EBME Forums Forums Free discussion Free discussion Ventilators for covid-19

As we all know, for years the bean counters have had the upper hand. They see stockpiling as an (unnecessary) expense.

They have preached the mantra that "just in time" (aka "just too late") is the answer.

JIT relies on everything running well, with no glitches at any point(s) in the chain. That's especially risky when the chain extends around the globe, as we're now seeing. Who would have thought it?

Those of us who know better (generally based on sorry experience) - the logisticians and military types - tend to regard stockpiling as a prudent imperative.

On a happier note, perhaps we shall now begin to see the end of (or at least a massive reduction in) "globalization", and manufacturing (not to mention jobs) coming back "on shore".

Strategies for addressing respiratory failure, including protective mechanical ventilation and high-flow nasal oxygen (HFNO) or non-invasive ventilation (NIV).

Intubation and protective mechanical ventilation
Special precautions are necessary during intubation. The procedure should be executed by an expert operator who uses personal protective equipment (PPE) such as FFP3 or N95 mask, protective goggles, disposable gown long sleeve raincoat, disposable double socks, and gloves. If possible, rapid sequence intubation (RSI) should be performed. Preoxygenation (100% O2 for 5 minutes) should be performed via the continuous positive airway pressure (CPAP) method. Heat and moisture exchanger (HME) must be positioned between the mask and the circuit of the fan or between the mask and the ventilation balloon.
Mechanical ventilation should be with lower tidal volumes (4 to 6 ml/kg predicted body weight, PBW) and lower inspiratory pressures, reaching a plateau pressure (Pplat) < 28 to 30 cm H2O. PEEP must be as high as possible to maintain the driving pressure (Pplat-PEEP) as low as possible (< 14 cmH2O). Moreover, disconnections from the ventilator must be avoided for preventing loss of PEEP and atelectasis. Finally, the use of paralytics is not recommended unless PaO2/FiO2 < 150 mmHg. The prone ventilation for > 12 hours per day, and the use of a conservative fluid management strategy for ARDS patients without tissue hypoperfusion (strong recommendation) are emphasized.

Non-invasive ventilation
Concerning HFNO or non-invasive ventilation (NIV), the experts' panel, points out that these approaches performed by systems with good interface fitting do not create widespread dispersion of exhaled air, and their use can be considered at low risk of airborne transmission.Practically, non-invasive techniques can be used in non-severe forms of respiratory failure. However, if the scenario does not improve or even worsen within a short period of time (1–2 hours) the mechanical ventilation must be preferred.

See: https://www.ncbi.nlm.nih.gov/books/NBK554776/

Hello Murdoch,
Some Ventilator service manuals are available here:
http://www.frankshospitalworkshop.com/equipment/ventilators_service_manuals.html

Hope that helps.

Well said Dustcap... "Hospital trusts will soon be realizing that EBME departments have a huge roll to play"

Good Afternoon all,
Firstly - many thanks for the comprehensive response from all you - it's been very useful and informative already.
I'll try and address some of the questions/points that have been raised as best I can (please bear in mind that my knowledge both on ventilation and the current requirements is limited!)
1) This call is not for NIV, it's for ventilators suitable for intubation
2) I've seen the statistics from ventilated patients from Wuhan - doesn't make for good reading, but at least some lives have been saved
3) I'm developing my understanding of the machines used with anaesthesia vs standard ventilators, but any further pointers on this would be good - out of the "legacy machines" can you advise which would be the best to focus on for a starting point?
4) looks like some good work underway to get database (can't beat a spreadsheet!) of available equipment nationally, so that resources can be pooled - it's not the scope of what I'm looking at, but sounds great.
5) In terms of the initial spec that UK Gov has produced, I will PM it to each of you for your review - I'm not sure if I'm allowed to share in public domain directly, so that seems best (anyone else wanting a copy just send me note)
6) Completely agree that the simplest approach is the licencing of an older model for general manufacture - it's the equivalent of issuing Boer war rifles to the home guard in WW2 - certainly not ideal, but will definitely do a job. A design from scratch seems
7) Basic functionality, reliability and ease of use seem to be the order of the day
8) Within limits, there will be a relaxation of the medical device regulations
9) I believe that the existing manufacturers are being engaged with, hence my interest in older devices that might be from companies that are now defunct, or no longer manufacture ventilators.
Thanks M.

If I've missed any of the questions in the thread, please remind me!

For background, see John's article.

Re: "anaesthesia vs standard ventilators" ... there are various ways of classifying ventilators (such as their cycling methods, and (or) method of operation).

However, for our purposes here, anaesthesia ventilators - sometimes known as "theatre ventilators" (especially those from earlier times) are (were) invariably gas driven only (that is, no electrical power required). They are (were) of the pressure cycled, positive pressure type. They usually sat underneath an anaesthesia machine, to form part of the tubing circuit to (and these days, from) the patient.

On the other hand, ITU-type ventilators are usually volume cycled, and include comprehensive controls (settings) and various levels of alarm circuitry. All this requires electrical power. The gas supplies are generally taken from the hospital PMG system.

For the exercise in hand, we should only be considering the latter type of ventilator - the ITU-type (of which the old Siemens Servo 900C, or - more recently - Puritan-Bennett 840 are but two well known examples).

Clinically, the thing to bear in mind is that anaesthesia (theatre) ventilators are normally used on healthy lungs; whilst ITU ventilators may (and often are) used on damaged or diseased lungs.

Briefly responding to your points:-

1) Yes
2) Ignore all that
3) None of those already mentioned (see PM) ... we need an ITU-type
4) Yes; we love databases
5) Yes; I've read that (and wonder who they copied it from)
6) The Lee-Metford and Lee-Enfield were (are) amongst the best rifles known to Man
7) Yes; as always
8) I don't like that idea*
9) Who are we expecting to actually produce these new ventilators?

* What will happen to any "new" - and possibly sub-standard - machines once the crisis has passed?

PS: "A design from scratch seems ... "? See your point 6)

**********

Whilst acknowledging that there is a worldwide demand for ventilators at the moment (and not that many manufacturers), I believe we need someone at an appropriate level in the NHS to make a shortlist (of three or so) of the preferred ventilators currently in service, then approach the manufacturer of each to see if they can supply the numbers required (doubtful) and in the time required (even more so). Then, if requirements cannot be met, and licensing and what-have-you can be obtained, then other non-OEM manufacturers should be requested to mass-produce the most preferred model. That is, clone an existing and successful design. Again, I see problems there ... not least the (non-) availability of components, the production of circuit boards etc., etc. ... and do we in the UK have such manufacturing capabilities these days, anyway? But lastly, who would be in charge of co-ordinating such a project - a Government department?

Apologies Geoff - missed the end of that sentence, should have read something like "a design from scratch seems a needless exercise, given that there will be some solid, proven solutions that will have been used over the past 50+years" or words to that effect.

I've replied more fully in PM.

Yes; I agree with that.

See also Dustcap's post earlier today at #75023.