A plan to buy thousands of medical ventilators from a group including the Renault and Red Bull Formula One teams has been cancelled amid signs that symptoms specific to Covid-19 could make building new devices more difficult than hoped. The NHS needs to increase its stock of ventilators from 10,000 to at least 18,000 and the government has been scrambling to procure enough in time for a peak of cases expected by the end of the month. Efforts to source more have involved enlisting UK manufacturers, importing devices from overseas and even borrowing them from the set of the BBC medical drama Holby City. The Cabinet Office confirmed that a provisional request for thousands of one model, called BlueSky, would not go ahead because clinicians feared the device was not sufficiently complex to be suitable for treating Covid-19. The Guardian understands that this ventilator, formerly known as Remora, involved a collaboration between the Renault and Red Bull Formula One teams. They were working with a small Essex-based specialist, Lifeline Technologies, whose founder, Dr Alastair Darwood, designs medical devices. The devices had not been formally ordered or paid for because they were yet to receive regulatory approval. While the BlueSky machine was capable of ventilating patients, clinicians on the government’s technical design authority and the Medicines and Healthcare products Regulatory Agency (MHRA) found it was not suited for treating Covid-19. This is because fluid builds up in the lungs of coronavirus patients faster than in people suffering from other ailments. The devices must be switched to a different setting while the patient’s lungs are being cleared and the BlueSky machine did not lend itself to frequent changes. A Cabinet Office spokesperson said the decision had been taken “following a reassessment of the product’s viability in light of the ever-developing picture around what is needed to most effectively treat Covid-19”. Formula One teams are assisting with several ventilator projects under the umbrella title Project Pitlane. A spokesperson for Formula One said: “The F1 team project leads for BlueSky – Aston Martin Red Bull Racing and Renault DP World F1 Team – have shown brilliant dedication and skill throughout the project and should feel proud of the work they have undertaken to develop a new device with an NHS entrepreneur and will continue to provide vital contributions to Project Pitlane.” One source familiar with multiple ventilator projects said the issues that affected BlueSky showed why regulators could not rush through new devices. “People are still testing these things in clinical trials and our understanding is evolving every day, so that might be part of why it’s taking a bit longer,” they said. The MHRA approval process can take years but officials are working round the clock to move faster. One device, made by Oxfordshire-based Penlon with backing from manufacturers such as Airbus and Rolls-Royce, is expected to win approval soon because it varies only slightly from proven machines. The Ventilator Challenge UK consortium has offered to build 5,000 of these and some have already been delivered to hospitals where doctors are performing clinical trials. The same consortium has also delivered the first of up to 10,000 ParaPAC ventilators made by Luton-based Smiths Medical, which are already approved for use. But tens of thousands of the machines that have won provisional orders from the government are yet to be rubber-stamped. They include 10,000 of the Zephyr Plus model made by the defence firm Babcock and German medical device specialist Drägerwerk. The Zephyr Plus has the advantage of being based on existing designs. Dyson’s brand new CoVent prototype is not thought to have undergone rigorous testing yet, while another device made by a Cambridge-based company called Science Group is also untried.