Applying gas exchange principles
Disease can impair lung function when it alters the alveolar exchange surface, obstructs the airways or interferes with vessels supplying the lungs.
Lung cancer
In lung cancer, loss of normal control over cell division can produce a tumour. A growing tumour may obstruct an airway or compress nearby blood vessels, disrupting normal lung function.
COPD
Chronic obstructive pulmonary disease (COPD) is a group of lung conditions that includes chronic bronchitis and emphysema. Damage within the lungs or airways can decrease airflow, reduce gas exchange, or affect both.
Emphysema and the exchange surface
Emphysema can produce larger air spaces with fewer separate alveoli, decreasing the total surface available for diffusion.
- A smaller alveolar surface area reduces the rate at which oxygen enters the blood.
- Reduced oxygen uptake contributes to breathlessness.
- With less oxygen available for aerobic respiration, less energy can be released, contributing to fatigue.
Exam Tip: Use the information given about a disease rather than relying on memorised disease detail. Connect the stated change in lung structure to gas exchange or ventilation, then use that effect to explain the symptom.