Cheap AND simple respiration detector

[Neon John]

Hey guys,

I'm looking for some interesting ideas that are both practical AND
cheap to monitor respiration air flow.

I've developed a collapsed lung and my pulmonologist has put me on a
CPAP machine to try and reinflate it. Problem is, after 6 weeks of
trying, I can't stand the thing. I want to do some self-research and
see what I can learn, particularly if the CPAP is having any effect.

So I want to build a quickie anemometer. Actually, 2. One to look at
my nose flow and another to look at my mouth flow. It's important to
capture the flow waveform, as (at least on the spirometer) one can see
where the bad lung quits working and the good one finishes the
exhalation.

During my sleep study, they attached a rig that held a tiny tube in
front of each nostril and one in front of my mouth. The tubes lead to
a box containing pressure transducers, conditioners and something to
stick the signal on an Ethernet cable. Of course I don't want to do
something that complicated. Ideally this would be something that I
could knock out in a day using materials on-hand.

What I'm thinking about is Arduino-based, something that would
digitize each waveform and spit it over the USB bus to a capture
program. Then I can analyze the data in OO or GnuPlot or whatever.
Very minimal software effort desired.

First thought was a low range MEMS pressure transducer but looking on
Digikey and Mouser, they're kinda expensive and require signal
conditioning and amplification, at least on the ones they keep in
stock.

Second thought is a self-heated thermistor bead. Major problem is the
signal would have to be linearized which would take a little more
software effort than I want to dedicate to this project.

Third idea is a self-heated LM35. With a 50 ma load on the output an
LM35 in the TO-92 package self-heats about 10 deg C. I can shoot the
signal right into an Arduino's analog input with no conditioning.
Question that remain include whether the low air flow of sleep
breathing will cool the thing enough to matter and what its time
constant is. Another problem is that a TO-92 package is kinda large
to have dangling from one's nose and upper lip.

So I thought I'd toss this problem out to you guys and see what
innovative ideas you come up with.

Thanks,
John
John DeArmond
http://www.neon-john.com
http://www.fluxeon.com
Tellico Plains, Occupied TN
See website for email address

 

[RobertMacy]

Hey guys,

I'm looking for some interesting ideas that are both practical AND
cheap to monitor respiration air flow.

I've developed a collapsed lung and my pulmonologist has put me on a
CPAP machine to try and reinflate it. Problem is, after 6 weeks of
trying, I can't stand the thing. I want to do some self-research and
see what I can learn, particularly if the CPAP is having any effect.

ARRRGGG!!! our radiation expert! Sorry to hear about lung.
QUESTION: does your collapsed lung pose a pneumonia threat? With treatment
like no drinking, antibiotics. that kind of thing?

Anyway all ideas sound great.

A few years ago, as part of a portable patient monitoring system; I
designed a volumetric sensor for measuring expiration.

The principle was based upon the variation of magnetic field strength vs
distance. Using four coils, two transmit and two receive, with eeach coil
transmitting its own, unique tone; it was possible to make four distance
measurements and fairly accurately calculate lung volume. Very battery
friendly because the 3.3 volt battery only needed to supply a total of 10
mA for the whole sensor system. The sensors could measure anywhere from 6
inches to over 27 inches. Accuracy? At a distance of 8 inches, I measured
1 mil rms. Yes, that's 1/1000 of an inch of rms noise.

The coils were constructed of 100 turns on a 6 layer 1/32 inch PCB about 1
1/2 to 2 inch round, so the 'coils' easily fit into a wearable fabric
'jacket' and being so flat, the patient could easily sleep on the coils
without noticing, well not noticing too much.

The client was ecstatic when they saw the 'clean' waveforms of breathing -
they were used to seeing very ratty looking waveforms.

Why the detail? if that piece of electronics you plan on using has
something like a soundcard in it with two channels out and two channels in
you can easily make the whole sensor system yourself.

 

[Adrian Tuddenham]

I'm looking for some interesting ideas that are both practical AND
cheap to monitor respiration air flow.

If you can break the glass without breaking the filament, a small low
voltage lamp makes a good quick-responding anemometer. Put it in one
limb a Wheatstone Bridge circuit which passes enough current to heat it,
then monitor the changes in off-balance voltage as the filament is
cooled by the air currents.


