BIOM1001 MOD4 LEC4 - Breathng, lung volumes & diseases

What is Anatomical Dead Space

Space in respiratory tract where there is air, but gas exchange does not take place. (Conducting airways)

Equates to ~150ml out of 500ml normal breath.

What is tidal volume?

The volume of air breathed in and out during quiet breathing

What is the difference between Pulmonary and Alveolar Ventilation

Pulmonary ventilation:

• is the volume of air breathed in and out per minute (ml/min)

• Pulmonary ventilation (ml/min) = tidal volume (ml/breath) * ventilation rate (breaths/min)

Alveolar Ventilation

• is the amount of air involved in gas exchange

• Alveolar ventilation = (tidal volume-dead space) * ventilation rate.

What is lung volume

Lung Volume:

• amount of air in lungs at different stages of breathing

Used to clinically diagnose lung pathologies, measured with spirometer.

What are the lung volume terms, and what do they mean?

Tidal Volume (TV)

• air inspired or expired during quiet breathing

Expiratory reserve volume (ERV)

• Extra air (in addition to TV) expired during forced expiration

Inspiration reserve volume (IRV)

• extra air (in addition to TV) inspired during forced inspiration

Residual Volume (RV)

• air left in lungs after forced experiation

What is dynamic small airway closure?

During forced expirations, pressure in intrapleural space becomes higher than in small airways → closure of smaller airways, trapping air in lungs.

What are three Lung Capacities

Inspiratory Capacity (IC)

• maximum volume of air that can be inspired

• TV + IRV

Vital Capacity (VC)

• maximum amount of air that can be breathed in and out

• TV+IRV+ERV

Functional Residual Capacity (FRC)

• Volume of air in lungs after normal expiration

• ERV + RV

Total Lung Capacity (TLC)

• Maximum volume of air that lungs can hod

• VC + RC

What influences Lung volumes?

Physiological factors

• age

• Height

• Anatomical build

• Gender

• Fitness

Pathological factors

• lung diseases

What are the two classes of respiratory disease?

Obstructive Lung Disease

• Difficulty with exhalation

• Air gets trapped in the lungs (higher residual volume)

Examples:

• asthma, Emphysema, Chronic bronchitis

Restrictive Lung Disease

• difficulty with inhalation

• Not enough air brought into the lungs (lower inspiratory capcity

Examples

• Pulmonary Fibrosis, COVID-19, Pneumonia

How does asthma work?

Is an obstructive disease

Periods of inflammation (thickened airway walls) of small airways

• inflamed small airways create greater resistance in airways

• Causes early dynamic small airway closure, increasing residual volume

• increased mucus production

• Airway hyperresponsivenss to allergens → bronchoconstriction

Triggered by allergens

Treated with bronchodilators and anti-inflammatory drugs.

How does COVID-19 work?

1. Inflammation - virus infects lungs, triggering immune response causing inflammation in lung tissue + alveoli

2. Oedema - fluid leaks into alveoli, reducing gas exchange and making lungs harder to expand

3. Scarring (fibrosis) - as lung heals, fibrotic tissue can form, makes lungs stiff, reduces lung volumes

4. ARDS - causes very poor oxygen levels and respiratory failure