Why is it significant that water vapor pressure in the respiratory tract is 47 mmHg?

Why is it significant that water vapor pressure in the respiratory tract is 47 mmHg?

• A. It is the maximum capacity of oxygen
• B. It affects the calculation of effective PO2
• C. It indicates lung inflammation
• D. It is a measure of lung capacity

Answer: (B)

The significance of water vapor pressure in the respiratory tract being 47 mmHg is primarily related to its effect on the calculation of effective partial pressure of oxygen (PO2) in the alveoli. The human respiratory system operates under conditions where the air that reaches the alveoli is saturated with water vapor, which exerts a pressure of 47 mmHg at body temperature (37°C). When calculating the effective PO2 in the alveoli, the total pressure (typically atmospheric pressure at sea level is about 760 mmHg) must be adjusted to account for the pressure exerted by water vapor. Therefore, the effective PO2 is derived from subtracting the water vapor pressure from the total pressure, which affects the degree of oxygen available for diffusion into the bloodstream. A higher water vapor pressure means that less of the total pressure at any given moment is due to the oxygen, which is crucial for understanding gas exchange and ensuring that tissues receive adequate oxygenation. This aspect is critical in various clinical settings, such as in assessing a patient’s oxygenation status and understanding how conditions like hypoxia may arise if the effective partial pressure of oxygen is decreased due to factors like increased humidity or other pulmonary issues.

The significance of water vapor pressure in the respiratory tract being 47 mmHg is primarily related to its effect on the calculation of effective partial pressure of oxygen (PO2) in the alveoli. The human respiratory system operates under conditions where the air that reaches the alveoli is saturated with water vapor, which exerts a pressure of 47 mmHg at body temperature (37°C).

When calculating the effective PO2 in the alveoli, the total pressure (typically atmospheric pressure at sea level is about 760 mmHg) must be adjusted to account for the pressure exerted by water vapor. Therefore, the effective PO2 is derived from subtracting the water vapor pressure from the total pressure, which affects the degree of oxygen available for diffusion into the bloodstream. A higher water vapor pressure means that less of the total pressure at any given moment is due to the oxygen, which is crucial for understanding gas exchange and ensuring that tissues receive adequate oxygenation.

This aspect is critical in various clinical settings, such as in assessing a patient’s oxygenation status and understanding how conditions like hypoxia may arise if the effective partial pressure of oxygen is decreased due to factors like increased humidity or other pulmonary issues.