RGI. 10 Obstructive and Restrictive Lung Diseases2024-25 WT

Types of Lung Diseases

• Obstructive Lung Disease

  • Problems in expelling air from the lungs

• Restrictive Lung Disease

  • Problems in drawing air into the lungs

• Both types can lead to shortness of breath with exertion; other specific symptoms may vary

• Some respiratory diseases display both obstructive and restrictive characteristics

• Additional respiratory issues can arise from:

  1. Gaseous diffusion issues across alveoli

  2. Neuromuscular disorders affecting respiratory muscles

  3. Poor lung perfusion (blood flow to the lungs)

  4. Ventilation-perfusion imbalance

lSpirometry Measurements

• A spirometer measures lung function

• Distinguishes between:

  • Restrictive Lung Disease

    • Reduced inspiratory reserve volume (IRV)

    • Increased residual volume (RV) in obstructive disease

  • Obstructive Lung Disease

    • Reduced vital capacity (VC) and increased residual volume (RV)

    • Implication: Less fresh air brought into lungs during exertion

Important Measurements

• Forced Expiratory Volume in 1 Second (FEV1): Volume of air expelled in the first second of a vital capacity measurement

• Forced Vital Capacity (FVC): Total volume of air expelled

• FEV1 is typically 80% of FVC

• FEV1/FVC Ratio: Used to diagnose obstructive vs. restrictive respiratory diseases

Obstructive Lung Disease

• Characteristics:

  • FEV1 reduced to <80% of normal range

  • FVC slightly reduced or normal

  • FEV1/FVC ratio reduced to < 0.7

• Conditions:

  • Asthma, Chronic Obstructive Pulmonary Disease (COPD)

  • COPD is the 4th most common cause of death worldwide

  • Further classification of COPD: chronic bronchitis and emphysema

Asthma

• Mechanisms of airway obstruction:

  1. Thickening due to inflammation & histamine-induced edema

  2. Excess mucus plugging the airways

  3. Smooth muscle hyper-responsiveness

• Complete obstruction can lead to death

• Triggers: specific irritants or immune stimulation causing acute attacks

• Prevalence: 9-10% of children in the USA, with higher rates in polluted areas

Chronic Bronchitis

• Inflammatory condition due to chronic exposure to irritants (e.g., smoke, pollution)

• Results in thick mucus production and airway narrowing

• Inhibition of cilia function leads to infection vulnerability

• Frequent coughing fails to clear mucus, leading to infections

Emphysema

• Caused by macrophage response to chronic irritation (especially smoke)

• Results in:

  1. Collapse of small airways (bronchioles)

  2. Breakdown of alveolar walls

  3. Disintegration of lung tissue

• Obstructs airflow due to bronchiolar collapse

• Damage to tissue is exacerbated by a deficiency in alpha-1 antitrypsin in some patients

Cystic Fibrosis

• Most common genetic disease in the USA (1 in 2,000 Caucasian children)

• Caused by CFTR gene mutation affecting chloride channel function

• Results in progressive tissue damage primarily in lungs and pancreas

• Lung Pathology:

  • CFTR regulates secretion of chloride and bicarbonate; mutation leads to dehydrated mucus

  • Dehydrated mucus obstructs airflow, traps pathogens, and makes breathing difficult

Restrictive Lung Disease

• In restrictive lung disease, both FVC and FEV1 are reduced, but the FEV1/FVC ratio may remain normal

• Causes include lung tissue damage or stiffness due to structural changes or musculoskeletal abnormalities

Causes of Lung Fibrosis

• Chronic Infection: Residual damage after pneumonia or tuberculosis

• Chronic Industrial Exposure: Silica, asbestos, bird droppings

• Drug-Induced: Certain chemotherapy drugs and antibiotics

• Radiation-Induced: Exposure during treatment for cancers

• Sarcoidosis: Inflammatory granulomas in lungs and lymph nodes

• Lung Surgery: Possible damage contributing to fibrosis

Tuberculosis (TB)

• Caused by Mycobacterium tuberculosis

• Diagnosed based on long-term lung tissue damage:

  1. Cavitation

  2. Fibrosis

  3. Irreversible bronchiole dilation

• Treatment: Requires prolonged antibiotic course

Post-Tuberculosis Lung Damage

• TB survivors may develop obstructive or restrictive lung disease, or both

Musculoskeletal Abnormalities

• Polio: Infects motor neurons causing paralysis; affects breathing muscles and results in muscle atrophy

• Myasthenia Gravis: Autoimmune disease impeding voluntary muscle contraction, can weaken diaphragm

• Obesity: Compresses lungs, leading to restrictive lung dynamics and possible hypoventilation syndrome (OHS)

Conclusion & References

• For more information contact: Prof. Warren Thomas, wathomas@rcsi-mub.com

• References:

  • Chiras 9th Ed Ch 9 pp 202-210

  • Sherwood 9th Ed Ch 13 pp 455-463