Philip.
I've just received some information from a company called Ferno (UK) Ltd. in Cleckheaton (honestly!), West Yorkshire, Tel.01274 851999, which has four ventilators from Mediline - the Pulse 100, 200, 300 & 400, They look as though they are primarily for ambulance / emergency team use, but could be suitable for your application.
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Today is the day you worried about yesterday - and all is well !