Alveolar Air Systems lecture 2

Measuring Gas Pressure

• The equation used to measure dry gas is not specified in the provided text.
• PGas represents the partial pressure of a gas in the equation.

Dalton's Law of Partial Pressure

• The sum of the partial pressures of a gas is equal to the total pressure of the gas mixture, according to Dalton's law of partial pressure.

Atmospheric Pressure

• Nitrogen gas is responsible for the majority of atmospheric pressure.

Barometric Pressure

• Barometric pressure decreases as altitude increases.

Saturation of Inhaled Air

• The saturation of inhaled air takes place in the nose and mouth.
• Inhaled air becomes 100% saturated in the airway at a temperature of 37°C (normal body temperature).

Partial Pressure of Nitrogen Gas

• The partial pressure of Nitrogen gas inhaled in the trachea is 0.79 × PBar (barometric pressure).

Saturation with H2O Pressure

• Saturation with H2O pressure is dependent on the partial pressure of water vapor.

Surfactant in Alveoli

• Type II cells in the alveoli are responsible for secreting surfactant.
• The function of surfactant in the alveoli is to reduce the surface tension of water, allowing the alveoli to expand and contract more easily during breathing.

Oxygen Diffusion

• Oxygen is driven from the alveoli into the tissue due to the partial pressure gradient.

Carbon Dioxide Diffusion

• Carbon dioxide diffuses from the blood into the alveoli and out of the alveoli into the atmosphere.
• The partial pressure of carbon dioxide in the alveoli is approximately 40 mmHg.
• Carbon dioxide diffuses from the blood into the alveoli because of its higher partial pressure in the blood.

Alveolar Type I Cells

• Alveolar type I cells are flat, squamous cells that line the alveoli and are responsible for gas exchange.

Alveolar Gas Equation

• The alveolar gas equation is used to calculate the partial pressure of oxygen in the alveolus.
• The value of the respiratory quotient (R) used in the alveolar gas equation is 0.8.
• PIO2 represents the partial pressure of oxygen in the alveolus.
• The formula for calculating PIO2 is PIO2 = Pio2 - (PACO2 / R).
• PACO2 represents the partial pressure of carbon dioxide in the alveolus.
• An increase in PACO2 occurs during hypoventilation, and a decrease in PACO2 occurs during hyperventilation.

Respiratory Gas Exchange

• The equation used to calculate respiratory gas exchange (R) is R = (CO2 produced / O2 consumed).
• The usual value of respiratory gas exchange (R) is 0.8.
• The equation for calculating respiratory gas exchange (R) in terms of CO2 and O2 is R = (VCO2 / VO2).