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Modification of a domiciliary ventilator to increase FiO2: an off-label modification which may be of value in COVID-19
  1. Yoseph Mebrate1,
  2. Steven Phillips1,
  3. Debbie Field2,
  4. Ivy Mumuni1,
  5. Paul Josse3,
  6. David Alexander4,
  7. Rishi Das-Gupta5,
  8. Richard Trimlett6,
  9. Michael I Polkey2,7
  1. 1 Department of Biomedical Engineering, Royal Brompton and Harefield NHS Foundation Trust, London, UK
  2. 2 Department of Respiratory Medicine, Royal Brompton and Harefield NHS Foundation Trust, London, UK
  3. 3 Department of Design, Brunel University College of Engineering Design and Physical Sciences, Uxbridge, Hillingdon, UK
  4. 4 Department of Anesthesia, Royal Brompton and Harefield NHS Foundation Trust, London, UK
  5. 5 Department of Innovation and Technology, Royal Brompton and Harefield NHS Foundation Trust, London, UK
  6. 6 Department of Cardiothoracic Surgery, Royal Brompton and Harefield NHS Foundation Trust, London, UK
  7. 7 Thoracic Medicine, National Heart and Lung Institute, Imperial College London, London, UK
  1. Correspondence to Professor Michael I Polkey, Respiratory Medicine, Royal Brompton Hospital and National Heart and Lung Institute, London SW3 6NP, UK; m.polkey{at}


Although nasal continuous positive airway pressure or non-invasive ventilation is used to manage some patients with acute lung injury due to COVID-19, such patients also demonstrate increased minute ventilation which makes it hard, if the device is used in line with the manufacturer’s instructions, to achieve adequate oxygen delivery. In addition, if a hospital contains many such patients, then it is possible that the oxygen requirements will exceed infrastructure capacity. Here we describe a simple modification of two exemplar ventilators normally used for domiciliary ventilation, which substantially increased the fraction of inspired oxygen (FiO2) delivered.

  • non invasive ventilation

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  • Contributors YM and MIP equally contributed on all aspects of this work from conception, design, development to completion/reporting, and together produced the first draft of the manuscript. SP and IM helped with experimental data acquisition. PJ and RD-G helped with 3D design printing. DF, DA and RT, using their clinical experience of treating COVID patients, provided valuable conceptual insights which helped the develop the idea. All authors read and approved the final manuscript. The evolution of this idea stemmed from colleagues in NW London and in discussions with clinical colleagues (DF/RT/DA/MIP). Manufacturing and adapting the adaptation was undertaken by BME/innovation at RBHFT (YM/SP/IM/RD-G). The original idea was developed by YM. MIP produced the first draft of the MS and all authors have seen and approved the draft.

  • Funding This was supported by the Royal Brompton and Harefield NHS Trust and Brunel University London.

  • Disclaimer Although the design for the adaptors described in this article is provided free to users (see supplementary files 2 and 3), RBHFT and Imperial College have filed a patent application to protect the innovation which at least in theory could result in financial gain to the institutions in the future, although authors' principal current aim is to protect their ability to disseminate the method to health care providers who may wish to use it. Clinical use of this modification is entirely at the risk of the user. The authors and their institutions accept no responsibility for the consequences of clinical use.

  • Competing interests MIP serves as a paid consultant for Philips and JFD.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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