3.2.8 The Effects of Lung Disease

Key Lung Diseases and Their Effects:

1. Pulmonary Tuberculosis (TB):

• Cause:
  • Infection by Mycobacterium tuberculosis.
• Effects:
  • Immune response forms tubercles (hard lumps) in the lungs.
  • Lung tissue is damaged, reducing surface area for gas exchange.
  • Symptoms:
  • Persistent cough, chest pain, fatigue, fever, and weight loss.

2. Pulmonary Fibrosis:

• Cause:
  • Scarring of lung tissue due to infection, toxins, or autoimmune conditions.
• Effects:
  • Alveolar walls thicken, increasing the diffusion distance for gases.
  • Lungs become less elastic, reducing their ability to expand.
  • Symptoms:
  • Shortness of breath, dry cough, fatigue, and chest discomfort.

3. Asthma:

• Cause:
  • Allergens, cold air, or exercise triggering inflammation of the airways.
• Effects:
  • Airways narrow due to inflammation and excess mucus production.
  • Reduced air flow leads to less oxygen reaching alveoli.
  • Symptoms:
  • Wheezing, breathlessness, tight chest, and coughing during attacks.

4. Emphysema:

• Cause:
  • Long-term exposure to irritants like smoking or air pollution.
• Effects:
  • Breakdown of alveolar walls, reducing surface area for gas exchange.
  • Loss of elastic fibres reduces recoil ability, trapping air in lungs.
  • Symptoms:
  • Shortness of breath, chronic cough, and difficulty exhaling fully.

General Effects of Lung Diseases on Gas Exchange:

1. Reduced Surface Area:

• Diseases like emphysema destroy alveoli, reducing the area available for diffusion.

2. Increased Diffusion Distance:

• Conditions like pulmonary fibrosis thicken the alveolar walls, slowing gas exchange.

3. Reduced Air Flow:

• In asthma, airway narrowing reduces the volume of air reaching the alveoli.

4. Reduced Lung Elasticity:

• Diseases like emphysema prevent the lungs from fully deflating, impairing ventilation.

Key Symptoms Across Lung Diseases:

• Shortness of Breath: Caused by reduced oxygen uptake and difficulty in expelling air.
• Fatigue: Due to low oxygen delivery to tissues.
• Cough: Attempt to clear mucus or debris from the airways.
• Chest Pain: Linked to inflammation or pressure in the lungs.

Diagnosis and Monitoring:

5. Spirometry:

• Measures lung function, including:
• Forced Vital Capacity (FVC): Maximum volume of air that can be forcibly exhaled.
• Forced Expiratory Volume in 1 Second (FEV1): Volume of air exhaled in the first second of forced expiration.
• Diseases often reduce these values, with the ratio of FEV1/FVC helping to differentiate between obstructive and restrictive conditions.

6. Oxygen Saturation:

• Measured using a pulse oximeter to monitor oxygen levels in the blood.

7. Chest X-rays:

• Identify structural damage or infections in the lungs.