A Randomized Double-Blind Study Testing the Effects of Pregabalin on Diabetic Neuropathy

The LifeShirt System, developed by VivoMetrics, is a lightweight vest with embedded sensors that continuously collect information on a range of cardiopulmonary parameters. It was used to collect and store the respiratory rate, posture, activity level, QRS complexes, and R-R intervals via a 3-axis accelerometer and a 3-lead, single channel electrocardiogram.

Heart rate variability parameters generated by the frequency domain analysis included: total power (area under the curve) over all frequencies, very low frequency (VLF, 0-0.04 Hz),low frequency (LF, 0.04-0.15 Hz), and high frequency (HF,0.15-0.4 Hz).

Heart Rate Variability parameters generated by the frequency domain analysis included: Low Frequency / High Frequency (LF/HF), as well as normalized LF (normalized LF=LF/[total power-VLF]) and normalized HF (normalized HF=HF/[total power-VLF]).

Heart rate variability parameters yielded by time domain analysis included the mean of all R-R intervals (ANN), standard deviation of all R-R intervals (SDNN), root mean square of successive differences (RMSSD), and standard deviation of the averages of R-R intervals for all 5-minute segments within the block (SDANN).

Heart rate variability parameters yielded by time domain analysis included the number of N-N intervals that differ by more than 50 milliseconds from adjacent intervals divided by the total number of all N-N intervals (pNN50).

Pain severity was evaluated using the Visual Analog Scale, the Modified Brief Pain Inventory-Short Form, and the Neuropathy Pain Scale. The Visual Analog Scale was scored within a range of 0-100 with 0=no pain and 100=the worst imaginable pain. The Brief Pain Inventory is made up of two parts: total pain and pain interference. The total pain score is the sum of most, least, average, and now pain scored within a range of 0-10 with 0=no pain and 10=pain as bad as you can imagine. The pain interference score is the sum of affective and activity interference - how pain interfered with general activity, mood, walking ability, normal work, relationships, sleep, and enjoyment of life. It was scored within a range of 0-10 with 0=pain does not interfere and 10=pain completely interferes. The Neuropathy Pain Scale total is the sum of 10 items -cold, sharp, deep, dull, hot, intense, itchy, sensitive, surface, and unpleasant pain scored within a range of 0-10 with 0=no pain and 10=most pain.

Anxiety symptoms were measured using the Spielberger State-Trait Anxiety Inventory Scale (STAI) for symptoms of anxiety. State anxiety: score range, 20-80 (higher score=greater levels of state anxiety). Trait anxiety: score range, 20-80 (higher score=greater levels of trait anxiety).

The Beck Depression Inventory Scale measures symptoms of depression, score range, 0-63 (higher score=greater severity of depressive symptoms)

The Sheehan Disability Scale was used to evaluate functional impairment in work/school, social and family life, score range, 0-10; the 3 items can be summed into a single dimensional measure of global functional impairment that ranges from 0(unimpaired) to 30 (highly impaired).