When somebody has ARDS, when is non-mechanical ventilation used, vs mechanical ventilation? (I'm talking no intubation, no sedation)

Question

I'm a lay person.

When somebody has ARDS, when is non-mechanical ventilation used, vs mechanical ventilation?

(I'm talking no intubation, no sedation)

From what I understand, mechanical ventilation involves air being forced in, rather than breathed in naturally.

Added elaboration

This is not answered here When can mechanical ventilation be performed without intubation? That question is asking about an A and a B, where A is with intubation and B is not.

But my question is asking about an A and a B, where both A and B are without intubation. But A is non-mechanical ventilation and B is mechanical ventilation.

Answer 1

To clarify there are different types of ventilation where ventilation means to assist the delivery of oxygen to a patient.

Non-invasive Ventilation (NIV)

• Without significantly increasing pressure in the airways

  • Masks

  • high flow nasal cannula

• Positive airways pressure

  • CPAP

  • BPAP

• Negative Pressure Ventilation

  • Iron lungs

Invasive Ventilation

• intubation or tracheostomy delivered

It sounds like you're asking when treating a case of ARDS when does one switch from using a mask/cannula to using CPAP/BPAP.

Several types of helmets are commercially available in Europe, each with different features. There are no helmets commercially available for use with NIV in the US, but one helmet is approved for use in bariatric chambers to protect against excessively high oxygen tensions. This graphic shows a representative image of helmet interface used to deliver noninvasive ventilation. Shown are ventilation ports for the administration and removal of gas flow and a rubber seal at the neck, while others have additional optional features including ports for the introduction of catheters and under-arm straps for extra security to ensure a tight seal.

ARDS is by definition a severe illness and it's usually only at the very early stages that a patient can be managed using NIV positive airways pressure ventilation.

Noninvasive ventilation (NIV; ie, ventilation via a mask or nasal prongs with breaths delivered by a NIV device) may be reserved for the occasional patient with mild ARDS who is hemodynamically stable, is easily oxygenated, does not need immediate intubation, and has no contraindications to its use. This approach is based upon our experience and conflicting data regarding the benefit of NIV (eg, prevention of intubation, improved mortality) in this population. Importantly, when NIV is implemented, frequent evaluation is necessary and clinicians should have a low threshold for intubation.

However, there are risks from such an approach

In contrast, a study of patients with hypoxemic respiratory failure, many of whom had ARDS, reported increased mortality in association with NIV when compared with patients treated with high flow nasal cannula (HFNC)

So, at least some studies suggest that switching from masks/cannula to using positive airways pressure could increase mortality. Whereas other studies suggest using a helmet may reduce the mortality and increase the number of days free of intubation.

https://www.uptodate.com/contents/ventilator-management-strategies-for-adults-with-acute-respiratory-distress-syndrome

Answer 2

Obviously depends on the exact case at hand, but from what I know, non mechanical ventilation (ie. Venti mask, etc.) Is only used for very mild ARDS where there is fairly good oxygenation and the patient is hemodynamically stable (good blood pressure and heart rate), able to keep their airway open, no copious secretions, etc. (https://www.ncbi.nlm.nih.gov/pubmed?term=22020236). In moderate or severe ARDS, intubation is usually used (most cases end up requiring at least some form of ventilation).

Yes, you are absolutely correct. Mechanical ventilation is when there is pressure forcing air in, while non mechanical is not forcing any air in and rather providing more oxygen flow.

Answer 3

note- I won't accept my own answer, as discussion with others here has helped contribute to it.

I'm a lay person.

Having discussed this with people, I now see there is some confusion in the question, which if cleared up, would make for a clearer question. To address the confusion, the question asks.

"When somebody has ARDS, when is non-mechanical ventilation used, vs mechanical ventilation? (I'm talking no intubation, no sedation)"

One person I spoke to has said

All ventilators are mechanical. And when people say mechanical, hands-free is meant - not manual. Machine operated. And a ventilator would be forcing air in at set intervals. (Note- there are CPAP machines that give a continuous supply of air, but they are not ventilators. https://geekymedics.com/cpap-vs-niv-bipap )

Masks being fed a steady air supply wouldn't be ventilators.

HFNC - not a ventilator. (it doesn't force air in at set intervals).

NRB - not a ventilator

NIV e.g.(NIPPV/NPPV or NPV) - are ventilators

BVM https://www.redcross.org/store/disposable-bvm-bag-valve-mask-adult-size/760002.html wouldn't be considered a ventilator 'cos it's hand operated.

Also, regarding the term "mechanical ventilator" I think it's not really used much as the qualifier doesn't add anything, as when somebody says ventilator, they mean that hands free machine device forcing air in in a timed manner, it's a machine, hands free, not manual. The term "mechanical ventilator" gets 523K results on google. The term "mechanical ventilation" gets 6.6 million results.

The term ventilation is not particular to medicine and means supplying air to some enclosed space. Medicine does have non-mechanical ventilation. A Bag Valve Mask https://en.wikipedia.org/wiki/Bag_valve_mask would be a form of manual ventilation. And as that link mentions, you also have "mouth to mouth ventilation", whicj would also be manual.

In terms of English, machines that don't force air e.g. HFNC would not be ventilation devices 'cos it helps get oxygen in, rather than helps with breathing(getting air in/out).

A BPAP or CPAP machine for sleep apnea machine that does a bit of the work of breathing, could perhaps be a ventiation device. But not a ventilator. A ventilator is capable of handling a person's breathing completely. Like a sleep apnea BPAP machine but with more power.

Specific to medicine, is the term "mechanical ventilation", a form of respiratory therapy, with ventilators. https://www.resmed.co.uk/healthcare-professional/respiratory-care/respiratory-therapy/ And when they speak of non-invasive ventilation, they talk of non-invasive ventilators.

So the question could be split into the question about mechanical ventilators, and a question of, when somebody has ARDS, when are they moved from HFNC or NRB, to NPPV and eventually perhaps to an (invasive) ventilator(i.e. ventilator with intubation).