....on the other hand, you may not feel like stuffing a broken light bulb
up your nose....

 

[Phil Hobbs]

Hey guys,

I'm looking for some interesting ideas that are both practical AND
cheap to monitor respiration air flow.

I've developed a collapsed lung and my pulmonologist has put me on a
CPAP machine to try and reinflate it. Problem is, after 6 weeks of
trying, I can't stand the thing. I want to do some self-research and
see what I can learn, particularly if the CPAP is having any effect.

So I want to build a quickie anemometer. Actually, 2. One to look at
my nose flow and another to look at my mouth flow. It's important to
capture the flow waveform, as (at least on the spirometer) one can see
where the bad lung quits working and the good one finishes the
exhalation.

During my sleep study, they attached a rig that held a tiny tube in
front of each nostril and one in front of my mouth. The tubes lead to
a box containing pressure transducers, conditioners and something to
stick the signal on an Ethernet cable. Of course I don't want to do
something that complicated. Ideally this would be something that I
could knock out in a day using materials on-hand.

What I'm thinking about is Arduino-based, something that would
digitize each waveform and spit it over the USB bus to a capture
program. Then I can analyze the data in OO or GnuPlot or whatever.
Very minimal software effort desired.

First thought was a low range MEMS pressure transducer but looking on
Digikey and Mouser, they're kinda expensive and require signal
conditioning and amplification, at least on the ones they keep in
stock.

Second thought is a self-heated thermistor bead. Major problem is the
signal would have to be linearized which would take a little more
software effort than I want to dedicate to this project.

Third idea is a self-heated LM35. With a 50 ma load on the output an
LM35 in the TO-92 package self-heats about 10 deg C. I can shoot the
signal right into an Arduino's analog input with no conditioning.
Question that remain include whether the low air flow of sleep
breathing will cool the thing enough to matter and what its time
constant is. Another problem is that a TO-92 package is kinda large
to have dangling from one's nose and upper lip.

So I thought I'd toss this problem out to you guys and see what
innovative ideas you come up with.

Sorry to hear about the lung. You're in my prayers.

I second Spehro's hot-wire anemometer idea. Maybe a tungsten micro-size
Christmas bulb? You probably have a string or two lying around. Low
thermal mass is the key to fast response, of course, and unlike the
thermocouple, the hot wire responds to the temperature of the sensing
element more than that of the leads.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[Spehro Pefhany]

So I thought I'd toss this problem out to you guys and see what
innovative ideas you come up with.

Is there any information you can glean from the CPAP machine itself?

They dumb down the interface and try to lock the functionality up, but
you may be able to find software that will allow access to the data.

For a "hot wire" anemometer you could try self-heating a smaller
transistor than a TO-92, for example an SC-70. Not too hard attaching
wires to something that size if you have good eyes or a microscope.
King's law equation.. and there is some IFD stuff IIRC.

Best regards,
--sp

 

[Spehro Pefhany]

Adrian's, sorry!

Cheers

Yup.. I was just about to.. say that..

Another type of bulb is those little bulbs you can find in railway
hobby shops-- much smaller (and more expensive) than Xmas bulbs.

I have some that are less than 0.05" diameter.. and they will work
with maybe 5-10mA.

Best regards,
--sp

 

[Neon John]

ARRRGGG!!! our radiation expert! Sorry to hear about lung.
QUESTION: does your collapsed lung pose a pneumonia threat? With treatment
like no drinking, antibiotics. that kind of thing?

Thanks everybody for your concern. Here's the rest of the story. It
started about 25 years ago. I was picking up a small lightweight box
(proper posture) when I felt a flick on my neck. Like an insect had
landed. I swatted at it and gave it no further thought. That was the
disc at C5 slipping out into my spinal canal.

After spending an agonizing 3 day weekend at a trade show (lesson #1 -
Hoarde opiates!), I got in to see a spinal specialist. The MRI showed
the disc sticking out a couple of mm. He prescribed traction therapy,
the disc slipped back in and all was well. So I thought. Turns out
the disc didn't quite slip back in all the way.

Fast forward 20 years. No intervening neck or back pain but I started
to slowly lose my endurance. I owned a small chain of restaurants and
it got so bad that I had to close them. I retired and moved here to
the mountains of Tellico.

