Transcutaneous Electrical Nerve Stimulation on Nervous System in Patients With Hypertension.

Data collection was performed at the Laboratory of Clinical Investigation (LIC) Institute of Cardiology. Initially, patients rested for 30 minutes, and during this period has been completed the evaluation form with the identification data and questions about the patient's clinical status, such as checking blood pressure, weight and height. Patients were randomized to group of high frequency (100 Hz / 200μs), low frequency (4 Hz / 200μs) or placebo. The placebo group received an active current for 30 seconds, and then gradually decreased for 15 seconds to not pass any current. This approach aims at masking the investigator and subject (RAKEL et al., 2010). Eligible subjects were randomly assigned in blocks, by electronic randomization (www.randomization.com). The adhesive electrodes were used, size 9x5 cm, placed in bilateral paravertebral region of the T1 segment of the thoracic spine at L2 lumbar spine. Before the application of TENS (IBRAMED®), the skin was cleaned in place of the current application with alcohol to avoid any barrier conduction of electrical current. The sessions took place at the same time of the day, throughout the protocol, the participants were comfortably accommodated in an acclimatized room (23ºC) in a supine position, head elevation of 30º with knees resting on a wedge. All the participants were forbidden to perform exhaustive exercises and intake caffeine at least two hours before the intervention and instructed to have a meal before the assessment. TENS was applied for thirty minutes, with the frequency defined according to randomization. The intensity of the current was delivered at sensory-level intensity, adjusted every 5 minutes by the sensory threshold, during the 30 minutes as tolerated by each subject, but without motor contraction or pain reported by the subject. The analysis of autonomic control was performed by means of a sensor placed on the middle finger, and connected to the Finapres (Ohmeda 2300, Colorado, USA) by recording beat to beat. Then, the conversion signal was performed using the powerlab (LAB chart). The analysis will be performed using the software Kubios.