Treating coronavirus: what's intensive care?

24 March 2020

Interview with 

Charlotte Summers, Addenbrooke's Hospital

VENTILATOR

A patient on a ventilator in a hospital.

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A small number of coronavirus patients get more severe symptoms. So when doctors have to treat those symptoms, what do they actually do? Chris Smith asked Charlotte Summers, an intensive care doctor at Addenbrooke’s Hospital in Cambridge...

Charlotte - The main reason that they present to us is because they are not able to get enough oxygen in, because their lungs are not functioning efficiently.

Chris - Why?

Charlotte - The gap between the oxygen coming into the airway sacs and your blood has got a bit bigger, and so the diffusion of the gas from the alveolus into the bloodstream is compromised. So actually you're not getting enough oxygen from the air across into your blood and off to the remote tissues for your organ functions.

Chris - And if I just breathe a bit more often, is that not sufficient to compensate for the fact that my lungs aren't pushing as much oxygen as quickly into the blood? I just breathe a bit more, that should compensate, shouldn't it?

Charlotte - It's about supply and demand. When the gap between your lung tissue and your blood has got bigger, the speed at which you breathe does not necessarily compensate enough for the profound lack of oxygen that you get.

Chris - When someone shows signs that they're not getting enough oxygen into the blood - and I presume you can measure that - what's the first thing you do?

Charlotte - The first thing's really simple: we give them supplemental oxygen. So we do that via facemasks, or via some tubing that goes into the nose, to give you an increased amount of inspired oxygen.

Chris - And how does that help? Because if you've got that gap between where the oxygen is and where the blood is that needs the oxygen, how does having more oxygen there to start with compensate?

Charlotte - Well like any other substance pretty much in biology, things move from an area of high concentration to an area of low concentration. If I can increase the size of that concentration gradient, then actually I'm probably increasing the efficiency of the oxygen transfer from the alveolus into the blood.

Chris - And in what fraction of patients will that be enough?

Charlotte - So in the setting of coronavirus, it looks like about 1020% of people out of all of the people who get the virus probably need to come to hospital, and most of the people who are coming into hospital are coming in because they're unwell enough to need some support for their breathing.

Chris - When would they become a candidate for you then?

Charlotte - So if giving you supplemental oxygen wasn't enough, then you get to meet people like me.

Chris - So if a person gets taken to intensive care, what sorts of things do you do to keep people alive?

Charlotte - We can use tight-fitting facemasks that blow air into your lungs to try and open up congested bits of your lung. If that's not working, then actually we end up saying, "fine, we need to put you to sleep using drugs - so very much like a general anaesthetic that you would have for a surgery - and pop a tube down into your trachea that securely sits in your airway, so that we can use a mechanical ventilator to blow air into your lung and try and take over the work of your breathing completely.

Chris - Why is is blowing air in in that way any different than a person breathing for themselves? What can you achieve by that, that I can't achieve by just taking a deeper breath?

Charlotte - What it's aiming to do is to stop inflamed and congested bits of your lung collapsing at the end of you breathing out, by providing some pressure; but also providing support for your muscles breathing in and out, and the extra work of breathing that you have to do when you're profoundly lacking in oxygen.

Chris - How long are they probably going to need that ventilation, and what is that doing? Is it giving time for the lungs to recover themselves and just keep the person alive while that happens, or is there something else going on?

Charlotte - It's a supportive therapy, it is not a cure. It is just buying time for your body and whatever therapies can be instituted to do their work. In coronavirus there are no validated therapies and things that have been shown to be of clinical benefit, so all we have is supportive therapy and the hope that your body can heal itself over time with us looking after it as best we can. The length of time that people are needing mechanical ventilation is actually days to weeks currently based on some of the data that's coming out of Europe, so it's not something that happens for a very few hours. And every day you are on a ventilator the consequences of being ventilated climb, and your muscles get a little bit weaker, and the road back to being the person that you were when you came into hospital is just that little bit longer.

Chris - Charlotte Summers there from Addenbrooke's Hospital. We've also had an email to chris@thenakedscientists.com from John Blanning who says, "can you tell us how many people who go into the Intensive Care Unit on a ventilator actually survive with coronavirus?" I put this question to Ari Ercole, consultant ITU physician, who said actually, the numbers are not that encouraging. A significant proportion of people are not going to make it despite the best efforts of ITU. So that is a very sobering message.

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