Efficiency of oxygen administration: Sequential gas delivery versus “flow into a cone” methods

Objective:Fio2 values of a new oxygen mask that exploits efficiencies afforded by sequential gas delivery (SGD) were compared to those of a nonrebreathing mask (NRM) and a Venturi oxygen mask. Design:Prospective, single-blinded, randomized study. Setting:Laboratory study. Subjects:Eight healthy male volunteers. Interventions:Volunteers breathed through each of the masks at various minute ventilations (&OV0312;e). Oxygen flows were 2, 4, and 8 L/min to the SGD mask but only 8 L/min to the other masks. Measurements and Main Results:Net Fio2 was calculated from end-tidal fractional concentrations of oxygen and CO2 with the alveolar gas equation. Only the SGD mask at an oxygen flow of 8 L/min consistently provided both Fio2 >0.95 (at resting &OV0312;e) and higher Fio2 than the other masks at all &OV0312;e. The SGD mask delivered Fio2 comparable to other masks at only a fraction of the oxygen flow and was characterized by a consistent relation between Fio2 and oxygen flow for a given &OV0312;e. Conclusion:We conclude that SGD can be exploited to provide Fio2 >0.95 with oxygen flows as low as 8 L/min, as well as accurate and efficient dosing of oxygen even in the presence of hyperpnea.

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