ISCHEMIA-INDUCED REDUCTION OF SOMATOSENSORY INPUT DECREASES BALANCE; ADDED VIBRATORY NOISE PARTIALLY RESTORES FUNCTION

In this project we mimicked loss of sensation in the feet, commonly seen in diabetic patients, through an ischemic protocol, a reduction of circulation in young healthy adults. This loss of sensation resulted in changes in balance like those seen in diabetic patients that are prone to falls. We then tested the effectiveness of a vibratory device to improve balance. Purpose (a): We investigated the feasibility of using vibrotactile biofeedback to improve balance in healthy young adults in which the somatosensory information from their feet has been temporarily decreased. We hypothesized that though stochastic resonance, vibratory noise applied just proximal to a region of reduced somatosensation will improve ability to maintain balance. Methods (b): Ten healthy young individuals aged 18 to 25 years old gave informed consent and participated in this study. We experimentally induced “somatosensory loss” in non-diabetic young healthy subjects using pressure cuffs wrapped around the ankles, kept inflated at 220-250mmHg for 35 min. A vibrotactile biofeedback system was positioned just above the pressure cuffs. An array of vibrotactile actuators, under a Texas Instruments MSP430 microcontroller, produced vibration at two frequencies: a barely perceptible low frequency and a high vibration frequency. Data was collected at baseline before the pressure cuffs were inflated and during the last 15 minutes of the ischemic protocol under three conditions: no vibration, low frequency and high frequency vibrations. Outcome measures included: centre of pressure (COP) variability with subjects standing with feet side by side/ one foot, with eyes open/closed; plantar surface pressure sensation and vibratory threshold evaluated with Siemens Monofilaments and Rydel-Seiffer tuning fork, respectively. Results (c): In single limb support with eyes closed, ischemia increases the COP variability (p=.01) and the addition of vibrotactile feedback at both frequencies decreases it baseline values. Plantar surface pressure sensation threshold increased after ischemia (p=.03) and was decreased with the added vibrotactile feedback. The vibratory extension threshold measured at the hallux IP joint was decreased by ischemia (p. Conclusions (d): The ischemic protocol produced balance changes in healthy young adults. The vibratory biofeedback was able to partially compensate for the experimental induced sensory loss and improve balance function. Most diabetic patients become “visually dependent” due to peripheral neuropathy, and may experience falls at night or when they turn their head or talk to someone while walking. The next step of this research is to test the effectiveness of a vibrotactile biofeedback to decrease the risk for falls in diabetic adults with peripheral neuropathies