Let's say with CPAP you have the air infused with Oxygen. I don't know if that's always the case but suppose that's the case.

What then is the difference between a high flow device, like a HFNC, and a CPAP device?

Both involve a continuous airflow

I've heard that with HFNC it's just oxygen fed in, not air. But i've also read that with HFNC there is humidification, which suggests to me that the oxygen is mixed with air. So which is it?

Is the difference that with CPAP the air isn't humidified?

And is it the case that HFNC involves PEEP and CPAP doesn't.. So, for example this link https://academic.oup.com/bjaed/article/17/2/57/2907850 mentions that HFNC "provides PEEP"

This link http://www.aast.org/Assets/5e4309dd-c952-4a56-b2c9-7060670a7573/635376719195570000/non-invasive-positive-pressure-ventilation-guideline-3-26-14-june-2014-pdf speaks of a machine and two pressures that can change. IPAP and EPAP. It says "CPAP is active when IPAP = EPAP". and "Bi-level positive airway pressure (BiPAP): provides two pressure levels, IPAP and EPAP "

No doubt for BiPAP, IPAP would be different to EPAP to lead to breath going in and out.

It also says "PEEP when IPAP > EPAP"

So would that be indicating that CPAP doesn't involve PEEP, but HFNC does?

I understand from https://www.criticalcarepractitioner.co.uk/mechanical-ventilation-peep-positive-end-expiratory-pressure/ that PEEP ensures that the Alveoli don't collapse completely.. so, some inflow of air

I get that BiPAP would adjust IPAP and EPAP.. and cause breathing to occur.

But HFNC is meant to leave breathing down to the patient/user. So I don't really see that there is a difference between levels the pressures IPAP And EPAP, in the context of HFNC.. 'cos it maintains a constant pressure like CPAP does in that sense.

But then how can HFNC involve PEEP?

  • Hi; can you clarify the exact setup you’re thinking of? HFNC and mechanical ventilator intubation can both permit the patient to trigger the pressure from the ventilator or PEEP-supplying machine. HFNC seals off the nasal passages and if the mouth is closed, can generate positive pressure through the nasopharyngeal passage down into the lungs.
    – Henry Wei
    Apr 17, 2020 at 12:51


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