Roughly what value does intrapleural pressure hold throughout the breathing cycle?

1. Intrapleural pressure is the pressure inside the pleural cavity, between the visceral and parietal pleurae. 2. It fluctuates during inspiration and expiration but stays near one value. 3. That value is approximately minus 4 mm Hg, meaning 4 mm Hg below atmospheric. 4. It is always lower than, or negative to, intra-alveolar pressure, so any option putting it above atmospheric is wrong. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 22 "The Respiratory System", section 22.3 The Process of Breathing_