Wednesday, March 9, 2016

Information you will never need

Health care in Ukraine is free by the constitution.  It is illegal to pay a doctor or nurse at a state hospital or clinic.  However the state then steals all the money and pays them at Soviet rates of less than $70 per month, which of course they cannot live on.  So they require 'gifts' in appreciation for their services, which is only fair.  Some angry young doctor is taking the state to court to force them to either change the law or pay proper wages.

There are also private clinics with well trained specialists and modern equipment, for which you pay. Last week, I went to see my heart specialist at ProfiMed Clinic.  Not sure if the profi is profit or professional, not that it matters.  ProfiMed have a number of specialists on staff, do blood work and also some out-patient stuff.

Tanya comes in with me and since she knows me better than I know myself, converses with the doctor and fills me in after.  My blood pressure was 150/80 or something.  Not good enough so I am on one more pill of some kind, come back in a month.  My heart rate however surprised her.  "How can you have high blood pressure with a heat rate about 45-55?" "Elephants have much lower heart rates than smaller mammals" which made them laugh.

And which brings me to today's lecture, boys and girls. How do you compare the heart rates of mice and elephants? The answer is a variant of Kleiber's Law on the relationship between body mass and metabolic rate.

Metabolic rate is, in simple terms, measurable in calories (or joules*), the amount of heat lost per unit of time by the body of an animal. We know that large animals need more energy to survive than small animals but how much more?  A 4 tonne elephant is 160,000 times larger than a 25 gram mouse.  But it does not need 160,000 time more food in a day.  Bigger animals use food more efficiently than small animals.

Heat loss is a function of surface area. Heat production is a function of body mass.  Thing of an animal as a sphere.  Surface area is a function of the radius squared (r2).  Body mass, on the other hand is the volume of the sphere which is a function of the radius cubed (r3).  So there is some argument that Metabolic Rate varies with Body Mass to the two-thirds power (MRWkg2/3).  But 2/3 is not quite right.  

Max Kleiber, sometime in the 1930's, determined that a more accurate formula was Metabolic Rate varies with Body Mass to the three-quarter power (MRWkg¾).  This is simple.  Multiply the body weight in kg (or lb) by itself three times, then take the square root twice.  Any calculator can do it. 

The formula for heart rate** or pulse (P or bpm) is a little trickier to understand but simpler to do. P186*W-1/4.  An easier way to write it so it can actually be calculated is P 186*(1/W1/4). Something to the ¼ power just means take the square root twice.

Mouse – 25 grams – calculated heart rate 465
Cat – 2.5 kg – calculated heart rate 148
Human – 100 kg – calculated heart rate 59
Elephant – 4000 kg – calculated heart rate 23

Obviously these are ballpark as individual heart rates vary widely, even in an acceptable range but it does illustrate my point.  Elephants have lower heart rates than smaller mammals.

Thus endeth today’s lesson.  




*Would you refer to the week's groceries as the 'family joules'?
**My thanks to my friend and mentor, Professor Emeritus Dr D.A. Christensen, U of S, for sending me photocopies of pages from Kleiber's timeless book, "The Fire of Life"

14 comments:

  1. That was a fairly hot topic, BF. And well handled.

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    1. Thanks, Rob. Sometimes I like to get into stuff I learned in Grad School. Physiology was one of my favourite subjects. Kept my Brody and Kleiber until I moved too often and too far away

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  2. Gosh, that's about as tricky as the formula I used for adding chlorine to my rainwater tank after a week of heavy rains combined with dirty gutters to muck up the water in my holding tank. Got my gutters cleaned this week and then as I was doing the calculations on how many litres of water were in my tank (31,000L), and how much chlorine I needed to add, I realised this is one of the few times in my life when those geometry formulas I learned long ago actually come in handy.

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    1. I used the Metabolic Rate formula for calculating relative pasture needs for big and small cows, but that was about it. Your water tank is a cylinder or a squashed sphere?

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    2. Hm-m-m! I can't even visualise what a squashed sphere would look like.

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  3. My heart rate generally runs 70 to 90, but I'm a smoker.

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  4. normal blood pressure for me used to be 210/200...that was normal...we have it almost normal now..140/74 which gets me high fives from the nurse and receptionist..my pulse rate is 64...you can stand me on railroad tracks with train coming and it's still 64..I call walmart ..HOUSE OF SATAN.

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    1. How did you live at that high blood pressure? No stroke or heart attack? Your guardian angels were working overtime. 64 is a good pulse rate. Mine is usually 60 or less.

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  5. My pulse has always been slow: lower forties. When I go to the VA for a check the machine always red lights and I have to explain I don't need a crash cart. I was very physically active up through age forty and I think the slower heart rate adjust for my now lack of activity - a good thing.
    the Ol'Buzzard

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    1. A few years ago, Tanya took my BP and my pulse was 50. then she took it again in a couple hours and it was 40. She called the ambulance. That was exciting

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  6. "The family joules" - bahahaha!!! I often joke that I have the heart rate of a gerbil. (A 5'-10" gerbil, so there goes the 'larger animal' theory.) I'm in good shape, my blood pressure is that of a 22-year-old, and if I'm lying down half asleep my heart rate is in the 50s... but even sitting and typing raises my heart rate to 72 bpm. When I'm kickboxing, it'll rev up to over 170 bpm, which is supposed to kill old folks like me. Wait for it...
    *keels over and croaks*

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  7. 72 is normal for a female, I think. Women have a higher body metabolism than men as I recall. 170 is pretty wild. You get right into it, don't you. Any Viking Berserkers in your family history?
    Regardless of my low pulse rate, my pace maker still makes the garage door go up and down when I see your pictures for the book covers.

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    1. Aw, thanks! *blushes* And I'm pretty sure I do have some berserker blood - I traced our family back to County Wexford, Ireland, which was one of the main Viking settlements 'way back in the day: https://en.wikipedia.org/wiki/History_of_Ireland_(800%E2%80%931169) It takes a lot to make me mad, but if somebody actually manages it, don't get in my way. At least I don't have a big red beard... yet... ;-)

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