Evaluation of two oxygen face masks with special regard to inspiratory oxygen fraction (FiO₂) for emergency use in rescue helicopters

Abstract 

Introduction

Effective oxygenation during acute respiratory insufficiency depends on the inspiratory oxygen fraction (FiO₂) and the oxygen face mask used. Recent studies demonstrated significant advantages of the Hi-Ox80 mask as compared with a basic mask. The aim of this study was to measure FiO₂ in the laryngopharynx of patients and to apply these data to the setting in rescue helicopters.

Methods

In spontaneously breathing patients, FiO₂ was measured with an O₂-sensor (Draeger Medical, Luebeck, Germany) in the laryngopharynx, depending on the adjusted oxygen flow. Flow increments of 1 up to 12 L/min were analyzed using a basic oxygen mask (Intersurgical Ltd., Berkshire, UK) and a Hi-Ox80 mask (Viasys Healthcare GmbH, Hoechberg, Germany) in a randomized order on the same patient. Data were applied to the special helicopter environment and analyzed with respect to oxygen delivery per minute and resulting equipment benefits. Statistika (StatSoft GmbH, Hamburg, Germany) and t-test were used for statistical analysis. P ≤ .05 was considered statistically significant.

Results

Twenty patients with a mean age of 69 ± 7 years were investigated. At a low oxygen flow up to1 L/min, the Hi-Ox80 mask was not superior to the basic mask (FiO₂ at 1 L/min 24% ± 3% vs. 27% ± 5% and partial pressure of arterial oxygen [paO₂] 164 ± 68 vs. 193 ± 53 mmHg; NS). Using a flow of 2 L/min or more, a significant difference for the FiO₂ and paO₂ in both masks was found (P ≤ .05). Using the Hi-Ox80 face mask in a rescue helicopter with standard oxygen flows, it demonstrated 3.24 times longer oxygen availability because of a reduced required oxygen flow and therefore a potential calculated weight reduction.

Conclusions

The Hi-Ox80 mask allows more effective use of the administered oxygen flow. Efficiency of the new mask is greater; hence, similar flow adjustment produces a significantly higher FiO₂. Thus, oxygen, cost, and weight savings are feasible.

• * Based on data of Figure 3 (oxygen flow required for a given FiO₂), duration of oxygen flow was calculated for a 2-L oxygen pressure bottle. The graph shows how long oxygen flow is available with a 2-L pressure bottle, if a special FiO₂ is required. Example: Whereas the maximum duration is limited to 34 minutes when using a basic mask and an FiO₂ of 0.4 (black arrow), duration is extended to 110 minutes for the same FiO₂ when using a Hi-Ox80 mask (dotted arrow). This results in a duration extension of 3.24. Alternatively, absolute costs for oxygen also may be reduced by a calculated factor of 3.24. Black line 5 Hi-Ox80 mask; gray line 5 basic mask.
• * Data are presented for increments of 1 L in oxygen flow. Black line indicates same costs when using a basic mask or a Hi-Ox80 mask. The area left or below the black line indicates the basic mask may be more profitable; area above the black line shows the Hi-Ox80 mask to be more profitable. Exemplary analysis of profitability for both masks in the out-of-hospital setting within an rescue helicopter and a 2-L oxygen pressure bottle (2,900 psi): Maximum duration (min) to amortize the Hi-Ox80 mask depending on the selected oxygen flow (L/min). The higher price for the Hi-Ox80 mask was amortized after a delivery of 126 L oxygen. At a flow of 5 L/min, both masks are redeemed (due to the high refill price) after 25 minutes. Exemplary costs: basic mask, $0.60; Hi-Ox80 mask, $13.00; 400-L oxygen refill, $40.