Gas Laws and Their Applications
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Questions and Answers

What does the Ideal Gas Law express when n remains constant?

  • Pressure is inversely proportional to temperature
  • Pressure varies directly with volume
  • Volume increases with an increase in pressure
  • The product of pressure and volume remains constant (correct)

    • According to Boyle's Law, what happens to pressure when volume is reduced while temperature is constant?

  • Pressure remains unchanged
  • Pressure increases exponentially
  • Pressure increases inversely (correct)
  • Pressure decreases linearly

    • Which law indicates that the volume of a gas is proportional to its temperature when pressure is held constant?

  • Dalton’s Law
  • Charles’ Law (correct)
  • Gay-Lussac’s Law
  • Ideal Gas Law

    • What does Gay-Lussac’s Law indicate when the volume of a gas remains constant?

    <p>Pressure varies directly with temperature</p> Signup and view all the answers

    In a mixture of gases, what do Dalton’s Law state about the total pressure?

    <p>Total pressure is equal to the sum of partial pressures</p> Signup and view all the answers

    What is the water vapor pressure in the alveoli at body temperature?

    <p>47 mmHg</p> Signup and view all the answers

    What is the correct representation of the Alveolar Gas Equation when FiO2 is greater than or equal to 60%?

    <p>PAO2 = (PB - PH2O) FiO2 - PaCO2</p> Signup and view all the answers

    Which factor is NOT involved in the passive diffusion of gases in the lungs?

    <p>Increased temperature</p> Signup and view all the answers

    In the alveoli, what is the partial pressure of CO2 when the PAO2 is 100 mmHg?

    <p>46 mmHg</p> Signup and view all the answers

    At sea level, what is the barometric pressure exerted by atmospheric gases approximately?

    <p>760 mmHg</p> Signup and view all the answers

    What time frame is required to reach equilibrium for gas diffusion across the alveolar-capillary membrane?

    <p>0.25 sec</p> Signup and view all the answers

    According to Fick's Law, what factors influence the rate of gas diffusion?

    <p>Surface area and tissue thickness</p> Signup and view all the answers

    Under which condition would O2 diffusion be expected to be increased according to Graham's Law?

    <p>Increased solubility coefficient of O2</p> Signup and view all the answers

    What variable is NOT considered a factor in diffusion-limited gas flow?

    <p>Blood flow at the alveoli</p> Signup and view all the answers

    Which gas dissolves more in water per mmHg of partial pressure at 37°C?

    <p>CO2 with 0.59 ml/mmHg/ml H2O</p> Signup and view all the answers

    What is the primary reason for the change in the O2 cascade from dry gas to mean systemic capillary pressure?

    <p>Addition of water vapor</p> Signup and view all the answers

    Which statement about the solubility coefficients given for gases is accurate?

    <p>CO2 is approximately 20 times more soluble than O2</p> Signup and view all the answers

    If alveolar fibrosis occurs, how would this most affect gas exchange?

    <p>Decrease in gas diffusion rate due to increased thickness</p> Signup and view all the answers

    What is the molecular weight (MW) of oxygen?

    <p>32</p> Signup and view all the answers

    Which scenario best exemplifies perfusion-limited gas flow?

    <p>Normal blood flow with no barriers</p> Signup and view all the answers

    The Ideal Gas Law states that the pressure is directly proportional to the volume when the number of molecules and temperature remain constant.

    <p>False</p> Signup and view all the answers

    Boyle's Law describes a direct relationship between pressure and volume when temperature is held constant.

    <p>False</p> Signup and view all the answers

    The water vapor pressure in the alveoli at body temperature is 44 mmHg.

    <p>True</p> Signup and view all the answers

    In alveolar gas exchange, the partial pressure of carbon dioxide in the alveoli is typically 60 mmHg.

    <p>False</p> Signup and view all the answers

    Oxygen diffuses from areas of lower partial pressure to areas of higher partial pressure in the lungs.

