In accordance with one aspect of the present invention for controlled delivery of medicament to the respiratory system of a patient, a measured quantity of a medicament, i.e., a bolus 32 is introduced into the inspiratory flow stream of a patient, via a breathing tube 18, and inhaled by the action of the patient's breathing cycle of the course of a breathing cycle of the patient, numerous properties or characteristics of the medicament, i.e., the bolus, the inspiratory flow, like properties or characteristics of the expiratory flow, and/or other useful information are derived. The derived information is employed to control subsequent delivery of boli to the patient, including the delivery of each bolus as a function of the commencement or progression of the breathing cycle, as input for calculations or determinations which are useful in analyzing the effectiveness of delivery of the medicament to the patient, patient compliance, direction of flow through the breathing tube, and other uses.