Overview of Thoracic and Lung Ultrasound
Thoracic ultrasound, a method of using sound waves to create images of the chest area, has grown increasingly common in the past decade. This trend is largely due to its widespread use in on-the-spot care during emergencies and trauma situations, as well as its incorporation into training programs. Furthermore, ultrasound has several benefits over traditional methods like radiography, such as avoiding delays in care and exposure to radiation.
For patients who are too unstable for delays brought on by transport to a CT scanner or even for a bedside chest x-ray, doctors can readily use a bedside ultrasound. Plus, numerous studies have pointed out that this method often matches or even surpasses the accuracy of conventional radiography, namely chest x-rays, in identifying medical issues. Moreover, a bedside ultrasound can help doctors differentiate amongst medical conditions that standard radiography might have difficulty identifying.
Anatomy and Physiology of Thoracic and Lung Ultrasound
The chest area, or what doctors call the ‘thoracic anatomy’, is made up of various parts including chest muscles (such as the muscles between your ribs and chest muscles), the breastbone, ribs, cartilage that links the ribs, a twin-layered membrane called the pleura, and of course, the lungs. In the middle, you find the heart and the large blood vessels. The lower boundaries of the chest cavity are marked by the diaphragm, a muscle that helps with breathing, the liver on the right, and the spleen on the left.
Interestingly, when doctors use ultrasound to view the chest, it’s often not the exact layout of the lungs they’re interested in. Instead, they’re usually studying the peculiar patterns or ‘artifacts’ created by the ultrasound bouncing off air-filled parts of the chest, like the lungs. Looking at the lung tissue itself usually tells them more about any lung disease or damage.
Under normal conditions, doctors can’t tell apart the two layers of the pleura because they are so close together. What they can see is the line that marks where the pleura is, along with any unusual ultrasound patterns created by air scattering, which could mean a problem in the lungs.
Why do People Need Thoracic and Lung Ultrasound
Doctors use a tool called a thoracic ultrasound for different reasons. Often, they use this to check for injuries after an accident. This special exam, known as EFAST, can identify various injuries like lung punctures (pneumothorax), chest bleeding (hemothorax), broken ribs, injuries to the lung tissue (pulmonary contusions), and blood collections under the skin of the chest wall (chest wall hematomas).
The thoracic ultrasound isn’t just used for accident-related injuries. Doctors also use it to look for swelling caused by extra fluid (pleural effusions), infections like pneumonia and serious pus-filled infections (empyema), fluid build-up in the lungs (pulmonary edema), long-term lung diseases (chronic obstructive pulmonary disease or COPD), blood clots in the lung (pulmonary embolism), and a serious lung condition known as ARDS.
So, if you’re having symptoms like chest pain, trouble breathing (dyspnea), fever, and low oxygen levels (hypoxia), your doctor might use a thoracic ultrasound to find out what’s causing these issues.
When a Person Should Avoid Thoracic and Lung Ultrasound
There are not really any reasons why someone can’t have an ultrasound scan. Sometimes, people who need to be in an operating room right away for surgery might not have time for an ultrasound first. However, most emergency rooms can do an ultrasound test very quickly, since it doesn’t take a lot of time to complete. This means that, in most cases, people can usually get a fast ultrasound before needing any surgery. The ultrasound helps doctors figure out what is going on and how to help you.
Equipment used for Thoracic and Lung Ultrasound
The doctor uses a tool called a 9 to 12 MHz linear-array transducer to examine the chest wall and the pleura, which is the thin layer that wraps around your lungs. This tool helps them see these body parts in greater detail. However, if the patient has well-developed chest muscles or extra fatty tissue under the skin, the doctor might need to use a different tool that operates at a lower frequency.
In the case of examining further structures, like looking for a lung condition such as pulmonary edema (fluid in the lungs), pneumonia (lung infection), or pleural effusions (extra fluid in the space around the lungs), a lower frequency tool such as a 3.5 to 5.0 MHz phased array or curvilinear transducer is ideal. These tools operate at a lower frequency, making them better for seeing deeper structures within the body.
Who is needed to perform Thoracic and Lung Ultrasound?
