AssessmentsAnatomy clinical correlates: Pleura and Lungs
USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 62-year-old man presents to the emergency department for evaluation of facial swelling. Over the past several weeks, he has noticed his face has become “puffier,” particularly in the morning. In addition, he has a new cough and shortness of breath on exertion. His own past medical history is unremarkable, though his father passed away from a pulmonary embolism. The patient takes no medications. He has smoked one pack of cigarettes per day for thirty years. He does not use alcohol or illicit drugs. Temperature is 37.6°C (99.7°F), pulse is 111 /min, and blood pressure is 131/66 mmHg. Respirations are 18/min, and oxygen saturation is 96% on room air. Physical examination demonstrates distended neck veins and bilateral facial fullness without tenderness to palpation or erythema. Which of the following is the most likely etiology of this patient's clinical presentation?
Content Reviewers:Scott Caterine, BSc (Hons.), MSc, MB, BCh, BAO (Hons.), Viviana Popa, MD
Contributors:Ursula Florjanczyk, MScBMC, Jennifer Montague, PhD, Sam Gillespie, BSc, Anca-Elena Stefan, MD
Before you start watching this video, relax, and take a deep breath.
Think about the air filling up your lungs, which are located on either side of your thoracic cavity.
Now, we often take breathing for granted because it is under autonomic control, and it’s not until we have trouble breathing when we realize just how important our lungs are.
There are many conditions that can affect the lungs, which can have a huge impact on our day to day lives.
Now let’s look at some causes for lung ailments, starting with injuries of the cervical pleura and lung apex.
Both these structures project through the superior thoracic aperture into the neck.
The first is the right part of the infrasternal angle, the other two parts are the right and left posterior costovertebral angles which are inferomedial to the 12th ribs and posterior to the superior poles of the kidneys.
So kidney surgery can pose a risk for pleural injury.
Pleuritic chest pain is caused by irritation to the pleura, which results in a classical ‘sharp’, stabbing pain that gets worse when you breathe in, and is exacerbated even further by deep inhalation and exhalation.
Pleuritic chest pain can have multiple causes, including a pneumothorax, which is when there’s air trapped within the pleural cavity, or a pleural effusion, when fluid builds up in the pleural cavity.
Inflammation of the pleura can cause pleuritic chest pain, which is often the result of infection or inflammatory diseases such as rheumatoid arthritis, and may even result in an empyema where infected fluid builds up in the pleural cavity.
So for example, if there’s irritation of the parietal pleura caused by something like an infection or effusion overlying the mediastinal and central areas of the diaphragm, then we get referred pain to the dermatomal areas supplied by the same spinal levels.
So in this case, the central diaphragm is innervated by the phrenic nerve which is supplied by spinal levels C3, C4 and C5, so the dermatomes of the same spinal levels C3, C4 and C5, which innervate the root of the neck and shoulder, could result in referred pain to the neck or shoulder.
Now let’s look at a procedure called a thoracentesis, also known as a thoracocentesis, which when a hypodermic needle is inserted through an intercostal space and into the pleural cavity to remove pleural fluid, blood or pus from the pleural space.
With a thoracentesis, the needle can be inserted between the 6th and 8th rib on the midclavicular line, between the 8th and 10th rib along the midaxillary line, or between the 10th and 12th rib along the paravertebral line.
If the individual sits in an upright position, the intrapleural fluid accumulates in the costodiaphragmatic recess due to gravity.
Okay, now just a few words on pneumothorax.
On clinical examination, the chest wall on the affected side might appear bigger than the normal side.
On palpation, chest expansion is uneven due to decreased chest wall movement of the affected side and tactile fremitus is decreased on the affected side.
On percussion, the extra air in the pleural space causes hyperresonance on the affected side, and breath sounds are diminished on the affected side.
The space beyond the visceral line is mostly black, because the space where the lung should be is filled with air.
When there’s only a small amount of air in the pleural space, the individual is usually hemodynamically stable, and can be treated conservatively.
However a larger pneumothorax can result in significant collapse of the corresponding lung and requires advanced treatment.
A tension pneumothorax typically has a more severe clinical presentation.
See, that’s because air can’t get out, so it rapidly accumulates in the pleural cavity, compressing the other organs in the mediastinum, including the heart, leading to increased thoracic pressure, which causes lower systemic venous return to the heart and a decreased cardiac output.
Other clinical signs include increased heart rate and breathing rate, d distended neck veins and distant muffled heart sounds.
So, typically the quickest way to allow for air evacuation is needle thoracostomy which is often done in the second intercostal space on the affected side, at the midclavicular line, which decompresses the chest and provides an escape route for the trapped air.
Since anatomy always comes in handy, you can identify the second costal cartilage by using the sternal angle.
Speaking of which, chest tubes can be used for a variety of other reasons as well.
In this case, the chest tube is inserted in either the 4th or 5th intercostal space at the anterior axillary or mid axillary line, and then guided through the skin, subcutaneous tissue, serratus anterior, intercostal muscles, and parietal pleura.
In order to safely do this and prevent injury to surrounding structures, we use the triangle of safety, which is formed anteriorly by the lateral border of the pectoralis major muscle, posteriorly by the lateral border of the latissimus dorsi muscle and inferiorly by a horizontal line from the nipple or 5th intercostal space.
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