robin082006
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Physiological S2 splitting: inspiration-->decreased intrathoracic pressure--->increased venous return to right heart-->increased right heart preload.
I look for increaed right ventricular preload but no see. So I go with D
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| nadiabarati
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my answer was D also. But the correct answer is C! and I don't understand why?
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| nadiabarati
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Option C (Right ventricular afterload decreases) is correct. More negative intrathoracic pressure on inspiration increases transmural pressure across the pulmonary vasculature, dilating vessels and reducing impedence (afterload) to the right ventricle. Duration of right ventricle ejection is longer, delaying pulmonic valve closure.
here is the explanation! I don't get it
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| robin082006
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Neither do I.
Do not understand the last sentence.
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| general malaise
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hmmm....how i understand it is its basically saying that during inspiration pulmonary vascular resistance decreases therefore allowing more blood to be pumped out of the RV, and since more blood being pumped out it causes the delay of pulmonary valve closure since there is increased pressure in RV
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| drpkaur
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Physiological S2 splitting: inspiration-->decreased intrathoracic pressure--->increased venous return to right heart-->increased right heart preload
therefore right ventricular output is increased,then pulmonary vessels expand and resistance toblood flow from pulmonary artery to rt ventricle decreases(afterload) so that blood flows easily to pulmonary circiut and volume of blood in pulmonary circuit increases....so rt ventricular afterload decreases..
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| robin082006
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Dear drpkaur,
The question asks what change contributes to splitting, not simply the change associates with splitting. That make people confuse.
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| doc179
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I think both generalmalaise and drpkaur are right
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| nadiabarati
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generalmalaise decreased afterload means that less resistance to blood outflow so less time is needed for blood to eject out of right ventricle! why do you say more time
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| drpkaur
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hi guys
i searched for this info here and there and now i found that in detail as follows ok-mechanism of physiological S2 splitting: During inspiration,more neg intrathoracic pressure-blood is drawn into thorax and the the right ventricular stroke volume increases.the duration of Rt ventricular systole lengthens and P2 component is slightly delayed...Conversely the left ventricular stroke volume falls during inspiration because the greater negative intrathoracic pressure enlarges the capacity of the left atrium and pulmonary veins and reduces left atrial pressure and hence left ventricular filling and stroke volume ..thus the Left ventricular systole is shortened and A2 occurs earlier and P2 later so that the splitting of the second sound widens...........
During expiration ,the changes are exactly opposite and the splitting narrows.....
this is the whole process regarding splitting S2....rest i have made clear earlier in my previous message..
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