Roll your own pressure alarm brainstorm session

[archangle]

One thing a lot of us really need is a good pressure alarm that we can hook to our CPAP machines.

I'd like to see some sort of gadget you can hook to your machine and if the pressure goes off, an alarm goes off until you turn it off.

This would be a great help to people concerned about not waking up if the machine quits blowing. Some people use a power outage alarm, but that doesn't help if the machine simply quits blowing.

Something like this could also help those who take the mask off and turn the machine off in their sleep.

I haven't seen any commercially available device to do this.

I have a few ideas how to do this, but maybe we should do a brainstorm session to see if we can figure out how to do this.

Do any of you have ideas how to do this?

For those of you unfamiliar with the rules for brainstoming sessions, here's one version of the rules.

http://www.brainstorming.co.uk/tutorial ... rules.html

[archangle]

I'll start off.

My idea is to get an oxygen connector like this:



Hook up a hose and hook the other end up to a plastic bag with a small hole in it.

Stuff the bag into a cardboard box smaller than the inflated bag. Screw the box to the wall with the open side of the box toward the floor.

Turn your CPAP machine on, let the bag fill up and stuff something between the bag and the box such that it will fall out if the pressure goes off.

Rig something such that the falling object will hit something and pull a string and make a lot of noise. Maybe a metal bowl that will ring. Maybe tie a string to it that will set some kind of alarm off if pulled.

[Starlette]

I'm going to say it before someone beats me to the punch...Create an app for Droid and Iphone that has a dual sensor on it:

1) Like you said, if the power goes out. This would have been VERY beneficial a couple weeks ago when we were hit with a lightening storm about 1am.
The power went out. Luckily, I was up and didn't put my Hybrid on. The power never went on till early morning.

2) Sensor to know when the pressure is either hitting maximum pressure for some time or going off the charts.

Both sensors will wake you up to do something about the situation.

My 2 cents for the evening.

Starlette

[LSAT]

I like the rube goldberg idea
http://www.rubegoldberg.com/

[archangle]

I'm going to say it before someone beats me to the punch...Create an app for Droid and Iphone that has a dual sensor on it:

Good idea, It would be really good if someone made a reasonably priced commercial pressure sensor for android. I wonder how to kludge up an android pressure sensor at home.

Androids usually have accelerometers built in. You could use something like the bag idea to tilt the android if the pressure drops off. The android can tell when it's tilted.

Or forget the box and let the stream of air coming out of the oxygen line blow out through a little hole near the android's microphone and let the android listen for the sound of the air blowing out. If the CPAP machine is noisy enough, you could just set the android on the top of the CPAP machine and let it listen or feel for the vibration.

You'd need to have some sort of optional password lock on the android to prevent the "take the mask off in your sleep" crowd from just turning it off. You could also have a "potty break" timer to let you take care of business without fooling with it.

[BasementDwellingGeek]

I'm thinking, perhaps erroneously, that stand by current will be much less than when the blower is blowing at therapy pressure. A current sensor inline with the power to the unit should be able to tell if the the unit is in use or standby. Much like the CPAP's auto start function the unit would enable at the first increase in power. There should be enough margin to avoid false positives, possible with a minimum required duration so as to not trigger on momentary glitches. Or maybe long enough for a potty break? It should also have a battery backup, not to power the CPAP machine, but for an power outage alarm.

[-tim]

My idea is to get an oxygen connector like this:



Hook up a hose and hook the other end up to a plastic bag with a small hole in it.
...

I can get cheap door alarms at the local $2 shop that could be hooked to switch with a lever arm to the bag that archangle suggested.

[archangle]

I'm thinking, perhaps erroneously, that stand by current will be much less than when the blower is blowing at therapy pressure. A current sensor inline with the power to the unit should be able to tell if the the unit is in use or standby. Much like the CPAP's auto start function the unit would enable at the first increase in power. There should be enough margin to avoid false positives, possible with a minimum required duration so as to not trigger on momentary glitches. Or maybe long enough for a potty break? It should also have a battery backup, not to power the CPAP machine, but for an power outage alarm.

There's definitely some possibility there, now how to kludge up a current sensor? Once again, androids have a magnetic sensor of some sort for the compass function.

