https://www.indiegogo.com/projects/airing-the-first-hoseless-maskless-micro-cpap#/story
My immediate thought upon seeing the mock up was: balony, with a capital 'B'.
It is a tiny thing looking a little like a plastic moustache. I do not see how such a small package could store enough power to run a CPAP device. It is a simple question of moving mass. People breath about 5 liters of air per minute at a low activity level. That’s 2400 liters in an-8 hour period. Air weighs about 1.2 gm/l = 2.88 KG moved in an an 8 hour period. And that illustration did not seem to have much space for a battery. Not to mention space for the magical flapping air pumps derived from CPU coolers!
And they claim a price of $3 per device… And it’s disposable.
They also say they are using a zinc air battery, which has energy density of 470 Wh/kg or .47 Wh/gm. Let’s generously say that they have 10 gm of battery—that’s 5 watt hours. Lets even more generously say that they have 8 watt hours. That’s 1 watt continuously for a night of sleep.
They are saying they can operate a CPAP machine on 1 watt, have it be the sized of a junor tootsie bar, and sell it for $3 per device.
The question I’m asking here is what should we do as engineers? Ethically, I mean. I really hate to see people taken in by such an obvious scam.
The site claims that the device can provide 20 cm H₂O (which is ~1961 Pa). Apparently some hypothetical normal man breathes at a rate of 6 liters (i.e. 0.006 cubic meters) per minute at rest [1]. If you pump a volume V of fluid across a pressure difference of ΔP, you've done work V·ΔP, which is 11.76 Joules per minute or 0.1961 Watts. Keep in mind that this is the work done, not the power consumed, but let's be generous and assume a 100% efficient blower. We'll also assume that no power is harvested during exhalation.
In eight hours, that's 1.56 Watt hours.
Duracell's zinc-air chemistry claims up to 442 Watt hours / kg [2]. That's about 3.5 grams of zinc-air goo per night, ignoring packaging, blower loss, etc.
This seems entirely plausible to me.
[1] http://www.normalbreathing.com
[2] http://media.ww2.duracell.com/media/en-US/pdf/gtcl/Technical...
Edit: In the interest of precision, I should add that the analysis is accurate for an incompressible flow. Air is definitely compressible, so, if you pump air, more volume is going into the pump than is coming out, and you're heating up the air (adiabatically if your pump is any good). So, with a compressible fluid, you have to consider not on the work done moving the fluid across a pressure difference but also the energy you've stored in the fluid by pressurizing it. The pressure difference for CAP is tiny here, though, so this would be a miniscule correction to the math above.
W = P(b)V(b) ln(P(a)/P(b))
(https://en.wikipedia.org/wiki/Compressed_air_energy_storage)
CPAP requires roughly 10 cm of water pressure = 0.01 Bar Sea level atmospheric pressure is roughly 1 bar So the device has to pressurize to 1.01 Bar Now I’ve looked it up, and a typical CPAP machine moves 20 to 60 liters per minute Let’s say 30 liters per minute = 1800 liters per hour
W = (1.007)(1.8)ln(1/1.007) = (1.81)*(-00698) = 0.0127 MJ = 3.53 Watt Hour
So assuming perfect efficiency you would still need 28.64 watt hours of battery, just to do the compression.
470 Wh/kg for Zinc-air battery implies this device requires a 60gm battery (2 oz to those of us of a certain age)
I looked up CPU fan efficiency (what they say they derived it from) and PEAK fan efficiency only approaches 25%
http://www.nmbtc.com/fans/white-papers/fan_efficiency_import...
So, you’d really need an 8 oz battery hanging from your nose to make this work, not counting what you need to run the electronics, etc.
Part of the claimed innovation here is that the thing sticks directly into the user's nose. If it seals well, it's plausible that there's very little wasted air, which would account for the factor of roughly five.
(Also, you used the formula for isothermal compression, I think. A tiny little device like they showed would probably move air quickly enough through its fan that it would be closer to adiabatic. This doesn't matter much for the small pressure change involved.)