Got to the point where taking a shower was fully exhausting. I
visited my brother in his dental office one day. The walk from the
parking lot left me dizzy and faint. He took one look at me, dragged
me to a treatment chair and strapped on a nose mask with about 8
liters of oxygen. In a little while I felt better than I had in a
year or more.

After I recovered he dragged me to the emergency room. They did all
the acute cardiac emergency drills and found out that my ticker was
fine. Fortunately a high school and neighborhood friend who is now a
pulmonologist (triple board certified) was on call. He saw who it was
and started throwing the works at me.

He had a fluorocine "sniff test" performed. I sat in front of a
fluoroscope with video capabilities and while bathed in radiation, did
a great big snort. With a normal person, the diaphragm moves down
rapidly in a quick smooth motion. Only half of mine did. The other
half just laid there.

A week of tests, except for an MRI, determined that my left diaphragm
was paralyzed and that's why my lung had collapsed. After 2 months
(!) of fighting with my insurance company for an MRI, I finally got
one a couple of weeks ago. Here's the money shot

https://dl.dropboxusercontent.com/u/81715047/the_bulge_zoom.jpg

The disc had hardened and the vertebrae on either side has grown bone
to support it. My pulmonologist thinks that this abnormality has
damaged the nerves that drive the left diaphragm that exit at C5.

I'm to see a spinal guy in a couple of weeks. He'll probably want to
remove that disc and the protruding bone and fuse the two vertebrae.
That's to stop further damage.

The nerve damage has been happening for so long that there's not much
hope of a recovery. Best we can do is stop it where it is. Right now
I'm strapped to an oxygen concentrator in the daytime like some old
geezer and an oxygen enriched CPAP at night.

I thought I could get used to the CPAP and I've really given it a good
hard go but I'm beginning to loathe the thing. That's why I want to
do some testing to see if it's doing anything. I want to be able to
present hard data to the doc when I see him instead of just bitching
about the CPAP.

Anyway all ideas sound great.

Yes they do. Thanks guys. I think Adrian's tungsten hot wire
anemometer is going to be the way to go. I have a spool of fine
tungsten wire that I acquired as part of my accelerator project so I
can wind my own and not have to try to break bulbs.

A few years ago, as part of a portable patient monitoring system; I
designed a volumetric sensor for measuring expiration.

The principle was based upon the variation of magnetic field strength vs
distance. Using four coils, two transmit and two receive, with eeach coil
transmitting its own, unique tone; it was possible to make four distance
measurements and fairly accurately calculate lung volume.

Very interesting. What did you do, look at the phase shift as
distance varied or something like that? Have you ever published the
design? Even though it's more than I want to do for this project, I'm
very interested.

Why the detail? if that piece of electronics you plan on using has
something like a soundcard in it with two channels out and two channels in
you can easily make the whole sensor system yourself.

As I mentioned before, I plan to use an Arduino to do the A/D
conversion, time stamp the data and probably some smoothing and then
squirt it to a Linux box for analysis. I don't do application
software so I'll probably just whip together a utility that will
condition the data so GnuPlot can display it. Maybe have a second
display channel where the utility flags any apnea events.

Oh, last part of your question. The lung is dry so there's not much
chance of pneumonia or infection. There is actually a little function
left so air moves in and out. Doc had me get the pneumonia
vaccination series even though I'm technically too young but that's
it. And the oxygen, of course.

FAQ:

Q: Why not use a BeagleBoard?
A: Because it's a total POS with one of the worst Linux ports I've
ever seen. Anybody want a couple?

Q: Why not a Raspberry Pi?
A: Cuz I don't have one.

Q: Why don't you do <complicated design>?
A: Because this is something I want to knock out over a weekend using
available materials.

Again, thanks everybody for your good ideas. Lots of stuff to think
about.

John

John DeArmond
http://www.neon-john.com
http://www.fluxeon.com
Tellico Plains, Occupied TN
See website for email address

 

[Neon John]

Oops. I won't get a reading comprehension award for the above. I
misread the thread. (I'm fighting a cold or flu and the brain is
temporarily out of gear.) The OP complained of chest pains and
suggested that it might be a collapsed lung caused by the CPAP
machine. Nobody agreed, although there was mention that pain during
the first few weeks was common. Sorry for the muddle.

