COPD: Changes to Airways and Alveoli

Revision notes

Persistent airflow limitation

Chronic obstructive pulmonary disease (COPD) involves persistent limitation of airflow, commonly associated with chronic bronchitis and emphysema. Tobacco smoke is a major risk factor; occupational exposures, air pollution and inherited factors can also contribute. COPD is not simply another name for a short-lived chest infection.

In chronic bronchitis, persistent inflammation and excess mucus narrow airways. Ciliary clearance is impaired, so mucus and pathogens can accumulate. Airflow resistance increases and recurrent infections can worsen symptoms. The structural problem is mainly in the conducting airways, although effects extend throughout the respiratory system.

In emphysema, alveolar walls and elastic tissue are damaged. Neighbouring air spaces merge, reducing total gas-exchange surface area. Loss of elastic recoil makes expiration less effective and promotes air trapping. Larger air spaces therefore do not mean improved exchange: available wall area has been lost.

Consequences across scales

Reduced ventilation and exchange can lower oxygen delivery. During exercise, muscle demand for oxygen rises, so a reduced reserve becomes especially apparent. Fatigue and breathlessness can result. State these as physiological consequences rather than using a single symptom to diagnose someone. Oxygen and carbon dioxide changes vary with disease severity and are not identical in every patient.

Interpret lung-function data

FEV1 is the volume forcibly exhaled in the first second; FVC is the total forced vital capacity. Their ratio helps describe airflow obstruction. In a simplified example, reduced first-second emptying relative to total exhaled volume suggests obstructed flow. Formal diagnosis uses clinical evaluation and appropriate reference criteria; a revision calculation is not a diagnostic tool.

When comparing data, use matched conditions and reference values appropriate to the person. Age, height, technique and effort influence spirometry. A graph of volume exhaled against time should show slower early emptying for an obstructed example, not claim that the person has stopped breathing altogether.

Worked application and data skills

Fictional results: FEV1 = 1.5 L and FVC = 3.0 L. FEV1/FVC = 1.5/3.0 = 0.50, or 50%. A comparison sample has 3.2/4.0 = 0.80, or 80%. The first sample expels a smaller fraction in the first second. This supports an obstructive pattern in this teaching example; it is not enough by itself to diagnose an individual.

Common misconceptions

Larger emphysematous spaces mean less intact exchange area. COPD has multiple contributing mechanisms. A ratio and a percentage express the same comparison differently.

Examination tips

Separate chronic bronchitis mechanisms from emphysema mechanisms, then connect both to reduced respiratory performance.

Check your understanding

Five original questions. Use Tab to move between controls, arrow keys within a radio group, and Enter or Space on buttons. Feedback appears after Check Answer. Try Again clears the question. Attempts are not saved.

Sources and scope

Scope: Unit 1 A3.1.3. Original BTECRevision notes, schematics and questions. Independent resource; not endorsed by Pearson.

Official Pearson specification. Scientific review references are listed in the accompanying QA report.