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RespiraWorks / Ventilator

Fully-featured ICU ventilator design, optimized for manufacture using commonly available components and free to license. Repository tracks all mechanical, electrical and systems design, software, requirements and regulatory documentation.
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BTPS Integration #591

Open esc-works opened 4 years ago

esc-works commented 4 years ago

Leaving this here to address later—sorry if I am bad at writing issues.

BTPS Correction is used to convert flow and volume measured at ambient conditions to the conditions within the lungs. Ambient conditions are called ATP (ambient temperature, pressure); the conditions within the lungs are called BTPS (body temperature, pressure, water vapor saturated).

Currently, the flow measurement and integration does not correct for the fact that the inspiratory flow is generally at atmospheric temperature, pressure, and humidity, while the expiratory flow has been saturated with moisture in the patient as well as increased in temperature. This has not been an issue during prototyping as there is no heat or mass transfer in the test lung.

The following link describes a standard correction to account for this fact.

https://d3cumwfln92soa.cloudfront.net/8a716ac3fd123ce0becd7b56596582d4fc4c0c47/appnote-btps-correction-v01r.pdf

I believe by my review this can be implemented solely in software without additional instrumentation, but only if the user enters approximate values for altitude and current temperature. We may later want to add sensors, I may make another issue on the hardware side here, as I believe this can be relatively easily (at least, pressure and humidity) accounted for in the circuit board with an additional sensor.

neelfirst commented 4 years ago

Related HW issue: https://github.com/RespiraWorks/SystemDesign/issues/17 required ATP sensors (ambient temperature, pressure)

jlebar commented 4 years ago

sorry if I am bad at writing issues

This is a fantastic issue. Thanks, Ethan.

One thing to note, volume zeroing will "fix" this. The problem is, volume will be off by 10% (if I'm reading this document correctly), and the shape of the volume curve also won't look quite right.

martukas commented 3 years ago

Related to #652

martukas commented 3 years ago

We have to way to confirm that our corrections are correct without having humidifier, heater and probably more sophisticated test equipment.