Comparison of three Methods of applying high flow nasal oxygen: in vitro study

Introduction

High flow nasal (HNF) requires precise control of the fraction of inspired oxygen (FiO₂) and flow contributed as well as an adequate adjustment of temperature and humidity of the gas provided. There are several equipments for HNF. We evaluated the FiO₂ and flow supplied with three different systems

Methods

There have been analyzed: (1) 'Oxygen Therapy' from Dräger Evita-XL®; (2) Fisher & Paykel Airvo® option; and (3) pack of flowmeters Debson®. Measurements were made in the distal part of the circuit that is used in clinical practice. Variables: programmed and measured FiO₂, programmed and measured flow. We used the Oxygen Monitor Ohmeda 5120® and Flow Meter® Fisher-Porter. Before each measurement we checked and/or calibrated each of them. All measurements were performed at room temperature in the ICU of our hospital (23 to 26º).The data were processed using SPSS v.15.0.1, accepting a significance level of 95%.

Results

(1) FiO₂ variation -0.001 ± 0.09 (-0.01 to 0.002); FiO₂ percentage variation -0.012 ± 1.88 (-0.27 to 0.25); r² = 0.999 and r = 0.998 (P < 0.000). Flow variation (l/minute) 5.45 ± 3.23 (4.94 to 5.96); flow percentage variation 19.59 ± 11.63 (17.75 to 21.43); r = 0. 997 and r² = 0.994 (P < 0.000). (2) FiO₂ variation -0.007 ± 0.26 (-0.011/-0.003); FiO₂ percentage variation -1.4040 ± 4.73 (-2.15 to -0.67); r = 0.996 and r² = 0.992 (P < 0.000). Flow variation (l/minute) 3.82 ± 3.85 (3.04 to 4.69); flow percentage variation 9.76 ± 8.08 (8.11 to 11.41); r = 0.969 and r² = 0.939 (P < 0.000). (3) FiO₂ variation -0.005 ± 0.26 (-0001 to 0009); FiO₂ percentage variation -0.72 ± 5.2 (-1.5 to 0.1); r = 0.996 and r² = 0.992 (P < 0.000). Flow variation (l/minute) 3.91 ± 1.26 (3.69 to 4.13); flow percentage variation 12.77 ± 5.33 (11.84 to 13.7); r = 0.996 and r² = 0.992 (P < 0.000). See Figure 1.

Figure 1

Programmed and measured flow.

Conclusion

The FiO₂ percentage variation in the Airvo® is higher than the other two devices, with no clinical relevance. The flow percentage variation of Evita XL® is superior to the other two devices; this may have some clinical relevance.