Boyle's Law Reconsidered: A Graphical Analysis

Boyle's Law forms the basis for many phenomena observed in the clinical practice of respiratory therapy. For this reason, we have sought to teach Boyle's Law to our respiratory therapy students in some depth. In doing so, we have found a geometric or graphical approach to be useful. Many students understand and retain the concepts embodied in the Boyle's Law relation more easily when the graphical approach is developed alongside the conventional mathematical model. These complementary approaches are developed in this paper in an effort to clarify the theoretical basis of such commonly observed events and processes as ventilator compliance determinations, the delivery of therapeutic gases from high pressure cylinders, the pressure/volume relations associated with the performance of a Valsalva maneuver and the principle of operation of the plethysmograph or “body box.”