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00:00:02,375 --> 00:00:03,000
So here we are.

3
00:00:03,000 --> 00:00:04,790
We have our two
lungs and the heart.

4
00:00:04,790 --> 00:00:06,430
I'm just going to
quickly label stuff.

5
00:00:06,430 --> 00:00:09,287
We've got our right and left
lung, and we've got our heart.

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00:00:09,287 --> 00:00:10,745
And I want to make
sure I label all

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00:00:10,745 --> 00:00:12,450
of the four chambers
of the heart.

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00:00:12,450 --> 00:00:15,440
I've taken away a
lot of the vessels.

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00:00:15,440 --> 00:00:17,600
I just want to focus
on a couple of things

10
00:00:17,600 --> 00:00:21,630
here-- mainly, the blue
blood vessel coming off

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00:00:21,630 --> 00:00:24,040
of the heart-- the one I've
drawn in blue-- which I'm

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00:00:24,040 --> 00:00:26,480
going to label here as
the pulmonary artery.

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00:00:26,480 --> 00:00:30,390
Remember, again, arteries
go away from the lungs.

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00:00:30,390 --> 00:00:33,630
So this is our pulmonary
artery, even though it's

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00:00:33,630 --> 00:00:36,580
got deoxygenated blood in it.

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00:00:36,580 --> 00:00:39,080
A little counterintuitive,
but I think you got it now.

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00:00:39,080 --> 00:00:41,970
So this is our pulmonary
artery, and it's

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00:00:41,970 --> 00:00:44,320
going to the left
and right lungs.

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00:00:44,320 --> 00:00:48,120
And if we assume that there's,
let's say, 5 liters of blood

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00:00:48,120 --> 00:00:49,694
flowing through the
heart per minute,

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00:00:49,694 --> 00:00:51,110
that means that 5
liters are going

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00:00:51,110 --> 00:00:53,490
to go through this vessel.

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00:00:53,490 --> 00:00:55,840
And some of that is
going to go to the right,

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00:00:55,840 --> 00:00:58,880
and some is going
to go to the left.

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00:00:58,880 --> 00:01:01,440
Let's say I told you that
2 and 1/2 liters goes

26
00:01:01,440 --> 00:01:03,620
to the left lung per minute.

27
00:01:03,620 --> 00:01:05,110
Let's just assume that.

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00:01:05,110 --> 00:01:07,240
Then you know that
the other half

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00:01:07,240 --> 00:01:09,960
of that 5 liters-- the rest
of it, 2 and a 1/2 liters--

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00:01:09,960 --> 00:01:11,290
must also go to the right.

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00:01:11,290 --> 00:01:13,780
Because whatever
goes into this tube--

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00:01:13,780 --> 00:01:16,130
almost like a straw--
on one end has

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00:01:16,130 --> 00:01:17,900
got to come out
on the other end.

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So you just, basically,
add up what's exiting.

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00:01:20,260 --> 00:01:22,560
And it's got to equal
what's entering.

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So here we have
the idea of flow.

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00:01:24,840 --> 00:01:26,980
And we've talked about
flow in other videos,

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00:01:26,980 --> 00:01:28,770
but basically, I just
want to restate it.

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00:01:28,770 --> 00:01:31,170
It's a volume over
a period of time.

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00:01:31,170 --> 00:01:33,680
And in this case, we're
using liters over minutes.

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00:01:33,680 --> 00:01:35,940
But really any kind of
volume over time you

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00:01:35,940 --> 00:01:37,790
could describe as blood flow.

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00:01:37,790 --> 00:01:40,600
Now, let's say that a
tragic event occurs,

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and I end up having
a surgery to my lung.

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00:01:45,860 --> 00:01:47,770
Let's say underneath
this yellow line

46
00:01:47,770 --> 00:01:51,430
is my lower lobe and
above it is my upper lobe.

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00:01:51,430 --> 00:01:54,640
Let's say my lower lobe,
it needs to be removed.

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00:01:54,640 --> 00:01:56,790
It's a pretty drastic
thing to have happen,

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00:01:56,790 --> 00:01:59,160
but let's say this
is what happens.

