Automated Oxygen Flow Titration to Maintain Constant Oxygenation

Abstract

BACKGROUND:

One century after the introduction of the oxygen flow meter into clinical practice, we have developed a device, FreeO₂, that automatically titrates the oxygen flow delivered to spontaneously breathing patients, with the aim of maintaining a stable S_pO2 . We evaluated this system in healthy subjects during induced hypoxemia.

METHODS:

Hypoxemia was induced in 10 healthy subjects while breathing a gas mixture of variable F_IO2 (air + nitrogen). Each subject performed 3 hypoxemic challenges with the addition, in a random order, of either: air with constant flow (1.5 L/min); oxygen with constant flow (1.5 L/min); or automatic oxygen flow titration. Subjects were blinded to the intervention. Oxygen flow, S_pO2 , end-tidal CO₂, respiratory rate, and heart rate were recorded every second. The primary outcome was the time with S_pO2 between 92% and 96%.

RESULTS:

The S_pO2 target (92–96%) was achieved a median of 26.0%, 36.8%, and 66.5% (P < .001) of the time with air, constant oxygen, and automated oxygen titration, respectively. Severe oxygen desaturations (S_pO2 < 88%) were respectively observed at a median of 33.7%, 12.7%, and 0.4% of the time (P < .001). Hyperoxia was present a median of 4.1%, 39.1%, and 14.5% of the time (P < .001). Tachycardia was present with air and with constant oxygen flow, but not while using automated oxygen titration. These results were obtained with a mean and maximal oxygen flow of 1.3 L/min and 7.6 L/min with the automated titration.

CONCLUSIONS:

In this model of induced hypoxemia, the FreeO₂ system that automatically titrates the oxygen flow was more efficient at maintaining the S_pO2 target, while ensuring a statistically significant reduction in the rates of severe hypoxemia and hyperoxia, in comparison with air or constant oxygen flow. These beneficial results were obtained with less oxygen, in comparison to a constant oxygen flow.