Effect of head-up tilt on cardiovascular responses in normal young volunteers.

Since the cardiovascular effects of tilting are influenced by degree as well as duration of the tilt, we planned to study the time course of blood pressure and heart rate (HR) responses during 30 degrees, 60 degrees, 80 degrees head up tilt (HUT). The study was conducted on 20 volunteers aged 18-20 y who were tilted on a tilting table. Blood pressure was determined by sphygmomanometer and HR was calculated from R-R interval of ECG. 30 degrees HUT produced an insignificant decrease in systolic pressure (SP) and pulse pressure (PP) while diastolic pressure (DP), mean pressure (MP) and rate-pressure-product (RPP) registered an insignificant rise. The changes produced by 60 degrees and 80 degrees HUT were more marked than those produced by 30 degrees HUT. While SP and PP decreased significantly, HR and RPP increased significantly. In conclusion, 30 degrees HUT produces insignificant changes while 60 degrees and 80 degrees HUT produce significant changes in SP, PP and RPP.