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Questions and Answers
What is the total pressure of gases in a given mixture?
What is the total pressure of gases in a given mixture?
- The average pressure of the gases
- The sum of individual pressures of all gases (correct)
- The pressure of the most abundant gas
- The pressure of the gas with the highest solubility
How is the partial pressure of a specific gas determined?
How is the partial pressure of a specific gas determined?
- By dividing its concentration by the total volume
- By using its fractional concentration multiplied by the total pressure (correct)
- By subtracting its pressure from the atmospheric pressure
- By adding the gas's concentration to the atmospheric pressure
What is the value of partial pressure of O2 at sea level in dry inspired air?
What is the value of partial pressure of O2 at sea level in dry inspired air?
- 47 mm Hg
- 160 mm Hg (correct)
- 99.33 mm Hg
- 150 mm Hg
What happens to partial pressure of inspired oxygen, PIO2, when at a higher elevation?
What happens to partial pressure of inspired oxygen, PIO2, when at a higher elevation?
What will occur to PIO2 when receiving supplemental oxygen at an FIO2 of 80%?
What will occur to PIO2 when receiving supplemental oxygen at an FIO2 of 80%?
What does Henry's Law state regarding the concentration of a gas in a liquid?
What does Henry's Law state regarding the concentration of a gas in a liquid?
What factors affect the partial pressure of gases in the alveoli?
What factors affect the partial pressure of gases in the alveoli?
What is the formula to calculate the partial pressure of inspired oxygen in humidified air?
What is the formula to calculate the partial pressure of inspired oxygen in humidified air?
Why is the concentration of a gas in solution solely due to dissolved gas considered?
Why is the concentration of a gas in solution solely due to dissolved gas considered?
What does the term 'partial pressure' refer to?
What does the term 'partial pressure' refer to?
Which gas is the most abundant in Earth's atmosphere?
Which gas is the most abundant in Earth's atmosphere?
What is the average atmospheric pressure at sea level?
What is the average atmospheric pressure at sea level?
Which law states that in a mixture of gases, the total pressure is equal to the sum of the partial pressures of each gas?
Which law states that in a mixture of gases, the total pressure is equal to the sum of the partial pressures of each gas?
What percentage of oxygen is typically present in the air?
What percentage of oxygen is typically present in the air?
Which of the following is NOT a factor affecting the partial pressures of gases?
Which of the following is NOT a factor affecting the partial pressures of gases?
What physical process governs gas exchange between the lung and blood?
What physical process governs gas exchange between the lung and blood?
How does the motion of gas molecules relate to gas pressure?
How does the motion of gas molecules relate to gas pressure?
Which statement correctly describes bulk flow in relation to gas exchange?
Which statement correctly describes bulk flow in relation to gas exchange?
What factors would affect the partial pressure of inspired oxygen?
What factors would affect the partial pressure of inspired oxygen?
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Study Notes
Partial Pressure
- The pressure a single gas exerts in a mixture of gases
- Atmospheric pressure = Barometric pressure
- Most abundant gas in our atmosphere: nitrogen
- % of Oxygen in air: 21%
- Average atmospheric pressure at sea level: 760 mmHg
Calculating Partial Pressure
- Partial pressure of a specific gas: Px = Patm x Fx (Px = partial pressure of a gas in mmHg, Patm = atmospheric pressure, Fx = fractional concentration of gas)
- For air: Patm = PN2 + PO2 + PH2O + PCO2
Calculation of PO2 and PIO2
- PO2 = Patm x FO2 = 760 mm Hg x 0.21 = 160 mm Hg
- PIO2 = (Patm – PH2O) x FIO2 = (760 mm Hg - 47 mm Hg) x 0.21 = 150 mm Hg
Thought Experiments on PIO2
- Lower at the top of Mt. Humphrey’s compared to Phoenix because Patm is lower at high elevation, FIO2 doesn’t change
- Higher when receiving supplemental oxygen (increasing the FI02 to 80%) through a non-rebreathing mask because FIO2 increased, Patm is unchanged
Concentrations of Dissolved Gases
- Equilibrium reached when Px (gas) = Px (liquid)
- Henry’s Law: Concentration of a GAS (in liquid) = Px x solubility
- Concentration of a gas in solution is ONLY due to dissolved gas, not relevant if bound, e.g.to hemoglobin, or chemically modified, e.g.into HCO3-
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