No prob. I can certainly confirm that CPAP makes your chest hurt.

I can also tell that it's expanding my lung capacity - at least
temporarily. I can do my normal morning wake-up activities without
the oxygen after wearing the CPAP but by the time I'm cooking
breakfast, the feeling of suffocation is back and out comes the
oxygen.

John

John DeArmond
http://www.neon-john.com
http://www.fluxeon.com
Tellico Plains, Occupied TN
See website for email address

 

[Tom Miller]

No prob. I can certainly confirm that CPAP makes your chest hurt.

I can also tell that it's expanding my lung capacity - at least
temporarily. I can do my normal morning wake-up activities without
the oxygen after wearing the CPAP but by the time I'm cooking
breakfast, the feeling of suffocation is back and out comes the
oxygen.

John

Is there anyway they could make a pacemaker like device that would stimulate
the diaphragm?

Are there many cases like yours that would even make this worth designing
such a device? Or is this more like an orphan medical condition?

Sure hope you can find some relief for it.

Regards

 

[mike]

Tungsten wire is available on eBay:
<http://www.ebay.com/bhp/tungsten-wire>
<http://stores.ebay.com/Hypertriton/Tungsten-Wire-Bare-/_i.html?_fsub=2279640015>
Looks like you can obtain some really small diameter wire for cheap.
Besides anemometers and hight temp thermometers, tungsten wire is also
used for the cross hairs on rifle scopes and surveying equipment.
However, at 0.0045 ohms/C tempco, you'll need some serious gain to see
any changes produced by low velocity air movement. You might also
need a tiny spot welder to attach the tungsten wire.

The difficulty is getting response at the junction but not conducting
the heat down the connecting wire.
I've used the broken bulb technique, but it's likely go get covered
with gunk when you stuff it up your nose.

It can't be all that hard to buy a REAL thermocouple.
I have a commercial HVAC hot wire anemometer.
Has two thermocouples in the head.
The big one is about the size of a baby gnat.
The small one is somewhat bigger than a grain of salt.

from the op
Second thought is a self-heated thermistor bead. Major problem is the
signal would have to be linearized which would take a little more
software effort than I want to dedicate to this project.

Linearization of the data is likely the easiest part of this project.
And how linear does it need to be if you're looking for relative
measurements?

Q: Why don't you do <complicated design>?
A: Because this is something I want to knock out over a weekend using
available materials.

You have a condition that's having a MAJOR negative impact on your life
and you can't be bothered to spend more than a weekend to address it?

There are a lot of smart people here willing to collaborate.
Use 'em and git-er-done.

 

[Adrian Jansen]

Tungsten wire is available on eBay:
<http://www.ebay.com/bhp/tungsten-wire>
<http://stores.ebay.com/Hypertriton/Tungsten-Wire-Bare-/_i.html?_fsub=2279640015>
Looks like you can obtain some really small diameter wire for cheap.
Besides anemometers and hight temp thermometers, tungsten wire is also
used for the cross hairs on rifle scopes and surveying equipment.
However, at 0.0045 ohms/C tempco, you'll need some serious gain to see
any changes produced by low velocity air movement. You might also
need a tiny spot welder to attach the tungsten wire.

There used to be tiny glass coated thermistor probes for this sort of
thing. STC R25 rings a bell. Very fast response, much greater
resistance change than heated wire types, and the fact that its a bead
means the sensor is localised to a small area.

LTC had a neat trick for linearising. Electrically heat the bead to
keep the temperature constant, that gets around all the thermistor
linearity effects. Then measure the power input, which is directly
proportional to a function ( something like the cube, I think ) of the
airflow. Its trivial to measure the voltage and current with a couple
of ADC channels. From that, you can compute the resistance and power
directly. Use PWM from the micro to control the drive current.

 

[Syd Rumpo]

Hey guys,

I'm looking for some interesting ideas that are both practical AND
cheap to monitor respiration air flow.

So I thought I'd toss this problem out to you guys and see what
innovative ideas you come up with.

Thanks,
John

Tubes connected to cheap electret microphones. Air passes over the end
of the tube and the sound volume is related to the flow rate.

Perhaps some filtering too? I use a headset for Skype, and breathing on
the microphone manifests as a 'roar' in the earphones, naturally louder
for heavier breathing. If the tubes are the same length and diameter,
then each sensor should have similar sensitivity. Maybe a mesh on the
tube ends would make them less directional, if that's a problem.

