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Friday 20 March 2020

C-19 Sensemaking

Breathe easier

Ventilators are going to do crucial work in the weeks and months ahead – helping to keep coronavirus patients alive. But they’re in short supply, as are the people who can manage them. It’s time for emergency measures

By Paul Emery

What, exactly, is a ventilator? And why have you been hearing so much about them? The best place to start might be with some simple biology. The coronavirus causes enormous problems because of its effect on breathing – wards across the world are filling with patients who have pneumonia across both of their lungs.

The lungs’ fundamental job is to get oxygen into the body and, on the other side of the ledger, remove carbon dioxide. The effects of the virus impede that – and doctors have relatively few options for releasing patients from that grim effect.

Normally, we breathe air, which is 21 per cent oxygen. When a patient’s lungs start to fail, we can help them by increasing the amount of oxygen in the air with supplemental oxygen gas. In fact, we can go all the way up to 100 per cent.

But, sometimes, increasing oxygen alone is not enough to help someone’s breathing. Sometimes, we need to help people’s breathing by increasing the pressure of the gas going into the lungs, so it gets into the blood more easily.

One of the most effective ways we have of doing this is putting a patient into an induced coma by sedating them, putting a breathing tube into their throat and mechanically “ventilating” them. We use a machine to breathe for them – that is what the ventilator does. You’ve probably seen them on medical TV shows, where they tend to look like an accordion or bellows, shuffling up and down.

That might seem extreme as a basic treatment. But the problem with coronavirus is that less extreme options are unlikely to work. Non-invasive ventilation – blowing air through a tight-fitting mask or up the patient’s nose – is a pretty poor option for dealing with the corona pneumonia.

Why so? First, this sort of method is just less effective than invasive ventilation. Indeed, many patients receiving these therapies progress to requiring ventilation and it is currently felt that they do better if invasively ventilated earlier.

Second, these non-invasive devices generate a lot of aerosolised coronavirus. That is to say, they create a viral mist. This is incredibly dangerous for the staff taking care of those patients, especially in hospitals where protective equipment is in short supply.

Third, less invasive measures require very high gas flows, which, when you have a lot of sick people, means that you can potentially use up your hospital’s oxygen supply.

So the ability to ventilate people is going to be enormously important – real life and death stuff. Ramping up the ability to ventilate is – rightly – seen as one of the UK’s challenges.

The Department of Health and Social Care has 5,000 intensive care ventilators. It says it might need another 20,000. Some of that capacity can be met from repurposing other ventilation equipment elsewhere in the NHS. But the sheer number of ventilators is not the whole issue. For a start, not all ventilation equipment is the same.

For example, in a pinch, it can repurpose machines used by anaesthetists. During surgery, patients are often ventilated – but the machinery we use in surgery is a little different and not quite right for an ICU.

Purpose-built ventilators for use in intensive care have clever internal computers, highly accurate sensors and flow switches. They use turbines to generate pressure, have multiple modes of ventilation and allow patients to breathe for themselves at the same time as being ventilated. Machines designed for anaesthetics may not be built like this.

Some anaesthetic machines are very simple to operate – but these ones tend to use bellows, not turbines, to drive air in and out of the lungs. They are simply not as delicate or sensitive as the ICU machines. This is fine during the hours it takes to run an operation – but using one for 7-10 days to ventilate someone is less than ideal.

Some newer anaesthetics machines have delicate turbine ventilators just like the ICU machines, but their user interfaces make them complex to use and deploy. Frankly, they are not user-friendly for anyone – and when we wheel them into an ICU, we will be asking people to use them in ways they were not designed for, and without much training.

Indeed, people are going to be one of our major capacity problems. We are also going to be asking a lot of our healthcare staff. In normal times, each ventilated patient has an intensive care nurse dedicated to them 24 hours a day. This might seem excessive; that is what the “intensive” in “intensive care” means.

Remember: these are patients that need to be fed through a tube in their nose. They need lines of fluids into them to deliver life-saving drugs. They need to be turned every three hours to prevent pressure sores and wounds. Without care, all of these things can be sources of lethal infection.

An ICU unit treating COVID-19 patients at a hospital in Wuhan, China

Much of what happens on an ICU is about buying time so people can recover on their own. But one treatment we do have that buys a ventilated patient time to get better is something called “proning”. Proning involves placing a patient face down for 12-16 hours a day to allow their lungs to oxygenate better without the weight of the body on them.

That takes up to eight people to do properly, without pulling those invasive, life-saving devices out. And it needs to be done to every ventilated patient twice every day.

Patients in the ICU also need to be given lots of medications and have minute adjustments made minute-to-minute. The patients also need physiotherapy and nutrition, as well as advice relating to infectious diseases.

And all this information, all this work, needs to be recorded and transmitted. This is an incredibly complex, specialised and highly skilled job. These staff are also at the greatest risk of contracting coronavirus themselves as they are exposed to those who are most unwell.

So the machines are a huge bottleneck, but so are the people. We are currently talking of going from ratios of one patient per intensive care specialist to three-to-one as we model for staff sickness and expansion of services.

We are looking at retraining doctors and nurses from other disciplines: surgeons and anaesthetists are already being redeployed as we cancel surgery. We are looking at using machines in contexts they were not designed for and placing them in the hands of people who have little experience of them.

But this is a crisis. Needs must. Anaesthetics machines and surgeons learning intensive care on the job will, we hope, save thousands of lives. But, when this is over, we will need to consider why we were so unprepared for what we are facing.

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Dr Paul Emery

Dr Paul Emery is an anaesthetist.