Relationships between physiological responses and presyncope symptoms during tilting up in patients with spinal cord injury

This study attempted to use the eyesight range to quantify presyncope symptoms (PS), assess the relation between angle of head-up tilt, severity of injury on the American Spinal Injury Association (ASIA) scale, and PS on physiological signals, and determine the notable signals that represent PS in spinal cord injury (SCI) patients. Thirty-eight quadriplegic SCI subjects were recruited, in which the mean blood pressure (MBP), oxygen saturation (SpO₂), heart rate (HR), and the low-frequency/high-frequency (LF/HF) ratio of the HR variability were measured during tilting up of the head. The SpO₂ and LF/HF differed significantly with the level of PS. These findings of the studied variables suggest that SpO₂ and LF/HF are the physiological signals that are most sensitive to detect in PS, and could be used for the optimal biofeedback design of tilt-table training systems aimed at overcoming posture hypotension in SCI patients.