Respiratory Variation

by Carlo Raj, MD

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    00:01 Now let us talk about respiration and our focus here is going to be upon our S2. So before we begin, you tell me about S2 again. S2 is a diastolic event, is it not? Yes. What happens during diastole? You have closure of the aortic followed by the pulmonic.

    00:18 We had A2, P2. Larup, darup, larup. Larup is S1, let us leave that alone. Let us focus on S2. Now if you’ve understood everything that I have said up until now, when I talk to you about the splitting of your S2 physiologically, then this will make sense doing inspiration.

    00:34 Now work with me here. Ready. Deep breath, diaphragm contracts moves down. What happens to your venous return? Tell me. Increased. Good. So you have increased your venous return to the right side upon inspiration. Where is there more blood? Well there are two doors.

    00:50 One is over there and one is over there. And even 1000 people running through that door and you have two people running through that door, which door is going to close first? Obviously the one with two people. If you tell me, 1000 people, I can’t help you.

    01:04 I really can’t. So here we go. Inspiration is more amount of blood on the right side.

    01:10 That is your 1000 people. That is going to take a long time for that door to close. What is that door with the 1000 people right now? That's your P2. So your second heart sound, your pulmonic valve closing upon inspiration is going to be much more delayed than your aortic. What do we call this? A physiologic split. Take a look at the inspiration, please.

    01:34 You see that widening of A2, P2. Doesn't that widening the space between A2, P2 look longer in length than upon expiration. Upon expiration, what happens to your diaphragm? Diaghragm comes up, thoracic pressure increases and so, therefore, your venous return is not as much on the right side. And so therefore what will happen to distance between A2, P2? It is decreased a little bit. Now, is this pathologic? No. It is called a physiologic split.

    02:03 This is occurring in you and me right now. When we inspire expire, we have changes in the span and length of A2, P2. Hope that is clear.

    02:12 That's the physiologic split. Let's continue, now we have something called a persistent or, more importantly, a widened split. Right off the bat, I wish to tell you, do not confuse your widened split with the fixed split. "Dr. Raj, it sounds like the same darn thing." Granted perhaps.

    02:32 But medically and clinically not at all. Two distinct diagnoses that must be understood right off the bat. Widened is not the same thing as fixed. What does widened mean? Well, let us say that your patient has something like right bundle branch block. What does a block mean to you? Well, the reason I ask you that is because, I am not stating the obvious.

    02:55 A block does not mean that no impulses are passing through. You have heard of AV block, you have heard of first-degree, second-degree AV block? Have you not? And what happens in those blocks? There is delayed conduction of the impulses. Correct? So in right bundle branch block, you will have a delayed conduction through the right bundle. Is that clear? When you have a delayed conduction through the right bundle, then what happens to your P2? It closes a little bit later, but it is not fixed. It is not fixed. I want you to take a look at normal and you take a look at your second heart sound. Expiration, inspiration.

    03:35 When do you have that widening? Only during inspiration and that is called a physiologic split. That is what normal is. A physiologic split. I want you to compare that to the wideened or the persistent, not the same thing as fixed. Right bundle branch block. When should you have more widening? During inspiration. Take a look at inspiration here under persistent, do you see that? Good. And do you have widening? Sure you do, but it is a lot wider than what it was with inspiration or normally. Take a look at expiration.

    04:07 Expiration, the widening is a little bit lessened, but it is still longer than what was found in normal. Is that clear? You still have variation like an accordion, back and forward, you still have that inspiration, expiration, widening and closing of the lengthened span, but this is called persistent. Our diagnosis and differentials include right bundle branch block and pulmonic stenosis. Why isn't left bundle branch block here? You see that why isn't LBBB here? Because the left bundle branch block would mean what? Close your eyes. It means I can't have proper conduction to the left bundle branch. So where is my depolarization passing through? Through the right bundle branch. So which valve is going to close first? Pulmonic, then your aortic. Is that clear? It has nothing to do with persistent split. That is called a paradoxical split, isn't it? So a left bundle branch block is going to give you a parodoxical split. Is that simple. In right bundle branch, it was going to give you something like your persistent or a widened split. Then we come to our fixed. Are we clear here? It is important that you pay attention to terminology. I want you to take a look at normal. We have gone through that plenty, just leave that alone. You know about the physiologic split.