Cheers

 

[Lasse Langwadt Christensen]

Den tirsdag den 7. januar 2014 00.18.11 UTC+1 skrev Adrian Jansen:

There used to be tiny glass coated thermistor probes for this sort of

thing. STC R25 rings a bell. Very fast response, much greater

resistance change than heated wire types, and the fact that its a bead

means the sensor is localised to a small area.



LTC had a neat trick for linearising. Electrically heat the bead to

keep the temperature constant, that gets around all the thermistor

linearity effects. Then measure the power input, which is directly

proportional to a function ( something like the cube, I think ) of the

airflow. Its trivial to measure the voltage and current with a couple

of ADC channels. From that, you can compute the resistance and power

directly. Use PWM from the micro to control the drive current.

I'd think you'll also need to measure the temperature of the air

afair the MAFs used on many cars have shielded termistor and a hot wire
in the flow and keep a constant temperature difference

and remember that is doesn't take direction into account and the it
measures mass flow, not volume

-Lasse

 

[Glen Walpert]

Thanks everybody for your concern. Here's the rest of the story. It
started about 25 years ago. I was picking up a small lightweight box
(proper posture) when I felt a flick on my neck. Like an insect had
landed. I swatted at it and gave it no further thought. That was the
disc at C5 slipping out into my spinal canal.

After spending an agonizing 3 day weekend at a trade show (lesson #1 -
Hoarde opiates!), I got in to see a spinal specialist. The MRI showed
the disc sticking out a couple of mm. He prescribed traction therapy,
the disc slipped back in and all was well. So I thought. Turns out the
disc didn't quite slip back in all the way.

Fast forward 20 years. No intervening neck or back pain but I started
to slowly lose my endurance. I owned a small chain of restaurants and
it got so bad that I had to close them. I retired and moved here to the
mountains of Tellico.

Got to the point where taking a shower was fully exhausting. I visited
my brother in his dental office one day. The walk from the parking lot
left me dizzy and faint. He took one look at me, dragged me to a
treatment chair and strapped on a nose mask with about 8 liters of
oxygen. In a little while I felt better than I had in a year or more.

After I recovered he dragged me to the emergency room. They did all the
acute cardiac emergency drills and found out that my ticker was fine.
Fortunately a high school and neighborhood friend who is now a
pulmonologist (triple board certified) was on call. He saw who it was
and started throwing the works at me.

He had a fluorocine "sniff test" performed. I sat in front of a
fluoroscope with video capabilities and while bathed in radiation, did a
great big snort. With a normal person, the diaphragm moves down rapidly
in a quick smooth motion. Only half of mine did. The other half just
laid there.

A week of tests, except for an MRI, determined that my left diaphragm
was paralyzed and that's why my lung had collapsed. After 2 months (!)
of fighting with my insurance company for an MRI, I finally got one a
couple of weeks ago. Here's the money shot

https://dl.dropboxusercontent.com/u/81715047/the_bulge_zoom.jpg

The disc had hardened and the vertebrae on either side has grown bone to
support it. My pulmonologist thinks that this abnormality has damaged
the nerves that drive the left diaphragm that exit at C5.

I'm to see a spinal guy in a couple of weeks. He'll probably want to
remove that disc and the protruding bone and fuse the two vertebrae.
That's to stop further damage.

The nerve damage has been happening for so long that there's not much
hope of a recovery. Best we can do is stop it where it is. Right now
I'm strapped to an oxygen concentrator in the daytime like some old
geezer and an oxygen enriched CPAP at night.

I thought I could get used to the CPAP and I've really given it a good
hard go but I'm beginning to loathe the thing. That's why I want to do
some testing to see if it's doing anything. I want to be able to
present hard data to the doc when I see him instead of just bitching
about the CPAP.




Yes they do. Thanks guys. I think Adrian's tungsten hot wire
anemometer is going to be the way to go. I have a spool of fine
tungsten wire that I acquired as part of my accelerator project so I can
wind my own and not have to try to break bulbs.



Very interesting. What did you do, look at the phase shift as distance
varied or something like that? Have you ever published the design?
Even though it's more than I want to do for this project, I'm very
interested.


