 2-3 minutes give the physician a reliable diagnosis of acute dyspnea or shock. Add to this testing for free abdominal fluid, evaluating aorta and DVT diagnosis of lower extremities and then we have a full RUSH protocol (also known as FATE):
  RUSH: Rapid ultrasound for Shock and Hypotension

Yes folks, the ultrasound is certainly here to stay!