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Pneumonia is due to inflammation of the lung alveoli from an infection. Typically, fluid that’s filled with white blood cells starts to fill up the alveoli, and that inflammatory fluid essentially replaces the air that’s normally in the alveoli, and that fluid interferes with gas exchange.
Pneumonia typically causes a fever, cough, and shortness of breath, along with tachypnea and tachycardia, and occasionally hypoxemia. If the infection is near the pleural surface, it can cause pleuritic chest pain, which is pain that worsens with inspiration. On chest exam, there’s dullness on percussion; increased tactile fremitus, which is an increased sensation of vibration when palpating over the affected area and asking the individual to speak; and egophony, which is increased resonance of transmitted sounds and makes the letter “E” sound like the letter “A”. On auscultation, bronchial breath sounds or inspiratory crackles may be heard.
The diagnosis of pneumonia is based on having clinical signs and symptoms along with abnormal chest imaging, most commonly a chest x-ray. In pneumonia, a chest x-ray typically shows either a lobar consolidation or a diffuse, interstitial infiltrate. Pneumonia has to be distinguished from atelectasis which is when there’s collapse of a region of the lung, a complication that often occurs in individuals after surgery. On a chest x-ray, atelectasis shows up as a wedge-shaped region with it’s apex at the hilum with an ipsilateral shift of structures due to volume loss. In contrast, in a pneumonia there’s usually normal or increased volume with a consolidation that doesn’t have an apex at the hilum and no shift in structures. Now, in addition to imaging, some lab tests suggestive of pneumonia include an elevated white blood cell count, and elevated markers of inflammation like procalcitonin and C-reactive protein. It’s thought that these generally increase much more in bacterial pneumonia versus viral pneumonia.
Pneumonia is an infection of the lungs that results in air sacs being filled with fluid. It may be caused by bacteria, viruses, or fungal infections. Pneumonia is a serious condition that requires prompt diagnosis and treatment. It is diagnosed based on symptoms like cough and fever and an abnormal chest x-ray which might show a lobar consolidation or an interstitial infiltrate, and in some cases, there may be cavitation or pleural effusion.
Pneumonia is classified into community-acquired pneumonia, or CAP, and hospital-acquired or ventilator-associated pneumonia, or HAP and VAP. CAP is pneumonia in which the organism was acquired anywhere in the community outside the hospital. HAP and VAP are defined as pneumonia starting more than 48 hours after admission to a hospital or endotracheal intubation, respectively.
Decision-making tools like the CURB-65 are essential to determine whether a CAP patient should be treated outpatient, inpatient, or in the intensive care unit, and the antibiotic choice depends on the setting. Sputum samples for gram stain and culture as well as blood cultures should be obtained for individuals with CAP in the intensive care unit, as well as those with HAP or VAP. Complications of pneumonia include parapneumonic effusion, empyema, and lung abscess. Preventative measures to decrease the risk of acquiring pneumonia include providing pneumococcal and influenza vaccines.
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