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00:01:59,160 --> 00:02:02,810
What would change in
terms of my blood flow?

51
00:02:02,810 --> 00:02:05,120
Well, the thing that
is going to change

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00:02:05,120 --> 00:02:08,910
is my resistance
is going to change.

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00:02:08,910 --> 00:02:10,090
Let's think about it.

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00:02:10,090 --> 00:02:12,790
Before I had this surgery,
I had a certain amount

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00:02:12,790 --> 00:02:15,170
of resistance in
this blood vessel

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00:02:15,170 --> 00:02:17,254
and also some resistance
in this blood vessel.

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00:02:17,254 --> 00:02:18,670
And let's say it's
about the same,

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00:02:18,670 --> 00:02:20,590
just to kind of
make things easy.

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00:02:20,590 --> 00:02:22,810
Let's say the resistance
was about the same.

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00:02:22,810 --> 00:02:25,280
So again, I had a surgery.

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00:02:25,280 --> 00:02:32,430
And before they removed the
lower lobe-- just to make sure

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00:02:32,430 --> 00:02:35,140
we are clear on what
this surgery was-- so

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00:02:35,140 --> 00:02:36,260
removed the lower lobe.

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00:02:36,260 --> 00:02:38,890


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00:02:38,890 --> 00:02:42,020
So before the surgery-- I'll
write "before" up here--

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00:02:42,020 --> 00:02:43,440
what was the resistance?

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00:02:43,440 --> 00:02:47,570
Well, the resistance I
was facing was-- remember,

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00:02:47,570 --> 00:02:49,600
we have a branch here.

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00:02:49,600 --> 00:02:52,000
So we have to add up
the total resistance.

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00:02:52,000 --> 00:02:53,300
You remember how to do this.

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00:02:53,300 --> 00:02:56,320
Total resistance--
I'll call it R total--

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00:02:56,320 --> 00:03:02,310
equaled 1 divided by
1 over R-- because we

73
00:03:02,310 --> 00:03:05,620
said that's what the resistance
is right there-- 1 over R

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00:03:05,620 --> 00:03:09,962
plus 1 over R. And that second
one is because of this guy.

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00:03:09,962 --> 00:03:11,170
So we just kind of add it up.

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00:03:11,170 --> 00:03:12,003
And I would say, OK.

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00:03:12,003 --> 00:03:17,730
Well, that's equal to
1 over 2 divided by R.

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00:03:17,730 --> 00:03:19,690
And I can flip the
whole thing around.

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00:03:19,690 --> 00:03:26,260
And I get R divided by
2 or 1/2 R. So this is

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00:03:26,260 --> 00:03:27,652
my total resistance-- 1/2 R.

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00:03:27,652 --> 00:03:30,110
It's a little counterintuitive--
the fact that you actually

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00:03:30,110 --> 00:03:33,810
have half of the resistance
just because you have a fork.

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00:03:33,810 --> 00:03:36,100
The fork in the road--
meaning this fork right

84
00:03:36,100 --> 00:03:40,380
here-- offers you a chance
to go one of two ways.

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00:03:40,380 --> 00:03:42,900
And as a result, the
resistance falls in half.

86
00:03:42,900 --> 00:03:45,620
So after my surgery,
what was my resistance?

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00:03:45,620 --> 00:03:48,090
Well, in my surgery, this
all kind of went away.

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00:03:48,090 --> 00:03:49,780
This is now all gone.

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00:03:49,780 --> 00:03:53,060
Because my surgery removed the
lower lobes, this is now gone.

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00:03:53,060 --> 00:03:55,490
So what is my new R total?

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00:03:55,490 --> 00:03:57,260
Well, if I had to
calculate it again,

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I would say, OK, R total.

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00:03:58,680 --> 00:04:00,320
In this case, it's
actually really easy

94
00:04:00,320 --> 00:04:02,440
because it's just
whatever's left.

95
00:04:02,440 --> 00:04:06,120
In this case, the total
is going to be just R.

96
00:04:06,120 --> 00:04:12,770
So really, my resistance
went from half R to R.