As I mentioned before, I plan to use an Arduino to do the A/D
conversion, time stamp the data and probably some smoothing and then
squirt it to a Linux box for analysis. I don't do application software
so I'll probably just whip together a utility that will condition the
data so GnuPlot can display it. Maybe have a second display channel
where the utility flags any apnea events.

Oh, last part of your question. The lung is dry so there's not much
chance of pneumonia or infection. There is actually a little function
left so air moves in and out. Doc had me get the pneumonia vaccination
series even though I'm technically too young but that's it. And the
oxygen, of course.

FAQ:

Q: Why not use a BeagleBoard?
A: Because it's a total POS with one of the worst Linux ports I've ever
seen. Anybody want a couple?

Q: Why not a Raspberry Pi?
A: Cuz I don't have one.

Q: Why don't you do <complicated design>?
A: Because this is something I want to knock out over a weekend using
available materials.

Again, thanks everybody for your good ideas. Lots of stuff to think
about.

John

John DeArmond http://www.neon-john.com http://www.fluxeon.com Tellico
Plains, Occupied TN See website for email address

You could just buy one, for example:
<http://www.cooking-hacks.com/airflow-sensor-breathing-ehealth-medical>
from:
<http://www.cooking-hacks.com/documentation/tutorials/ehealth-biometric-
sensor-platform-arduino-raspberry-pi-medical>

There are a wide variety of breathing sensors on the market. Sleep
studies typically measure airflow separately at nose and mouth, plus a
chest strap "breathing effort" sensor or two.

 

[[email protected]]

Is there anyway they could make a pacemaker like device that would stimulate
the diaphragm?

Darn good idea, so I searched. Yes, they make "diaphragm stimulators"
and "diaphragm pacemakers." Unfortunately I only saw units for totally
paralyzed people that bang your whole diaphragm with an external rhythm,
nothing that used the existing, natural impulses for timing.


http://www.averybiomedical.com/
http://www.synapsebiomedical.com/news/media/pdf/FDAApprovalPressRelease.pdf

Are there many cases like yours that would even make this worth designing
such a device? Or is this more like an orphan medical condition?

Sounds like all John really needs is a bit of golden jumper wire, either
the jump the damage, or to tie the two sides together.

No idea if it's that simple--he might also need a buffer amp. for the
one side to drive the other...

Sure hope you can find some relief for it.

Yessir, that's for sure.

James Arthur

 

[Robert Baer]

Hey guys,

I'm looking for some interesting ideas that are both practical AND
cheap to monitor respiration air flow.

I've developed a collapsed lung and my pulmonologist has put me on a
CPAP machine to try and reinflate it. Problem is, after 6 weeks of
trying, I can't stand the thing. I want to do some self-research and
see what I can learn, particularly if the CPAP is having any effect.

So I want to build a quickie anemometer. Actually, 2. One to look at
my nose flow and another to look at my mouth flow. It's important to
capture the flow waveform, as (at least on the spirometer) one can see
where the bad lung quits working and the good one finishes the
exhalation.

During my sleep study, they attached a rig that held a tiny tube in
front of each nostril and one in front of my mouth. The tubes lead to
a box containing pressure transducers, conditioners and something to
stick the signal on an Ethernet cable. Of course I don't want to do
something that complicated. Ideally this would be something that I
could knock out in a day using materials on-hand.

What I'm thinking about is Arduino-based, something that would
digitize each waveform and spit it over the USB bus to a capture
program. Then I can analyze the data in OO or GnuPlot or whatever.
Very minimal software effort desired.

First thought was a low range MEMS pressure transducer but looking on
Digikey and Mouser, they're kinda expensive and require signal
conditioning and amplification, at least on the ones they keep in
stock.

Second thought is a self-heated thermistor bead. Major problem is the
signal would have to be linearized which would take a little more
software effort than I want to dedicate to this project.

Third idea is a self-heated LM35. With a 50 ma load on the output an
LM35 in the TO-92 package self-heats about 10 deg C. I can shoot the
signal right into an Arduino's analog input with no conditioning.
Question that remain include whether the low air flow of sleep
breathing will cool the thing enough to matter and what its time
constant is. Another problem is that a TO-92 package is kinda large
to have dangling from one's nose and upper lip.

So I thought I'd toss this problem out to you guys and see what
innovative ideas you come up with.

