Pneumonia

 Pneumonia Is an inflammatory process of the lung parenchyma that is commonly caused by infectious agents.

Causes of pneumonia

• Bacterial (the most common cause of pneumonia) 
• Viral pneumonia 
• Fungal pneumonia 
• Chemical pneumonia (ingestion of kerosene or inhalation of irritating substance) 
• Aspiration pneumonia (food, liquids, vomits from the mouth into your lungs)

Classification of pneumonia According to areas involved

Lobar pneumonia; if one or more lobe is involved 

Broncho-pneumonia; the pneumonic process has originated in one or more bronchi and extends to the surrounding lung tissue.

Bronchopneumonia is more common than lobar pneumonia

Types of pneumonia

• Community-acquired pneumonia (CAP), 
• Hospital acquired pneumonia (HAP), 
• Pneumonia in the immuno compromised host, 
• Aspiration pneumonia

Community-acquired pneumonia 

It occurs either in the community setting or within the first 48 hours of hospitalization. 

Pneumonia caused by Streptococcus pneumoniae (pneumococcus) and Haemophilus influenzae.

It is most prevalent during the winter and spring, when upper respiratory tract infections are most frequent.

Hospital-acquired pneumonia

It also known as nosocomial pneumonia, is defined as the onset of pneumonia symptoms more than 48 hours after admission to the hospital. 

HAP accounts for approximately 15% of hospital-acquired infections. 15% to 20% of intensive care patients. pneumonia that is associated with endotracheal intubation and mechanical ventilation.

The common organisms responsible for HAP include the pathogens Pseudomonas, Staphylococcus Aureus (MRSA), Escherichia coli.

Pneumonia in immunocompromised host

Immuno-compromised states occur with the use of :

    • corticosteroids, 

    • chemotherapy, 

    •use of broad-spectrum antimicrobial agents, 

    • AIDS, • genetic immune disorders 

    • (mechanical ventilation). 

Pneumonia in the compromised host may be caused by the organisms also observed in CAP or HAP (S. pneumoniae, S. aureus, H. influenzae, P. aeruginosa, M. tuberculosis).

 Aspiration pneumonia

It resulting from the entry of endogenous or exogenous substances into the lower airway

The most common form of aspiration pneumonia is bacterial infection from aspiration of bacteria that normally reside in the upper airways.

Other substances may be aspirated into the lung, such as gastric contents, chemical contents, or irritating gases. 

Complications

• Respiratory failure and Hypotension 
• Atelectasis may occur at any stage of acute pneumonia. 
• Pleural effusions occur in at least 40% of bacterial pneumonias. 
• An empyema occurs when thick, purulent fluid accumulates within the pleural space where the infection is located. 
• Super infection may occur with the administration of very large doses of antibiotics, such as penicillin, or with combinations of antibiotics.

Risk Factors 

    • Cigarette smoking 

    • Immuno-suppressed patients 

    • Prolonged immobility 

    • Depressed cough reflex (due to medications, or weak respiratory muscles); 

    • Abnormal swallowing mechanism 

    •  Placement of nasogastric, oro-gastric, or endotracheal tube

     • Antibiotic therapy - Alcohol intoxication 

    • General anesthetic, sedative. 

    • Advanced age 

    • Respiratory therapy with improperly cleaned equipment

Clinical Manifestations

    • Dyspnea, tachypnea, orthopnea 

    • Cough (productive but may be dry if the patient is dehydrated: requires hydration to loosen and                expectorate viscous sputum) 

    • Purulent sputum may be tinged with blood 

    • Cyanosis • Pyrexia, tachycardia, sweating 

    • Pain especially with lobar, over affected lobe 

    • Some patients exhibit an upper respiratory tract infection (nasal congestion, sore throat), 

    • poor Appetite

Diagnostic Findings

• physical examination, 
• chest x-ray studies,
• sputum studies and sputum culture. 
• Pulse oximetry or arterial blood gas analysis

Medical Management

• Antibiotic (erythromycin, azithromycin [Zithromax], or clarithromycin [Biaxin]), doxycycline (Vibramycin). 
• Antipyretics may be used to treat headache and fever; 
•  Mucolytic medications. 
• Warm, moist inhalations. 
• Antihistamines may provide benefit with reduced sneezing and rhinorrhea. 
• Nasal decongestants to relieve nasal congestion. 
• If hypoxemia develops, oxygen is administered. 

Preventive Measure

• Promote coughing and expectoration of secretions. 
• Stop smoking. • Initiate special precautions against infection.
• Perform suctioning and chest physical therapy if indicated. 
• Promote frequent oral hygiene. 
• Observe the respiratory rate and depth during recovery from general anesthesia 
• Promote frequent turning, early ambulation and mobilization, 
• Healthy balanced diet. 
• Make sure that respiratory equipment is cleaned properly.