What is the water vapor pressure in the respiratory tract?

• A. 47 mmHg
• B. 25 mmHg
• C. 100 mmHg
• D. 30 mmHg

Answer: (A)

The water vapor pressure in the respiratory tract at body temperature (37°C or 98.6°F) is indeed approximately 47 mmHg. This value is based on the physiological conditions of the airways where inhaled air becomes saturated with water vapor as it passes through the upper respiratory system and into the lungs.

At this temperature, the capacity of air to hold water vapor increases significantly, reaching saturation at around 47 mmHg, which is essential for the maintenance of mucosal surfaces and the prevention of desiccation of the respiratory epithelium. Thus, the respiratory tract's environment is crucial for optimal gas exchange and overall respiratory function.

Understanding this value is also important for medical practices such as intubation and mechanical ventilation, where maintaining appropriate humidity levels is vital for patient care. Other pressure values listed would not accurately represent the conditions found in a healthy human respiratory tract under normal body temperature.