1. A patient is admitted to the hospital with a case of blood acidosis due to decreased responsiveness to hypoxia. As the biomedical engineer in charge, you are tasked to design a simple ventilation assist device to replace a recently broken down one. The $P_{CO_2}$ and $P_{O_2}$ of the patient's blood has been determined to be 55 mmHg and 31 mmHg, respectively. Given that the alveoli have a functional surface area of 70 m$^2$ and alveolar-capillary thickness of 2µm, a) What percentage of oxygen would the 800mmHg gas supply of your device need in order to establish an oxygen diffusion rate of 600 m$^3$s$^{-1}$? [$O_2$ solubility = 0.024m$^2$s$^{-1}$Pa$^{-1}$, M = 32] b) Calculate the total resistance offered by the lungs to the diffusion of oxygen if the rate of oxygen-haemoglobin combination is 2000 s$^{-1}$ Pa$^{-1}$. [Volume of blood in pulmonary capillary is 70 ml].
Added by Carolyn L.
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This can be done using the alveolar gas equation: PAO2 = (FiO2 x (Pb - PH2O)) - (PaCO2 / RQ) where PAO2 is the partial pressure of oxygen in the alveoli, FiO2 is the fraction of inspired oxygen (which we need to calculate), Pb is the barometric pressure (which Show more…
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A COPD patient had a PO2 of 60 mmHg and their hematocrit analysis showed a hemoglobin content of 10 g/dL. Given that at 100% saturation, 1 g of hemoglobin contains 1.34 mL of oxygen and that the solubility coefficient of this gas is 0.003 mL/(dL blood/mmHg), what is the total O2 content? Show calculations.
Adi S.
The partial pressure of oxygen in the lungs is about $150 \mathrm{mm}$ of Hg. (The partial pressure is the pressure of the oxygen alone, if all other gases were removed.) This corresponds to a concentration of $5.3 \times 10^{24}$ molecules per $\mathrm{m}^{3}$. In the oxygen-depleted blood entering the pulmonary capillaries, the concentration is $1.4 \times 10^{24}$ molecules per $\mathrm{m}^{3} .$ The blood is separated from air in the alveoli of the lungs by a $1-\mu \mathrm{m}$ -thick membrane. What is the rate of transfer of oxygen to the blood through the $5 \times 10^{-9} \mathrm{m}^{2}$ surface area of one alveolus? Give your answer in both molecules/s and $\mu \mathrm{mol} / \mathrm{s}$. Assume The diffusion coefficient for oxygen in tissue is $2 \times 10^{-11} \mathrm{m}^{2} / \mathrm{s}$. Give your answer to 1 significant figure.
Problem 1 The solubility of oxygen in plasma at 37 °C is 1.33 x 10⁻⁶ mol L⁻¹ mmHg⁻¹. The heme concentration in red blood cells is 0.0203 mol/l= 4Cₔဧ. The blood volume fraction (hematocrit) is typically 0.45 for men. Determine the fraction of oxygen in solution and that bound to hemoglobin in arterial and venous blood. The solubility of oxygen in red blood cells is 1.5 x 10⁻⁶ mol L⁻¹ mmHg⁻¹. The partial pressure of oxygen for arterial blood is 95 mmHg while the partial pressure for the venous blood is 38 mmHg. The partial pressure (P₅₀) of oxygen for 50 % saturation (S̄) is 26 mmHg. Problem 2 The permeability of normal rabbit arterial endothelium to low-density lipoproteins (LDL) is 5 x 10⁻⁹ cm s⁻¹. The diffusion coefficient of LDL in the rabbit arterial wall is 1 x 10⁻¹⁰ cm² s⁻¹. The rabbit pulmonary arterial trunk thickness is 0.57μm. a) Determine the Biot number b) What does this result indicate about the endothelium as a barrier to LDL transport?
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