The present invention extends to methods, systems, computer program products, and circuits for conserving oxygen during the delivery of oxygen to a user. Embodiments of the invention use a microphone to detect breathing sounds indicative of different portions of a breathing cycle. Sounds not related to the breathing cycle are filtered out of the signal. Using the breathing sounds, a microprocessor differentiates inspiration from other portions of the breathing cycle. When inspiration is detected, a valve is transitioned to permit the flow of oxygen from an oxygen source to a user to deliver an appropriate bolus of oxygen. The microprocessor can also detect fault conditions, such as, for example, apnea, failure to deliver a bolus of oxygen, and restrictions in the flow of oxygen from the oxygen source to a user.
