1. What happens to the blood pressure immediately on performing a Valsalva strain, and why?
ANS: During the strain, the blood pressure rises by an amount equal to the increase in intrathoracic pressure because the aorta, like all structures in the thorax, must reflect changes in intrathoracic pressure.
2. What happens to the blood pressure, pulse pressure, and heart rate while the strain is maintained for 10 s?
ANS: The blood pressure and pulse pressure decrease, and the heart rate increases. This occurs because the increased intrathoracic pressure obstructs venous return, and therefore progressively decreases stroke volume and cardiac output. The reflex sympathetic outflow due to the decreased stroke volume and blood pressure causes tachycardia.
3. What happens to the blood pressure, pulse rate, and heart rate on release of the strain?
ANS: For a few beats the blood pressure falls owing to decreased flow into the LV, because there are a few seconds of decreased flow from relatively empty pulmonary vessels. Then the blood pressure overshoots to above control levels and the pulse pressure increases because the increased sympathetic outflow caused by the Valsalva maneuver persists for at least 5-10 s after the release of the strain and increases peripheral resistance. Added to this is the temporary increase in venous return to the heart of blood that had been dammed up by the increased intrathoracic pressure. This flow reaches the LV after a few seconds and causes an increase in LV stroke volume. The increased pressure on the carotid sinus, in turn, causes a reflex bradycardia.
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Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...