Shocking: Electric Pulses Relieve Pain

Pictured above Oscium’s iMSO measures the electrical pulses at the output of a medical device frequently used for managing chronic pain. Modern technology has given pain management specialists an alternative to prescriptions or surgery for treating patients suffering from mild to severe chronic pain. These potable, battery powered medical devices provide a variety of therapeutic electrical stimulus programs. With iMSO-104 users can capture the stimulus waveforms for comparison and analysis.

Definitions:

  • TENS: Transcutaneous electrical nerve stimulation (TENS) is the use of electric current produced by a device to stimulate the nerves for therapeutic purposes.
  • Transcutaneous: a procedure that is performed through the skin.

View TENS Waveform Using iPhone Oscilloscope

Captured in the screenshot below is the output waveform from one channel of a AA battery powered TENS unit. Two cycles of the program are visible. Most notable details of the captured waveform for this particular program are the frequency (120 Hz) and the maximum peak voltage (42.7 V). According to online resources describing the theory behind this treatment protocol, TENS is successful when used with lower frequencies a voltage levels that do not induce muscle contractions. In this specific instance, muscle contractions occurred when the amplitude exceeded 60 Vp-p.

Figure 1: TENS output waveform captured with iMSO oscilloscope and iPhone display.

Benefits of TENS Therapy

The nervous system in the human body responds to electrical impulses to perform voluntary and involuntary functions. People can use this artifact of human anatomy with some simple electronics to manage chronic pain. Here are some accepted reasons for the effectiveness of this method: (medical-dictionary.thefreedictionary.com)

  1. Interruption of pain impulses from the periphery to the central nervous system
  2. Increased production of endorphins
  3. Improved blood supply to the affected part; increased circulation encourages healing and helps reduce muscle spasm.

TENS Waveforms for Different Therapy Programs

There seems to be three common elements to the TENS units investigated for this post, from the data available online. Simply put, the three elements of a TENS circuit fall out as follows:

  1. Waveform generator: The signal parameters that vary are amplitude, frequency, and pulse width. These parameters are adjusted with analog RC tuning circuits or controlled precisely using a digital controller. Waveform shaping control signals often take the form of a saw tooth, a pulse (square wave), or a step function.
  2. Transistor stage: The driving signal is applied to the gate of a transistor. As the transistor switches on and off, following the driving signal, a small current is permitted to flow from the battery, through the transistor, and through a coil. The coil in this leg of the circuit is one half of a magnetically coupled coil pair. The relative sizes between the two halves determines whether or not the output is larger or smaller than the signal at the input.
  3. Output stage: The second half of the magnetically coupled coils forms the TENS unit output stage. The semi-adhesive pads of the TENS unit, red for positive and black for negative, are connected across the terminals of the coil.


Figure 2: Functional diagram of the three circuit elements in common TENS units. 

Figure 3: Most TENS units consist of the electrodes/pads, a pair of positive and negative leads, and the TENS unit itself.

Oscium's handheld oscilloscope is now available with universal platform support! So, if you're interested in using the scope on iOS, Android, PC or Mac, Oscium supports you. Please go to iMSO-204x for more information.