    <p>False</p> Signup and view all the answers

    The rate of diffusion of CO2 is 10 times faster than that of O2 according to Graham's Law.

    <p>False</p> Signup and view all the answers

    Fick's Law states that the rate of gas diffusion is directly proportional to the thickness of the tissue.

    <p>False</p> Signup and view all the answers

    The solubility coefficient of O2 at 37°C is higher than that of CO2.

    <p>False</p> Signup and view all the answers

    Equilibrium for gas diffusion is typically reached in about 0.5 seconds.

    <p>False</p> Signup and view all the answers

    A decrease in the surface area of the tissue will enhance the rate of gas diffusion according to Fick's Law.

    <p>False</p> Signup and view all the answers

    Study Notes

    Gas Laws

    • Ideal Gas Law: Describes the relationship between pressure (P), volume (V), number of molecules (n), gas constant (R), and temperature (T) in Kelvin. The equation is PV = nRT.
    • Boyle's Law: At constant temperature, pressure is inversely proportional to volume. If volume is reduced, pressure increases.
    • Charles' Law: At constant pressure, volume is directly proportional to temperature. If temperature increases, volume increases.
    • Gay-Lussac's Law: At constant volume, pressure is directly proportional to temperature. If temperature increases, pressure increases.
    • Dalton's Law: In a mixture of gases, the total pressure is equal to the sum of the partial pressures of each individual gas.

    Atmospheric Gases

    • Partial pressure of oxygen (PBO2) is higher than the partial pressure of oxygen in the alveoli (PAO2).
    • Alveolar oxygen mixes with alveolar carbon dioxide (PACO2) and alveolar water vapor pressure (PH2O).

    Water Vapor Pressure

    • Alveolar gas is 100% humidified at body temperature, with an absolute humidity of 44 mg/dL.
    • Water vapor pressure (PH2O) is 47 mmHg.

    Alveolar Gas Equation (PAO2)

    • PAO2 = [(PB - PH2O) x FiO2] - PaCO2 x 1.25
    • If FiO2 is ≥ 60%, the factor 1.25 is omitted: PAO2 = [(PB - PH2O) x FiO2] - PaCO2

    Diffusion of Pulmonary Gases

    • Definition: Passive movement of gas molecules from high pressure to low pressure.
    • In the Lungs: Gas diffuses across the alveolar-capillary membrane (ACM), which is composed of:
      • Liquid lining of intra-alveolar lining
      • Alveolar epithelial cell
      • Basement membrane of the capillary endothelium
      • Plasma in the capillary blood
      • RBC membrane
      • Intracellular fluid of the RBC until a hemoglobin molecule is encountered.

    O2 and CO2 Diffusion

    • Venous Blood: PVO2 = 40 mmHg and PVCO2 = 46 mmHg (ΔP = 6 mmHg).
    • Capillary System: PAO2 = 100 mmHg and PACO2 = 40 mmHg (ΔP = 60 mmHg).

    Pressure Gradient Across the ACM

    • Large pressure gradients favor rapid diffusion of both O2 and CO2.

    O2 and CO2 Diffusion Equilibrium

    • Equilibrium is reached in ~0.25 seconds.
    • Transit time across the ACM is 0.75 seconds.
    • In exercise, transit time is shorter, allowing less time for gas diffusion.

    Gas Diffusion

    • Fick's Law: The rate of gas diffusion is directly proportional to the surface area of the tissue and inversely proportional to the thickness.
    • Clinical Implications:
      • Decreased surface area (alveolar collapse or fluid) reduces diffusion rate.
      • Decreased PAO2 (high altitude or alveolar hypoventilation) reduces diffusion rate.
      • Increased thickness (alveolar fibrosis or edema) reduces diffusion rate.

