P L6 - Resp. mechanics Flashcards
What are the factors that influence compliance?
- lung volume
- elasticity
- surface tension
Compliance is _______ to lung volume
proportional
At FRC what is the airway pressure equal to?
Airway pressure = atmospheric pressure = 0 mmHg
Respiratory resistance arises from? Which is the more dominant resistance force?
- Tissue resistance (20%)
- Frictional resistance due to air flowing thru the airways (80%)
Factors affecting airway resistance?
- Airway calibre
- Airway generation
- Airway profile
- Lung vol.
What system (autonomic/somatic) moderates the airway calibre?
autonomic
which part of the ANS causes the following:
- Increase in airway caliber (bronchodilation)
- Decrease in airway caliber (bronchoconstriction)
Increase: sympathetic (B2 adrenergic - relax VSM)
Decrease: Parasympathetic (muscarinic)
Airflow profile – what are the 2 flow types? Which occurs at high/low velocity? Which ones have high/low resistance?
Laminar – At low flow rates/ low velocity
– Low resistance
Turbulent – At high flow rates/high velocity
– High resistance
what number determines whether flow is turbulent or laminar? above what value will flow be turbulent?
Reynold’s number
flow is turbulent when Re>2000
Features of turbulent flow:
_____ density gas
______ flow (v)
______ radius (r)
______ viscosity
High, Large, Large, Low
What type of flow would we find in the following:
- Large airways
- Small airways
- Large airways —> Turbulent
- Small airways –> Laminar
Which type of airways are a major site of resistance?
medium bronchi
Relationship of elastic recoil and radial traction?
The greater the elastic recoil – the greater the radial traction
Parenchyma?
The connective tissue surrounding the airways of the lung.
Relationship between inspiration, expiration and resistance
Inspiration – Decrease in airway resistance as airways pulled open by radial traction
Expiration – increased airway resistance as inward recoil forces increase.
At FRC ______ want to collapse and _____ wants to expand. The combined system however ______
Lungs
Chest wall
doesnt have a tendency to collapse or expand.
Is inspiration/expiration more compliant?
Expiration
During deflation, the lung volume at any given pressure is _________ than during inflation.
greater
At higher volumes lung requires ______ pressure to expand
more. (compliance decreases at higher vol.)
Compliance is measured on the ______
limb of the pressure-volume loop
expiration
Which one is less compliant:
- air-liquid interface in the alveoli
- Saline- liquid interface in alveoli
Air-liquid interface
— saline-liquid interface is easier to fill and empty.
Elasticity depends on?
- elastin fibre content
- surface tension
Fluid Secretion in Lungs- Active transport of _____ accompanied by water flow from the ______ to the ______
Cl-
Interstitium
airspace
Fluid Absorption in Lungs- Active transport of _____ accompanied by water flow _____ its _______ gradient
Na+
down
osmotic
Is surface tension at the end of expiration in alveoli reduced or increased? Why?
Surface tension at end of expiration is reduced – as alveoli become smaller and thus the conc. of surfactant increases thus reducing surface tension.
Compliance formula?
Compliance = change in V/change in P
Work of breathing formula?
Work = pressure x volume