Maybe a heat sensor attached to the power brick would be of some use.

[BasementDwellingGeek]

I was thinking something like an ACS712ELCTR-05B-T, or ACS714ELCTR-05B-T for less than 4 bucks in unit quantities to measure the the current flow up to 5 amps on the mains. Capable of withstanding 4x overcurrent.

see application 4 on page 12http://www.allegromicro.com/Products/Cu ... sheet.ashx

The A-to-D converter could be part of an inexpensive microcontroller. Add a few caps and a crystal, a transformer and bridge & voltage regulator and a few miscellaneous parts such as switches, speaker or buzzer, a socket and power cord/plug so it can be installed inline, and an enclosure, some leds to indicate active or standby state of the monitor.

The microcontroller can be programmed to sample the current 120 times per second and note the peak value. Through some experimentation a table of machine states can be determined, such as below value x is standby, x to y is blower at 4 cmH2O, y to z is blower at 4 with heater on, etc.

Other routines keep track of state changes and durations to issue the alarm.

All in an Altoids tin.


I haven't paid much attention to the newer Android devices. I am still using an original G1. I seem to recall that it is not capable of hosting any external hardware via the USB port. Can the newer ones? If not the interface would need act as the host.

[jnk]

Something like this could also help those who take the mask off and turn the machine off in their sleep. I haven't seen any commercially available device to do this.

I thought the System One, for example, already had some sort of Mask-Off-alert thingy.

If so, why not just use that machine and attach an amplified speaker to the speaker wires to increase the volume to a sufficient level?

Or have I missed the whole point again?

I often do.

Personally, I am unaware of my machine ever malfunctioning so that it 'simply quit blowing' without power going off for the local grid or without my having removed my mask. Is the machine's power shutting off on its own a big problem these days for some brands for some reason? I remember something like that a while back, but I assumed the problem had been addressed at the manufacturers' level.

[archangle]

Good idea. Or a microphone next to the beeper and an amplified speaker. That helps the mask off problem for PRS1. It wouldn't help the problem of power outages or taking the mask off and turning the mask off in your sleep problem.

There have been a number of reports of machines just stopping blowing or turning themselves off in the middle of the night. I suspect a number of these are humans or pets pushing the buttons, but some of them are probably actual machine malfunctions. Some people got machines replaced, but I'm not sure there was a real problem diagnosis or if machines just got replaced.

I think Doric recently had an electrical outlet intermittent problem that would drop power to her machine and cause it to shut off in the middle of the night. I have a PRS1 that has a poor connection where the DC plugs in the back, but it has never shut off in the middle of the night, only when I move it.

It would be neat if there were also some solution to help the "turn it all off in your sleep" people. Plenty of people turn the machine off, take off the mask, and store it neatly, and don't remember waking up in the morning. Maybe a long hose going to a pressure alarm across the room. Maybe with a combination lock to turn it off. A computer with some sort of "drunk test" type of thing you have to answer before it will shut the alarm off.

[MaxDarkside]

Adding/amending to the bag in a box: Add when the bag inflates, it opens a micro switch and thus when it deflates, it closes the micro switch energizing an alarm circuit. The alarm circuit has a on/off switch in the same wire so you can enable/disable it. It can be a little box and sit next to the machine, pressured by a T-fitting between the machine outlet and the hose. Alarm circuit is powered by a battery.

There are pressure switches also commercially available.

[jnk]

Good idea.

I don't think you've ever said that to me before, archangle.

So I hope you don't mind if a get a little verklempt.

[archangle]

This would be a really easy thing to make commercially. Unfortunately, nobody has done so yet. I suspect that if anyone ever makes it commercially, the risk of lawsuits and the medical mafia will require regulation and it will cost $100+. It would be really neat if we could figure out how to roll your own from some sort of existing readily obtainable items.

There are commercially available basement flooding alarms. Maybe there's a way to make a pressure loss spill water onto one of these. Tie it to the string such that the alarm drops into a bucket of water when the pressure cuts off.

[archangle]

Good idea.

I don't think you've ever said that to me before, archangle.

So I hope you don't mind if a get a little verklempt.

I figured you'd take it as an insult.