Abstract: The invention is a portable spirometer for measuring the respiration rate of a patient. In detail, the invention includes a housing having a top and bottom, and first and second ends with an air passage extending therethrough. An air flow sensing member is movably mounted within the passage, the member movable forwards and backwards in response to the directional flow of air in the passage as the patient breaths in and out one end of the passage. A position sensing system is mounted within the housing for sensing the position of the air flow sensing member, the sensing system providing a first output signal when the air flow sensing member moves forward and backwards. A circuit is coupled to the sensing system for counting the number of times per unit time the air flow sensing member moves forward and backwards and provides a second signal proportional thereto.