Lecture 4 (Respiration 1) Flashcards
What factors have a role in determining air flow? (4)
-Type of air flow
-Resistance of the pathway
-Pressure gradients generated across the airways.
-Links between lung volume, resistance and airflow
What are the 3 types of airflow?
Laminar
Unstable
Turbulent
What determines air flow type?
Reynolds number (Re)
What are the Reynolds number (Re) values for laminar, unstable and turbulent flow?
-Re < 2000 – laminar flow
-Re between 2000 and 3000 - flow is unstable switching between laminar and turbulent
-Re >3000 – turbulent flow
What influences Reynolds number in terms off fluid? (2)
Viscosity and Density
What state is airflow usually in?
Turbulent
(laminar sometimes in terminal airways)
How is laminar flow proportional to pressure and resistance? (2)
-Proportional to the pressure gradient
-Inversely proportional to the resistance
Where is the flowrate maximum?
In the center
Describe the pressure gradient in alveoli when breathing in and out? (2)
-Pressure in alveoli is sub atmospheric when breathing in
-Pressure in alveoli is greater than atmospheric when breathing out
Describe the relationship between flow rate and pressure difference in turbulent flow state?
Under conditions of turbulent flow, the flow rate is proportional to square root of the pressure difference
Describe the relationship between flow rate and pressure difference in laminar flow state?
Under conditions of turbulent flow, the flow rate is proportional to the pressure difference
What is transitional airflow?
As air reaches branching points goes from laminar to turbulent back to laminar
What is airway generation number?
More branches of airways going deeper into lungs
How does CSA in airways affect velocity at trachea, further down branches and terminal airways? (3)
-Small CSA at trachea / bronchioles so high velocity
-Further down branches CSA increases so velocity drops as you go down generations
-Velocity drops down to nearly 0 at terminal airways
What is COPD?
Chronic Obstructive Pulmonary Disease (COPD)
What is COPD?
Group of progressive obstructive lung diseases characterised by an increase in airway resistance and decrease in airflow
What are 2 examples of COPD? (2)
Chronic Bronchitis – long standing inflammation of the bronchi and bronchioles
Emphysema – destruction of alveoli walls
How do you manage COPD?
A progressive disease – no cure – control the symptoms
Bronchodilators – anticholinergics or 𝛃2 adrenorecptor agonists.
Glucocorticosteroids (reduce inflammation in airways)
How does COPD cause reduced airflow? (2)
-Inflation in lumen causes in to narrow
-Destruction of alveoli walls affects elasticity of airways and makes them flimsy)
What is the impact of resistance on flow is determined by?
Poiseuille’s law
What is Poiseuille’s law?
Airway resistance is proportional to gas viscosity and the length of the tube but is inversely proportional to the fourth power of the radius
What is resistance proportional?
Resistance is proportional to 1 / radius of fourth power
What are the percentages of air way resistance for : (3)
Pharynx-Larynx -
Airways >2mm diameter –
Airways <2mm diameter –
Pharynx-Larynx - 40%
Airways >2mm diameter – 40%
Airways <2mm diameter – 20%
How does COPD affect these values: (2)
Pharynx-Larynx - 40%
Airways >2mm diameter – 40%
Airways <2mm diameter – 20%
Total airway resistance - 1.5cm H2O .s.litres-1
-Huge increase in airway resistance for small airways and total resistance due to inflammation
-Pharynx and Larynx both contribute the same to the resistance
Pharynx-Larynx - 12%
Airways >2mm diameter – 18%
Airways <2mm diameter – 70%
Total airway resistance - 5.0 H2O .s.litres-1