I'm not sure if this device is plausible, but I know this calculation is not useful. You're calculating the mass of air moved, which, first of all, does not itself say much about the energy required to do so; for instance, horizontal motion doesn't require any net energy (though any real device doing so will of course need to do something to accelerate and decelerate, there's nothing to say it can't be very, very cheap). Second you appear to be discussing it as if there isn't a pair of lungs right there providing motive power. I do that much moving of the air every day (plus a bit, probably, I'm a tall guy) with no batteries at all.
This thing is not responsible for "moving all that air"... it's responsible for a pressure increase of the air, which is at least somewhat equivalent to saying it's responsible for "moving air" but only a fraction of the value you computed. They say it is supposed to do from 1 to 20 "centimeters of water". According to the Great and Mighty Internet, 20 cmH20 is 0.02 atmospheres, just to give some perspective. I do not have the math to calculate the energy requirement that represents when the air is in motion itself; my physics would only be sufficient to calculate the energy implied in pressurizing a closed container from 1 to 1.02 atmospheres, which is useless in this case. Perhaps someone else can pop up for that.
(Bear in mind I took a full standard College physics-for-non-majors course set, using full calculus, and what I know from that is that what I know is inadequate... if that also describes your experience, your education is inadequate too. We're going to need to hear from someone with more specialized education.)
My suspicion is that yes, this device is plausible, but the final version is going to be larger than the versions shown. Whether it crosses over the invisible line where people become unwilling to wear it is anybody's guess, but... sleep apnea sucks and those masks do suck too, so there's some room for these guys to work in. I'd classify this as a "considered risk" rather than "two orders of magnitude impossible". I reserve the right to change this assessment as more data comes in, especially a (good!) physics analysis of the real energy required to do this.
(As a side note to GP: Reducing/stopping pressure on the exhale is problematic also... for some of us many of our problems are actually on the exhale.
I've never used on of these devices so I'm curious about it.
How do you exhale? If it's forcing air in at a decent pressure then does it detect an exhale or are you expected to just push on through?
It seemed like from the video they airing would add pressure to the inhalation and switch off for the exhalation, or at least that's what I'd try and do, but then I don't know much about these things!
[0] http://www.rpc.com.au/pdf/battery-powering-products-usa.pdf
Ha. I work at a company that makes medical devices. It's just so damn easy, you know! Seems like a pretty blunt case of handwaving away this critical step. This is an electric device that controls if you can breath. This thing has a non-trivial risk of hurting someone through electrocution (it's plugged into your conductive mucus) or asphyxiation (though hopefully you'll wake).
So yeah, they'll clearly just POST to the FDA certification API and get a response within a minute.
Also, all physical perks have the disclaimer: "Subject to FDA clearance and doctor’s prescription in the US and local regulation abroad."
From a financial perspective, I can't imagine getting the device certified in multiple countries is going to be cheap. Would they also be expected to check doctors prescriptions in various languages somehow before delivering?
> what should we do as engineers?
One promising technology is a small pace-maker-like device that is implanted in the chest and stimulates the hypoglossal nerve while you sleep: http://www.medscape.com/viewarticle/834474
When I see something like that my first question is if the doctors involved are real or not.
So the world of doctors and medicine is one that's highly regulated, has a lot of hierarchy and deference built in, and doesn't train people for things other than their job.
This leads people to not value knowing much other than their job since the the hierarchy means that they'll get abused if they offer advice, and the regulation means that nobody can really listen to it anyhow.
What you end up with is people who are fairly trusting and not terribly knowledgeable outside of their discipline. So if an engineer (or someone engineer-ey) tells a doctor that something can be done and there's no obvious reason it can't be (cell phones are powered all day off of a battery, it's not going to fly, it doesn't cure cancer, etc) then it's entirely possible they'll just say "great! when do we start" rather than try and figure it out for themselves. And I mean things today are crazy from the perspective of someone who spent 20-30 years getting educated to make what, $100k-$300k? How many 30-something website billionaires are there? It would be really easy for someone to say "if this wunderkind says it can be done good enough for me" and go along with things.
