INCOMPLETE !3.1 lung ventilation Flashcards
To meet the demands of gas exchange what is needed ?
- very large surface area
- very large number of very small compartments
- proximity to blood supply
Conducting airways continue of what ?
- trachea branches to primary bronchi
- further division to lobar (secondary) & segmental (tertiary) bronchi
- divisions continue until become bronchiole and terminal bronchioles
where does gas exchange occur ?
respiratory airways
what do respiratory airways comprise of ?
- respiratory bronchioles
- alveolar ducts
- alveoli
Each alveolus surrounded by a .1…
Branching blood vessels in the pulmonary circulation, forming a ..2.. like the airways
- capillary
- tree
What 2 features of the pulmonary circulation mean that no fluid should not form in the lungs ?
- low resistance
- low pressure
difference between pulmonary circulation and systemic system
It receives entire cardiac output so it’s supply driven
AND NOT deman led like systemic system
Typical pulmonary arterial pressure ?
14 - 18 mmHg (mean)
Typical systolic and diastolic pulmonary arterial pressure ?
systolic: 20-25
diastolic: 4-12
What’s the difference between what the hydrostatic and oncotic pressure gradient drive ?
hydrostatic pressure gradient -> drives fluid from the pulmonary microcirculation into the interstitium
oncotic (colloidal osmotic) pressure -> gradient favours movement of fluid in the opposite direction
What 3 factors does gas exchange which occurs via diffusion depend on ?
- area
- gradients
- diffusion resistance (nature of barrier & gas)
What are gradients in gas exchange created by ?
- alveolar air composition
- gases in blood returning to the lung
slide 11 area…
Values of pO2 & pCO2 of alveolar air which has a different composition to the atmosphere ?
pO2 normally 13.3 kPa
pCO2 normally 5.3 kPa
Typical values of pO2 and pCO2 in mixed venous blood, but varies with metabolism
pO2 = 6.0 kPa
pCO2 = 6.5 kPa
Why will oxygen diffuse into blood and carbon dioxide out ?
pO2 in alveolar gas(13.3) > pO2 in returning blood (6.0) (<—)
pCO2 in alveolar gas (5.3)< pCO2 in returning blood (6.5) (–>)
What makes up the 5 cell membranes, 3 layers of cytoplasm and 2 layers of tissue fluid for the nature of barrier with diffusion resistance ?
- diffusion through gas to alveolus
- epithelial cell of alveolus
- tissue fluid
- endothelial cell of capillary
- plasma
- red cell membrane
What are the 2 factors of nature of gases regarding diffusion resistance ?
- gases diffuse through gases at rate inversely proportional to molecular weight (big molecules diffuse slower, carbon dioxide slower than oxygen)
- gases diffuse through liquids at rate proportional to solubility (more soluble, faster diffusion & CO2 much more soluble than O2 so diffuses 21 times faster)
Compare speed of diffusion of CO2 and O2
CO2 diffuses much faster than O2 overall
approximately 21 times faster
What diseases will affect oxygen diffusion more ? (re-word Q!!)
Diseases that increase the amount of fluid
Why is exchange of oxygen always the limiting step in gas exchange ? (workbook has answer ….!)
gas diffusion not limiting in normal lung …
alveolar ventilation …
Ventilation involves the expansion of lungs this increases the volume of what ?
- respiratory bronchioles
- alveolar ducts
therefore air flows down airway to them due to pressure gradient
How is ventilation measured ?
use of a spirometer
Spirometer Q ….
what is tidal volume ?
volume in and out with each breath
what is inspiratory reserve volume ?
extra volume that can be breathed in over that at rest
what is expiratory reserve volume ?
extra volume that can be breathed out over that at rest
what is residual volume ? [alter answer !!]
- volume left in lungs at maximal expiration
- volume does not change
- cannot be measured by spirometer
- use helium dilution
Difference between lung capacities and lung volumes ?
Lung volumes change with breathing pattern, but capacities do not because measured from fixed points in breathing cycle
Name the 4 lung capacities and which ones can be measured by spirometry [alter Q and A]
- Vital capacity (VC) [can be measured]
- Total lung capacity (TLC)
- Inspiratory capacity (IC) [can be measured]
- Functional residual capacity (FRC)
how is vital capacity measured from ?
max inspiration to max expiration
when does vital capacity often change ?
in disease
calculation for total lung capacity is what ?
Total lung capacity (TLC) = Vital Capacity (VC) + Residual Volume (RV)
What is functional residual capacity and how can it be calculated ?
Volume of air in lungs at resting expiratory level
FRC = Expiratory reserve volume + residual volume
What is inspiratory capacity ?
Biggest breath that can be
taken from
resting expiratory level
What are the typical values of the volumes and capacities dependent on ?
sex , age, race , state of health
Typical value of the following volumes:
1. tidal
2. residual
3. inspiratory reserve
4. expiratory reserve
- 0.5 L
- 2.5 L
- 1.5 L
- 1.5 L
Typical values of the following capacities ?
1. Functional residual
2. inspiratory
3. vital
4. total lung
- 3L
- 3L
- 4.5L
- 6L
pulmonary ventilation rate…
dead space..
what is physiological dead space ?
serial (anatomical) dead space + distributive (alveolar) dead space
What is serial dead space the volume of ?
the conducting airways (up to and including the terminal bronchiole)
serial dead space is measured by ..1…
and typically is about ….2… litres
- nitrogen washout
- 0.15 L
Distributive dead space includes what ?
Some parts do not support gas exchange
- dead or damaged alveoli * alveoli with poor perfusion
What must dead space be filled with each breath ?
with air
What do the following stand for ?
1. PVR
2. AVR
3. DSVR
- pulmonary ventilation rate
- alveolar ventilation rate
- dead space ventilation rate
calculation of alveolar ventilation rate (AVR) ?
& how to calculate DSVR ?
PVR - DSVR
where DSVR = DS volume x RR
Ventilation perfusion matching …
ventilation perfusion mismatch …
