Ok I researched but I don't understand what they are saying. Transpulmonary pressure= alveolar pressure-pleural pressure= elastic recoil of the lung. How is transpulmonary pressure equal to the elastic recoil of the lung? I don't understand what you get when you substract pleural pressure from alveolar pressure. Also while I was reseaching this pneumothorax came up. It seems that elatic recoil of the lung is pushing one way and the chest wall is pushing one way. When equilibrium is reached between these two pleural space is negative. So when you puncture air fills the pleural space and becomes zero. So how does this make the lung collapse? Thank you!! Moonbear,Andy or anyone please explain!!