97
00:04:12,770 --> 00:04:16,240
And so my resistance really,
by removing the lower lobe,

98
00:04:16,240 --> 00:04:16,959
it doubled.

99
00:04:16,959 --> 00:04:18,834
My resistance went much higher.

100
00:04:18,834 --> 00:04:20,500
So this is the first
interesting point--

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00:04:20,500 --> 00:04:23,350
that by having a
half a lobe removed,

102
00:04:23,350 --> 00:04:24,785
my resistance went way up.

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00:04:24,785 --> 00:04:27,690
So on this side, my
resistance after the surgery

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00:04:27,690 --> 00:04:29,650
is much higher
than it used to be.

105
00:04:29,650 --> 00:04:31,890
Now, remember this
flow-- 5 liters a minute.

106
00:04:31,890 --> 00:04:34,040
Now, you still have that
much blood coming in,

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00:04:34,040 --> 00:04:37,427
but now there's extra
resistance on the left side.

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00:04:37,427 --> 00:04:38,760
So what's the blood going to do?

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00:04:38,760 --> 00:04:40,580
Well, it's going to
say, well, why would I

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00:04:40,580 --> 00:04:42,570
go that way when
I can go this way?

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00:04:42,570 --> 00:04:44,990
So more of the blood's
going to kind of go this way

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00:04:44,990 --> 00:04:48,350
because there's more
resistance on the left side.

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00:04:48,350 --> 00:04:51,300
And so I can actually--
I don't know exactly what

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00:04:51,300 --> 00:04:54,370
the amount of flow would be--
but I can kind of take a guess.

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00:04:54,370 --> 00:04:57,410
And I would say, well, my guess
is that the flow will be lower.

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00:04:57,410 --> 00:04:59,770
So I'm actually going
to redo these numbers.

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00:04:59,770 --> 00:05:01,700
I'm going to give
you new numbers.

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00:05:01,700 --> 00:05:05,620
And let's say the new flows--
I'll write them in green--

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00:05:05,620 --> 00:05:09,080
are going to be 3 liters a
minute and 2 liters a minute.

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00:05:09,080 --> 00:05:11,260
They still have to add
up to 5, of course.

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That's not changed.

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00:05:12,690 --> 00:05:15,570
But you have more blood
going to the right lung.

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So here let me
introduce another word.

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So we've talked
about flow, but now

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00:05:19,470 --> 00:05:20,982
let me talk about perfusion.

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00:05:20,982 --> 00:05:23,440
And sometimes people actually
think they're the same thing.

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They sometimes will use
them kind of synonymously.

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But really, perfusion
is volume over time.

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And so, so far you're thinking,
well, it is about the same.

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But actually, it's all
divided by amount of tissue.

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00:05:39,190 --> 00:05:41,110
And when I say amount,
I could do either

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be talking about a volume of
tissue or a weight of tissue.

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So amount of tissue.

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Just to kind of make this
a little bit more concrete,

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00:05:50,030 --> 00:05:54,240
I'm going to assume that I'm
going to use 100 grams here.

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And that's often used.

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Not always.

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00:05:55,810 --> 00:05:57,210
Sometimes you'll
see other units.

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But I'm going to
use 100 grams here.

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So let's now think about
this entire scenario

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00:06:03,140 --> 00:06:04,980
with the new numbers--
2 liters a minute

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00:06:04,980 --> 00:06:07,716
and 3 liters a minute--
in terms of perfusion.

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What would that mean?

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00:06:08,590 --> 00:06:12,510
Well, let's say I
weigh out my two lungs.

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00:06:12,510 --> 00:06:15,580
And here I only have an upper
lobe on my left side left.

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00:06:15,580 --> 00:06:20,950
So let's say that
weighs half a kilogram.

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00:06:20,950 --> 00:06:23,700
And let's say, on the right
side, I've got 1 kilogram.

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00:06:23,700 --> 00:06:25,600
Let's say this is 1 kilogram.

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00:06:25,600 --> 00:06:27,930
These are the weights
of my two sides.

