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Lecture 5 Resp

# Lecture 5 Resp - NPB113 Diffusion and Uptake of Gas...

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1 February 23, 2010 NPB113 Diffusion and Uptake of Gas & Transport of Gases in Blood 5-1 Flow Limited and Diffusion Limited Peak Uptake of Gases by the Blood & Alveoli Peak rate of Gas Uptake by blood from the alveoli or by the alveoli from the blood can be either Flow Limited – uptake solely determined by the rate of blood flow past the gas exchange surface. Flow limited system indicates that there is sufficient time for equilibration of partial pressures of the gas while the blood is in contact with the gas exchange surface – alveoli. Diffusion Limited – uptake solely determined by the diffusion gradient for the gas and is independent of blood flow past the gas exchange surface. Diffusion limited system indicates that there is not equilibration of partial pressures across the gas exchange surface and the quantity of gas taken up/unit time solely determined by the partial pressure. Uptake of oxygen and carbon dioxide in the lung is normally flow limited – pulmonary capillary blood and alveolar gases reach equilibrium within ¾ of the time that the blood is in contact with the gas exchange surfaces. Thus, before the blood is ¾ the way along the pulmonary capillaries, there is equilibration of partial pressures for oxygen and carbon dioxide between the alveoli and the blood.

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2 February 23, 2010 NPB113 Diffusion and Uptake of Gas & Transport of Gases in Blood 5-2 Diagram of Flow Limited and Diffusion Limited Systems for Gas Exchange
3 February 23, 2010 NPB113 Diffusion and Uptake of Gas & Transport of Gases in Blood 5-3 Questions regarding Flow and Diffusion Limited Systems What will happen to gas uptake in a flow limited or diffusion limited gas exchange system if there is a decrease or increase in the partial pressure of the alveoli? If the rate of blood flow through a flow limited system increases, can the gas uptake convert to a

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Lecture 5 Resp - NPB113 Diffusion and Uptake of Gas...

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