Effect of Position on Valsalva Maneuver: Supine vs. 20 Degree Position

摘要

Blood pressure (BP) changes in response to the Valsalva maneuver (VM) reflect the integrity of the baroreflex that regulates BP. Performing this maneuver in the standard supine position often prevents adequate venous preload reduction, resulting in a rise rather than a fall in BP, the “flat top” Valsalva response. We determined whether performing the Valsalva Maneuver (VM) at a 20 degree angle of head up tilt (20_deg) improves preload reduction, thereby reducing the frequency of flat top responses, improving reflex vasoconstriction, and increasing the Valsalva ratio (VR). 130 patients were evaluated in a prospective study. Each patient performed the VM in both supine and 20_deg positions.Flat top responses were present in 18% of subjects when supine. 20_deg position reduced the flat top response by 87%. The components of the response that are dependent on preload reduction (VR and phases II_E, II_L, and IV) also showed significant improvement with 20_degree.A 20 degree angle of tilt is sufficient to reduce venous preload, decreasing flat top response rate and improving the VR and the morphology of the VM. We recommend this modification for laboratory evaluation of the VM, whenever a “flat-top” response is seen.