why does intrapleural pressure become more negative during inspiration
Making the world better, one answer at a time. The intraplural pressure becomes more negative simply because as the inspriatory muscles (diaphragm, external intercostals) act to increase thoracic volume, the intrapleural space increases in volume somewhat, thereby decreasing the pressure (Boyle's Law).aking the world better, one answer at a time. The intraplural pressure becomes more negative simply because as the inspriatory muscles (diaphragm, external intercostals) act to increase thoracic volume, the intrapleural space increases in volume somewhat, thereby decreasing the pressure (Boyle's Law).