Respiratory Tract Infections Overview

Respiratory Tract Infections

• Common conditions impacting conducting airways involve inflammation of mucosal layers, often triggered by infections.
• Pathogens stimulate immune cells, leading to further inflammation.
• Common Cold: Caused by viruses, leading to histamine/prostaglandin release, and inflammation. Symptoms include sinus pain, nasal congestion, runny nose, sneezing, watery eyes, scratchy throat, and headache. Blocking of the eustachian tube can cause ear stuffiness and pain, increasing risk of ear infection.
• Seasonal Rhinitis (Hay Fever): Inflammation of the nasal cavity due to an inflammatory response to specific antigens (pollen, mold, dust). Symptoms are similar to the common cold.
• Sinusitis: Inflammation of sinus cavities, caused by infection or irritation. Swelling causes intense pain due to pressure on the surrounding bone. Untreated infections risk spreading to brain tissue or affecting eyesight.
• Pharyngitis, Laryngitis, Bronchitis: Inflammation of the pharynx, larynx, and bronchi, respectively, commonly caused by viral or bacterial infections. Often associated with influenza (various viruses). Acute bronchitis is mostly viral; chronic bronchitis is caused by irritation like smoke or recurrent infections.

Pneumonia

• Inflammation of the lungs due to bacterial or viral infection or foreign substance aspiration.
• A rapid inflammatory response leads to swelling, engorgement, and exudation of protective sera.
• The respiratory membrane is affected, reducing gas exchange. Common symptoms include difficulty breathing, fatigue, fever, noisy breath sounds, and poor oxygenation.

Tuberculosis

• Caused by Mycobacterium tuberculosis. Slow replication, highly resistant to destruction.
• Spread via respiratory droplets. Primarily infects lung tissue.
• Can be asymptomatic or cause lung tissue destruction in immunocompromised individuals. Symptoms may include cough (potentially bloody), fatigue, shortness of breath, fever, chills, weight loss, and night sweats.

Ventilation and Gas Exchange Disorders

• Numerous disorders affect lower respiratory tract, impacting gas exchange.
  • Atelectasis: Incomplete expansion of alveoli due to pressure (e.g., tumor, pneumothorax, pleural effusion) or airway blockage (e.g., mucus plug, edema, secretions). Can occur post-surgery due to anesthesia, pain, and decreased coughing. Also linked to insufficient surfactant. Symptoms include crackles, dyspnea, fever, cough, hypoxia, and chest wall movement changes.
  • Bronchiectasis: Chronic dilation of bronchi and bronchioles with chronic infection and inflammation. Epithelial cells replaced with scar tissue. Loss of mucus and ciliary movement leads to chronic lower lung infections. Often associated with underlying medical conditions like immune suppression, cystic fibrosis, or chronic inflammatory conditions.
  • Asthma: Reversible bronchospasm, inflammation, and hyperactive airways triggered by allergens, irritants, infections, exercise, or emotions. Inflammation mediated by eosinophils, lymphocytes, and mast cells; cytokine mediated inflammation with mucous and edema causing obstruction. Symptoms include wheezing, shortness of breath, chest tightness, and cough. Status asthmaticus is a life-threatening, non-responsive extreme case.
  • COPD: Progressive and not fully reversible chronic airway obstruction. Characterized by emphysema and chronic bronchitis; both leading to impaired airflow on expiration, lung inflation, and impaired gas exchange. Emphysema involves elastic tissue loss, alveolar wall destruction and hyperinflation. Chronic bronchitis involves long-term airway inflammation, mucus secretion, and edema. Diagnosis via spirometry (breathing test). Symptoms are low peak flow rate of expired air in conjunction with shortness of breath and/or productive cough.
  • Cystic Fibrosis (CF): Hereditary disorder affecting epithelial linings of respiratory, gastrointestinal, and reproductive tracts. A defective gene on chromosome 7 makes linings impermeable to chloride, decreasing sodium and water excretion. Resulting in thick secretions obstructing airways. Leading to recurrent infections and potential lung tissue destruction. Treatment includes preventing and treating infections, chest physical therapy, and nutritional therapy.