1. Chapter 4 Airflow in the Respiratory System

2. Reference P
P42- 48

3. Resistance of the Ventilation
Elastic Resistance
Determined by the Compliance
Lung and Thoracic Cage Compliance
Inelastic Resistance
Airway Resistance

4. Inelastic Resistance airway resistance pulmonary tissue resistance
Friction
80% – 90%
pulmonary tissue resistance
viscosity and inertia
10 %– 20%

5. Airway Resistance the resistance to air flow in the airways due to
internal friction between gas molecules
friction between gas molecules and the walls of the airways

6. Types of Air Flow

7. Laminar and Turbulent Airflow
The gas flow in the larger airways (nose, mouth, glottis, and bronchi) is turbulent
Breath sounds heard with a stethoscope reflect the turbulent airflow
Gas flow in the smaller airway is laminar
Laminar flow is silent

8. Laminar flow
… is when concentric layers of gas flow parallel to the wall of the tube.
The velocity profile obeys Poiseuille’s Law

9. Poiseuille and Resistance
Airway Radius or diameter is KEY.
 radius by 1/2  resistance by 16 FOLD
think bronchodilator here!!

10. Factors Determining Airway Resistance
Lung volume
Bronchomotor tone
Airflow patterns

13. 3. Air Flow Patterns Laminar – small airways
Turbulent – nose, mouse and large airways
The more turbulence, the more resistancee

14. Site of Airways Resistance

15. Obstruction of Airway in Disease
Blocking of the airway by secretions
Bronchitis
Reduction in airway diameter due to contraction of smooth muscle or swelling
Asthma
Collapse of the airway due to disruption of the supporting parenchyma
Emphysema