Anyone who has received the proper training can perform an examination of the chest using ultrasound. At present, the specific training required for chest ultrasound is not clearly defined in many programs. However, it is generally accepted that trainees need to successfully complete between 25 to 50 exams, which are carefully checked for quality, in a specific use of the technology.
Preparing for Thoracic and Lung Ultrasound
During a medical test or evaluation, patients are generally recommended to either lie down or sit, depending on the situation. The position the doctors choose depends on how the body behaves under certain situations. For instance, if a patient has excess fluid in the layer covering their lungs (called a pleural effusion), sitting might be better. This is because gravity helps the fluid collect at the lower part of the lungs, making it easier to assess.
If there’s air captured in the space around the lungs (a condition called pneumothorax), it will rise to the highest point in the area it is trapped. In this case, the position of the patient might depend on where this area is. Nevertheless, if a patient has certain type of lung infection like community-acquired pneumonia, the doctor can spot it no matter what position the patient holds during the evaluation.
How is Thoracic and Lung Ultrasound performed
When a doctor examines your chest cavity, they take a look at the surrounding borders including the chest wall, diaphragm, liver, spleen, heart and major blood vessels. To do this, they use a tool that works like a small radar device which can provide detailed images of the underlying tissues. If you’ve had an injury or trauma, this tool can help the doctor check for bruising and internal bleeding, especially if a broken rib has torn any blood vessels. This tool is also great for identifying air leakage or fluid accumulation between the layers of the lungs, and even tiny breaks in the ribs that might be missed by ordinary x-rays. Sometimes, a break or fracture might be confirmed by surrounding blood accumulation.
This tool can also spot abnormalities in the lining of the lungs, such as the introduction of air or fluid. Usually, the layers lining the lungs appear as one line because they slide over each other as you breath. If there’s a leak of air into the lung lining space, this sliding motion becomes disrupted causing a static appearance. This missing sliding movement often indicates a collapsed lung. With this tool, the doctor also checks for the rise and fall of your chest wall and lungs, typically creating a beach or sea-like image. If there’s a disruption, such as a collapsed lung, the image will show more like a barcode.
Contrary to leaking air, fluid collections in the lung lining transmit sonographic signals very well and helps the doctor detect any fluid build-up. Sometimes, if the fluid is blood due to chest injury, pooled blood may be seen. This device can detect as little as 5 to 20 ml of fluid! In massive fluid collections, the lung may be seen floating and waving as you breathe! The volume of fluid build-up can also be estimated and if it needs to be taken out or tested, the needle entry can be guided real-time for utmost safety.
Lastly, when there are diseases causing fluid to build up in the tiny air sacks of your lungs, a flash-light-like image appears. They move with your breath and look like they are being swung back and forth. These signs indicate fluid build-up in the lungs, often seen in cases like heart failure and can be detected before there’s fluid accumulation in the air sacks. These signs are monitored in several lung fields and typically at least 3 or more have to be noted in at least 2 fields for a diagnosis.
Possible Complications of Thoracic and Lung Ultrasound
There are few risks with using a chest ultrasound, aside from some discomfort if the probe touches a sensitive area such as a broken rib. While an ultrasound can quickly be performed by a trained professional right at the patient’s bedside, it’s important to note that urgent treatments shouldn’t be delayed if an ultrasound isn’t going to greatly impact patient care. If an ultrasound is used to guide a treatment procedure, like draining fluid from the chest (thoracentesis), it’s crucial that all important body structures (like the diaphragm, liver, spleen, lung, and chest wall) are recognized before starting. This helps to avoid accidentally causing harm. Watching the needle or tube in real time through the ultrasound is also recommended.
What Else Should I Know About Thoracic and Lung Ultrasound?
The use of ultrasound scans for the chest area (known as thoracic ultrasound) has quickly become more common in the last decade. This is mainly because emergency doctors have started using handheld ultrasound devices (POCUS) more often during their training and the ultrasound machines have become better. This ultrasound method is a fast way to diagnose and view diseases in the chest and can make diagnoses and procedures more accurate. This happens without exposing the patient to any harmful radiation.
