lecture 16 - respiratory system 3 Flashcards
consequences of dead space
last out first in
conducting system filled with stale air at the end of expiration (high PCO2) which returns to the lungs on inspiration
this reduces the overall PO2 and raises PCO2
mixing of old and fresh air
factors affecting diffusion of gas in the respiratory system
pressure gradient of the gas
solubility of the gas in liquid - gas needs to be soluble to be transported
temperature
what is Daltons law?
the total pressure (P) exerted by a mixture of gases is equal to the sum of the pressures exerted by the individual gases
what is partial pressure of a gas?
the pressure of an individual gas in a mixture
determined by its relative abundance in the mixture and is independent of the molecular size of the gas
= P(atmos) x % of gas
what is Henry’s law?
at constant temperature, the amount of gas thats dissolved in a liquid depends on the solubility of the gas in the liquid and the partial pressure of the gas
CO2 is more soluble than O2
• more CO2 in solution
why theres a need for O2 carrying molecules
characteristics of pulmonary circulation
low pressure system
high flow
right ventricle –> pulmonary trunk –> pulmonary arteries –> lungs –> pulmonary veins –> left atrium
what is Flicks law of diffusion?
diffusion is proportional to the SA, conc gradient and barrier permeability
flux = (P x ∆C) / X
P = permeability of barrier x SA ∆C = concentration gradient X = diffusion distance
SA, permeability and distance are usually constant, so conc gradient is the main drive for gas exchange
what is the symbol for alveolar pressure?
P(A)
P(A)O2 and P(A)CO2 are inversely related during changes in ventilation
hyperventilation
results in increased P(A)O2 and decreased P(A)CO2
hypoventilation
results in decreased P(A)O2 and increased P(A)CO2 and hypoxemia
what does hyperbaric mean?
higher than normal pressure
what is hyperbaric oxygen therapy?
person placed in chamber and exposed to higher than normal PO2 leads to increased P(A)O2 levels and O2 exchange
used to treat conditions benefitting from increased O2 delivery • severe blood loss • crush injuries • anaemia • burns • general recovery
how is hyperbaric oxygen therapy used to treat decompressive sickness?
seen in divers who ascended too rapidly
used by dissolved gases in the blood coming out of solution and forming bubbles in the blood stream
therapy forces gases back in solution, eliminating bubbles
emphysema
destruction of alveoli means less SA for gas exchange
fibrotic lung disease
thickened alveolar membrane slows gas exchange
loss of lung compliance may decrease alveolar ventilation
