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 ((V) over dotE). 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 (V) over dotE) and higher FIO2 than the other masks at all (V) over dotE. 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 (V) over dotE. 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.