Pneumonia is an inflammatory condition of the lung especially affecting the microscopic air sacs (alveoli) that is associated with fever, chest symptoms, and a lack of air space (consolidation) on a chest X-ray. Pneumonia is typically caused by an infection by bacteria, viruses, fungi, or parasites, but there are a number of other causes. Diagnostic tools include x-rays and examination of the sputum. Vaccines to prevent certain types of pneumonia are available. Treatment depends on the underlying cause. Presumed bacterial pneumonia is treated with antibiotics.
Pneumonia can be classified in several ways. It is most commonly classified by where or how it was acquired (community-acquired, aspiration, healthcare-associated, hospital-acquired, and ventilator-associated pneumonia), but may also be classified by the area of lung affected (lobar, bronchial, or acute interstitial), or by the causative organism.
People with infectious pneumonia often exhibit symptoms such as a productive cough, fever accompanied by shaking chills, shortness of breath, sharp or stabbing chest pain during deep breaths, confusion, and an increased respiratory rate. Pneumonia fills the lung's alveoli with fluid and hinders oxygenation . In the elderly, confusion may be the most prominent symptom. The typical symptoms in children under five are fever, cough, and fast or difficult breathing. Fever, however, is not very specific, as it occurs in many other common illnesses, and may be absent in those with severe disease or malnutrition. In addition, a cough is frequently absent in children less than two months old. More severe symptoms may include central cyanosis, decreased thirst, convulsions, persistent vomiting, or a decreased level of consciousness. Some causes of pneumonia are associated with classic, but non-specific, clinical characteristics. Physical examination may sometimes reveal low blood pressure, a high heart rate, or a low oxygen saturation. Examination of the chest may be normal, but may show decreased chest expansion on the affected side. Harsh breath sounds from the larger airways that are transmitted through the inflamed lung are termed bronchial breathing, and are heard on auscultation with a stethoscope. Rales (or crackles) may be heard over the affected area during inspiration. Percussion may be dulled over the affected lung, and increased, rather than decreased, vocal resonance distinguishes pneumonia from a pleural effusion. Struggling to breathe, confusion, and blue-tinged skin are signs of a medical emergency.
A chest radiograph is frequently used in diagnosis . In people with mild disease, imaging is needed only in those with potential complications, those who have not improved with treatment, or those in which the cause in uncertain. If a person is sufficiently sick to require hospitalization, a chest radiograph is recommended. Findings do not always correlate with severity of disease and do not reliably distinguish between bacterial infection and viral infection. X-ray signs of bacterial community-acquired pneumonia usually show lung consolidation of one lung segmental lobe. However, radiographic findings may be variable, especially in other types of pneumonia. Radiographs of viral pneumonia cases may appear normal, hyper-inflated, have bilateral patchy areas, or appear similar to bacterial pneumonia with lobar consolidation. A CT scan can give additional information in indeterminate cases.
Typically, oral antibiotics, rest, simple analgesics, and fluids suffice for complete resolution. However, those with other medical conditions, the elderly, or those with significant trouble breathing may require more advanced care. Antibiotic choice depends initially on the characteristics of the person affected, such as age, underlying health, and the location the infection was acquired. With treatment, most types of bacterial pneumonia can be cleared within two to four weeks and mortality is very low. Viral pneumonia may last longer, and mycoplasmal pneumonia may take four to six weeks to resolve completely.