Further even if 90% of the doctors out there had the background and training and everything to spot this as a fraud, that still leaves 10% which is a large pool of people who you could dupe.
I assure you that even if the doctors are "real" in any given B2C commercial endeavor, there are plenty of frauds practicing medicine. I've seen them first hand. Although we are highly regulated, there is significant risk to one doc whistleblowing on another. I've seen lawsuits for slander. So, the bad apples generally are able to remain in the health care system indefinitely.
As for this particular device, it doesn't pass the sniff test IMO.
[0] http://physiciandirectory.brighamandwomens.org/?Index=10&Las...
Their constraints do seem very tight but I can conceive at least one way in that you could shrink the device down. There would be multiple actions in such a device:
1. During the inhale increase pressure. As noted by the image[1] this is achieved in the device with "blowers."
2. During the exhale present a restriction to airflow, but don't cut it off entirely. You could use something similar to an aperture to restrict airflow here.
3. Between the exhale and inhale maintain pressure. If you use an aperture-like-device you can simply close the aperture completely.
This means that the device becomes partially passive, reducing power requirements. I'm no expert but let's assume that you are only inhaling 50% of the time - this cuts down the amount of time the "blowers" need to run by 50% (or can double their power consumption or something in-between). My uneducated opinion is therefore: remotely plausible.
http://res.cloudinary.com/indiegogo-media-prod-cld/image/upl...
And you do not escape the fact that the device has got to move almost 3 kg of mass with about 1 watt.
I have another try at communicating the idea.
It sounds like the main problem with sleep apnea is that the air passages are collapsed when it comes time to start inhaling - preventing the process from occurring. Therefore the core of the solution is having "inflated" air passages at the point when inhalation starts.
The idea is to kick-start the next inhalation with the current exhalation. When you exhale you increase the pressure in your air passages which is work ("wattage") that completely goes to waste - it all goes out your nose/mouth. The device would gradually restrict the passage of air out of the nose (as the exhalation process completes), eventually cutting it off completely. This means that once you have completely exhaled your air passages would still be "inflated." This is what (2) and (3) do. In this situation conventional CPAP would be providing pressure (even though it's not needed) and would hence be wasting work.
That is the special sauce: relying on the human to do work that they don't have problems with. This will reduce the amount of work you need to do to assist with their medical condition: possibly down to 1 watt, or at least way less than you'd need with conventional CPAP.
> 1 watt
The problem is collapsed airways and not dysfunctional lungs, there's still plenty of wattage there: all you need to do is keep the air passages open using (1).
As I said: a long-shot, remotely plausible. Most importantly: if the above is a plausible idea there is no guarantee that it's the same as theirs or that they even have one. Show me the patents.
At the same time it's better to ask questions before initiating a witch-hunt. I think the first plan of action would be for them to prove that they have a working device instead of the seemingly common "warning off people" suggestion. A better suggestion to people is encourage them to ask for proof.
I looked up Stephen A. Marsh (see http://www.fundairing.com/ under 'inventor').
Interesting guy - a strange history. He also is CEO of Encite LLC (also located in Burlington, MA). He does have many patents in fuel cells, etc.
Previous to Encite LLC he was CEO of a now-defunct technology startup Integrated Fuel Cell Technologies, Inc. (IFCTI)
Encite LLC was formed from IFCTI, through some obtuse legal machinations.
http://www.potteranderson.com/delawarecase-185.html
I am no expert in law, but it sounds like he basically ran IFCTI into the ground as CEO, then bought it and its resources back at a large discount via Encite LLC. The previous board members tried to sue him but lost due to some ambiguities in the laws.
Maybe someone else has more?
BTW having used a CPAP I know it is not possible to generate the volume and pressure (particularly the pressure) needed by something this size without a quantum leap in current technology.
I can't devise a method to prove and explain my conclusion. Perhaps someone more versed in the area can.
Talk about it and spread the word to others that this is impossible to do.
There's also some interesting discussion here, mostly to the tune of "it won't work":
http://www.eevblog.com/forum/crowd-funded-projects/the-airin...
