Pneumonia

Pneumonia is an acute infection of the lung parenchyma that often impairs gas exchange. Many types of organisms can cause pneumonia, including viral, bacterial, fungal, protozoal, mycobacterial, mycoplasmal, or rickettsial organisms. The infection may also be described by location: bronchopneumonia, lobular pneumonia, or lobar pneumonia.

Pneumonia is also classified into three types—primary, secondary, or aspiration pneumonia. Primary pneumonia results directly from inhalation or aspiration of a pathogen, such as bacteria or a virus; it includes pneumococcal and viral pneumonia. Secondary pneumonia may follow initial lung damage from a noxious chemical or other insult (super-infection) or may result from hematogenous spread of bacteria from a distant area. Aspiration pneumonia results from inhalation of foreign matter, such as vomitus or food particles, into the bronchi. Aspiration pneumonia is more likely to occur in elderly or debilitated patients, those receiving nasogastric tube feedings, and those with an impaired gag reflex, poor oral hygiene, or a decreased level of consciousness.

Causes

Pneumonia can be classified in several ways. Depending on the microbiologic etiology, pneumonia can be bacterial, viral, fungal, protozoan, mycobacterial, mycoplasmal, or rickettsial in origin. (See Diagnosing and treating the types of pneumonia, pages 246–249.)

In bacterial pneumonia, an infection initially triggers alveolar inflammation and edema. Capillaries become engorged with blood, causing stasis. As the alveolocapillary membrane breaks down, alveoli fill with blood and exudate, resulting in atelectasis. In severe bacterial infections, the lungs assume a heavy, liverlike appearance, as in acute respiratory distress syndrome (ARDS).

Viral infection typically causes diffuse pneumonia and first attacks bronchiolar epithelial cells, causing interstitial inflammation and desquamation. It then spreads to the alveoli, which fill with blood and fluid. In advanced infection, a hyaline membrane may form. As with bacterial infection, severe viral infection may clinically resemble ARDS.

In aspiration pneumonia, aspiration of gastric juices or hydrocarbons triggers similar inflammatory changes and also inactivates surfactant over a large area. Decreased surfactant leads to alveolar collapse. Acidic gastric juices may directly damage the airways and alveoli. Particles with the aspirated gastric juices may obstruct the airways and reduce airflow, thereby leading to secondary bacterial pneumonia.

Certain predisposing factors increase the risk of pneumonia. They include chronic illness and debilitation, cancer (particularly lung cancer), abdominal and thoracic surgery, atelectasis, common colds or other viral respiratory infections, chronic respiratory diseases, influenza, smoking, malnutrition, alcoholism, sickle cell disease, tracheostomy, exposure to noxious gases, aspiration, and immunosuppressive therapy.

Complications

Complications from pneumonia may include septic shock, hypoxemia, respiratory failure, empyema, lung abscess, bacteremia, endocarditis, pericarditis, and meningitis.

Assessment Findings

The main symptoms of pneumonia are coughing, sputum production, pleuritic chest pain, shaking chills, shortness of breath, fever, and rapid, shallow breathing. Physical signs vary widely, ranging from diffuse, fine crackles to signs of localized or extensive consolidation and pleural effusion. There may also be associated symptoms of headache, sweating, loss of appetite, excess fatigue, and confusion (in older patients).

Diagnostic Tests

Chest radiography shows infiltrates with characteristics specific to the type of pneumonia present.
Sputum stain demonstrates acute inflammatory cells; Gram stain and sputum culture may identify the organism. Tracheobronchial secretions or brushings or washings obtained via bronchoscopy may be used for smear and culture.
Positive blood cultures in the patient with pulmonary infiltrates strongly suggest pneumonia produced by the organisms isolated from the blood cultures.
Pleural effusions, if present, should be tapped and fluid analyzed for evidence of infection in the pleural space.

Treatment

Antimicrobial therapy varies with the causative agent and should be reevaluated early in the course of treatment. Supportive measures include humidified oxygen therapy for hypoxemia, mechanical ventilation for respiratory failure, a high-calorie diet and adequate fluid intake, bed rest, and an analgesic to relieve pleuritic chest pain. Patients with severe pneumonia who are on mechanical ventilation may require positive end-expiratory pressure to facilitate adequate oxygenation.

Nursing Considerations

Maintain a patent airway and adequate oxygenation. Monitor pulse oximetry and arterial blood gas levels. Administer oxygen as ordered.
Teach the patient how to cough, breathe deeply, and clear secretions. In severe pneumonia that requires endotracheal intubation or tracheostomy (with or without mechanical ventilation), suction as needed to remove secretions.