m6 (3/?) - obstructive lung diseases, COPD

obstructive lung diseases

• physiological explanation

• unifying symptom

• unifying sign

• diseases due to airway obstructions that worsen with expiration, as lung emptying becomes slowed

• symptom = dyspnea

• sign = wheezing

bronchial asthma

chronic inflammatory disorder of bronchial mucosa, causing hypersensitivity and airway constriction

hypersensitivity # that bronchial asthma corresponds to

Type 1 hypersensitivity - allergy response

2 phases of bronchial asthma response

1. early / acute phase

2. late phase

early/acute phase: bronchial asthma

type 1 hypersensitivity repsonse: allergen exposure in bronchial mucosa activates B cells to produce IgE → IgE complexes with mast cells → mast cells degranulate and release chemicals (histamine, leukotrines, prostaglandins) causing vasodilation, increasing capillary permeability.

mucosal edema, mucosal secretion, and bronchial smooth muscle contraction also occurs

late phase: bronchial asthma

4-8 hours after early response and may be more severe

1. inflammatory chemicals are released: chemokines in early response attract neutrophils, eosinophils, lymphocytes to area → bronchospasm, edema, mucous secretion

2. cell damage, mucous accumulation to ciliated epithelial cells. mucous accumulates more and can lead to irreversible long-term airway damage

3. obstructed airway makes expirations difficult and air becomes trapped in alveoli → blood perfusion over alveoli decreases, causing capillary collapse → hypoxemia occurs

hypoxemia stimulates respiratory centre → hyperventilation → CO2 diffuses out of blood → hypocapnia → respiratory alkalosis

describe what continues to occur in late stage bronchial asthma after hypoxemia worsens, hypocapnia occurs, and respiratory alkalosis occurs

airway obstruction increases air trapping, hyperexpanding lungs and thorax, and decreasing tidal volume. CO2 levels begin rising and hypercapnia occurs, leading to respiratory acidosis → now a life-threatening situation requiring mechanical ventilation!

mainstays of bronchial asthma treatment

• avoiding allergens

• inhaling bronchodilators, anti-inflammatories

• acute attack = adrenaline

COPD

chronic obstructive pulmonary disease characterized by airway obstruction causing difficult exhalations

examples of COPD diseases

• emphysema

• chronic bronchitis

chronic bronchitis

hypersecretion of mucous and chronic cough for at least 3/12 months of year, for at least 2 consecutive years

most common cause of chronic bronchitis

smoking

physiological development of chronic bronchitis

1. chronic irritant inspiration → airway inflammation → edema, thick mucous

2. continued inflammation increases size, number of mucous glands, goblet cells in airway epithelium

3. inflammation harms ciliated epithelial cells, so mucous is not cleared

4. airways narrow from thickened bronchial wall, making expiration difficult

5. obstruction leads to hypoxemia

6. airways collapse early in expiration, causing air trapping → decreased tidal volume, hypoventilation, and hypercapnia

are pathologic changes in chronic bronchitis reversible?

no

treatment of chronic bronchitis

• ceasing smoking

• bronchodilators

• chest physical therapy

• antibiotics (infection)

• steroids

• oxygen therapy

emphysema