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NIV: thoughts and tips

Non Invasive Ventilation (NIV) comes in a variety of forms, machines and names.  It is something that has really changed the way we manage some common ED scenarios, however it is often misunderstood and done poorly.

I have just finished reading through the course manual for an upcoming Emergency Skills Course I am doing next month – and was disappointed by the low priority given to NIV.  CPAP was often being included as an afterthought or a “try if all else fails” option.  However, in the modern ED,  NIV should be front and centre, a first line option in respiratory failure.

Why is this so?

  • My guess is that many junior docs and older docs who trained in the pre-NIV era find it all a bit confusing and are afraid of getting it wrong.
  • Most NIV machines use horribly fancy acronyms to describe what they do and unfortunately there is not a lot of uniformity over different models.  BiPAP, CPAP, EPAP, IPAP, PS…… it can be a little bewildering.
  • There are plenty of myths and overly rigid lists of indications, contraindications and no-nos for NIV – this is an area of practice where the evidence is still convulsing and new uses and protocols are being devised – so it will confuse the newcomer.
  • NIV can do harm – pop a pneumothorax, crash the BP, barotrauma etc – but most of these are uncommon, and certainly less problematic than the alternative – namely intubation and ventilation!

The fact is though, that NIV can really turn a dire situation into a manageable one in a short period of time.  This is a wonderful tool for those of us who work in remote settings, where there is not much back-up and we need to temporize critically ill patients until help can arrive.  Used well, NIV is a powerful tool in our small hospitals, so I thought I would collate some pearls from the ether into one place for your reference and guidance.

Indications for NIV – the list is growing, but as of now it includes:

  • Good evidence and experience for NIV in acute pulmonary oedema, COPD exacerbation, immunocompromised patients.  Neonatal use is common in RDS, premature lung disease.
  • Some evidence and increasing experience for NIV in : severe asthma, pneumonia, CF, postoperative respiratory failure
  • Emerging, but unproven use in :  neurological disease (eg AMS), traumatic chest injury, ARDS

When it comes to the nitty-gritty practical application of the mask to the patient – we doctors usually leave this up to the nursing staff.  Usually they are more experienced!  In my search I found this wonderful 10-step approach to initiating NIV on the patient who is “having the worst day of their life”.  Seth from MDAware (@mdaware) posted this pearl on his site a while back – it is now getting laminated and stuck on my machine in ED!  check out: Selling Icecream in the Desert.

Now to the bit most of us find tricky, fist fights erupt between medical registrars over this one – and confusion seems to reign – should they have CPAP or biphasic NIV?

I could write for about 5 pages on this but I will try to condense it into a few simple lines.

  • Biphasic (BiPAP, IPAP + EPAP) ventilation includes CPAP – so if you are using BiPAP, you are using CPAP too.
  • CPAP is good for patients with problems related to “oxygenation” which might include recruitment of “dead space” and decreasing shunting of blood through the non-ventilated areas of lung.
  • BiPAP is good for patients with “ventilation” issues – those with a rising CO2 on the blood gases, the one with an obstructive problem often.
  • Here is the heresy – it doesn’t really matter which one you use initially – if you choose a low pressure BiPAP setting you are covering your bases for CPAP and improving ventilation.
  • Most patients do not have a pure diagnosis of APO over COAD – we are not great at deciding which it is anyway!
  • The big trials (see 2005 meta-analysis, 3CPO) struggled to show a difference between the two modes – so both of the Med registrars were right (or wrong) if you like – so be like Jordan and “Just Do IT”.
  • In patients with low cardiac output states, sepsis or with weak hearts – you need to be aware of the potential to make them crash – so you need to be gentle with your settings and titrate up with close monitoring.

Now a myth to bust: Can you give sedation to patients on NIV?

Traditionally we have said “No”, but in reality we do this all the time and with careful supervision it seems to be safe.  Using small aliquots of fentanyl, ketamine or short-acting benzos seems to be popular in most places I have visited.  The key is to stand at the bedside and monitor the patient – they will be unlikely to come to too much harm if you or a nurse are standing there coaching them.

