So - the candidates from #ESICMphysio are off to engage in their workshops - so I thought... let's hold a virtual workshop here on MECHANICAL VENTILATION! #FOAMed @ESICM 
Let's start off at the very beginning. This is a HUGE topic... obviously not going to cover everything. But let's start off at the very beginning and look at my Tweetorial from yday from Prof Barnes talk on the physics of ventilation... #ESICMphysio
@MedCramVideos do a REALLY good series for beginners - for free - on YouTube - 5+ videos on Ventilators and how they work: youtube.com/results?search…
You can see that ventilators *essentially* can be programmed into 2 simple options - PRESSURE (where we set the pressure and get a volume BASED on the pressure) or VOLUME - (where it will deliver a volume that is not based on a pressure). Or you can mix the two and get a hybrid.
Within these two discrete types of ventilation... there are even more options! openanesthesia.org/modes_of_mecha… Some of them are more 'corporate' than others - based on what companies have designed to be 'superior' than other forms of ventilation. What is the evidence? #ESICMphysio
Back in 2004 - Branson et al asked this very question... sure the physics is different, but what about the clinical outcomes? researchgate.net/publication/84…
Our ventilation practices vary HUGELY across the world... even down the road from another hospital... bmcresnotes.biomedcentral.com/articles/10.11… Is this because the subtle differences don't always make a difference? Despite sound physiological reasons why they might on paper? #ESICMphysio
Something to specifically point out is HFOV (Oscillatory Ventilation) is rarely used. A narrative review in 2019 said "It maximizes alveolar recruitment and is a great tool in alveolar recruitment that can be beneficial in preventing lung injury." ncbi.nlm.nih.gov/pmc/articles/P…
To understand properly the difficulties of mechanical ventilation - you need to understand ARDS. What's the definition of ARDS? Well... that's not so easy to answer... litfl.com/acute-respirat… #ESICMphysio #FOAMed
In patients with ARDS, low tidal volume ventilation (initial TV 6ml/kg PBW) had lower mortality and more ventilator-free days. You need to know all about this trial if you don't already: wikijournalclub.org/wiki/ARDSNet #ESICMphysio #FOAMed
This allowed quite extensive guidelines to be issued on how we manage patients with ARDS and how to escalate their management #ESICMphysio #FOAMed ficm.ac.uk/sites/default/… and bmjopenrespres.bmj.com/content/6/1/e0…
Notably these publications suggest ventilation strategies like HFOV is not used; and nitric oxide avoided (more on that here: onlinelibrary.wiley.com/doi/full/10.11…) #ESICMphysio #FOAMed
Much of the discussion around difficult ventilation revolves around PEEP... which I have covered from basic to advanced issues in a Tweetorial, yesterday, here: #ESICMphysio
2018, a SR reported that "for ARDS patients who responded to increased PEEP by improved oxygenation, high PEEP could reduce hospital mortality, ICU mortality and 28-d mortality. High PEEP does not increase the risk of clinically objectified barotrauma." ncbi.nlm.nih.gov/pmc/articles/P…
The difficulties with PEEP continue however - but in 2019 my @ESICM colleague @GicoBellani published a paper to assist decision making in PEEP conundrums: ccforum.biomedcentral.com/articles/10.11…
An early guide of how to manage ARDS was suggested in 2019 also. Themes of lung-protective ventilation, low tidal volumes, higher PEEP and PRONING come into play annalsofintensivecare.springeropen.com/articles/10.11… #ESICMphysio
It's useful to understand the 'Open Lung' concept of ventilation WRT ARDS. @litfl cover this very well --> litfl.com/open-lung-appr… We basically want the lungs OPEN with PEEP.... in combination with lower tidal volumes. But you'll hear this being talked about a lot. #ESICMphysio
Another conundrum in mechanical ventilation is PRONING. To understand this, you need to understand West Zones in the lungs... covered well here: derangedphysiology.com/main/cicm-prim…
So - proning (or lying on your front) changes your lung PERFUSION. rc.rcjournal.com/content/respca…
In the normal human lung - proning = "central posterior portions of the lung are more compressed in the supine posture, likely by the heart etc, vs central anterior portions in the prone, and that this limits regional perfusion in the supine posture." ncbi.nlm.nih.gov/pmc/articles/P…
Response to prone positioning=quite variable and hard to predict. Large RCTs and meta-analyses show that prone position in conjunction with a lung-protective strategy, when performed early and in sufficient duration=?improved survival in patients with ARDS ncbi.nlm.nih.gov/pmc/articles/P…
On a pathophysiology based review - authors said, "Prone positioning seems to = additional beneficial effect vs ventilator-induced lung injury. In patients with severe ARDS, early use of prolonged prone positioning + lung-protective strategies decreases mortality significantly."
So, proning is recommended - and it's likely beneficial when it's done early...? What do you think the uptake of proning is in your own unit? Does it matter to your decision making process if you have ECMO readily available to you or not? :) pulmccm.org/ards-review/pr…
Looks like someone else has had the same though on ECMO, Proning and ARDS... clinicaltrials.gov/ct2/show/NCT04… Anyone care to predict any outcomes?
@ccpractitioner So - let's move on to Ventilator Induced Lung Injury.. litfl.com/ventilator-ass… @LITFLblog Mechanical ventilation with application of pressure to the lung, whether positive or negative, can cause damage known as ventilator-associated lung injury (VALI) #ESICMphysio
Which means that we have to look at volume, pressure, bio, atelecto- & shear trauma all separately and together in order to minimise such lung damage! As we discussed yday on our mechanical ventilator Tweetorial - damage begets more damage! #ESICMphysio
Prof Barnes yday commented that upcoming research (not yet published) will highlight the 'physics' problem of achieving constant flow during both phases of insp and exp. @srrezaie talks more about different modes of ventilation here: rebelem.com/simplifying-me…
