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.
