Overview :
The Valsalva Ratio is used to indirectly
measure assess the blood pressure response to a Valsalva
procedure, when direct arterial line measurement is not
available.
During the Valsalva maneuver, 4 phases are
seen normally:
(1) phase 1:
due to intrathoracic and intra-abdominal pressure there is
aortic compression and an increase in peripheral resistance
that results in a transient decrease in heart rate and an
increase in blood pressure;
(2) phase 2:
the increase in intrathoracic pressure results in a decrease
in venous return and cardiac output, with a compensatory
increase in heart rate
(3) phase 3:
once the expiration stops, there is a further drop in blood
pressure as the aortic compression stops;
(4) phase 4:
the blood pressure increases as the cardiac output increases,
resulting in a reflex bradycardia.
Patient Instructions: The patient exhales
against a resistance of 40 mm Hg for 20 seconds.
Valsalva ratio =
= (longest R-R interval in phase 4) /
(shortest R-R interval in phase 2)
Interpretation:
A ratio > 1:20 is normal.
A ratio <= 1:20 is abnormal.
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