Radon anxiety and cancer with CPAP

[Pesser]

CPAP pressure is usually less than 20 cmH2O. Normal air pressure is around 1000 cmH2O.

AFAIK - atmospheric pressure (at sea level) in cmH2o is 0 (zero).

If it were 1000 cmH2O there would be flow "into" the cpap machines instead of "out", no?

Refering to: http://www.engineeringtoolbox.com/press ... d_569.html

Make your way down to "pressure"; convert PSI:
PSI at sea level is about 14.7. mmH20 is 703; 703x14.7=10,334.1. To convert this into CMh20 we divide by 10. This gives us 1,033.41.
Can anyone check this to make sure I'm right?

[Guest]

If it were 1000 cmH2O there would be flow "into" the cpap machines instead of "out", no?

When your cpap pressure is 15cmH20 there would be flow into the machine IF Atmos were 1000 cmH2O. With a pressure diff of 985 cmH2O which way would the flow be?

[Pesser]

If it were 1000 cmH2O there would be flow "into" the cpap machines instead of "out", no?

When your cpap pressure is 15cmH20 there would be flow into the machine IF Atmos were 1000 cmH2O. With a pressure diff of 985 cmH2O which way would the flow be?

No! Your room is at 1,000cmh20. When your machine is set at 15cmh20 it ramps up enough pressure to deliver the additional 15 cmh20, giving you 1,015 cmh20. If your room pressure was 0; you would explode. Your CPAP would not be able to get the air pressure needed because at 0cmh20 there is no air! That would mean there is no air pressure. You would need to be in outer space.

[Guest]

If it were 1000 cmH2O there would be flow "into" the cpap machines instead of "out", no?

When your cpap pressure is 15cmH20 there would be flow into the machine IF Atmos were 1000 cmH2O. With a pressure diff of 985 cmH2O which way would the flow be?

No! Your room is at 1,000cmh20. When your machine is set at 15cmh20 it ramps up enough pressure to deliver the additional 15 cmh20, giving you 1,015 cmh20. If your room pressure was 0; you would explode. Your CPAP would not be able to get the air pressure needed because at 0cmh20 there is no air! That would mean there is no air pressure. You would need to be in outer space.

One of us is not understanding this correctly, it could be me but your explanation is not the way I understand it. It it were 1000 + 15 cmH2O why wouldn't they say 1015 cmH2O? If that is what it is.

ooops I just exploded and I am outta here.

[PlinkerCraig]

The machines are set to cmH20 over atmospheric pressure, not absolute pressure. Indeed normal atmospheric pressure of 29.92 inches of mercury is pretty close to a 30 foot column of water which is pretty close to 10 meters which equals 1000 cm.

Personally I worry more about dust mites than Radon.
The folks that invented the Radon scare probably also gave us the huge Y2K hysteria.

[palerider]

If it were 1000 cmH2O there would be flow "into" the cpap machines instead of "out", no?

When your cpap pressure is 15cmH20 there would be flow into the machine IF Atmos were 1000 cmH2O. With a pressure diff of 985 cmH2O which way would the flow be?

No! Your room is at 1,000cmh20. When your machine is set at 15cmh20 it ramps up enough pressure to deliver the additional 15 cmh20, giving you 1,015 cmh20. If your room pressure was 0; you would explode. Your CPAP would not be able to get the air pressure needed because at 0cmh20 there is no air! That would mean there is no air pressure. You would need to be in outer space.

