What is the baseline intrapleural pressure?

• A. 0 mmHg
• B. -4 mmHg
• C. -6 mmHg
• D. 4 mmHg

Answer: (B)

The baseline intrapleural pressure is typically around -4 mmHg during the resting state in an adult human. Intrapleural pressure refers to the pressure within the pleural cavity, the thin fluid-filled space that surrounds the lungs. It is usually negative relative to atmospheric pressure due to the elastic recoil of the lungs and the chest wall pulling away from each other. This negative pressure is crucial as it keeps the lungs inflated and facilitates the process of breathing.

The value of the intrapleural pressure can vary slightly among individuals and with different respiratory phases, but a typical resting baseline is approximately -4 mmHg. This negative pressure is essential for effective ventilation; when intrapleural pressure becomes equal to or less negative than atmospheric pressure, the lungs may collapse or not expand properly during inhalation. Hence, the value of -4 mmHg accurately represents the commonly accepted baseline intrapleural pressure in a healthy respiratory system.