4 5 Pulmonary Fibrosis Asthma and Emphysema Learning

4. 5 Pulmonary Fibrosis, Asthma and Emphysema

Learning Objectives • What are fibrosis, emphysema and asthma? • How does each of these diseases affect lung function?

What makes an efficient gas exchange surface? • What happens when this is impaired?

Pulmonary Fibrosis - Cause • Idiopathic (unknown cause) • Thought to be due to microscopic lung injury • Some individuals more suscpetible

Pulmonary Fibrosis - Pathophysiology • The epithelium of alveoli becomes scarred and thickens leading to “honey comb lung”. • Fibrosis also reduces the elasticity of the lungs.

Pulmonary Fibrosis Symptom: Shortness of breath • Most of the air space in the lungs is filled by fibrous tissue so less gas taken in at each breath. • Thickened epithelium of alveoli lengthens the diffusion pathway for gas exchange with the blood. • Breathing out difficult due to loss of elasticity.

Pulmonary Fibrosis Symptom: Chronic dry cough • Fibrous tissue obstructs the airways causing a reflex action to remove the obstruction. Symptom: Chest pain • Build up of pressure due to the mass of fibrous tissue. Scarring and damage caused by the tissue and coughing. Symptom: Weakness and fatigue • Due to lack of oxygen and therefore respiration

Asthma - Cause • Allergens such as pollen, animal fur and the faeces of dust mites

Asthma - causes • Affects up to 10% of the population, genetics play a role. • Triggers include air pollution, additives in food, exercise, cold air, stress. . . • The hygiene hypothesis may explain why it is more common in developed countries.

Asthma - Pathophysiology • An allergen or trigger causes white blood cells on the linings of the bronchi and bronchioles to release histamine which causes: – Inflammation of airways – Increased epithelial mucus secretion – Muscle surrounding the bronchioles contracts, causing constriction.

Asthma - Symptoms • Due to the constriction of the bronchi and bronchioles a patient experiences: – Difficulty in breathing – Wheezing when breathing – Tight feeling in the chest – Coughing

Emphysema - cause • One in five smokers develop the disease • Developed over a period of 20 years, only detected when too much damage has occurred.

Emphysema – Pathophysiology • Healthy lungs contain a tissue made of the protein elastin. The tissue stretches when we breathe in and springs back when we breathe out. • In Emphysema, the elastin becomes permanently stretched and the walls of the alveoli break down

Emphysema - Symptoms • Shortness of breath – Due to a reduction in the ability to exhale – reduced surface area of alveoli limits gas exchange with the blood. • Chronic Cough – Clear damaged tissue and mucus • Bluish skin colouration – Lack of oxygen

Lung Disease Match up • Pulmonary Fibrosis • Thickened epithelium • Asthma • Constricted airways • Emphysema • Alveoli wall breaks down