What happens to intrapleural pressure during spontaneous inspiration?

During spontaneous inspiration, the primary mechanism at play is the contraction of the diaphragm and intercostal muscles, which increases the volume of the thoracic cavity. As the thoracic volume expands, the pressure within the pleural cavity (intrapleural pressure) becomes more negative. This decrease in intrapleural pressure is crucial because it creates a pressure gradient that allows air to flow into the lungs from the atmosphere, facilitating inhalation.

The negative intrapleural pressure helps to keep the lungs inflated and is essential for normal respiratory mechanics. During inspiration, as the lung expands, the intrapleural pressure decreases further below atmospheric pressure, enhancing the airflow into the lungs. This physiological adjustment is a fundamental aspect of respiratory mechanics and is necessary to drive the oxygen intake that occurs during breathing.