Respiratory Mechanics Flashcards
What is airflow driven by?
Pressure gradient
What is the relationship between flow and pressure difference?
They’re directly proportional
What is the relationship between the pressure difference and resistance in airways?
Inversely propotional
What are the sources of respiratory resistance?
Tissue resistance
FRICTIONAL RESISTANCE TO FLOW OF AIR THROUGH AIRWAYS
What factors affect airflow resistance?
Airway calibre - internal diameter
Airway profile
Airway generation
Lung volume
What is airway calibre modulated by?
ANS
Decreased by bronchoconstriction and secretions
Increased by Beta2 adrenergic
What is laminar flow?
Orderly, low resistance, low flow rate
What is turbulent flow?
Disorganised, high resistance, high flow rate
What is laminar flow directly proportional to?
ΔP/R
What is Poiseuille’s Law?
If radius is halved, resistance is upped by 16
1/r^4
What is turbulent flow directly proportional to? What does this mean for turbulent flow?
V^2 = ΔP
Higher pressure needed to drive flow
What determines the type of flow present?
Reynold’s number
>2000=turbulent flow
When is turbulent flow likely?
High density gas
Large flow & radius
Low viscosity
What flow is found in both large and small airways respectively?
Turbulent, laminar
Where is a major site of resistance?
Medium bronchi
Why is this location a major site of resistance?
Short length
Frequent branching with extreme turbulence
Airways have parallel layouts
What is the parenchyma?
Connective tissue surrounding airways of the lung
During quiet breathing, when is resistance increased and decreased?
Increased during expiration
Decreased during inspiration
Why does resistance increase during expiration?
Outward tethering force diminishes
Inward elastic recoil forces increase which decrease the radius
