A new transient sham TENS device allows for investigator blinding while delivering a true placebo treatment

Abstract

This study compared a new transient sham transcutaneous electrical nerve stimulation (TENS) that delivers current for 45 seconds to an inactive sham and active TENS to determine the degree of blinding and influence on pain reduction. Pressure-pain thresholds (PPT), heat-pain thresholds (HPT), and pain intensities to tonic heat and pressure were measured in 69 healthy adults before and after randomization. Allocation investigators and subjects were asked to identify the treatment administered. The transient sham blinded investigators 100% of the time and 40% of subjects compared to the inactive sham that blinded investigators 0% of the time and 21% of subjects. Investigators and subjects were blinded only 7% and 13% of the time, respectively, with active TENS. Neither placebo treatment resulted in significant changes in PPT, HPT, or pain intensities. Subjects using higher active TENS amplitudes (> or =17 mAs) had significantly higher PPTs and lower pain intensities to tonic pressure than subjects using lower amplitudes (<17 mAs). HPTs and pain intensities to tonic heat were not significantly changed. The transient TENS completely blinds investigators to treatment and does not reduce pain, thereby providing a true placebo treatment.

Perspective: This article presents the benefits of a new transient sham TENS device for use in prospective, randomized, clinical trials. This device facilitates blinding of subjects and investigators to eliminate expectation bias and determine the true efficacy of TENS for use in clinical populations.

Figure 1

CONSORT trail flow-chart.

Figure 2

Pressure temporal summation measurement during TENS application. Pressure device includes a pressure transducer and a lever with a movable weight to grade the force delivered. The pressure stimulus is delivered through a 1 cm² probe over the extensor muscle mass.

Figure 3

Percent change from baseline to after treatment for: A) heat pain thresholds; and B) pressure pain thresholds for each group (Active TENS, Inactive Placebo TENS, and Transient Placebo TENS.

Figure 4

Temporal summation to pressure and heat stimuli. A) Pressure pain intensity scores pre and post treatment for each group from 0–120 seconds; B) Average pressure pain intensity scores pre and post treatment for each group; C) Heat pain intensity scores pre and post treatment for each group from 0–120 seconds; D) Average heat pain intensity scores pre and post treatment for each group. A=Active TENS; IP=Inactive Placebo TENS; TP=Transient Placebo TENS.

Figure 5

A) Scatter plot and correlation between percent change in Pressure Pain Threshold (PPT) and TENS pulse amplitudes; B) percent change in PPT for low (0–16mA) and high (17–25mA) TENS pulse amplitudes; C) scatter plot and correlation between change in average pain intensity during temporal summation and TENS pulse amplitudes; D) change in average pain intensity scores during pressure temporal summation and low (0–16mA) and high (17–25mA) TENS pulse amplitudes. Those receiving higher TENS pulse amplitudes in the active TENS group (17–25mA; N = 17), had a significant increase in PPT compared to those receiving lower pulse amplitudes (< 17mA; N = 13)(F1,29 = 9.8, p = 0.004).