The inhalation therapy assembly and method of use described herein increases the efficiency of metered dose inhalers by allowing delivery of the doses to a collapsible reservoir which can be manually pumped, ensuring that medicants contained therein are properly and completely delivered to the patient. Terminal and proximal valves of the one-way diaphragm type allow flow of the aerosol medicants while preventing improper expulsion. An exhalation valve is adjustable to ensure the patient expires suitably to permit proper medicant absorption.