There has been a lot of chatter about the DSI techniques in the medical blogosphere – and it is catching on.  For me what I like about using NIV to prepare a sick patient for intubation is that it gives me a dynamic idea as to what will happen to their output when we do intubate and place them on IPPV.

In the old days we would take a sick patient – one breathing with regular negative pressure and swap this for positive pressure ventilation – a dramatic swing in thoracic pressures, with often dire outcomes.  Peri-intubation arrest being the one we all hope to avoid.  By using NIV at mild pressures (5 – 10 cm) we are changing the haemodynamics in a more reversible and gentler manner – you can watch the art. line or other monitors and see what happens to their output – you get a feel for how brittle they are before you push in the meds and get into a scenario where it is IPPV or nothing and you lost your window to optimise their volume, pressors etc

I am a true NIV enthusiast – I find it really satisfying to see patients who look really sick and scared settle quickly and relax.  Doesn’t always work, but it is a great option to try when they roll in the door.

Let me know your thoughts. Casey

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Comments

  1. Absolutely -- every country hospital has a portable ventilator (usually that stalwart, the oxylog) and new models allow us to deliver CPAP. Use to avoid intubation and turn around a “wet as a fish” APO are to be seized upon

    Big issue is that (i) we may not have done this since rotations int eh big tertiary ED and (ii) both doctors and nursing staff quickly de-skill. I once worked somewhere where the CNC (head nurse) induced new staff with the comment ‘and this is the Oxylog 2000 plus…but don’t ask me how to use it” -- not inspiring when the ‘team’ on the ground at 3am is a locum Dr and the same nursing staff.

    perhaps a master class on vents for rural docs? (we’ve got the oxylog 2000+ locally -- there’s a great post on ‘own the oxylog 3000′ elsewhere)

  2. Matthieu G. says:

    I share your enthusiasm.

    Thank you for the MDaware link. Great tips, but there is one point I disagree with: I never start with the mask strapped on the patient. I hold the mask myself first while talking to the patient, loosely first than more tight if well tolerated, and occasionally remove it to let the patient talk. Even better, have the patient hold the mask himself. If he is too weak to do it, the situation looks grim. I routinely use sedation for NIV initiation, favoring small aliquots of benzodiazepine (diazepam 2-4mg IV).

    Regards

    • Seth Trueger says:

      Interesting take. I like getting the mask fitted properly (not very tight) before starting ventilation because a lot of machines alarm if there’s a mask leak.

  3. I think you’re a pretty smart guy.

    Tight fitting (leak free) face mask, start slow on using these modes.

    First, bring the PEEP up to 5 cm H2O (otherwise known as the EPAP).

    Then bring the pressure support up to 7, then 10 (otherwise known as the IPAP).

    Watch the tidal volumes delivered, the adequacy of the mask seal, and the alleviation of the upper airway obstruction/snoring if sedated or obtunded.

    Good method also to use in sick patients needing sedation for a procedure in your facility.

  4. Great tips, start slow

    I’m going to come back to the difficulty for some of us in the bush (rural Oz, but I guess this would apply equally to Canada, isolated N America, other regional areas)…namely that we don;t do this often and when we do, it is usually early hours, with nursing staff who may be even less experienced…and with patients who are sicker than usual

    Of course, a good argument for ongoing training..and low cost sims like iALSI and other apps make this do-able. Also an argument for logistics over strategy.

    Me? I plan for 3am with locum doctor and agency nurse -- if the system can survive that, it can cope with most things

    Which is why I love these posts..and am a firm believer now in checklists and SOPS.

    Good case therefore for standardisation of SOPS for services -- wouldn’t it be great to have access to the RFDS or retrieval service SOPS for oxylog, NIPPV etc available in these smaller hospitals, and cross training of staff etc

    An App would be even better! I hear this mob have something available

    http://www.emrs.scot.nhs.uk/index.php/service-user-area/sop/clinical-sops

  5. Michael Rodda says:

    Thanks for the feed. I agree. I have been teaching a similar technique for a few yeasr now. It is nice to know someone else has the a similar approach. I try and start at 50% O2 and escalate my CPAP up until the sats are in the 90’s% (T.E. Oh Intenesive Care manual, when to move to NIV criteria.) Then add PS if required. Selling Icream in the desert was good. Thanks

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