Performance of Different Active Humidification Systems in High-Flow Oxygen Therapy.

BACKGROUND: We sought to evaluate the performance in terms of absolute humidity (AH), relative humidity (RH), and temperature of different heated humidifiers (HH) and circuits that are commonly used to deliver high-flow oxygen therapy in conventional ranges (30-60 L/min) and unconventional ranges (70-100 L/min). METHODS: In this prospective, observational study, an electronic thermohygrometer was used to obtain the required measurements. A mechanical ventilator was used as a source for high-flow nasal cannula oxygen therapy. For active humidification, the following equipment was used: a HH with standard disposable water trap circuit, 3 servo-controlled HH, and 7 circuits with a heated wire. Data on environmental conditions (ie, temperature, RH, AH) were collected from the laboratory during each measurement; the temperature, RH, and AH resulting from the application of 8 flows (30-100 L/min) were also recorded. Variables were compared with analysis of variance for repeated measurements with Tukey post hoc tests. A value of P < .05 was assumed to be significant. RESULTS: During the study, a statistically significant difference was found in the average AH for each flow for the different devices (P < .005). The highest AH values were recorded with the Fisher & Paykel MR850 and the Medtronic-DAR circuit (AH = 40.8 mg/L with flow of 50 L/min, P < .005), and the lowest AH values were recorded with the Flexicare FL9000 HH and the Flexicare circuit (AH = 11.4 mg/L with 100 L/min flow, P < .005). For flows > 50 L/min, the best performance for all flows in terms of AH was found with the Fisher & Paykel MR850 HH, regardless of the circuit used. CONCLUSIONS: During oxygen therapy with very high gas flows, HH devices behave differently and in many cases are inefficient in delivering adequate humidification, even at conventional flows. Caution is therefore recommended when selecting the device and flow settings for the implementation of high-flow nasal cannula oxygen therapy.

El frasco humidificador como sistema de humidificación del gas inspirado no cumple con las recomendaciones. Evaluación y comparación de tres sistemas de humidificación. Estudio de laboratorio / The humidifier bottle as humidification system of the inspired gas does not meet with the recommendations. Evaluation and comparison of three humidification systems. Laboratory study

Objetivos. Demostrar que el frasco humidificador (FH), como sistema de humidificación del gas inspirado, no alcanza los valores mínimos de humedad relativa (HR), humedad absoluta (HA) y temperatura (Tº) recomendados por la literatura. Secundariamente, comparar el rendimiento del FH y dos sistemas activos de humidificación (SAH). Materiales y métodos. Las variables principales fueron T° del agua, HR, Tº y HA del gas entregado. Se realizaron mediciones a diferentes niveles de Tº, volumen de agua y flujos. Resultados. El FH no alcanzó los valores recomendados de HR 100%, HA 30 mg/l y Tº 31ºC. El SAH sin circuito calefaccionado alcanzó valores recomendados en el NIVEL III con flujos de 20-60lpm, y en el NIVEL II con flujos de 20-30lpm. El SAH con circuito calefaccionado logró valores sugeridos en los NIVELES II y III (20-60lpm). Se encontró diferencia significativa (p<0,001 Global) para flujo, Tº y tipo de humidificador. El modelo ANOVA arrojó significación estadística (p<0,001) del término interacción de flujo y tipo de humidificador en cada nivel de Tº. Conclusiones. El FH no acondiciona el gas de acuerdo a lo recomendado. El mejor rendimiento fue con 300 ml y flujo de 1 lpm: Tº 23,92(±0,69), HR 74,02%(±6,53) y HA 16,02 mg/l (±1,86), estos valores apenas superan el 50% de lo mínimo sugerido en la literatura. Los SAH acondicionaron el gas adecuadamente. El modelo ANOVA arroja que existen otros factores involucrados en mantener la HA y que la significación varía en cada tipo de humidificador a cada nivel de flujo(AU)

Objetive. To demonstrate that humidifier bottle (HB) as inspired gas humidification system does not attain the minimum values of relative humidity (RH), absolute humidity (AH) and temperature (Tº) as recommended by the literature. Furthermore, to compare the HB performance with two active humidification systems (AHS). Materials and Methods. Main variables were: water Tº, RH, Tº and AH of delivered gas. Measurements were made at different levels of Tº, water and flows volume. Results. Recommended values of RH 100%, AH 30 mg/l and Tº 31º C were not reached by the HB. AHS without heating circuit reached recommended values in LEVEL III with flows of 20-60 lpm, and in LEVEL II with flows of 20-30lpm. AHS with heating circuit obtained recommended values in LEVELS II and III (20-60lpm). A significant difference (p<0.001 Global) for flow, Tº and humidifier type was found. ANOVA model showed statistical evidence (p<0.001) of interaction between flow and type of humidifier in each Tº level. Conclusions. The HB does not condition gas in accordance with recommended values. The best performance was with 300ml and 1lpm flow: Tº 23.92 (±0.69), RH 74.02% (±6.53) and AH 16.02 mg/l (±1.86) and these values hardly exceed the 50% of minimum recommended by literature. AHS conditioned gas in a proper way. ANOVA model shows that there exist other factors involved to maintain AH and that there are important differences between each type of humidifier and each flow level.(AU)