Chapter 4 Airflow in the Respiratory System

Reference P218 - 220 P42- 48

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

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

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

Types of Air Flow

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

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

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

Factors Determining Airway Resistance Lung volume Bronchomotor tone Airflow patterns

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

Site of Airways Resistance

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