Just curious: cmH2O vs PSI?

There are several online converters, such as:

http://www-users.med.cornell.edu/~spon/ ... essure.htm
http://www.sensorsone.co.uk/pressure-un ... rsion.html

On those sites you can see that cm H2O is a lot more "sensitive" than PSI. For example, 10cm H2O is only 0.142 PSI.

thud wrote:I was just curious if anyone knows how cmH2O relates to PSI? Like what would 19cm H2O be in PSI, etc.? Not that it matters but I was just wondering about that.

For a rough but easily visualized comparison think of this. Atmospheric pressure is about 14.7 psi, which will push up about 32 feet of water, i.e., about 1/2 psi per foot of water. There are 2.54 cm per inch, so about 30 cm/ft. 20 cm is 2/3 of a foot so will be about 2/3 x 1/2 psi or about 1/3 psi.

I love WolframAlpha for these kinds of questions. Here is the answer to your question:
http://www.wolframalpha.com/input/?i=19+cm+h2o+in+psi

So, it is indeed a direct proportion--but using much, much smaller units?

PSI = cmH2O * 0.014
cmH2O = PSI * 70.3

1 PSI = 70.3 cmH20
1 cmH2O = 0.014 PSI