    05:27 Now let us take a look at ASD. With atrial septal defect, this is my issue. It is the fact all of the time let us say that the most common genetically is ostium secundum. With an ostium secundum, say that the foraminal valves remain open and you would then create an atrial septal defect. What kind of shunt is that? A left to right shunt. So you are not going to have cyanosis, are you? No, because it's a left to right shunt. You can still have oxygenation to the tissue. That is not going to be an issue. But now with that blood, which is constantly moving, where are we moving from? Left atrium to right atrium, constantly. With the constant amount of blood going into the right atrium tell me about the pulmonic valve. It is always going to be fixed. It is always going to be widened. I want you to take a look at expiration, inspiration under fixed, our prime and main differential would be atrial septal defect in which there is not going to be any widening or physiologic split of A2, P2. We call this fixed. Number 1 differential, atrial septal defect. We will go one step further because any board exam clinically what have you, will want you to know or require you to know where on your chest you would hear the atrial septal defect murmur.

    06:48 But it first begins with your understanding of a fixed split. Now we have a paradoxical split. Now we can walk through this quickly. We have left bundle branch block. Take a look at normal please. A2, P2, expiration, inspiration. Take a look at paradoxical. What does paradoxical mean? Opposite.

    07:05 When was the last time you have heard of paradoxical? What is another common theme of paradoxial come into play? How about a paradoxial embolus? Remember DVT. A DVT would be a thrombus and if it embolizes, you end up in a pulmonary embolism. That is not paradoxical. But if you have something like a septal defect, then you might have a DVT, which will then embolize the opposite side and you call that what? A paradoxical embolus. Here we have a paradoxical split. Is that clear? So what is happening? There is no proper depolarization of the left bundle branch. So where is my conduction passing through? The right bundle branch. First P2, then A2. That is not normal. That is paradoxical split. What is another one? With an aortic stenosis, and we will get into this in a little bit. But it is a systolic murmur. The aortic valve does not want to open. And if it doesn't want to open, you are sure that it doesn’t want to close, so, therefore, you might have a paradoxical split. It is important that you understand the difference between number 1 physiologic split of S2. A widened split of S2. Differential right bundle branch block. Number 3, fixed split. Number 1 diagnosis, atrial septal defect. Are we good? Paradoxical split, simple.

    About the Lecture

    The lecture Respiratory Variation by Carlo Raj, MD is from the course Heart Sounds: Basic Principles with Carlo Raj.

    Included Quiz Questions

    1. Physiologic splitting of S2
    2. Fixed splitting of S2
    3. Widened splitting of S2
    4. Paradoxical splitting of S2
    5. Physiologic splitting of S1
    1. Delayed right ventricular emptying
    2. Delayed conduction through the left bundle branch
    3. Dilation of the aortic root
    4. Delayed left ventricular emptying
    5. Dilation of the pulmonic root
    1. Left bundle branch block
    2. Pulmonic stenosis
    3. Atrial septal defect
    4. Ventricular septal defect
    5. Aortic regurgitation
    1. Left-to-right shunt causing increased blood flow to the right side of the heart
    2. Right-to-left shunt causing increased blood flow to the left side of the heart
    3. Conduction delay with left bundle branch block
    4. Increased total peripheral resistance causing a reversal of a left-to-right shunt
    5. Decreased venous return reducing the amount of right ventricular filling
    1. Atrial septal defect
    2. Ventricular septal defect
    3. Pulmonic stenosis
    4. Aortic stenosis
    5. Aortic regurgitation
    1. Left bundle branch block
    2. Right bundle branch block
    3. Mobitz type II AV block
    4. Second degree AV block
    5. Atrial septal defect

    Author of lecture Respiratory Variation

     Carlo Raj, MD

    Carlo Raj, MD

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    Awesome lecturer.
    By Robert B. on 28. February 2022 for Respiratory Variation

    Love the way he teaches. Great sense of humor and very keen on review and incorporation of physiology.