Effect of Acu-TENS on airway obstructive disease

Abstract

Asthma and chronic obstructive pulmonary disease (COPD) are two conditions associated with airway obstruction which have a high global prevalence. Pharmacotherapy remains their mainstay of management but is associated with unwanted effects which has led to the application of alternative therapies, such as acupuncture. While acupuncture has been reported as a successful therapeutic adjunct for these conditions, it is itself invasive and requires an experienced acupuncturist to deploy this modality. Transcutaneous electrical nerve stimulation (TENS) is a non-invasive modality commonly used by the physiotherapist. When TENS is applied over acupuncture points (Acu-TENS), it has been shown to improve forced expiratory flow rate in the first second (FEV₁) in patients with COPD after one session of treatment. Neither the effect of Acu-TENS on patients with asthma, nor its long term effect, have been reported. This thesis first reports a pilot study which explored the effect of Acu-TENS on the post-exercise FEV₁and dyspnoea score, in eleven male subjects with normal health, (mean age of 25.0±1.3 years). These subjects acted as their own control and received in random order either, 1) Acu-TENS or 2) Placebo-TENS (same protocol but with no electrical output from the machine) for 45 minutes prior to a treadmill exercise test following the Bruce protocol, during two separate sessions, at least one week apart. TENS was applied to bilateral Dingchuan (EX-B1) and Lieque (LU 7) acupuncture points. Result of this pilot study showed that Acu-TENS was associated with a longer exercise duration (0.9±0.4 min, p=0.026) and a higher post-exercise FEV₁compared to Placebo-TENS (5.1±2.3%, p=0.047). This pilot study established that the Acu-TENS protocol adopted was safe and likely to enhance post-exercise bronchodilation which may facilitate exercise training in patients with asthma. This finding encouraged further investigation of the effects of Acu-TENS in patients with asthma and COPD. The first substantive study investigated the effect of Acu-TENS on post-exercise FEV₁in patients with asthma, adopting a similar stimulation protocol and testing method to that reported in the pilot study, except that a more conservative Naughton exercise protocol was adopted for exercise testing. Thirty subjects, mean age of 41.6±2.5 years, were randomly allocated into one of the three groups1) Acu-TENS, 2) Continuous-TENS (same as Acu-TENS but continued during the exercise test) and 3) Placebo-TENS (no electrical output from the TENS machine) prior to the treadmill exercise test. Monitoring of FEV₁was continued for 60 minutes after the exercise test. A longer exercise duration was achieved in both the Acu-TENS and Continuous-TENS groups compared to the Placebo-TENS group, but this did not reach a statistical significant value. Post-exercise decline in FEV₁(around 12%) was found in the Placebo-TENS group throughout the 60-minutes after exercise. In contrast, subjects in the Continuous-TENS group demonstrated an FEV₁raised from 1 to 6% at different measurement time points. Subjects in the Acu-TENS group showed an immediate decline in FEV₁(5.1%) after exercise, but then demonstrated an increasing trend to 2% above pre-exercise levels. The differences in the change of FEV₁did not reach statistical significance until 20 minutes after exercise. This effect remained until the 60-minute time point. These findings support the proposition that Acu-TENS is associated with a post-exercise bronchodilatory effect which appeared to be enhanced if the stimulation was continued during the exercise. The second and third studies evaluated the effectiveness of Acu-TENS (applied at Dingchuan, EX-B1) on patients with COPD. A possible association between Acu-TENS stimulation and blood endorphin and plasma inflammatory marker levels was also explored. Forty-four subjects, mean age of 69.1±1.6 years, were randomly allocated to receive either Acu-TENS or Placebo-TENS for 45 minutes. FEV₁, FVC, respiratory rate (RR), dyspnoea visual analogue scale (DVAS), β endorphin, Interleukin-8 (IL-8), C-reactive protein (CRP), Tumor necrosis factor-α (TNF-α)and differential white blood cells were measured. A post-intervention increase in FEV₁(19.6 %, p<0.001) and FVC (5.6%, p>0.05) were found in the Acu-TENS group compared to a decrease in the Placebo-TENS group (4.6%, p=0.026 and 4.6%, p=0.038 respectively). Both groups demonstrated a significant reduction in self perceived DVAS, however, the magnitude of reduction was 20.7% (p=0.006) greater in the Acu-TENS group. The post-intervention change in β endorphin levels was 18.3% (p=0.027) higher in the Acu-TENS group and was moderately correlated with the reduction in RR (p=0.033). These findings again confirmed that Acu-TENS was associated with improved FEV₁and that this could possibly be related to an increased β endorphin level. While the first few studies demonstrated an immediate post-stimulation positive effect of Acu-TENS on airway dilation, the last study evaluated the cumulative effect of daily Acu-TENS applied over 4 weeks. To ascertain if the stimulation was a result of point effect or a mere electrical effect, a sham group with TENS applied to a non-acupuncture point (Sham-TENS) was included in this study. The possible effect of Acu-TENS on autonomic nervous system modulation was also explored by analysis of the change in heart rate variability before and after the 4-week period. To determine if Acu-TENS has an accumulative effect which might lead to improvement of the distance covered in 6-minute walk test (6MWT) and the activity score obtained via the St. George's Respiratory Questionnaire (SGRQ), the 6MWT and SGRQ were included as additional outcome measures. Thirty subjects diagnosed with COPD, mean age of 71.9 ± 1.3 years, were randomly allocated into one of three groups: 1) Acu-TENS, 2) Placebo-TENS, 3) Sham-TENS (applied over the knee-cap) to receive a 4-week intervention program. Subjects in the Acu-TENS group attained a higher post-program increase in FEV₁and walking distance by 13.6% (p=0.012) and 11.4% (p=0.047) respectively, compared with the Sham-TENS group, while there was no difference when compared with the Placebo-TENS group (p>0.05). Immediate post-stimulation FEV₁measured during the first session of each of the 4 weeks showed that the improvement in FEV₁was most apparent at the beginning of the program, and more damped towards the end of the program. Psychosocial health is inversely related to the SGRQ activity score. Psychosocial health improved in the Acu-TENS group who showed a reduction in activity score (8.97±2.48, p=0.007) and total SGRQ score (5.17±5.41, p=0.028). Similar to the results in the previous study with patients with COPD, no statistically significant change in any inflammatory markers was found in any groups. There was however a significant rise in β endorphin level (p=0.012) observed in the Acu-TENS group. Spectral analysis of heart rate variability (HRV) provides information which reflects parasympathetic activity [high frequency (HF) changes] and combined parasympathetic and sympathetic activity [low frequency (LF) changes]. Modulation of autonomic nervous activity can be analyzed by changes in the logarithmic transformation of the power of LF and HF, or LF:HF, LF/(HF+LF) and HF/(HF+LF) ratios. This study showed a significant reduction in the LF data observed in Acu-TENS group (p=0.034) but not in the other groups. The findings suggest a 4-week Acu-TENS program may result in a decrease in sympathetic activity. In accord with the other studies reported in this thesis, this study showed that Acu-TENS was associated with improvement in FEV₁but the effect did not seem to be accumulative nor long lasting. Application of Acu-TENS for 4-weeks however led to improved physical activity. The working mechanism of Acu-TENS appeared to be associated with an increase in β endorphin levels but its effect on autonomic nervous system modulation was not apparent. In conclusion, the work in this thesis supports the effect of Acu-TENS on improvement in FEV₁and dyspnoea score in subjects with obstructive airways disease. The mechanisms involved are likely to be associated with an increase in β endorphin levels.