COVID-19 Positive End-Expiratory Pressure (PEEP) Valve Adapters
Thursday 14 May 2020
Positive End Expiratory Pressure (PEEP) is important in the treatment of patients with COVID-19 as it improves oxygenation and prevents the collapse of the patient’s airways at the end of each ventilator breath.
On 1 April 2020, Yorkshire Ambulance Service had 100 ventilators with built-in PEEP valves available to redeploy to NHS Nightingale Harrogate, with a further 400 ventilators which could be used with the addition of a separate PEEP valve. Unfortunately, national supply chain issues meant that the adapter to connect the PEEP valve to the ventilator tubing could not be sourced in a timely fashion.
NHS England, Embrace Yorkshire & Humber Infant and Children’s Transport Service, and Sheffield Hallam University collaborated to design and create connectors which would enable the ventilators to become operational if they were required before the supply chain issues were resolved.
- Paul Dickens: Regional Head of Emergency Preparedness, Resilience and Response, NHS England
- Dr Stephen Hancock and Ian Brathwaite: Embrace Yorkshire & Humber Infant and Children’s Transport Service
- Dr David Clegg, Tom Fox, and Mark Collier: Department of Engineering and Mathematics, Sheffield Hallam University
Embrace provided the specification and submitted an “Application for the use of a non CE-marked device on humanitarian grounds” with the Medicines & Healthcare products Regulatory Agency (MHRA). Armstrong Medical Ltd supplied the CAD file containing the dimensions of their PEEP valve to facilitate designing the connector. Sheffield Hallam University designed an initial prototype.
For speed, the connector interfaces were printed (see Figure 1), which took approximately 3 hours. After evaluation, the PEEP valve adaptor was found to have insufficient purchase and therefore the diameter of the connector was refined (see Figure 2). The thread was also adjusted so that the PEEP valve would sit at the 10 o’clock position when fitted.
Six CAD iterations later the design was finalised. The material selected was VeroBlue, a general-purpose plastic which is suitable for “medical devices and components” (Stratasys Direct, 2015). A trial piece was printed on 06 April.
The design was amended once more with a production batch printed in medium quality / speed at a resolution of 27 micron (0.001 in.) (see Figure 3). A batch of 20 required 28 hours to print and required 58 grams of material to produce. Cleaning required jet washing and soaking in an alkaline solution for 24 hours to remove the white support structure. The parts were then washed and dried in a dishwasher before packing (see Figure 5).
In total, 36 connectors were supplied on Tuesday 14 April. On Thursday 16 April, Sheffield Hallam University was informed that NHS Nightingale Harrogate had taken receipt of the OEM PEEP valves which come with the appropriate connectors. Therefore, the connectors designed and manufactured were no longer required for the time being.
Due to the time constraints and the availability of materials the parts were printed using VeroBlue. However, since printing, Stratasys have updated their website and if additional items are required the material of choice would be Biocompatible Polyjet: MED610 (Stratasys Direct, 2020) as this material has been approved and assessed against the residual risk to meet ISO 18562-1 .
Note: the connectors are specified as single use only.
This project demonstrated what can be achieved with collaboration between healthcare, academia, and industry in a short space of time. Had the worst-case medical situation materialised, these devices would have been used to save lives.