Blood Pressure Dynamics (cardiac output, stroke volume, HR & vascular resistance) Made easy!
Blood Pressure Dynamics (cardiac output, stroke volume, HR & vascular resistance) Made easy!
A simple model for Blood pressure dynamics, going through the basics of cardiac output, stroke volume, and heart rate.
00:00 Intro: One very simple equation!
00:24 Cardiac Output
00:54 Stroke Volume and Cardiac Output
01:22 Preload
01:43 Contractility
02:05 Heart rate and Cardiac Output
02:49 Vascular Resistance and Blood Pressure
04:13 Example: fight or flight response and blood pressure
04:42 Example: How sepsis affects blood pressure
05:20 Outro
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Content
0.399 -> a lot of people are quite nervous about
2 -> anything cardiac
3.12 -> and that's understandable if something
4.96 -> goes wrong with the heart then the
6.24 -> consequences can be fairly catastrophic
8.8 -> however the basics of blood pressure are
11.12 -> actually fairly easy
12.639 -> as almost everything can be described
14.4 -> with one simple equation
16.48 -> cardiac output times vast resistance
18.8 -> equals blood pressure
20.32 -> this video will hopefully provide a
22.08 -> simple model for understanding blood
23.84 -> pressure dynamics
29.199 -> cardiac output of course refers to the
30.96 -> work the heart does pumping blood out
32.88 -> into the body
34.399 -> here to represent cardiac output and the
36.399 -> heart we have an old-fashioned
37.92 -> hand-driven water pump the working of
40.399 -> the handle represents the contractions
42.16 -> of the heart
43.12 -> the water coming out of the nozzle
44.719 -> represents blood ejected during these
46.399 -> contractions
48 -> if we want to increase the flow of water
49.76 -> from the bump eg
51.199 -> cardiac output then there are two main
53.6 -> things we can do
56 -> the first thing is to increase the
57.36 -> volume of water being pushed out of the
59.12 -> pump with each push of the handle
61.68 -> and as we can see if our stick figure
63.68 -> puts a bit more effort in
65.519 -> then voila a greater volume of water is
68.24 -> ejected
69.92 -> the heart works in a similar way the
72.72 -> volume of blood ejected from the heart
74.32 -> with each contraction of the muscle
75.68 -> is referred to as stroke volume a couple
78.799 -> of things affect stroke volume
81.28 -> between contractions the chamber of the
83.04 -> heart fills with blood
85.759 -> as the ventricles fill the muscle is
87.6 -> stretched in order to hold a greater
89.28 -> volume
90.479 -> the amount the muscle stretches before
92.079 -> contraction is known as preload
94.96 -> this will be discussed in the next video
98.32 -> the more blood within the heart before
100 -> contraction the greater the stroke
101.52 -> volume
103.439 -> the other thing that affects stroke
104.799 -> volume is the force of contraction of
106.72 -> the cardiac muscle
108.479 -> it is this contraction of muscle that
110.96 -> forces the blood
112.159 -> out from the heart as we saw with our
115.52 -> stick figure
116.24 -> the harder the muscle works the greater
117.92 -> the stroke volume
119.6 -> so if increasing stroke volume is the
121.439 -> first thing we can do to improve cardiac
123.04 -> output
123.84 -> then what's a second the rate at which a
127.2 -> stick figure works a handle will of
128.879 -> course affect the volume of water pumped
131.36 -> the greater the rate the greater the
133.04 -> overall output
134.4 -> the heart is of course the same up to a
136.64 -> point
138 -> as we saw previously the heart must fill
140.319 -> with blood prior to contraction to
141.92 -> achieve a reasonable stroke volume
144 -> if it beats too rapidly then there will
146 -> not be time for adequate filling to
147.76 -> occur
148.319 -> and the volume of blood ejected will be
150.16 -> lower
151.44 -> overall cardiac output will therefore be
154.84 -> reduced
162.08 -> the second and equally important part to
164.239 -> the blood pressure equation
165.76 -> is the vascular resistance
171.28 -> this pump is pushing fluid through a
173.04 -> nozzle
174.4 -> as the nozzle is wide it provides very
176.4 -> little resistance as the water is pushed
178.239 -> through it
179.12 -> as a result the water comes out of the
180.959 -> end at very low
182.84 -> pressure this second pump is pushing the
186.159 -> same volume of water
187.519 -> at the same rate but through a much
189.599 -> thinner nozzle
190.959 -> this time the water is coming out of the
192.959 -> end at much higher pressure
194.959 -> the thin nozzle provides much more
196.56 -> resistance to the large volume of water
198.64 -> that is being pushed
199.599 -> through it blood vessels in the body
202.879 -> increase or reduce blood pressure in the
204.72 -> same way
206 -> they are capable of constricting
207.68 -> increasing resistance to the blood
209.28 -> being pushed out of the heart and
210.72 -> producing higher pressures
212.64 -> they can also dilate providing less
214.4 -> resistance and reducing blood pressure
217.84 -> this stick figure is holding a hose pipe
219.84 -> to represent vascular resistance
222.159 -> we can switch between a wide hose
223.92 -> producing very little resistance
225.68 -> and therefore reducing blood pressure or
228.799 -> a narrow one
230 -> increasing resistance and therefore
231.84 -> blood pressure
234.48 -> and that's really it for blood pressure
236 -> basics anything that increases or
238.48 -> decreases blood pressure
239.84 -> is going to fit in somewhere within this
241.599 -> equation we can increase cardiac output
244.319 -> by increasing the stroke volume and the
246.08 -> rate
246.959 -> we can then increase pressure even
248.56 -> further by increasing resistance to
250.64 -> cardiac output from the blood vessels
258.959 -> if we have a sudden shock
262.4 -> then the body's fight or flight response
264.16 -> kicks in
265.52 -> as part of that response the bodies
267.12 -> flooded with adrenaline
268.88 -> adrenaline binds with special receptors
271.04 -> on the heart muscle
272.56 -> which causes the muscle to contract more
274.16 -> forcefully increasing stroke volume
276.639 -> and causing the heart rate to increase
278.96 -> as a result cardiac output increases
280.88 -> leading to higher blood pressure
284.639 -> pressure one of the symptoms of acute
287.44 -> sepsis
288.08 -> is widespread vasodilation
291.12 -> vasodilation is helpful when an
293.04 -> infection occurs in just one area
294.88 -> of the body for example if you have an
297.6 -> infected finger
298.88 -> then vasodilation within that finger
301.039 -> allows more white cells
302.32 -> into the area to help combat the
303.84 -> infection
305.759 -> however when the infection spreads to
308.16 -> other parts of the body
309.6 -> then vasodilation will also become
311.759 -> widespread
313.039 -> this will significantly reduce
314.4 -> resistance to cardiac output and lead to
316.56 -> a significant drop in blood pressure
320.24 -> i hope you found this video useful in
322.32 -> the next one we'll look at giving fluids
323.919 -> for hypertension
325.44 -> don't forget to subscribe
Source: https://www.youtube.com/watch?v=O38TBFO-OKg