Can a carbon dioxide laser substitute for moxibustion?

Abstract

Dear Sirs, Thank you for the opportunity to respond to the letter to the editor from Drs. Jang and Park. We welcome and appreciate comments from readers of the journal and believe that discussion helps to improve clinical research in the field. We are pleased that our article [1] has generated a discussion and raised an important question: “Can a carbon dioxide laser substitute for moxibustion?” This was one of the questions that we attempted to answer in our pilot study. We concluded that the carbon dioxide (CO2) laser mimics and simulates moxibustion based on two facts: (1) the CO2 laser has a thermal effect similar to that of moxibustion. We previously reported that, after 3 min, a CO2 laser applied to an acupuncture point on a healthy volunteer raised the skin temperature by 1.22±0.37°C, indicating that the CO2 laser has a fairly persistent thermal effect [2, 3]. (2) The wavelength of the CO2 laser is very close to that of traditional moxibustion. The CO2 laser wavelength is reported to be 10.6 μm [4], which can be absorbed by the epidermis to a depth of 0.2 mm, while the wavelength of the infrared radiation peak of traditional indirect moxibustion is approximately 10 μm [5]. Dr. Jang and Dr. Park suggest in their letter that moxibustion heat reaches a different depth from that of the CO2 laser. To support this notion, one must know the thermal radiation depth reached by both laser and moxibustion. But, although there are reports that the thermal energy of the CO2 laser penetrates the epidermis to a depth of 0.2 mm [4, 6], there are no reports on the depth of penetration by moxibustion thermal radiation. We agree with the correspondents that a high drop-out rate in the control group at the 4-week time point is problematic. However, we only analyzed and reported the data from the 2-week time point, which had a relatively lower drop-out rate (4/20 of the control group and 1/20 of the treatment group) [1]. This should not cause the blinding issue that concerns the correspondents. Furthermore, as reported in our results, we asked patients to give their reasons for dropping out of the study. Of the total of 11 drop-outs in the placebo control group, four felt the treatment was “ineffective,” four were “too busy” to continue treatment, and three were lost to follow-up. None of these patients indicated that they were dropping out because they believed that they were assigned to the placebo control group. As most laser devices do not produce a thermal effect, patients were not aware that they were supposed to feel heat during the treatment. This method for validating blinding has been widely used and reported by others in the acupuncture literature [7], and, according to the data from our study, there is no evidence to show that the blinding in our study was unsuccessful, as assumed by the correspondents. Thus, we are confident with our conclusion that patient blinding was successful. However, as we indicated in the title of the article, this was a ‘pilot study’ to explore the feasibility of a clinical trial. Lasers Med Sci (2009) 24:291–292 DOI 10.1007/s10103-008-0587-6