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In the emergency case that more than one person must share a mechanical ventilator, the medical professionals lose per-patient monitoring of pressure and airflow.

To that end, what are the simplest available methods for measuring pressure and airflow in a 22 mm diameter pipe? Both without electronic interface, and with.

  • Aprrox pressure range: 0-100 cmH20
  • Approx airflow range: 0 - 100 litres per min
  • Roughly based on uk gov spec

My ideas so far:

Non-elec:

  • Pressure: basic manometer (literally cm height of water).
  • Airflow: A spring mounted, hinged flag with tab protruding into the airflow.

Elec (for interface to ADC/microcontroller/computer):

  • Pressure: Piezoresistive Silicon Pressure Sensor
  • Airflow: Paddle wheel meter

What are the most important trade-offs to think about in selection of air pressure and air flow sensors?

Is there any sensor type that is the obvious best choice?

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    $\begingroup$ Cone flowmeter with ball. Operates at a mostly fixed backpressure. Really easy to fabricate in quantity, easy to jigger for different flowrates, assuming you want to make a few million of them. $\endgroup$ – Phil Sweet Mar 21 at 17:28
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    $\begingroup$ What kind of precision and accuracy do you need? If some knowledge is better than none and you have minimal resources, clamp identical strings/ribbons in a clear section of tubing on each parallel line, set the overall flow rate/pressure using your main controls, and try to get each string/ribbon to swing to the same angle. If higher, we can definitely come up with more sophisticated answers. $\endgroup$ – ericksonla Mar 21 at 21:32
  • $\begingroup$ @ericksonla great idea re ribbons. Yes some info is better than none I'd say. The best performance possible that also allows rapid prototype and easy mass manufacture. Or off-the-shelf in plentiful supply. $\endgroup$ – atomh33ls Mar 21 at 21:37
  • $\begingroup$ @ericksonlaI've been thinking it might be a good plan to use a smart phones to translate a basic dial reading into a live graph using image recognition. The software problem might be easier to develop rapidly $\endgroup$ – atomh33ls Mar 21 at 21:40
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    $\begingroup$ I suggest that the problem is not just monitoring but adjustment of the flow rates between multiple patients. The goal is to allow adjustment across the patients. $\endgroup$ – Tiger Guy Mar 22 at 18:07
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This is the idea I came up with: Thanks to @PhilSweet and @ericksonlaenter image description here

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