CPAPtalk.com

ChicagoGranny wrote:

Guest wrote:doesn't it logically follow that atmospheric pressure is 0 mH2O not 1000 cmH20?

No.

your map further confuses things, because air pressure for weather maps is often rendered in millibars.

one millibar is equal to 1.01972 cm/h2o while it is an approximation, it is only that.

Pest wrote:

ChicagoGranny wrote:

Guest wrote:doesn't it logically follow that atmospheric pressure is 0 mH2O not 1000 cmH20?

No.

Bless yur heart granny. You are in over yur head. Yur pic of a weather map does NOT show pressures in cmH20 sweety. So its not a good comparison to a cpap pressure.

it's a relatively close approximation, and evidence that your first "logical conclusion" is a fallacy.

why am I wasting my time trying to educate someone who's not smart enough to be ale to spell "your"?

Midnight Strangler wrote: Perchancetodream wrote:
When you think about it it makes sense that if we are breathing air under pressure, a lot more air (and whatever is in it) will pass through our lungs than through the lungs of a non-user.


This is not true. A CPAP user will not take in any more air than is needed to properly oxygenate his bloodstream. His body's autonomous system regulates this while he is asleep.

Someone should have told you that was an 8y/o post you replied to.

Guest wrote:
Indeed it is (zero) when measured at cmH20.

Midnight Strangler wrote: I have no idea what this discussion is about and don't care to know, but this statement makes no sense. Maybe replacing the preposition "at" with an explanatory phrase would help?

Maybe you should have read what that was in reply to.

So you don't know what it means AND don't care to know but want to comment anyway? nts

Midnight Strangler wrote:Atmospheric pressure of the earth at sea level is 14.70 pounds per square inch or 1034 cm H2O. Even on the summit of Mt. Everest the atmospheric pressure is 343 cm H2O.

Did you mean mmH20?
When all this started I was talking about cpap pressures which are measured in cmH20.

It seems that everyone here is forgetting about units of measure.

Guest wrote:

ChicagoGranny wrote:

Guest wrote:doesn't it logically follow that atmospheric pressure is 0 mH2O

Guest wrote:So why did YOU choose the weather map then?

To show a dummy that atmospheric pressure is not zero.

Indeed it is when measured at cmH20. So now you can say YOU learned something today.
is your Google broke too?

btw - hurling insulting remarks does not make you right.

only, you're wrong, go to google, and do a search

chunkyfrog wrote:My machine is said to automatically adjust to work at higher or lower altitudes,
thus maintaining a consistent pressure differential between the airway and ambient (room) air.
Does this mean it has an altimeter inside?
Another thought: if air pressure were zero at sea level, wouldn't our blood boil and our eyes explode there?

no, it doesn't have an altimeter, because it doesn't need one.
it has a pressure sensor, that reads the relative pressure difference between the air pressure inside the tube at the outlet the room air. it's operates purely on the difference in pressure.

older machines didn't have pressure sensors, they just ran a fan at a speed... so they had to be adjusted for altitude, since there is less air above them at higher elevations, the pressure is lower, the air is thinner, and the fan has to spin faster to generate the desired amount of "relative' pressure difference.

relative pressure difference: https://www.youtube.com/watch?v=c5_ho2sc0fc

meathead wrote:only, you're wrong, go to google

you need to convert
From: cmH20
To: ATM
IF that is what you want to know.

chunkyfrog wrote:My machine is said to automatically adjust to work at higher or lower altitudes,
thus maintaining a consistent pressure differential between the airway and ambient (room) air.
Does this mean it has an altimeter inside?

It just maintains the set positive pressure differential versus atmospheric pressure. No altimeter needed. According to one study which covered up to 10,000 feet elevation, it works well.

For patients with OSA, descent in altitude from 10,000 ft (3048 m) to sea level does not significantly alter absolute CPAP pressure requirements. The change in fan speed currently utilized by many CPAP machines to adjust for barometric pressure change and keep the delivered CPAP pressure consistent at different altitudes is all that is necessary for obstructive sleep apnea patients traveling to lower elevation.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2864887/

Guest wrote:Someone should have told you that was an 8y/o post you replied to.