    Henry's Law

    • The amount of gas that dissolves in a liquid is proportional to the partial pressure of the gas.
    • Solubility Coefficients @ 37°C:
      • O2 = 0.024 ml/mmHg/ml H2O
      • CO2 = 0.59 ml/mmHg/ml H2O
      • CO2 is 24 times more soluble than O2

    Graham's Law

    • The rate of diffusion of a gas through a liquid is proportional to the solubility coefficient of the gas and inversely proportional to the molecular weight.
    • Gas Molecular Weights:
      • O2 = 32
      • CO2 = 44
    • O2 diffuses faster than CO2.
    • Combining Henry's and Graham's laws: CO2 diffuses 20 times faster than O2

    Perfusion-Limited Gas Flow

    • The rate of diffusion of gas through the alveolar wall depends on the amount of blood flowing past the alveoli.

    Diffusion-Limited Gas Flow

    • The rate of diffusion of gas through the alveolar wall depends on the integrity of the ACM.

    O2 and Diffusion vs. Perfusion-Limited Gas Flow

    • The rate of diffusion of gas through the alveolar wall depends on the integrity of the ACM in diffusion-limited gas flow.
    • The rate of diffusion of gas through the alveolar wall depends on the amount of blood flowing past the alveoli in perfusion-limited gas flow.

    Summary: O2 Cascade

    • Starting Point: Dry gas (159 mmHg)
    • Conducting Airways (149 mmHg): Addition of Water Vapor
    • End Expired Gas (114 mmHg): Mixing of deadspace.
    • Alveolar (101 mmHg): Addition of CO2.
    • Arterial Blood (97 mmHg): Intrapulmonary Shunting.
    • Mean Systemic Capillary Pressure (40 mmHg): O2 Diffusion into cell.
    • Cellular Cytoplasm --- O2 diffusion into cell.

    Ideal Gas Law

    • The Ideal gas law describes the relationship between pressure, volume, number of molecules, and temperature of a gas.

    Boyle's Law

    • Boyle's law states that for a constant temperature, the pressure of a gas is inversely proportional to its volume.
    • In other words, if the volume of a container is reduced, the pressure will increase proportionally.

    Charles' Law

    • Charles' law states that for a constant pressure, the volume of a gas is proportional to its temperature.
    • If the temperature of a gas increases, the volume will increase proportionally.

    Gay-Lussac's Law

    • Gay-Lussac's law states that for a constant volume, the pressure of a gas is proportional to its temperature.
    • If the temperature of a gas increases, the pressure inside will increase proportionally.

    Dalton's Law

    • Dalton's law states that in a mixture of gases, the total pressure is equal to the sum of the partial pressures of each individual gas.

    Partial Pressure of Atmospheric Gases

    • Atmospheric gases surrounding Earth exert a pressure at sea level of approximately 760 mmHg, which is also known as barometric pressure.
    • Barometric pressure decreases with altitude.

    Partial Pressure of O2 and CO2

    • The partial pressure of oxygen in the atmosphere (PBO2) is 159 mmHg, while the partial pressure of oxygen in the alveoli (PAO2) is 100 mmHg.
    • The partial pressure of carbon dioxide in the alveoli (PACO2) is 40 mmHg.
    • Alveolar water vapor pressure (PH2O) is 47 mmHg.

    Water Vapor Pressure

    • Alveolar gas is 100% humidified at body temperature, with an absolute humidity of 44 mg/dL.
    • The water vapor pressure is 47 mmHg.

    Alveolar Gas Equation (PAO2)

    • The alveolar gas equation can be used to calculate the expected partial pressure of oxygen in the alveoli (PAO2).
    • The equation is: PAO2 = [(PB - PH2O) x FiO2] - PaCO2 (1.25)
    • When FiO2 is greater than or equal to 60%, the 1.25 constant can be omitted from the equation: PAO2 = [(PB - PH2O) x FiO2] - PaCO2

    Diffusion of Pulmonary Gases

    • Diffusion is the passive movement of gas molecules from an area of high concentration to an area of low concentration.
    • In the lungs, gas diffuses through the alveolar-capillary membrane (ACM).
    • The ACM consists of:
      • Liquid lining of the intra-alveolar lining
      • Alveolar epithelial cell
      • Basement membrane of the capillary endothelium
      • Plasma in the capillary blood
      • Red blood cell (RBC) membrane
      • Intracellular fluid of the RBC until a hemoglobin (Hgb) molecule is encountered

