Optiflow™ Flow Matters
Oct, 2020

What systems and settings are used in NHF research?

Surveys of the studies comprising the body of NHF evidence found the majority used F&P Optiflow systems and flow settings between 45 and 60 L/min.


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Guideline recommendations for the use of Nasal High Flow (NHF), aka High Flow Nasal Cannula (HFNC), are supported by analyzed data from research investigating the effect of NHF on clinical outcomes, such as the reduced need for tracheal intubation. When selecting an NHF system, it is important to ensure the entire system, including design and device limits, can provide the therapy proven to deliver the expected outcomes.
 

Summary

  • The National Institutes of Health (NIH)*, the Australia and New Zealand Intensive Care Society (ANZICS) and the Surviving Sepsis Campaign (SSC)** recommend NHF for use in COVID-19 related hypoxemia.1,3
  • These recommendations are supported by findings from five systematic reviews with meta analysis.4-8
  • A review conducted by Fisher & Paykel Healthcare (F&P) showed that the flow rates used in the controlled published studies8-30 (analyzed by the five meta-analyses) ranged from 10 L/min to 60 L/min, and 82% of the studies required flows ≥ 45 L/min.
  • When this review was repeated on the 52 acute adult NHF controlled studies (with subjects n > 39), found using a systematic search of the PubMed database, it was again shown that the flow rates used ranged from 10 L/min to 60 L/min and that 85% of the studies required flows ≥ 45 L/min.
  • F&P Optiflow systems (including F&P Optiflow interfaces) and humidity settings of 37oC were widely used.

Guideline recommendations

Recent guidelines for the clinical management of COVID-19 from organizations such as the NIH, ANZICS and SSC recommend the use of NHF as respiratory support in adults. These recommendations are supported by systematic reviews with meta analysis which search for, review and analyze  clinical data from controlled studies such as Randomized Controlled Trials (RCTs). F&P conducted a review of the systems and settings used in studies from which analyzed data formed the basis of these recommendations.

*The NIH, a part of the U.S. Department of Health and Human Services, is the USA’s national medical research agency.
**The SSC is a collaboration between the Society of Critical Care Medicine (SCCM) and the European Society of Intensive Care Medicine (ESICM).

Reviews with meta analysis 

NHF recommendations from NIH COVID-19 Treatment Guidelines, the ANZICS COVID-19 guidelines, and the SSC Guidelines on the Management of Critically Ill Adults with Coronavirus Disease 2019 (COVID-19) are supported by the following systematic reviews with meta analysis: Zhao et al. 2017, Ou et al. 2017, Ni et al. 2018, Rochwerg et al. 2019 and Agarwal et al. 2020.1-8

Analyzed published studies 

These five reviews analyzed data from 22 published studies (mostly RCTs) and one presentation.9-31 The studies represent various NHF applications, including primary respiratory support, pre-oxygenation prior to intubation and post extubation respiratory support. The studies reported the NHF systems and settings that were used.


Systems and settings

The reported flow rates ranged between 10 L/min and  60 L/min with the majority requiring flows at the higher end of the range. Of the 22 published and analyzed studies, 20 (91%) used F&P Optiflow systems, including a F&P Optiflow patient interface and a F&P humidity delivery system with humidity setting of 37oC.

Wider body of evidence (acute adult NHF controlled studies)

To further investigate the body of evidence (beyond that analyzed in the five meta analyses4-8, the review method was repeated for the 52 acute adult NHF controlled studies9-25,32-66 with subjects n > 39, found using a systematic search of the PubMed database.  Again, the reported flow rates ranged between 10 L/min and 60 L/min with the majority requiring flows at the higher end of the range (85% of the studies required flows ≥ 45 L/min). The flow rates reported in the 52 controlled studies are shown in the chart below.
 
Graph

Of the 52 controlled studies, 94% used F&P Optiflow systems, including a F&P Optiflow patient interface and a F&P humidity delivery system with humidity setting of 37oC.
When selecting a NHF system, it is important to ensure the entire system, including device capabilities such as flow rate and humidity delivery, can provide the therapy to deliver the expected outcomes proven in the clinical body of evidence.

Definitions

  • F&P Optiflow system: A F&P purpose-built system for NHF – either an AirvoTM Optiflow system or a non-Airvo Optiflow system.
  • Airvo Optiflow system: A F&P Airvo system with integrated flow source, humidifier and humidity delivery system (F&P heated breathing tube and F&P auto-fill chamber). Used with a F&P Optiflow patient interface and able to deliver NHF anywhere in the hospital independent of medical air supply.
  • Non-Airvo Optiflow system: A F&P humidifier (e.g. MR850 system) and humidity delivery system (F&P heated breathing tube and F&P auto-fill chamber). Used with a F&P Optiflow patient interface and an independent flow generator such as a HFNC-capable ventilator. 
  • Systematic search of the PubMed database: Conducted on 17 September 2020 using pre-defined search terms. Filtered using an Excel database and checked by an internal clinical team.
  • Controlled studies: Outcomes RCTs, pilot RCTs, physiological RCTs, non-randomized controlled trials and randomized crossover trials which were either open label or blinded, single or multicentre. 
  • Hospital acute treatment areas: All in-patient treatment areas and emergency department. Excluding operating theatres, procedural suites, outpatient clinics and rehabilitation. 
  • Acute adult NHF: All NHF applications used in hospital acute treatment areas, including primary respiratory support, pre-oxygenation prior to intubation, post extubation respiratory support, post surgical respiratory support and respiratory support during medical recovery.
  • Estimated mean: Calculated as the mean of the reported range limits, or range limits and initial flow rate. 
  • Estimated max/min flow: Calculated from the reported mean and standard deviation or interquartile range, and/or the known flow limits of the system used. Where the mean alone is reported, no estimated maximum or minimum is calculated unless an initial flow (different to the mean) is reported in which case it is taken as one of the limits.


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