Better that he corrected the mistake after eight years than never. As shown by the activity today, people are still reading this thread.

Duck wrote: Guest wrote:
Someone should have told you that was an 8y/o post you replied to.

Better that he corrected the mistake after eight year than never. As shown by the activity today, people are still reading this thread.

The comment was tongue in cheek. If you are around long enough you will find out there is a person here who has a habit of saying that it's an old post. I tend to agree with you, there is value even in old posts.

Guest wrote:I tend to agree with you, there is value even in old posts.

That's a comma splice type of run-on sentence. Learn to use two sentences.

BTW, what's with "tend to agree"? Wishy-washy Guest?

Midnight Strangler wrote:

Guest wrote:I tend to agree with you, there is value even in old posts.

That's a comma splice type of run-on sentence. Learn to use two sentences.

BTW, what's with "tend to agree"? Wishy-washy Guest?

Really? Are you my mother or my teacher or are you here just to criticize, attack, and lambaste? Find someone/something else to critic. Oh and have a nice day, if you can.

While this is a super old post, it never hurts to repeat that everybody have a CO monitor on each floor, especially by bedrooms. My Dad was bothered for years about this - his co-worker and the guy's whole family (6 kids and wife) died from CO poisoning one winter. I always slept with my window open, but even that doesn't necessarily prevent it if it's high enough.

SewTired wrote:While this is a super old post, it never hurts to repeat that everybody have a CO monitor on each floor

*looks at electric heater, electric stove, electric water heater*
*scratches head*

(Looking at smoke detector)
Maybe not EVERYONE, but still a good idea in case there are gas appliances or an attached garage.
Too many people have no idea of the hazards in their own home.

palerider wrote:

archangle wrote:Atmospheric pressure is around 1000 cmH20. Max CPAP pressure is around 20 cmH2O.

your casual throwing around of approximation of facts creates chaos.

one atmosphere of pressure = 1033.23 cm/h2o absolute which means *nothing*.

max cpap pressure from commercially available home machines is 30cm/h2o *ABOVE AMBIENT PRESSURE" which *stares pointedly at "guest"* that the maximum pressure in a resmed bilevel cpap would be 1066.23 compared to a total vacuum (0 pressure).

none of that matters, because cpap pressure is related to the ambient pressure around the machine. 5, 10, 20, 30 cm/h2o *ABOVE AMBIENT*

Sorry. I'll try to type more slowly this time so you can understand.

If you take air at normal atmospheric pressure of around 1000 cmH2O absolute and add the maximum 20 cmH2O gauge pressure that CPAP machines do, you increase the pressure of the air you're breathing to around 1020 cmH2O absolute. PV=nRT. P is measured in absolute pressure.

This amounts to about a 2% increase in the concentration of CO in terms of grams per cubic meter and the eventual CO concentration in your blood.

If, for instance, your room air was at the 1,600 ppm "dead in two hours" CO concentration, the CPAP user would be receiving the equivalent of 1632 ppm CO concentration. It's probably not really going to make much of a difference. Maybe the CPAP user would be dead in 117 minutes instead of 120 minutes. (Of course, the 2 hour number isn't that precise anyway.)

If it's a bilevel machine set at 30 cmH2O, it might be 116 minutes instead of 120 minutes.

Goofproof wrote:Smoke rises in a room because it's a product of fire and is heated air, as it cools it falls and the solid combustion products fall out of the mix and deposit everywhere, as a smokers home everything is covered in nicotine, the gasses mix with the air. Jim

Good thing, too, or we'd suffocate when we stand up because oxygen is 14% heavier than nitrogen. I could sleep on the floor, wouldn't need that O2 Pump.......... We could wear a XPAP mask all day, and run a hose near the floor to it.

I think we're basically in agreement. The gases in the smoke may follow some path around the room, first rising because of the heat, maybe flowing down to the floor based on air currents, but once mixed, they stay mixed. The solid particles or droplets of liquid (if any) will settle out to some extent, although if they are small enough, they may form a colloidal suspension and stay airboard.