    O2 and CO2 Diffusion

    • Venous blood has a partial pressure of oxygen (PVO2) of 40 mmHg and a partial pressure of carbon dioxide (PVCO2) of 46 mmHg, resulting in a pressure difference of 6 mmHg.
    • As blood passes through the capillary system, it encounters a higher partial pressure of oxygen (PAO2) of 100 mmHg and a lower partial pressure of carbon dioxide (PACO2) of 40 mmHg, resulting in a pressure difference of 60 mmHg.

    Diffusion Across ACM

    • Diffusion across the ACM occurs due to the pressure gradient between the alveoli and the capillaries.
    • Equilibrium is typically reached within 0.25 seconds, while the transit time through the ACM is 0.75 seconds.
    • During exercise, the transit time is shorter, leaving less time for gas diffusion.

    Fick's Law

    • Fick's Law states that the rate of gas diffusion is directly proportional to the surface area of the tissue and inversely proportional to the thickness of the tissue.
    • Clinically, factors that can affect gas diffusion according to Fick's law include:
      • Reduced surface area (alveolar collapse or fluid)
      • Decreased partial pressure of oxygen in the alveoli (high altitude or alveolar hypoventilation)
      • Increased thickness of the ACM (alveolar fibrosis or edema)

    Henry's Law

    • Henry's Law states that the amount of gas that dissolves in a liquid is proportional to the partial pressure of that gas.
    • The solubility coefficient at 37°C for oxygen is 0.024 ml/mmHg/ml of water, while the solubility coefficient for carbon dioxide is 0.59 ml/mmHg/ml of water.
    • This means that carbon dioxide is 24 times more soluble than oxygen in water.

    Graham's Law

    • Graham's Law states that the rate of diffusion of a gas through a liquid is proportional to the solubility coefficient of the gas and inversely proportional to the molecular weight of the gas.
    • The molecular weight of oxygen is 32, while the molecular weight of carbon dioxide is 44.
    • This indicates that oxygen moves faster than carbon dioxide due to its lower molecular weight.
    • When combining Graham's and Henry's Law, carbon dioxide can diffuse 20 times faster than oxygen.

    Perfusion-Limited Gas Flow

    • Perfusion-limited gas flow describes situations where the rate of gas diffusion through the alveolar wall is dependent on the amount of blood flowing past the alveoli.
    • In this scenario, the diffusion process is not limited by the capacity of the ACM to transport gas but rather by the rate of blood flow.

    Diffusion-Limited Gas Flow

    • Diffusion-limited gas flow occurs when the rate of gas diffusion through the alveolar wall is determined by the integrity of the ACM.
    • In this case, the diffusion process is limited by the ability of the ACM to transport gas, which is affected by factors like thickening or damage to the membrane.

    O2 and CO2 Diffusion vs. Perfusion-Limited Gas Flow

    • For gases like oxygen and carbon dioxide, diffusion-limited gas flow is less common in healthy individuals.
    • However, in conditions like emphysema or pulmonary fibrosis, where the ACM is compromised, diffusion-limited gas flow can occur.

    Summary: O2 Cascade

    • This table summarizes the changes in partial pressure of oxygen (PO2) as it moves through the respiratory system, from the dry inspired gas to the cellular cytoplasm.
    • Each change has a corresponding reason for the change, highlighting the different stages of oxygen transport and utilization.

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    Gas Laws and Pulmonary Diffusion PDF

    Description

    This quiz explores the fundamental gas laws including the Ideal Gas Law, Boyle's Law, Charles' Law, Gay-Lussac's Law, and Dalton's Law. It also examines the concept of partial pressures in atmospheric gases and their implications in respiratory physiology. Test your understanding of these essential principles in gas behavior.

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