What would be the situation or conditions that make a Physical therapist to select continuous mode/intermittent mode/burst mode/acupuncture mode of using TENS? Is there any clinical guidelines or approved by APTA etc. between the preferred choice for using TENS by a PT?

TENS is a non-invasive method of electrical stimulation which primarily aims to provide a degree of symptomatic pain relief (of both acute and chronic pain presentations) by exciting sensory nerves and thereby stimulating either the pain gate mechanism and/or the opioid system.

The are no strict guidelines to the clinical applications of TENS. The effectiveness of TENS varies with the clinical pain being treated. In addition, the different methods of applying TENS are related to the different physiological mechanisms that accompany each pain presentation and sometimes, the patient’s tolerance. In other words, the PT is expected to apply his/her knowledge of the therapeutic benefits of the different TENS modes in order to determine which particular mode will be the most ideal as a pain management intervention depending on the specific pain presentation (and tolerance) of the patient.

For instance, with ‘normal/traditional’ TENS, the main pain relief is achieved during the stimulation, with a limited ‘carry over’ effect – i.e. pain relief after the machine has been switched off. With acupuncture (or lo) TENS, it takes some time for the opioid levels to build up, thus, the onset of pain relief may be slower than with the traditional mode. However, once sufficient opioid have been released, it will keep on working after cessation of the stimulation. Many patients find that stimulation at this low frequency at intervals throughout the day is an effective pain management strategy.

Furthermore, Brief intense TENS mode can be employed to achieve a rapid pain relief (e.g. in cases of acute presentations) but some patients find the strength of the stimulation too intense and will not tolerate it for sufficient duration to make the treatment worthwhile. Burst mode TENS interrupts the stimulation outflow at rate of 2 – 3 bursts/second. It is proposed that the application of Burst mode TENS can effectively stimulate both the pain gate and the opioid mechanisms simultaneously. Finally, in modulation mode, the machine delivers a less regular pattern of TENS stimulation in an attempt to reduce or minimize the accommodation effects of regular, patterned stimulation.

This link references an excellent article by Prof. Tim Watson on TENS which I highly recommend.

Reference 1