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. 2020 Jun 1;125(3):e310–e313. doi: 10.1016/j.bja.2020.05.035

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© 2020 British Journal of Anaesthesia. Published by Elsevier Ltd.

Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

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Fig 2 — A weighted-bellows CPAP pressure-source from five decades ago. Constructed from a radically modified Blease Pulmo-Sim Test Lung, as was used for testing ventilators. The bellows-arm supports a moveable bellows-weight that can be moved along the arm to alter the degree of CPAP: a necessary counterbalance-weight (to the left of the picture) is fixed to a metal rod that traverses the length of the bellows-arm. The metal rod has a screw-thread that is threaded through the bellows-weight, such that the weight can be moved in either direction along the arm simply by rotating the counterbalance weight. The ‘pivot’ of the bellows-arm lies within the cabinet (positioned just to the right of the counterbalance weight). The inset shows the critically important pressure-release valve on the top bellows-plate. It is photographed from behind and slightly above the bellows-arm. Steel bands to prevent the bellows bulging out with pressure are also shown.