Tilt table design for rapid and sinusoidal posture change with minimal vestibular stimulation.

Introduction: Cardiovascular response to fast posture change can be used to model individual orthostatic response under normal circumstances and after spaceflight. We set out to construct a computer-controlled tilt table suitable for repeated sinusoidal tilt motion as well as fast, single head-up tilt (HUT). The movement profile of the table was designed to prevent muscle tensing and limit vestibular stimulation.

Methods: On the new table, 20 healthy subjects underwent a protocol of fast HUT and sinusoidal tilt motion at 2.5 tilts per minute. BP was measured non-invasively (Finapres). Time domain dynamic response to HUT and frequency domain response to sinusoidal tilts were derived from the beat-to-beat BP and from interbeat-interval (IBI) series.

Results: Tilt motion did not induce dizziness and was experienced by all subjects as smooth. The systolic BP response to fast HUT correlated mildly with the systolic BP spectral power at the sinusoidal tilt frequency (R = 0.47). The IBI response to fast HUT correlated well with the IBI power at the sinusoidal tilt frequency (R = 0.74).

Discussion: In this study we presented a computer controlled tilt table capable of fast posture change and sinusoidal tilts. An exploratory protocol demonstrated that the table is suitable for obtaining cardiovascular response to posture change for modeling purposes.