Thanks,
John
John DeArmond
http://www.neon-john.com
http://www.fluxeon.com
Tellico Plains, Occupied TN
See website for email address

A crude no nonsense detector can be implemented by placing a light
cloth near the mouth and nose.
Amount of movement indicates velocity.

Potentially expensive expansion is to use Schlieren photography of
moving air. See:

 

[Spehro Pefhany]

That is nice, have to try it.

See: http://jesseenterprises.net/amsci/1966/10/1966-10-fs.html
http://jesseenterprises.net/amsci/1971/05/1971-05-fs.html
http://jesseenterprises.net/amsci/1974/08/1974-08-fs.html

(might not be suitable for use with a sleepiong human)


Best regards,
Spehro Pefhany

 

[Neon John]

You could just buy one, for example:
<http://www.cooking-hacks.com/airflow-sensor-breathing-ehealth-medical>
from:
<http://www.cooking-hacks.com/documentation/tutorials/ehealth-biometric-
sensor-platform-arduino-raspberry-pi-medical>

Thanks Glen, that looks very interesting. But I'm afraid that this is
going to turn into a Project instead of something I could just sling
together over a weekend. Still... Very appealing.

There are a wide variety of breathing sensors on the market.

Where would you suggest I start looking? Googling "breathing sensors"
got me all kinds of unrelated stuff.

Sleep
studies typically measure airflow separately at nose and mouth, plus a
chest strap "breathing effort" sensor or two.

As I mentioned before, I've already had two comprehensive (everything
- EEG, EKG, breathing, effort, etc) sleep studies that had so many
wires hanging off me I was amazed I could go to sleep at all Now
I have this one specific little measurement that I want to do. If my
debit card doesn't burn a hole in my pocket and I am forced to go your
suggested route then I think the hot wire anemometer is going to
be the solution.

Thanks again for your suggestion.
John

John DeArmond
http://www.neon-john.com
http://www.fluxeon.com
Tellico Plains, Occupied TN
See website for email address

 

[Neon John]

Is there anyway they could make a pacemaker like device that would stimulate
the diaphragm?

Don't know. Doc talked about a kind of surgery that involves slicing
and dicing both diaphragm muscles and attaching them together in some
manner so that they work together. We didn't go into details because
we first need to find out if the lung can be rescued. Getting the
muscle to work again won't be of much use of the lung has atrophied.

One of the tests scheduled in the near future is for him to run a bore
scope down my left bronchial tube and look around from the inside.
That will probably be the decisive test.

Are there many cases like yours that would even make this worth designing
such a device? Or is this more like an orphan medical condition?

Well, it must be common enough that my dock knew immediately to do the
sniff test in the ER but I'd never heard of it before so it's probably
not a pressing medical issue.

Sure hope you can find some relief for it.

Thanks much.
John
John DeArmond
http://www.neon-john.com
http://www.fluxeon.com
Tellico Plains, Occupied TN
See website for email address

 

[Neon John]

Is there any information you can glean from the CPAP machine itself?

They dumb down the interface and try to lock the functionality up, but
you may be able to find software that will allow access to the data.

I hacked into the "clinician menus" within an hour of getting the
thing powered up I found the clinician software a few hours
later.

The software has the ability to display breath-by-breath waveforms but
alas, my machine only saves summary data to the SD card. The next
model up does record that detail but I didn't know enough about them
to ask.

I'm embarrassed to say that I haven't taken this thing apart yet (what
kind of hacker is that?) but that's on the agenda. Wouldn't it be
neat if it has a processor to process the flow data and it
communicates with the main processor over SPI or I2C?

It has a VERY impressive blower servo control loop. It is fast enough
to maintain the set pressure even if I snap a breath on or off. No
overshoot that I can detect.

Hmm, I might be able to get a useable breath waveform from the
pressure transducer. Gotta open the thing up and look around.

John

For a "hot wire" anemometer you could try self-heating a smaller
transistor than a TO-92, for example an SC-70. Not too hard attaching
wires to something that size if you have good eyes or a microscope.
King's law equation.. and there is some IFD stuff IIRC.

Best regards,
--sp

John DeArmond
http://www.neon-john.com
http://www.fluxeon.com
Tellico Plains, Occupied TN
See website for email address