Maximum Inspiratory/Expiratory Pressures Make an Appointment Ask a Question Refer Patient Reviewed by Amy Olson and George Zeman (August 01, 2013) This test measures the amount of pressure your inspiratory and expiratory muscles can exert. It is helpful in evaluating possible respiratory muscle weakness. This information has been approved by George Zeman BS, RRT, CPFT and Amy L. Olson, MD, MSPH (August 2013).