Oxygen conserving devices, the TTO catheters, electronic pulsed DODS and reservoir cannulas, increase efficacy of oxygen delivery; TTO also improves cosmetic appearance, comfort and compliance. We speculated that pulsing of oxygen transtracheally can increase efficiency of TTO. We modified the DODS to include settable delays and a rapid pre-inspiratory trigger. The first part of the study was performed with nasal oxygen on seven subjects and the second part, with TTO on 17 subjects. Nasal oxygen results indicate improved delivery efficiency with more rapid response. The TTO results indicate no significant change for each delay setting, but there was improvement in delivery efficiency when DODS was combined with TTO vs continuous flow TTO. Thus, early inspiratory delivery increases efficiency of oxygen therapy. Small delays in response time are critical in nasal delivery but not important in TTO. Pulsed TTO is more efficient than continuous flow TTO and merits long-term studies.