Respiration circuit

[Duckvader]

I want to create a circuit that can measure respiration rate. The device is use to measure breathing intervals and not heart pulses.

Can anyone direct me to a suitable site or advice me on an approach to creat this ciruit.

I've seen some samples using a belt wrap to the chest and linked to a PC to gather the info but it doesnt specify any circuit.

Really appreciate it if anyone knows how to create one.

Thanks

 

[tunedwolf]

search out those baby breathing monitors, the ones that you put a pad in their cot with them...

 

[philba]

the belt method could be done in a number of ways. I assume it can't be restrictive. the antistatic conductive foam has variable resistance when you compress it - use a divider into a comparator. or use a photo interruptor in a sleeve. chest expansion pulls a blocking "paddle" out and a spring/elastic helps it to return. Maybe even a simple contact that expansion separates and a spring/elastic returns (or the other way around). Or use capacitance between two plates that slide against each other - the greater the expansion, the lower surface area in common and the lower the capacitance. measure capacitance via an oscillator or directly measure V rise time across the cap. Or maybe use an accelerometer (seems overkill). Or a strain gauge. Or...

Then, it's just a case of reading the output of the sensor and rejecting impossible data.

edit: the baby breath monitor seems to not monitor respiration but activity. It's a pad that goes under the mattress. Even when quietly asleep, a baby has some movement. no activity for 20 seconds and they trigger an alarm. I assume they have some sort of cutoff if the crib is empty. Must be pretty sensitive. I think it could to be too sensitive to use on awake people.

 

[stevez]

I spent a few minutes on this a few months ago. Apparently an ECG/EKG is modulated by respiration. I do not know if you can capture enough information with the two pads on an atheletic type HRM chest band. I would expect the circuitry to be less complicated that the software that you might need to separate the information on respiration. You might google on ECG or EKG and respiration.