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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