Effects of Pulmonary Artery Pressure – Pulmonary Blood Flow

by Thad Wilson, PhD

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    00:02 This is a graph that looks at pulmonary vascular resistance, which is the resistance of blood flow through the tubes of the lung.

    00:08 And then we’re comparing that to mean pulmonary artery pressure.

    00:13 So this is the pressure pushing the blood through those tubes.

    00:18 And this forms a very unique relationship in which at low pulmonary artery pressures, resistance is high.

    00:25 But as pulmonary artery pressure increases, you actually get a decrease in pulmonary vascular resistance.

    00:33 And this is fairly unique.

    00:34 So as pressure goes up, you have lowering of the resistance.

    00:40 What does this do for blood flow is as pulmonary blood flow increases as pulmonary artery pressure increases.

    00:49 So then they are more linearly related in a positive manner.

    00:52 This is a very interesting process.

    00:56 It means that it’s not governed in the same way as your systemic vasculature, that will be covered in the cardiovascular section.

    01:03 So this brings up a very unique point of view and that is we have from the previous slide, an increase in pulmonary artery pressure.

    01:12 And as pressure increases, the pulmonary vascular resistance decreases.

    01:18 So what that meant was as pulmonary artery increased, blood flow also increased.

    01:24 How does this happen? Well, it seems to occur via two mechanisms.

    01:30 And let me go through what those are.

    01:32 The first is going to be a recruitment and the second is a distension issue.

    01:37 But let’s kind of walk through these step by step.

    01:39 In normal pulmonary vasculature, some of the blood vessels are collapsed even during the rested state.

    01:47 There are some of the blood vessels that are not collapsed, but yet the blood is not moving very rapidly through those particular capillaries.

    01:59 So both of those items have low blood flow through them.

    02:05 There are some of the capillaries though, just as you would expect, are open and do conduct blood.

    02:11 So there’s a little bit of a notion here that you only get blood flow through some of the capillaries.

    02:17 Other parts of the capillaries are collapsed and some have just low blood flow.

    02:24 As pressure though increases, what you get is an opening of these blood vessels.

    02:30 First the ones that were previously collapsed start to open and the ones that were not conducting flow through very rapidly as the pressure increases, those are pushed through to a much greater extent.

    02:46 The ones that had had normal blood flow, widen.

    02:51 And so that is the distension component versus the recruitment component.

    02:56 So we have recruitment that occurs through the previously collapsed blood vessels.

    03:02 We had distension that occurred through the blood vessels that were already open that became wider.

    03:09 Therefore, we have an end result of an increase in perfusion or blood flow through the entire lung.

    03:16 So this is how the process of increasing pulmonary artery pressure increases pulmonary blood flow through both a recruitment and a distension mechanism.

    About the Lecture

    The lecture Effects of Pulmonary Artery Pressure – Pulmonary Blood Flow by Thad Wilson, PhD is from the course Respiratory Physiology.

    Included Quiz Questions

    1. Decrease
    2. Increase
    3. Increase, then decrease
    4. Decrease, then increase

    Author of lecture Effects of Pulmonary Artery Pressure – Pulmonary Blood Flow

     Thad Wilson, PhD

    Thad Wilson, PhD

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