0

I've been trying to think of the simplest, pre-existing item that could be used as a ventilator to support coronavirus patients that require it. I have come across this useful specification regarding what ventilators should ideally comply to: https://www.gov.uk/government/publications/specification-for-rapidly-manufactured-cpap-system-to-be-used-during-the-coronavirus-covid-19-outbreak

Unfortunately I do not have the equipment to measure the effectiveness of using a bike pump with respect to this specification.

Could a bike pump be used (are you in a position to test one against the above spec)? Otherwise, is there another common/household product that could be a successful substitute?

3
  • what sort of tidal volume will a bike pump produce? Mar 30 '20 at 21:31
  • In ARDS it's more about pressures produced, in my opinion. While a bike pump will produce airflow, VILI is probably easy to achieve with a bike pump.
    – Thomas
    Mar 30 '20 at 21:33
  • A bike pump? How do you propose dedicating one nurse to every patient exclusively for 24 hours a day for a week or more?
    – Carey Gregory
    Mar 30 '20 at 22:29
2

Even a cursory reading of the spec indicates that this will not work.

Specification

Must: Defines the minimum viable product clinically acceptable by clinicians [...]

  • RMCPAP must deliver inspired oxygen concentration in the range 35 – 80% to the patient, selectable by the user. [...]
  • All gas connectors and hoses must comply with BS EN ISO 5359:2014+A1:2017, ISO 5359:2014/AMD 1:2017 and BS 2050: 1978 Electrical Conductivity [...]
  • Must connect to wall pipeline oxygen supply via BS 5682:2015 compatible probes [...]
  • Must maintain a nearly constant airway pressure of between 5–15 cmH2O, with the ability to adjust the pressure [...]
  • Must either alarm or be provided with a suitable air entrainment system if the fresh gas supply fails [...]
  • Must have as low a resistance to expiration as possible [...]
  • Expiratory gas must be able to pass through an appropriate filter [...]
  • Must have a pressure safety release valve to protect the patient from high pressures, having a release pressure of no greater than 25 cmH2O. [...]
  • Must be securely attached to the gas outlet

A bike pump does not meet any of those criteria, this isn't even the complete list of "musts", and failing on a single criteria would already mean that the pump is not suitable. Adding enough peripherals to meet even some of the criteria would in all likelihood impossible, and if possible the resulting device would no longer resemble a bike pump.

You could probably use a bike pump to pump air into a lung, but given that a bike pump is designed to deliver up to 160 psi ("Portable pump psi ratings can vary. Some offer 90 psi, others up to 160 psi"), that's just an interesting way to kill a person, which is not usually what ventilators are for.

The closest to this plan I could find was a plan to convert an ambu bag into a ventilator. My experience with ventilators is rather more practical than theoretical, and given what fickle machines even state of the art ventilators are, I would probably choose death over that sort of improvised machine.

1
  • Airway pressure is a lot less than what a bike pump produces during a single pump action (in the usual setting of how its used).
  • Even though ventilators work in a similar way (cf. https://i.stack.imgur.com/PgmEZ.png), CPAP by definition needs to maintain a continuous airway pressure (CPAP = continuous positive airway pressure). The pressure to be held should be between around 3 mbar up to around 20-25 mbar. These are, again, exceedingly small pressures and need to be adjustable very explicitly.

One simple way of generating the kind of pressure in the airway one would want is trying to exhale against lips firmly pressed against each other; this produces around 20-40 mbar (depending on where you read about it).

Generally respiratory physiology is not a trivial subject, unfortunately. If you are interested, there are West's lectures, which are very accessible and free of charge: https://meded.ucsd.edu/ifp/jwest/resp_phys/

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.