Abstract: Method and apparatus are described for supplying medical gas such as oxygen to patients through flexible conduiting terminating in a cannula. Pulses of select duration of the oxygen are supplied in response to the negative pressure associated with a detected patient inhalation. Following the supply of a given pulse, the apparatus dwells for a predetermined interval, for example 0.6 seconds, whereupon a next pulse is supplied if inhalation continues. The first pulse supplied in response to any negative inhalation pressure has a quantity corresponding with a prescribed oxygen flow. Thus, subsequent pulses may supply oxygen ambulatory activities of the patient. The apparatus includes a triggering suppression feature avoiding the false pulsing effects otherwise occasioned by pneumatic transients generated by the pulsing technique. Additionally, a pulse triggering sensitivity which is manually adjustable is incorporated with the control circuit of the apparatus.