One of us is not understanding this correctly, it could be me but your explanation is not the way I understand it. It it were 1000 + 15 cmH2O why wouldn't they say 1015 cmH2O? If that is what it is.

ooops I just exploded and I am outta here.

that one would be you.

pesser is talking absolute atmospheric pressure. air around is under pressure. he's spot on converting the normal 14.7 psi air pressure at sea level to 1033.5122800951199 cm h2o.

where you're screwing up is not realizing that both sides of the cpap, and indeed you, are at this same 1033cmh2o pressure, so you don't notice anything,

the cpap operates at a *RELATIVE* pressure difference of between 4-20cmh2o (or 25-30 for bilevel/niv machines) compared to ambient (the existing 1033cmh2o. this all works because the outside of your chest/throat has 1033 (at sea level) cm pressure on it, and the inside has 1037-1057cm pressure.

anybody that's ever used a vacuum chamber knows that air has pressure, (or, indeed a regular household vacuum... they don't actually suck, they create a lower air pressure inside and the external pressure forces air in thorugh the nozzle..) someone asked me once what would happen if I opened the lid to my chamber vacuum sealer while it was operating. I had to laugh, and explain that when it had been running more than a few seconds, there was over a TON (2000lbs) of pressure holding that lid closed. (appx 13x13 lid and around 14psi air pressure outside=2366lbs) I like my chamber sealer, and it's amusing to watch cold tap water boil.

[palerider]

The folks that invented the Radon scare probably also gave us the huge Y2K hysteria.

the only reason that y2k was very mild was because tons of people worked their asses off to prevent it. (spoken as one of the people who was doing so).

I didn't have such a great new year that year, I was watching the servers that I managed, and my roommate at the time had to be in the office, telecommuting wasn't good enough for IBM at that point.

there were plenty of annoying things that still slipped thorugh the cracks, like some really old folks getting notices that they had to register for the draft and such.

[chunkyfrog]

Y2K was never an issue for land records, as everything goes back over 100 years.
This meant that 8 digit date fields were the norm.
IMO, six digit date fields were pretty short-sighted--whose dumb idea was that?

[palerider]

Y2K was never an issue for land records, as everything goes back over 100 years.
This meant that 8 digit date fields were the norm.
IMO, six digit date fields were pretty short-sighted--whose dumb idea was that?

just you wait till the y10k crisis gets here!!!!

early computer people, when bits and bytes were VERY expensive.

[PlinkerCraig]

We've drifted way off topic here. But I just want to add a brief first-hand history that could be fun to read.
In 1982 I had a summer coop job working for GE at their flight test center at Edwards Airforce Base. I worked in their software development lab mostly working on data analysis from jet engines. But between engine projects they asked me to add something to the payroll and accounting code. I remember they kept the birthdate and hire date of employees with two digits, like 62 instead of 1962. I thought "hmm, slim chance this code will still be in use by 2000, but either way I better make it work both before and after that date". Simple logic said we never employed people over a hundred years old so maybe 6 lines of code dealt with making sure date calculations would work no matter how long the code was in use.

Working for Hewlett-Packard leading up to Y2K I remember the first time I ever heard a computer salesman saying how great it would be for sales, and it was really great for sales until summer of 2000 when the hysteria died. Then sales took a dive back to normal.

[Goofproof]

Y2K was never an issue for land records, as everything goes back over 100 years.
This meant that 8 digit date fields were the norm.
IMO, six digit date fields were pretty short-sighted--whose dumb idea was that?

The same fellow that tnought up daylights savings time. It's his job to set in a cubicle and see how much he can screw the pouch. Jim

He's definitely presidential material.

[palerider]

We've drifted way off topic here.

you started it!

[Goofproof]

If it wasn't for post drift, most posts would be dull after 5 posts. Usually by 5 posts someone has stated the best answer, then the post continues with repeats of the previous answers in various makeshift variants.

Of the first 5 posts, one will be someone that doesn't no the answer, but has a keyboard that needs use.

One that doesn't read the post correctly, and answers based on what they thought the question was.

One that really answers the question pretty well, which many times is ignored.

One that clarifies the good answer, usefully.

By now it's time for a troll post.

By now it becomes a free for all, and the games begin!

[chunkyfrog]

Intelligent observation;
--What have you done to Goofproof?

[Guest]

that one would be you.

once again you (and the others) are right.

I knew there was pressure on both sides and there would have to be a diff in pressure or there would be no flow. I just felt the medical community would use absolute pressure. Wrong again.