>Formation IAP PRF has opposite directions,so IPP=IAP-PRF At the end of insp-expiration,so IPP=ASP-PRF If ASP=0,IPP=0-PRF=-PRF IPP:intrapleural pressure IAP:intra alveolar pressure PRF:pulmonary recoil force ASP:atmospheric pressure ➢Formation IAP & PRF has opposite directions, so IPP=IAP−PRF At the end of insp- & expiration, so IPP=ASP−PRF If ASP=0, IPP=0−PRF= −PRF IPP: intrapleural pressure IAP: intra alveolar pressure PRF: pulmonary recoil force ASP: atmospheric pressure