Lung Ventilation Flashcards
What does diffusion resistance depend on?
Nature of barrier and nature of gas
What does diffusion of gases depend on?
Area
Large gradients
Large diffusion resistance
What does gas have to diffuse through?
Alveolar wall Epithelial cell of alveolus Tissue fluid Endothelial cell of capillary Plasma Red cell membrane Haemoglobin
The bigger the molecule, the slower/faster it diffuses?
Slower
What does the rate of diffusion of a gas in liquid depend on?
Its solubility
What is more soluble, oxygen or CO2? How many times faster does it diffuse
Carbon dioxide
21 times faster than oxygen
What diffuses more quickly overall? Oxygen or carbon dioxide?
Carbon dioxide
What determines the gas composition of arterial blood and why?
The composition of alveolar air because the are in equilibrium
Define tidal volume. Normal value?
Volume in and out with each breath
0.5L
Define inspiratory reserve volume. Normal value?
Extra volume that can be breathed in over that at rest
2.5L
Define expiratory reserve volume. Normal value?
Extra volume that can be breathed out over that at rest
1.5L
Define residual volume. Normal value?
Volume left in the lungs at maximal expiration
0.8L
Define vital capacity. Normal value?
Measured from max inspiration to max expiration so is the biggest breath that can be taken
5L
Define inspiratory capacity. Normal value?
Biggest breath that can be taken from resting expiratory level (so the lung volume at the end of quite exportation)
Typically 3L
Define functional residual capacity. Normal value?
Volume of air in lungs at resting expiratory level
2L
(=expiratory reserve volume + residual volume)
What is ventilation rate and how is it worked out?
Volume of air breathed in and out per minute
=volume moved per breath x respiratory rate
What is a normal value of total lung capacity?
5.8L
What is the alveolar ventilation rate?
Volume of air that actually reaches the alveoli
What is the serial deadspace?
Volume of the airways
What is distributive dead-space?
Parts of the lung which are not airways but don’t support gas exchange such as dead/damaged alveoli or alveoli with poor perfusion.
What is physiological dead space? Normal value?
Distributive dead space + serial dead space
0.17L
How do you work our dead space ventilation rate?
Dead space volume x respiratory rate
How do you work out alveolar ventilation rate?
Pulmonary ventilation rate - dead space ventilation rate
