Lung ultrasound vs chest X-ray in diagnostics of lung diseases

Does lung ultrasound complement or replace the use of chest X-ray in the diagnostics of patients with lung disease?

Khalid Azzam: Lung ultrasound is probably the most interesting ultrasound, I would say. I use it when I am seeing patients on the medical wards on regular basis, almost daily. What I find very interesting about lung ultrasound is that for years we have never sent our patients to the diagnostic department to have an ultrasound of the lung, unless you were looking for pleural effusion, for fluids – which still is the standard of care. You would like to do an ultrasound of the lung to make sure that there is a pleural effusion, not to pick small amounts and stuff like that.

But then there are new findings, which are all artifacts that had been identified by Doctor Daniel Lichtenstein from France, an authority in this and all the work on lung ultrasound; artifacts have started with him and he is still working on it a great deal. So you look at the lung and the lung is full of air. When you put an ultrasound probe on the lung beyond the pleura, you actually lose everything if you are just looking at structures, like we do in the abdomen or anywhere else. But Doctor Lichtenstein has identified different patterns of artifacts. Some of them show what a normal lung is, which he calls the A lines, and some are abnormal, the B lines. A lines are lines which are parallel to the pleural line, and they are at the same distance from your probe. When you see these, you say, “OK, these is no interstitial pattern in the lung. The lungs are clear.” So if a patient comes with shortness of breath and you look through all the lung and they have A lines all over, they do not have pulmonary edema and they do not have pneumonia. What they probably have is pulmonary embolism (PE), or chronic obstructive pulmonary disease (COPD), or asthma. If you listen to their lungs and they are wheezy, it is more likely COPD or asthma. If you look at their legs and they have deep vein thrombosis (DVT), then it is most likely PE. Doctor Lichtenstein has created the BLUE-protocol – bedside lung ultrasound in emergency – which defined that very nicely.

So if you see the A lines, it is perfect. There is pleura sliding as well – because it is all about the pleura and the lung that is touching the pleura. After that it is all artifacts. So you look at the pleura, as the pleural sliding is very important. If you see pleural sliding missing and then you see a lung point, you can say for 100% that this is pneumothorax. This is not possible with a chest X-ray. There is nothing really good in knowing that this is 100% pneumothorax today, other than doing a bedside ultrasound, maybe a magnetic resonance imaging (MRI) or even a computerized tomography (CT) scan. If you have done a procedure on a patient, you stuck a needle in the lung or neck, and you want to know if the patient had a complication of pneumothorax – which will send the patient to chest X-ray, or we may miss a small one – you can finish your procedure using the ultrasound as guidance and then look and see if there is lung sliding. And if there is lung sliding, you know that there is no pneumothorax. So lung sliding is a very important component.

Then we look at the thing just next to the pleura and that gives us... there are B lines and B lines, as we said, go horizontally from the pleural line, down across all your screen; they obliterate your A lines. And these are abnormal. In these, there is an interstitial pattern. What is an interstitial pattern? It could be fluid, like in pulmonary edema, could be blood, like in pulmonary hemorrhage, could be just interstitial lung disease, could be pneumonia. It depends on the distribution. If you have a patient who is short of breath, has leg edema, and has B lines all over, they are coming with pulmonary edema. You do not have to think about anything else. You do not have to worry about things like, “Do I hear crepitation or not, the chest X-ray is soft, the patient is obese.” Now you can see there are B lines all across the lung, so it is pulmonary edema. If you see B lines in a localized area of the lung and the patient has a fever, this is pneumonia. You do not need to do a chest X-ray. We have looked at the meta-analyses done on lung ultrasound and pneumonia [which] show specificity and sensitivity using lung ultrasound in the high 90s – 98%, 97%. So it is a beautiful modality, it is not difficult to learn, and you will need to practice it – it is not going to happen overnight. But you learn it, you practice it, you can introduce it into your practice. You can save your patients repeated chest X-rays.

It is a big thing when we see patients in the intensive care unit (ICU), or even in medical wards at times, who come with, say, pulmonary edema, you have diagnosed them, and then every day they will have chest X-ray to look at how the pulmonary edema is progressing. You do not have to do this anymore. Imagine the dose of radiation – what is the cost that comes with daily chest X-ray? Today what we do is we scan the lung every day in the morning, see how much B-line load is there in the patient, and that gives us an idea about what their pulmonary edema looks like. I have had patients who probably had one chest X-ray during their hospital stay, managed through their admission by just doing their lung ultrasounds, checking their B lines, as well as looking at the inferior vena cava (IVC) to check whether you have diuresed the patient enough or not, if you have reduced the IVC size to somewhere where you potentially may prevent the readmission.

It is an innovative amazing modality that has been for years stuck in the ICU and now should come out and be used in regular medical wards by the internists as well.