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00:06:27,930 --> 00:06:31,400
And to figure out perfusion,
then all you really are doing

151
00:06:31,400 --> 00:06:34,370
is taking the flow-- because
remember, this whole chunk,

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00:06:34,370 --> 00:06:36,780
this whole part right
here is just flow--

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00:06:36,780 --> 00:06:39,140
and dividing it by
the amount of tissue.

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00:06:39,140 --> 00:06:41,460
So I could figure out
perfusion pretty easily.

155
00:06:41,460 --> 00:06:42,240
I could say, OK.

156
00:06:42,240 --> 00:06:44,970
Well, on the right side--
let's do right side first--

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00:06:44,970 --> 00:06:48,160
I've got 3 liters a minute.

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00:06:48,160 --> 00:06:51,120
I'm going to write that
as 3,000 milliliters,

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00:06:51,120 --> 00:06:53,750
just to make it a
little easier to see.

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00:06:53,750 --> 00:06:57,700
3,000 milliliters per
minute divided by-- I

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00:06:57,700 --> 00:07:02,290
said 1 kilo, which is
the same as 1,000 grams.

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00:07:02,290 --> 00:07:03,810
So what does that
turn out to be?

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00:07:03,810 --> 00:07:06,720
If I'm going to use 100 grams
as my denominator, I could say,

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00:07:06,720 --> 00:07:09,600
well, that's-- let's
see, 0s cancel.

165
00:07:09,600 --> 00:07:16,940
So I've got 300
milliliters per minute

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00:07:16,940 --> 00:07:21,800
per 100 grams of lung tissue.

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00:07:21,800 --> 00:07:23,491
And so this is for
the right side.

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00:07:23,491 --> 00:07:25,490
And I could do the same
thing for the left side.

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00:07:25,490 --> 00:07:27,740
I could say, well, what would
it be for the left side?

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00:07:27,740 --> 00:07:32,570
It would be-- I've
got 2,000 milliliters.

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00:07:32,570 --> 00:07:33,960
We said 2 liters.

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00:07:33,960 --> 00:07:37,720
And of course, the 2 and 3 I
was just kind of estimating.

173
00:07:37,720 --> 00:07:40,770
But we'd have to
actually measure

174
00:07:40,770 --> 00:07:43,290
to see what the actual flow is.

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00:07:43,290 --> 00:07:45,480
But here I've got 500 grams.

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00:07:45,480 --> 00:07:51,160
And so that works out
to 400 milliliters

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00:07:51,160 --> 00:07:55,792
per minute per 100 grams.

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00:07:55,792 --> 00:07:58,250
So what I wanted to show you
is an interesting thing, which

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00:07:58,250 --> 00:08:00,900
is that you can actually
have, on the one side--

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00:08:00,900 --> 00:08:03,240
if I said which side,
the right or the left,

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00:08:03,240 --> 00:08:07,910
after my surgery, which
side has more blood flow?

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00:08:07,910 --> 00:08:10,450
Well, then, this side
has more blood flow.

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00:08:10,450 --> 00:08:13,640
The right side has more flow.

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00:08:13,640 --> 00:08:18,339
But if I said which
one has more perfusion,

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00:08:18,339 --> 00:08:19,880
well, it turns out
that actually that

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00:08:19,880 --> 00:08:22,940
left upper lobe is actually
getting more perfusion.

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00:08:22,940 --> 00:08:25,590
So just because one
side has more flow

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00:08:25,590 --> 00:08:27,885
doesn't necessarily mean
that it has more perfusion.

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00:08:27,885 --> 00:08:29,510
Oftentimes that is
the case because you

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00:08:29,510 --> 00:08:32,070
can see how closely flow
and perfusion are related.

191
00:08:32,070 --> 00:08:35,159
But it just depends
on exactly what

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00:08:35,159 --> 00:08:37,760
the weight is for the tissue.

