The effect of chest wall transcutaneous electrical nerve stimulation on dyspnoea.

We studied the effects of transcutaneous electrical nerve stimulation (TENS) over the chest wall on breathlessness in normal subjects during exercise. Eleven male subjects performed a progressive incremental exercise test to break point on four consecutive days. TENS (continuous form, frequency 100 Hz, pulse width 200 microseconds) was applied during three of these tests-over the second intercostal spaces during inspiration ('in phase' with the underlying inspiratory muscle contraction) or expiration ('out of phase' with contraction) or over the deltoid muscles during inspiration (control), and not on the fourth occasion in random order. Breathlessness (Borg scale), heart rate, respiratory frequency, tidal volume, minute ventilation and minute oxygen uptake were measured. No significant differences were found for any of the measured variables between the four study days. We conclude that TENS under these circumstances has no effect on the sensation of breathlessness or on the measured physiological variables in normal subjects during exercise.