Author: Holly M
Third-year medical student
Do ventilators help COVID-19 patients?
In this article, I will provide an introduction to and discuss what ventilators are, how they work and what they are commonly used to treat in medical settings. Ventilators are a very current topic in the medical world and in the media, as they are being used to treat patients with COVID-19.
Questions about their efficacy, availability and ethical considerations are all being discussed, and could easily come up at a medical school interview. If you are really interested in this topic, it might be worth doing some extra reading. You can start with the resources I have included at the end of the article. I would keep making notes about the things you find particularly interesting or striking as you go along. Remember also that this is an evolving situation, and new research will continue to be published, so make sure you stay up-to-date and don’t just rely on this article, as it could become out of date.
When are ventilators used?
The first step when a patient arrives in the hospital and is severely unwell and short of breath is to check their oxygen saturation (which shows how much oxygen is in their blood). If it is low, then normally patients are given oxygen via a face mask, or nasal cannulae. However, this doesn’t always give enough support to patients who are acutely unwell, and so sometimes we need to elevate the patient care and start ventilation, especially if they are deteriorating or fail to improve. There are different types of ventilators, this article doesn’t cover all of them but just gives you an overview.
Types of medical ventilators
Intermittent positive pressure ventilation
One type of ventilation often used in ICU is intermittent positive pressure ventilation (IPPV). This requires an endotracheal tube (a tube that goes into the airway in the throat, which is called the trachea) and intermittently inflates the lungs using positive pressure.
Non-invasive ventilation (NIV) avoids the need for endotracheal intubation. NIV improves symptoms in chronic respiratory failure, but it doesn’t improve survival. NIV might be used for patients who aren’t candidates for invasive ventilation. Bilevel positive airway pressure (BiPAP) is a type of NIV and uses a tight-fitting facial mask or, sometimes, nasal cannulae to deliver oxygen.
Continuous positive airway pressure
Continuous positive airway pressure (CPAP) is a type of ventilation used for severe respiratory failure. It can be delivered to a patient via an endotracheal tube or a tight-fitting face mask. When an endotracheal tube is used, it is a type of assisted ventilation, and it should only be used if the patient has a reasonable prognosis as it is very invasive. If a tight-fitting face mask is used, this makes it a type of NIV and it is then used if a patient is still spontaneously breathing. CPAP makes the lungs less stiff, so it is easier for the patient to breathe.
Extracorporeal membrane oxygenation
Extracorporeal membrane oxygenation (ECMO) is used for very severe respiratory failure. It is a type of life support that is connected to vessels in the patient’s legs, neck, or chest via cannulae and pumps their blood into an artificial lung where it is then oxygenated. It is very invasive and there are lots of risks of complications. It is very specialist equipment and requires healthcare workers specially trained to be able to use it.
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What are ventilators generally used for?
The type of ventilation used and for how long depends on why the patient is unwell and their co-morbidities (other conditions that they have). Ventilators are used all the time in the hospital, for example, during surgeries by anaesthetists. Ventilators are used for patients suffering from respiratory failure. If a specific test, called an ABG (arterial blood gas), shows increased carbon dioxide in the patients’ blood, the patient may be transferred to ICU (intensive care unit) for ventilation. The increased carbon dioxide shows that they are struggling to breathe normally and can’t get rid of the carbon dioxide.
Respiratory failure causes
Respiratory failure can be caused by several different diseases. Asthma attacks, pulmonary oedema, COPD, smoke inhalation, pulmonary fibrosis, sedative drugs, brain tumours and neuromuscular diseases (such as motor neurone disease) can all cause respiratory failure.
Treatment for viruses
Ventilation can be used as a treatment for viruses such as avian influenza A viruses, and if patients with the severe acute respiratory syndrome (SARS) (caused by a type of coronavirus called SARS-CoV) develop respiratory failure and acute respiratory distress syndrome (ARDS). There are lots of other causes of ARDS that can also require ventilation. These include pneumonia, gastric aspiration, vasculitis, septicaemia, haemorrhage, multiple transfusions, pancreatitis, acute liver failure, malaria, head injury and aspirin or heroin overdose.
What are the consequences of using ventilation for patients?
There are good and bad consequences of using ventilators. The good are that they improve the patient’s ability to get rid of carbon dioxide, stop the patient from becoming exhausted by taking away the effort of having to breathe. They also increase the amount of oxygen the body receives. However, endotracheal tubes are dangerous. They can end up in oesophagus (the tube that connects the mouth and stomach) and cause abdominal distension. They can also end up too far down into one of the lung lobes, causing a lung collapse or pneumothorax.
Infections caused by ventilators
Patients can also develop pneumonia and infections from ventilators, this can affect around 20% of patients admitted to ICU. Often the infections are caused by more resistant pathogens, which means they are harder to treat. Examples of organisms causing common ventilator acquired infections are pseudomonas aeruginosa and various types of fungi. Intubation stops the patient’s mucociliary elevator from working, this is made up of cells (goblet cells) which create mucus to catch pathogens and cells with cilia to push the mucus up, so we cough the pathogen out. This makes it easier for the pathogen to get to the patient’s lungs and cause an infection.
Why are ventilators being used in the COVID-19 pandemic?
There have been suggestions that all patients with COVID-19 presented to a hospital should be intubated and placed on ventilation early. However, the World Health Organisation (WHO) guidelines say that doctors should use less invasive ventilation such as NIV and CPAP (with a face mask) first. This is because intubation and ventilation could be unnecessary for a patient’s recovery. It could cause more harm to the patient and take the limited resource of a ventilator away from another patient who may need it more. Research from Lombardy in Italy showed that with early intervention using NIV, 50% of patients avoided having invasive ventilation, and the risks associated with it.
Availability can be an issue
The last point from the WHO about the availability of ventilators is particularly important. There has been a lot of media coverage about the number of ventilators available in different countries, including our own. Would hospitals be able to cope with the number of potential patients requiring ventilation? It’s really worth thinking in detail about this topic and the ethical considerations and questions it brings up.
How effective are ventilators against covid-19
Some argue that invasive ventilators reduce the risk of COVID-19 transmission to health care workers, especially if used with an oxygen hood. However, good interface fitting for CPAP and NIV systems dramatically decrease widespread exhalation of the virus and actually, the endotracheal intubation needed for invasive ventilation leads to an increased risk of aerosolization of the virus, and so there is an increased risk of health care workers catching it.
Resources used and extra reading
This is a list of the articles and textbooks I used to help write this article, if you are interested in reading further into this subject, these could be a good place to start. I would advise dipping in and out of reading these, as attempting to read them all in one go could overload you with information!
– Oxford Handbook of Clinical Medicine Tenth Edition Ian B. Wilkinson, Kate Wiles, Harriet O’Neill, Tim Raine, Catriona Hall, Anna Goodhart
– Kumar and Clark’s Clinical Medicine 7th edition Parveen Kumar, Michael Clark
– Use of non-invasive ventilation in patients with COVID-19: a cause for concern? The Lancet Nishkantha Arulkumaran, David Brealey, David Howell, Mervyn Singer
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