Gas Composition & Exchange Flashcards
Mix of Gases in the air
- Nutrogen: 78%
- Oxygen: 21%
- Carbon Dioxide: 0.033%
Patm Equation
Patm = Poxy + Pnitro + Pcarbon dio
- Patm in humid air needs to account of Pwater
Oxygen and Carbon Dioxide Pressures in atmosphere
Poxy = 160mm hg
Pcarbon dio = 0.25mm hg
Oxygen and Carbon Dioxide Pressures in alveoli
Poxy = 100mm hg
Pcarbon dio = 40mm hg
- alveolar O2 is lower b/c it is not purely fresh, some of the air comes from the dead space which is stale
- alveolar CO2 is much higher because it is being offloaded from exhausted muscles
Hypoventilation
slow breathing, a decreased venitlation rate
- Poxy decreased
- Pco increases
Hyperventilation
fast breathing, a increased ventilation rate
- Poxy increases
- Pco decreases
Gas Exchange
gasses diffuse across alveolar epithelial cells and capillary endothelial cells
Diffusion Rate
- proportional to SA, membrane permeability, gradient
- inversely proportional to diffusion distance
Partial Pressures in the alveoli
oxygen: 100mm hg
carbion dioxide: 40mm hg
Partial Pressures in the Arteries
oxygen: 100mm hg
carbion dioxide: 40mm hg
Partial Pressures in the cells
oxygen: less than 40mm hg
carbion dioxide: greater than 46mm hg
Partial Pressures in the veins
oxygen: less than 40mm hg
carbion dioxide: greater than 46mm hg
Factors that decrease O2 reaching the alveoli
- low O2 content in the atmosphere
- low alveolar ventilation
- decreased lung compliance
- increased airway resistance
- CNS depression
Emphysema
destruction of alveoli (smoke) means less SA for exchange
Asthma
increased airway resistance affects partial pressure gradient
