PV=nRT

Yesterday, two crows chased our resident Cooper’s hawk down the valley, where it turned and made a stand on a juniper. One crow took off, but the other lit also. It looked like the hawk had captured something the crow wanted. (No, we won’t think about what kind of critter it likely was.) After a fairly long stand-off, the crow finally gave up.

I found out yesterday that my blood pressure is high. Technically it’s on the high side of pre-hypertension, but for a person who’s always had pretty low readings, it was daunting.

It’s also totally hereditary and thus no surprise. My mom has been on high blood pressure medication for almost twenty years. She’s in otherwise excellent health and the medication works well for her.

So far as bad apples in the genetic gift basket, this one isn’t so bad.

Still I’m annoyed.

Oh, I have a list of things to do, to try to lower it naturally. I can increase my magnesium and Co-Q10 from what I’ve been taking. David has me adding Hawthorne berry extract. I’ve been working the weight and body fat down, but now I need to get serious about that last ten pounds. I might have to back off drinking wine, my very favorite thing.

*sigh*

Amusingly – or not – I’ve had the gas law, PV=nRT, on my list of blog topics for a while. That’s the formula that describes how pressure, volume and temperature interact. It’s a fascinating equation, really, because so much of our world, and our physiology, is governed by it.

Basically it says that Pressure multiplied by Volume equals Temperature. The n and the R describe molecular action, which is pretty stable for most purposes, so we can safely ignore it for most purposes. That makes the equation P*V=T. Or, to put it in a way that makes more intuitive sense by using that algebra you figured you’d never need, Pressure = T/V.

Thus, the hotter something is? The more pressure you have. Think of a pressure cooker. The more you raise the temperature, the more pressure inside the pot. Once you take off the lid, you increase the volume from a little pot to a great big room, and the pressure decreases.

There are more factors when you get into liquids, but the overall principle is the same. Body temperature is relatively steady, so blood pressure becomes largely a function of volume. As arteries narrow, for whatever reason – constriction due to stress or a wallpaper of fat – the volume available decreases and pressure goes up. That’s why diuretics, like my mom takes, work well. Reduce the volume of blood and there’s less pressure.

For whatever reasons, too, computer screen time is being linked to elevated blood pressure and there’s strong evidence for email apnea. So I’m resolving to decrease my screen time. And also to get up from my computer once an hour and breathe, walk, do the dishes or Tai Chi.

It’s not easy for me. I tend to sit for hours, concentrating on my work until the driving need to pee forces me out of my chair.

Yeah, I know – not healthy behavior.

But I’ll get better about it.

9 Replies to “PV=nRT”

  1. Apparently, Kev, that's good! Us sedentary computer users are supposed to get up at least once every hour. So we won't die in our chairs.

  2. The driving need to pee is what I count on to keep me from developing deep vein thrombosis as I sit and type away on the WIP. I drink a lot of water (always have a glass next to me), so the NTP (Need To Pee) method seems to be working well enough.

  3. I was noticing my blood pressure starting to creep up also, after years of 110 or 105 over something. The nurses are quick to assure me that the number is just fine, but it bothers me a lot. Not enough to *do* anything about it yet, other than chock it up to stress.

    …sigh…

  4. Marcella, you mean the cats have YOU.

    I love "NTP" as a method, Linda. We should give workshops.

    Joan, I'm the same way. Always low and suddenly quite high. But it's already down today, with me focusing on RELAXING. Making sure I'm breathing all day is helping a surprising amount.

  5. Ah, we have neighborhood redtail hawks. Always makes me smile when I see them. One likes to stalk my next door neighbor's bird feeder.

    Your posts this week have got me thinking about how much online time and televsion I've been doing. Am thinking about taking a day a week to unplug…maybe I can expand it to two. Amazing how technology just winds into us, isn't it?

  6. High blood pressure sucks. Thanks for the quick chemistry or physics lesson(which ever that was). I had no idea of the screen time connection.

    Hawks – love em, Crows – meh, not so much.
    Yeah, I know crows are very intelligent, etc. I also know that a murder of crows(that name should tell us something)will harass an owl to starvation, and I've seen them kill a young scrub jay. I like the owls(and hawks) better.

  7. It is amazing, Laura. It creeps in and sucks up more and more of our lives. You'll have to report back on the unplugging experiment!

    I think it counts as physics, John Ross – though a lot of chemical laws depend on this equation, too. And yeah, I admit I was glad to see the hawk win the stand-off. The crow was willing to be a pest, but not to take the hawk on, crow-o y hawk-o.

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