During inspiration, what does the intrapleural pressure drop to?

During inspiration, the intrapleural pressure becomes more negative due to the increased volume of the thoracic cavity as the diaphragm and intercostal muscles contract. This contraction expands the lungs and generates a drop in pressure within the pleural cavity. The intrapleural pressure typically drops to around -6 mmHg during inspiration as the negative pressure helps facilitate the flow of air into the lungs. The negativity of the intrapleural pressure is essential for keeping the lungs inflated and preventing lung collapse, which would occur if the pressure equaled atmospheric pressure. Thus, the drop in intrapleural pressure to -6 mmHg during inspiration directly contributes to the mechanics of breathing.