At the end of inspiration, what is the typical value for intrapleural pressure (Ppl)?

The typical value for intrapleural pressure at the end of inspiration is around -10 cm H2O. This negative pressure within the pleural cavity is crucial for respiratory mechanics as it creates a gradient that allows the lungs to expand and fill with air. During the process of inspiration, the diaphragm and intercostal muscles contract, increasing the volume of the thoracic cavity and further decreasing the intrapleural pressure.

This negative pressure is essential because it keeps the lungs inflated by preventing them from collapsing, as it counteracts the elastic recoil of the lung tissue. By maintaining this sub-atmospheric pressure, the body ensures that the alveoli can open during inhalation, facilitating gas exchange.

Furthermore, at the end of inspiration, a more negative intrapleural pressure indicates that there is a greater gradient established between the alveolar pressure (which is typically at or slightly below atmospheric pressure) and the intrapleural pressure. This difference drives airflow into the alveoli.

In summary, the typical value of intrapleural pressure at the end of inspiration being around -10 cm H2O is a testament to the efficiency of the respiratory muscles and the mechanics of lung inflation.