Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. usually caused by infection with viruses or bacteria, and less commonly by other microorganisms. Symptoms typically include some combination of productive or dry cough, chest pain, fever and difficulty breathing. Diagnosis is often based on symptoms and physical examination. Chest X-rays, blood tests, and culture of the sputum may help confirm the diagnosis. The disease may be classified by where it was acquired, such as community- or hospital-acquired or healthcare-associated pneumonia.Signs and symptoms
People with infectious pneumonia often have:
1. productive cough
2. fever
3. shortness of breath
4. sharp or stabbing chest pain during deep breaths
5. increased rate of breathing
The typical signs and symptoms in children under five are fever, cough, and fast or difficult breathing, blue-tinged skin, unwillingness to drink, convulsions, ongoing vomiting, extremes of temperature, or a decreased level of consciousness. Viral pneumonia presents more commonly with wheezing than bacterial pneumonia. Pneumonia was historically divided into: -
1. Typical
2. AtypicalCause of pneumonia
Pneumonia is due to infections caused primarily by bacteria or viruses and less commonly by fungi and parasites. Although more than 100 strains of infectious agents have been identified, only a few are responsible for the majority of cases. Mixed infections with both viruses and bacteria may occur in roughly 45% of infections in children and in 15% of infections in adults. Most patients (62%) had no detectable pathogens in their sample, and unexpectedly, respiratory viruses were detected more frequently than bacteria. Factors that predispose to pneumonia: -
1. Smoking
2. Immunodeficiency
3. Alcoholism
4. chronic obstructive pulmonary disease
5. sickle cell disease (SCD)
6. asthma
7. chronic kidney disease
8. liver disease
Bacteria
Bacteria are the most common cause of community-acquired pneumonia (CAP), with Streptococcus pneumoniae. Other commonly isolated bacteria include Haemophilus influenzae, Chlamydophila pneumoniae, Mycoplasma pneumoniae.
Viruses
include rhinoviruses, coronaviruses, influenza virus, respiratory syncytial virus (RSV), adenovirus, and parainfluenza.
Mechanisms of pneumonia
Pneumonia frequently starts as an upper respiratory tract infection that moves into the lower respiratory tract. It is a type of pneumonitis (lung inflammation). The normal flora of the upper airway give protection by competing with pathogens for nutrients. In the lower airways, reflexes of the glottis, actions of complement proteins and immunoglobulins are important for protection.
Diagnosis of Pneumonia
Pneumonia is typically diagnosed based on a combination of physical signs and often a chest X-ray. In adults with normal vital signs and a normal lung examination, the diagnosis is unlikely. However, the underlying cause can be difficult to confirm, as there is no definitive test able to distinguish between bacterial and non-bacterial cause.
Physical exam
Physical examination may sometimes reveal low blood pressure, high heart rate, or low oxygen saturation. The respiratory rate may be faster than normal, and this may occur a day or two before other signs. Examination of the chest may be normal, but it may show decreased 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. Percussion may be dulled over the affected lung, and increased, rather than decreased, vocal resonance distinguishes pneumonia from a pleural effusion.
Imaging
A chest radiograph is frequently used in diagnosis. X-ray presentations of pneumonia may be classified as lobar pneumonia, bronchopneumonia, lobular pneumonia, and interstitial pneumonia. Bacterial, community-acquired pneumonia classically show lung consolidation of one lung segmental lobe, which is known as lobar pneumonia. Radiographs of viral pneumonia may appear normal, appear hyper-inflated, have bilateral patchy areas, or present similar to bacterial pneumonia with lobar consolidation.
A CT scan can give additional information in indeterminate cases. CT scans can also provide more details in those with an unclear chest radiograph and can exclude pulmonary embolism and fungal pneumonia and detect lung abscess in those who are not responding to treatments.
Healthcare
Health care–associated pneumonia (HCAP) is an infection associated with recent exposure to the health care system, including hospitals, outpatient clinics, nursing homes, dialysis centers, chemotherapy treatment, or home care. People may become infected with pneumonia in a hospital; this is defined as pneumonia not present at the time of admission (symptoms must start at least 48 hours after admission). It is likely to involve hospital-acquired infections, with higher risk of multidrug-resistant pathogens.
Differential diagnosis
Several diseases can present with similar signs and symptoms to pneumonia, such as:
1. chronic obstructive pulmonary disease (COPD)
2. asthma
3. pulmonary edema
4. bronchiectasis
5. lung cancer
6. pulmonary emboli
Prevention of Pneumonia
Vaccination
Vaccination prevents against certain bacterial and viral pneumonias both in children and adults. Influenza vaccines are modestly effective at preventing symptoms of influenza, immunizing health care workers decreases the risk of viral pneumonia among their patients. Vaccinations against Haemophilus influenzae and Streptococcus pneumoniae have good evidence to support their use. There is strong evidence for vaccinating children under the age of 2 against Streptococcus pneumoniae
Medications
When influenza outbreaks occur, medications such as amantadine or rimantadine may help prevent the condition, but they are associated with side effects.
By: B.M.T. Montadher Talib