exovent iron lung concept offers alternative to Covid-19 ventilators

The iron lung has been reimagined by a multidisciplinary team to potentially give the NHS an alternative model of ventilator to treat Covid-19 patients.

exovent (Credit-John-Hunter-Steer-Energy)

Dubbed exovent, the Negative Pressure Ventilator (NPV) is said to be non-invasive, so patients won’t need to have their windpipes intubated. Instead, they can remain conscious, take medication and nutrition by mouth, and talk on the phone. It can be used on a normal ward, keeping patients out of intensive care.

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Marshall Aerospace & Defence Group is said to be exploring the technical aspects of the scheme ahead of rapid production and roll-out of NPV, which is supported by WMG at the University of Warwick, Imperial NHS Trust and The Royal National Throat Nose and Ear hospital. Two intensive care units have agreed to trial the prototype ventilator support devices.

December 1956: improving iron lungs

With only a small number of moving parts, the components are available in the UK and are not required by other manufacturers currently commissioned by the government to build conventional Intermittent Positive Pressure Ventilators (IPPV). More types of ventilator can then be built simultaneously, with the aim of 5,000 exovents being produced per week. The team said more options can be provided to clinicians choosing the most appropriate device for each patient.

In use, the device fits over the patient’s torso and takes over their breathing through gentle and repeating pressure. It is claimed to increase the heart’s efficiency by up to 25 per cent compared to conventional ventilators which squeeze the chest, potentially reducing cardiac function. Furthermore, exovent is less likely to cause a pneumothorax (burst lung) as negative pressure ventilation produces less micro-trauma to the lung, and it does not require medical-grade compressed gases, which are at risk of shortage in the NHS due to heavy levels of demand for oxygen.

The ventilation support device is supported by Sir John Burn, professor of Clinical Genetics at Newcastle University, who is leading the development of a Covid-19 antigen test.

“The exovent team has cleverly adapted the old concept of the iron lung which was used for treating polio,” Sir John said in a statement. “This device is cheap, simple and it will work. I am convinced it provides a real alternative and is worthy of support.”

The task force's leading clinician Dr Malcolm Coulthard added: "The team has been working flat out for the last 10 days. We started out looking at negative pressure ventilator technology thinking that it would allow us to produce literally thousands of ventilators very quickly and cheaply to cope with the tsunami of people with pneumonia that may be upon us because of the Covid-19 virus.

“However, as soon as we looked into the science and the literature it immediately became apparent that this will allow us to produce less-invasive devices than the conventional units in current use, possibly better for patients’ hearts, at a fraction of the price, using off-the-shelf parts.

Exovent can provide an alternative choice to using Continuous Positive Airways Pressure (CPAP) by delivering continuous Negative End Expiratory Pressure (NEEP). This method does not require to be driven by pressurised air or oxygen, and additional oxygen that the patient needs can be provided with tubing or a face mask as required.”