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

Abstract

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 (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 e) and higher Fio₂ than the other masks at all 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 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.