Case Presented by: Dr. Meredith Hill
CC: “I can’t breath”
70-year-old man with a PMH of HTN who presents with shortness of breath. He states that he is increasingly short of breath over the last 3 weeks, and is significantly worse today. The patient complains of orthopnea and new bilateral lower extremity edema. He states he takes multiple medication, but ran out of them a few days ago. The patient denies chest pain, nausea, vomiting and abdominal pain. He denies fever and chills. Patient has a history of smoking, but quit several years ago.
VS: BP 182/104, HR 95, RR 22, Temp 36.1, Pulse ox 97 % on room air
General: Acute respiratory distress
Consitutional: Well-developed, well-nourished, pt in mild respiratory distress and can speak about 4-5 words at a time.
Respiratory: Decreased air entry at the bases, bilaterally. Accessory muscle use. No wheezing, but faint crackles heard bilaterally.
Cardiovascular: Regular rate and rhythm. Normal heart sounds – S1/S2 positive, no murmurs, rubs, or gallops. Good peripheral pulses felt in bilateral upper extremities, capillary refill is less than two seconds. 3+ pitting edema bilaterally. No JVD appreciated
Acute coronary syndrome
How can we use ultrasound to differentiate causes of this patient’s acute dyspnea?
The BLUE protocol can be used to assess this patient’s dyspnea. The linear array probe is used to assess 3 lung zones on each hemithorax. Make sure the probe indicator goes toward the patient’s head. You are looking for a view between 2 ribs. Maximizing the depth will also help.
You begin by ruling out pneumothorax. This is achieved by identifying lung sliding and assessing for A and B lines (Figure B and C).
A-lines (Figure B) are parallel to the lung pleura and B-lines (Figure C) are perpendicular. B-lines indicate subpleural interstitial edema. If a dyspneic patient has A lines in bilateral lung fields then pneumonia and pulmonary edema can be ruled out. If you identify bilateral B lines, then pulmonary edema may be the cause of the dyspnea. Identification of both A and B line may represent pneumonia. If you see the right lung with predominate A lines and the left with B lines (or vice versa) there is an increased likelihood for pneumonia.
You cannot really appreciate the sliding of the pleura in these still images but if you wanted to switch to M mode (Figure D) to assess for the “seashore” sign you could also use this to r/o PTX.
To evaluate for pulmonary embolism, a quick way to reduce the likelihood of the diagnosis is to evaluate for a DVT since most PEs originate from lower extremity DVTs. Begin the scan by placing gel to the groin and medial thigh at a distance about 10 centimeters distal to the inguinal crease and identify the common femoral vein. Check for compressibility. Scan distally and check for compressibility at the junction of the superficial femoral vein and deep femoral vein. Subsequently, move down to the popliteal vein, starting 2 cm proximal to the knee, compressing 3 separate times until you see the trifercation of the the popliteal vein into the anterior tibial vein, the posterior tibial vein, and the peroneal vein. If you confirm the presence of a DVT and identified an A-line on chest ultrasound, your suspicion for pulmonary embolism should increase.
In the case above, the bedside US revealed B lines in all lung fields and negative DVT scan. The patient was diagnosed with an acute exacerbation of heart failure.
Source: Lichtenstein et al. Relevance of Lung Ultrasound in the Diagnosis of Acute Respiratory Failure: The BLUE Protocol. CHEST July 2008 vol. 134 no. 1 117-125.