Respiration 2 Flashcards
Air flow =
Blood flow
What does blood flow through a vessel depends on?
–The pressure gradient
–Vascular resistance (r4)
In the case of smooth flow (laminar flow), What is the volume flow rate is given by?
the pressure difference divided by the viscous resistance (Poiseuille’s Law)
What does viscous resistance dependent on?
What is the fourth power dependent on?
This resistance depends linearly upon the viscosity and the length, but the fourth power dependence upon the radius is dramatically different.
Flow may be turbulent or laminar: Wherever a tube divides (airways, blood vessels) what happens to velocity and turbulent flow?
velocity increases and turbulent flow is more likely
![](https://s3.amazonaws.com/brainscape-prod/system/cm/300/327/401/a_image_thumb.png?1580148420)
What physical characterisitics is flow affected by?
Flow is affected by various physical characteristics:
- Flow requires a pressure gradient
- Flow depends on tube diameter
F ∝ r4
•3. Flow depends on tube length
F ∝ 1/l
•4. Flow depends on fluid/gas viscosity
F ∝ 1/η
F =
ΔP/R
What is resistance like in normal healthy airways?
What is airflow determined by?
- In normal healthy airways, resistance is low
- Airflow is determined by ΔP
What does Bronchoconstriction lead to?
Increased airway resistance e.g. in asthma
What is Bronchodilation?
Decrease airway resistance
What does Bronchodilation ensure?
How do inhalers work?
Pressure gradient established achieves maximum airflow with minimum resistance
e.g. ventolin and salbutmol inhalers that act on β-Adrenergic receptors across the smooth muscles that lines the bronciole tubules, causes blood vessels to dilate and open so breathing becomes easier
Describe Bronchoconstriction in disease (asthma)
Can respiratory conditions alter resistance?
Respiratory conditions can alter resistance
e.g. Asthma and Chronic obstructive pulmonary disease (COPD)
What happens if resistance increases?
If resistance increases then DPD must increase to maintain airflow Obstructive lung diseases with increased resistance = harder work to breathe
Can medication alter resistance?
understanding where particles may deposit along the respiratory tract e.g inhaled insulin
Is resistance altered by administering anaethetics?
Yes
What measures measures resistance via FEV1 and PEFR?
Spirometry
What makes resistance change in disease?
If the airways become narrowed because of disease (mucus blockage, inflammation, fibrosis), then resistance increases
Diseased lungs have altered tissue properties, not as flexible therefore more difficult to inflate
fibrotic livers are also problematic
When do lungs have to extend?
(inspiration) and return to their pre-inspiration volume/shape
What is pulmonary elasticity is governed by?
- Elastance; elastic recoil dictates how readily lungs rebound after having been stretched = ease of deflation
- Compliance; how much effort is required to stretch or distend the lungs = ease of inflation
How are Elastance and compliance related?
Elastance and compliance are inversely related
Explain some properties of stiff lungs
- Stiff lungs are more difficult to inflate but deflate more easily
- Stiff lungs have a high elastance, low compliance
What is the Elastic recoil of the lungs is partly due to?
properties of the parenchyma
Is elastin more/less compliant?
Elastin is more compliant
Is collagen more/less compliant?
collagen is less compliant
As well as elastin and collagen, Elastic recoil of the lungs is partly due to
Surface tension at the air-liquid interface in alveoli
What is surface tension?
- Surface tension is the force that makes water form droplets
- In liquids at air-liquid interfaces
- Results from the greater attraction of liquid molecules to each other (due to cohesion) than to the molecules in the air (due to adhesion)
- This creates surface tension
How does alveolar surface tension contribute to the lung’s elastic recoil?
- Air-liquid interface is important in the airways
- Pressure-volume curves of saline filled lungs demonstrate a lower elastance than air-filled lungs
- Elastic recoil of the lungs is a function of alveolar surface tension
How is compliance calculated?
- change in volume divided by change in pressure
- C = ΔV / ΔP
What does a compliance curve measure?
•measure changes in pressure and volume
C = ΔV / ΔP