193
00:08:37,760 --> 00:08:39,299
Kind of a classic
example of this

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00:08:39,299 --> 00:08:42,330
I'm going to write out over here
that you might hear people talk

195
00:08:42,330 --> 00:08:45,000
about sometimes is-- if
you say this side is high

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00:08:45,000 --> 00:08:48,550
and this side is low-- let's
do flow and perfusion--

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00:08:48,550 --> 00:08:50,649
they'll say, well,
if you have flow

198
00:08:50,649 --> 00:08:52,690
and you're trying to talk
about different organs,

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00:08:52,690 --> 00:08:55,800
one of the organs with the
highest flow in the body

200
00:08:55,800 --> 00:08:57,390
would actually be your liver.

201
00:08:57,390 --> 00:08:59,380
This is, let's say, your liver.

202
00:08:59,380 --> 00:09:00,900
This is your liver.

203
00:09:00,900 --> 00:09:03,600
And then, with a little
bit less blood flow

204
00:09:03,600 --> 00:09:06,230
would be your kidneys.

205
00:09:06,230 --> 00:09:09,290
This would be your
kidneys, let's say.

206
00:09:09,290 --> 00:09:10,730
I'll write K for kidney.

207
00:09:10,730 --> 00:09:12,355
Or actually, I guess
I'll spell it out.

208
00:09:12,355 --> 00:09:13,410
I have enough space.

209
00:09:13,410 --> 00:09:16,420
And then, something
that has almost no flow

210
00:09:16,420 --> 00:09:19,720
relative to the other
two would be bones.

211
00:09:19,720 --> 00:09:21,830
And actually, compared
to this, if you

212
00:09:21,830 --> 00:09:25,300
were to now talk
about perfusion,

213
00:09:25,300 --> 00:09:27,160
it would actually looks
slightly different.

214
00:09:27,160 --> 00:09:31,010
So for perfusion-- using
these same three organs--

215
00:09:31,010 --> 00:09:33,690
if I was to kind of rank
them based on which one gets

216
00:09:33,690 --> 00:09:36,390
the most perfusion
or blood perfusion,

217
00:09:36,390 --> 00:09:38,110
the kidney actually
does the best.

218
00:09:38,110 --> 00:09:41,392
So here you have to take a
certain amount of tissue.

219
00:09:41,392 --> 00:09:42,850
And it's got to be
the same amount.

220
00:09:42,850 --> 00:09:45,400
So I'm just imagining if I
took a little chunk of kidney

221
00:09:45,400 --> 00:09:46,420
tissue.

222
00:09:46,420 --> 00:09:47,795
And if I did the
exact same thing

223
00:09:47,795 --> 00:09:50,830
and I took a little
chunk of liver tissue.

224
00:09:50,830 --> 00:09:52,330
And this is kind
of the way to think

225
00:09:52,330 --> 00:09:54,496
about it is that, if you
want to balance things out,

226
00:09:54,496 --> 00:09:56,720
you've got to take the
exact same amount of tissue.

227
00:09:56,720 --> 00:09:59,700
In this case, it would
be 100 grams, let's say.

228
00:09:59,700 --> 00:10:02,497
Maybe these boxes are
100 grams of tissue.

229
00:10:02,497 --> 00:10:03,830
It would be something like this.

230
00:10:03,830 --> 00:10:05,120
And this would be the bone.

231
00:10:05,120 --> 00:10:08,380
So the liver ends up
not doing as well.

232
00:10:08,380 --> 00:10:11,280
It gets a little
bit less perfusion

233
00:10:11,280 --> 00:10:13,300
in terms of 100 grams.

234
00:10:13,300 --> 00:10:15,100
The kidney does a
little bit better

235
00:10:15,100 --> 00:10:16,410
when it comes to perfusion.

236
00:10:16,410 --> 00:10:18,184
And the bones-- the
sad, little bones--

237
00:10:18,184 --> 00:10:19,850
they actually don't
get much blood flow.

238
00:10:19,850 --> 00:10:23,130
And even if you do it
by 100 grams of tissue,

239
00:10:23,130 --> 00:10:25,609
they actually don't get
much perfusion either.

240
00:10:25,609 --> 00:10:27,650
So this is kind of another
way to think about it,

241
00:10:27,650 --> 00:10:29,066
and you might hear
these examples.

242
00:10:29,066 --> 00:10:31,550
So I wanted to give
them to you here.