During a transcutaneous electrical nerve stimulation (TENS) session for back pain, the patient reports a painful response during initial treatment while using biphasic pulsed current with conventional parameters. Which modification is MOST appropriate?

During a transcutaneous electrical nerve stimulation (TENS) session for back pain, the patient reports a painful response during initial treatment while using biphasic pulsed current with conventional parameters. Which modification is MOST appropriate?

• A. Decrease electrode size
• B. Decrease pulse width
• C. Increase pulse rate
• D. Switch to a monophasic current

Answer: (B)

When a patient reports a painful response during a TENS session with conventional biphasic pulses, the most effective adjustment is to shorten the pulse width. A shorter pulse width reduces the charge delivered per pulse (charge ≈ current × time), which lowers stimulation of the small nociceptive fibers while still allowing activation of the larger A-beta fibers that produce analgesia through the gate-control mechanism. This can make the sensation more comfortable without losing the therapeutic effect. Other changes are less helpful in this situation: using smaller electrodes would increase current density and potentially worsen discomfort; increasing the pulse rate can change the perceptual quality of the sensation without reliably reducing pain; switching to a monophasic current introduces different tissue effects and often more irritative sensations.

When a patient reports a painful response during a TENS session with conventional biphasic pulses, the most effective adjustment is to shorten the pulse width. A shorter pulse width reduces the charge delivered per pulse (charge ≈ current × time), which lowers stimulation of the small nociceptive fibers while still allowing activation of the larger A-beta fibers that produce analgesia through the gate-control mechanism. This can make the sensation more comfortable without losing the therapeutic effect.

Other changes are less helpful in this situation: using smaller electrodes would increase current density and potentially worsen discomfort; increasing the pulse rate can change the perceptual quality of the sensation without reliably reducing pain; switching to a monophasic current introduces different tissue effects and often more irritative sensations.