In recent months, there has been a worldwide surge in the demand for ventilators, as increasing numbers of people with Covid-19 pneumonia continue to require help with the work of breathing. It is estimated that between 15 to 30 per cent of people infected with Covid-19 who are admitted to hospital end up on an intensive care unit or similar facility, in need of ventilatory assistance, often for weeks rather than days. A mismatch between supply and demand has led to a number of initiatives, all aimed at immediately increasing the numbers of available ventilators to ensure that all those likely to benefit do not miss out.
By the end of March 2020, the NHS in the UK had a total of 8,175 ventilators. Anticipating an increased need, the British government set itself an arbitrary target of 30,000 ventilators, to better cope with peak demand at the height of the coronavirus crisis. The situation has prompted much discussion about the under-provision of ventilators in the UK. Unfavourable comparisons have been made with Germany, where an allocation of 33.7 intensive care beds per 100,000 inhabitants makes it the most well- equipped of all nations in Europe when it comes to ventilators. Across the Atlantic, open conflict between the federal government and several American states has broken out, with individual states bidding against each other for a limited supply of ventilators. Competition for ventilators is to be seen everywhere, as nations outbid each other in what has become a global auction house.
Supporting ventilation is all about improved mechanics, involving the replacement, by artificial means, of the pumping mechanism that normally provides the body with oxygen while simultaneously removing carbon dioxide. Gas exchange within the lungs is the driving process for all cellular respiration, which forms the very basis of life.
Normally, healthy adults breathe in and out around 12 to 20 times a minute, drawing in around 500 ml of air with each breath. Inspired air has a 21 per cent concentration of oxygen, and this suffices under normal circumstances. In patients with severe Covid-19 infections, lung inflammation caused by viral pneumonia can progress to adult respiratory distress syndrome (ARDS), when the lungs become stiff and are difficult to inflate. At the same time, the exchange of gases within the air sacs (alveoli) of the lungs is impaired as they fill up with fluid and their linings thicken from inflammation. The victims of ARDS thus require support with both high inflating gas pressures as well as higher concentrations of oxygen in the inspired gas.
The need for ventilatory support can be identified by a combination of clinical observations, including vital signs, and then confirmed by measuring the concentrations of oxygen and carbon dioxide in arterial blood samples. The decision to artificially ventilate an individual patient depends not only on recognising the need to support the work of breathing but also on predictions as to whether this type of support is likely to benefit. This means that some people, especially those with multiple and irreversible co-morbidities (coexisting medical illnesses) may not be artificially ventilated, leading to possible, although unfounded, accusations of rationing and deliberate withholding of care. In any case, mechanical ventilation does not automatically guarantee recovery. The likelihood of death is much higher in those requiring this form of treatment. Furthermore, prolonged ventilation can, by itself, increase the risk of both bacterial pneumonia as well as other forms of ventilator-induced lung injury.
Mechanical ventilation can be broadly classed as being either invasive or non-invasive. The invasion in question refers to the need, or otherwise, for placing a tube within the trachea (windpipe). Non-invasive methods include CPAP (continuous positive airway pressure) and BIPAP (bi-level positive airway pressure). With CPAP, the lungs remain inflated during both inspiration and expiration, and hence it cannot strictly be classified as a form of ventilation. With BIPAP the lungs are inflated with inspiration, but allowed to deflate with expiration. Patients with Covid-19 pneumonia may require either CPAP or in, more severe cases, invasive ventilation. Patients on non-invasive ventilation (NIV) remain conscious and should be able to cooperate with the process, while invasive ventilation can only be tolerated by people who are deeply sedated and paralysed. NIV can be provided on general wards in hospital, while invasive ventilation mandates admission to an intensive care unit.
Ventilators can be moved around between hospitals or may be obtained from stockpiles set up specifically to deal with major disasters. Any shortfall in numbers can either be made by the purchase of already manufactured ventilators or by stepping up the industrial production of ventilatory equipment.
The UK has taken several different initiatives to meet the recent increase in demand for ventilators. The government has approached both foreign governments as well as established British and international manufacturers with a view to purchasing ventilators. A Ventilator Challenge UK consortium has been set up, including a variety of major engineering firms, such as Airbus, BAE Systems, Rolls Royce and Siemens, among others. These firms will be expected to divert existing industrial production capacity, meant for other purposes, to the manufacture of ventilators. The British government has also specifically requested 10,000 ventilators from the vacuum cleaner and hairdryer manufacturing firm of Dyson. But merely increasing production is not enough. All newly manufactured ventilators have to meet stringent criteria, laid out by such bodies as the MHRA (in the UK) and the FDA (USA), to ensue that they can be depended upon to support life reliably when in use. This means that there is likely to be significant delay before new makes of ventilators are cleared for use on actual patients.
On 20 March 2020, the UK Department of Health published specifications for “rapidly manufactured ventilator systems”, inviting yet other firms to declare an interest in supplying ventilators suitable for Covid-19 victims. Some independent initiatives have, in the meantime, led to positive results. For example, a collaboration between the UCL Institute of Healthcare Engineering in London and the Mercedes Formula One racing team has boosted the production of CPAP machines. All of this activity has echoes of the Second World War, where munitions manufacture was undertaken on a massive scale by industry, guided by the support of academia.
There are many other obstacles in the way. Ventilators are made up of several components, which include power sources, humidifiers, corrugated tubing, regulators, valves, motors, electronic components, sensors and alarms. Global supply and transport chains of these components have been disrupted by the coronavirus pandemic. This disruption has been made worse by the fact that China, one of the countries most severely affected, is a major global supplier of ventilator components.
The coronavirus pandemic has provided a major stress test to the public healthcare sector. The supply of intensive care beds and ventilators, in particular, has come under renewed scrutiny and will no doubt lead to much corrective action in the aftermath. When even wealthy industrialised nations have significant supply chain problems, the pandemic is likely to devastate poorer nations, with predominantly agricultural economies, where the numbers of available ventilators can be counted in between one and three figures. One can only eagerly await the expected but as yet indiscernible “light at the end of the tunnel”, as nations try to find their own solutions to the problem of the lack of ventilators.
Ashis Banerjee (retired Consultant in Emergency Medicine)