I was hoping that someone in this community would know someone in indegogo responsible enough to say wait a minute, this is not plausible. I took a look at indegogo's terms of service and found only this:
"If the Campaign is claiming to do the impossible or it's just plain phony, don't post it. "
Which is pretty weak.
But I suppose the old saw that 'a fool and his money are soon parted' still applies in the crowdfunding world...
And here's a -real- battery powered CPAP machine, taking a laptop-type lithium ion battery:
http://www.cpap.com/productpage/Hoffman-Laboratories-Breathe...
The machine just has to maintain a positive pressure during certain portions of the breathing cycle.
What I see here is a possibly overly-ambitious design, but no obvious scam.
BTW, here is a video of Airing's Chairman: https://vimeo.com/130685879
One of the challenges we have currently is that the medical field is over regulated and there are excessive barriers to entry. Perhaps you can make your peace with the fact that it isn't your money and if people want to hope against hope for something better and pledge a few dollars, that is their choice. Then the developers might get their shot at developing something new. Maybe it won't meet every criteria they listed. Maybe it somehow will. Maybe it will be a complete flop. (Shrug)
Innovation only happens when there is some leeway for some of it to fail. $100k is a drop in the bucket for medical research. Why do you feel such a strong need to not even let them try? I suggest you let it go.
Skepticism is certainly warranted based solely on the timeline presented and my experience in medical devices.
As to the rest, you're operating on incomplete information. According to the NSPE, "Engineers may express publicly technical opinions that are founded upon knowledge of the facts and competence in the subject matter." You say, "what should we do as engineers", so I'll make the implicit assumption that you're an unlicensed "software engineer" like many on HN. If so, consider that you may be operating outside your area of expertise without complete knowledge of the device. I would make careful public statements: I, for example, wouldn't say "I performed a first-principles analysis and, as an engineer, I find the device claims are impossible."
Part of my reaction is that I am a patent attorney, and every patent attorney gets 'inventions' that come through the door from well-meaning but essentially clueless people. After a while you get to develop a bullsh*t detector. This one just rang my gong. I suffer from sleep apnea and I know what a real thing it is, and the idea of these guys just walking away with $$ from desperate people, just, again, rang my gong.
I will say that it has been fun seeing these posts--thank you!
I also don't think it is 'disposable'. I think it is recyclable and from what I've seen the $3 is dependent on recycling them.
http://www.murata-ps.com/emena/2012-05-22.html
I was also skeptical of the Airing claim, although after reading about the Murata piezo blower things, they're amazing, whether Airing is able to make a CPAP out of them or not.
Frankly, as an old, fat, CPAP using guy, I'd rather eat mouldy cheese than use a nasal pillow CPAP device. Plus, the Airing thing would have to be strapped to my face anyway; at my Rx pressure it'd blow out of my nose within an hour. The hose on my traditional BiPap turbine machine doesn't bother me at all.
I'd be delighted to have a smaller BiPap machine made out of these Murata things, if it meant a less bulky power supply and a smaller base unit.
Armed with this, I took interest in your response and checked out the math.
Interestingly, this device seems to produce the pressure!
Using their specifications of the piezoelectric pump on the page you sent.
Piezoelectric pump produces 1.5kPa. This converts to 15.3 cm WC (centimeters of water column) or cmH2O. 4-20 cmH2O is the range of a cpap!!
But, the airflow needed at that pressure is a critical issue as long as you want to breathe freely. The piezoelectric pump produces 0.8 liters per minute.
At http://www.sleepdex.org/cpap.htm it says a cpap produces 20 to 60 liters of air per minute (lpm).
To reach the lowest end you need 20 lpm. Calculate 20 / .8 = 25
So you need 25 of these piezoelectric pumps to reach the lowest possible; 75 of them to reach the high end. This is literally almost an order of magnitude.
And in case you thought so; piezoelectrics can't scale. They are very limited in size, by the physics of the vibrations.
So still not even close. It would require a quantum leap in technology over what we have available.
On the other hand, it might br hard to convince a lot of people that this isn't real. After all, most of humanity believes some version of supernatural nonsense which includes such things as people flying, resurrecting, partin seas, singing bushes, talking snakes, 6,000 year old earth, rapture, being chosen, paradise, etc. in other words, there's plenty of empirical evidence to show science and reason don't stand a chance. Yet.
That said, my dollars are staying snugly in my pocket for this campaign. It's pretty farfetched, and I don't like the metric they used to illustrate the actual pushing power. It doesn't add up.
So if it turns out that this treatment of sleep apnea can offset those increased healthcare costs, I could definitely see insurance companies being interested.
[1] Kapur V, Blough DK, Sandblom RE, Hert R, de Maine JB, Sullivan SD, Psaty BM (September 1999). "The medical cost of undiagnosed sleep apnea". Sleep 22 (6): 749–55. PMID 10505820
Have to meet my deductible first of course, but I suspect most insurance would LOVE to be paying only $3/day.
Wow... that's some great insurance! I've got decent insurance, but mine will only cover 80% of costs, on a mask every 6 months, and a machine every 5 years.
But they are extremely intrusive to sleep, especially if you have a partner. A better CPAP machine is needed. But I won't give them pre-order money, more because I've seen way too many bad crowd-sourcing projects than out of specific concerns towards this project.
For $3 I'll buy it on a whim and try it out. I'd try a larger one that was significantly smaller than a standard CPAP for $20, maybe even $50.
But whether or not the project is legit is kind of beside the point to me right now. Having done a lot of prototyping of my own, in both software and hardware, it bothers me to see people jump directly to crowdfunding before they've even built a hot-glue-and-wires version of a prototype. Prove the concept. It's not that freaking hard.
All they say they've done is built the shell of the noseplug. They haven't any idea how to get the electronics on the inside. Their FAQ page makes it sound like their understanding of cutting edge electronics comes from Popular Mechanics, or Boing Boing.
People act like hardware is so extra-special hard. It's not. It's no more or less difficult than hacking on software in your free time. The actual, core functionality of your project, whether it's hardware or software, should be possible to validate in less than a month. The rest of what it takes to turn any project into a real product will far eclipse the proof-of-concept work in the level of effort necessary. There's no such thing as "if you build it, they will come".
Okay, no, Elon Musk's Hyperloop can't be validated in a month. A brand-new, hyper-secure, microkernel operating system written in Rust wouldn't be, either. I'm not saying all ideas are possible in a month, I'm just saying the stuff people typically do in the given spaces as garage inventors are on the short-scale for validation.
It just takes up a little to a lot more space. But if you're dedicated, most people can find the space. I'm sure a few adults like supposedly involved in this project can rent out a small warehouse on their pocket cash together. I don't even work full-time, I live in one of the worst areas of the country for real estate prices right now, and even I could scrap together the money for a small warehouse, if I had to.
It's going to be hard if you don't have any experience in hardware. Yeah, but even making a simple CRUD app is going to be hard if you don't have any experience in software. We live in a golden age of hardware development. Nearly everyone and their neighbor in the US has a garage full of tools that could bootstrap a small industrial renaissance in a 3rd world country.
Or you don't even have to buy anything, design a flat-pack vector layout in Inkscape, email it to any of the thousands of laser-cutting services in the country, tell them you're fine buying scrap material, wait a couple of days, and you can make anything the size of a breadbox for about $50.
Need more complexity? Make a 3D model in blender, send it off to any of the dozens of (and growing) 3D printing services, wait a couple of days, and you can make anything the size of an old Walkman for about $50. Seriously, don't buy your own 3D printer unless you want to get into the business of maintaining 3D printers. Outsource that malarky.
But come on, if you don't believe in your project enough to put your own time and money into it, how do you expect us to believe in it? (though, I know that isn't really stopping anyone).
Re the flappy fan, I know I've read sometime in the past couple of years about a design that was trying to replace rotary fans, and it was piezoelectric in nature. I found a few but none that looked like they would develop any appreciable pressure. I think stacked piezeoelectrics could be built up in such away that you could create a material pressure differential, but not in something the size of a tootsie roll, and not anything that could move enough volume to let people breath.
