Abstract
Far-infrared (FIR) radiation therapy has been used for soothing effect in wound treatment. Studies have shown that FIR could enhance wound healing processes in rat models. Although these research results supported that FIR may play an important for wound healing, it had no consensus in clinical practices. It is suggested that more persuasive systemic clinical researches are needed to explore the effectiveness of FIR therapy for wound healing.
Keywords: far-infrared, wound healing, clinical research
Dear Editor,
Far-infrared (FIR) radiation is an electromagnetic spectrum with a wavelength of 3 to 100 μm. It has been observed that FIR can stimulate cell proliferation, increase tissue regeneration in vitro, and increase the topical skin temperature.1,2 Recent studies have been demonstrated that FIR has been used for soothing effect and reducing pain of the wound site after standard medical wound treatments, even in clinical observations where wounds under exposure to FIR decreased the wound healing times.3,4 However, FIR treatment is considered as an alternative medicine because no consensus has been reached regarding its role in the treatment of wounds.
This study is based on a medical literature review on the effects of FIR in the wound healing process. Studies written in English were searched in the PubMed database from January 1980 to August 2015 using the keywords “far infrared,” “wound,” and “healing.” The references cited in the articles retrieved from the search were also cross-searched. We focused on study design, period, and the outcomes from all the studies included. Related studies were assigned to the appropriate “level of evidence” according to the Oxford Centre for Evidence-Based Medicine 2011. There studies involved the inclusion criteria (Table 1).
Table 1.
Studies That Investigated the Application of Far-Infrared (FIR) in Wound Healing.
| No. | Authors | Year | Study Groups | FIR Treatments | Treatment Durations | Significance of Treatment Outcomes | Level of Evidence |
|---|---|---|---|---|---|---|---|
| 1 | Chew-Wun Wu et al | 2006 | Devascularization: Flap group, n = 6; ischemia-flap group, n = 6; and reperfusion-flap group, n = 6 | FIR emitter: generated 5-12 μm with a peak at 8.2 μm. Above rat at 20 cm | Time effect of FIR therapy and post-FIR effect: FIR for 30 minutes (n = 6), 45 minutes (n = 6), or 60 minutes (n = 6) | Skin blood flow increased significantly after the removal of the FIR emitter (P < .05 compared to baseline) | V |
| 2 | Yasuo Kamiyama et al | 2003 | Full-thickness skin wound on all rats. Control group at 24.0°C to 25.0°C (n = 10); Group A exposed to FIR at 26.5°C to 27.5°C (n = 50), and Group B absence of FIR at the 6.5°C to 27.5°C (n = 50) | FIR emitter, 40 cm above the rats, from the ceramic-coated sheet ranged from 5.6 to 25 μm with a maximal intensity of 8 to 12 μm | For 14 days | 1. Healing rate: Group A was faster than Group B and control group (P < .0172) | V |
| 2. Fibroblast infiltration: Group A was greater than Group B (P < .0183) | |||||||
| 3. Collagen regeneration: Group A was greater than Group B (P < .001) | |||||||
| 4. Secretion of TGF-1: Group A was greater than Group B (P < .001) | |||||||
| 5. Collagen area: Group A was greater than Group B (P < .0124) | |||||||
| 3 | Paturu Kondaiah et al | 2007 | Two tooth extraction wound sites in opposite arches (n = 30) | Low-power FIR laser irradiation exposure randomly to one site of wounds | 14 days | TGF-β1 expressed in laser-irradiated wounds (P < .05) | V |
It was indicated that FIR did not enhance the blood flow of the interested area during the exposure, but after removing the FIR source, the blood flow increased.5 Another study showed that rats with a full thickness wound on its dorsal side under FIR exposure had a better healing rate and also more fibroblast and collagen aggregations than other rats that did not undergo FIR treatment.6 Only in the animal model and tooth extraction wound sites were the induced expressions of TGF-β1 identified after FIR exposure.7
From these studies, the authors found that FIR enhanced or stimulated biological effects such as increasing the blood flow of the exposure site, fibroblast proliferation, collagen fiber generation or accumulation, and TGF-β1 secretion. Although these phenomena are key elements for increasing wound healing, it cannot be said that putting it into clinical practice of wound care will provide similar results. Furthermore, among these studies, tissues were affected by electronically generated FIR sources, which produce heat and FIR at the same time. It was hard to clarify that these observations were due to electromagnetic radiation or heat-activated systemic reaction such as enhancing microcirculations. Therefore, non-electronically generated FIR sources (nonheating device) should be used for further animal or clinical studies. Further studies are required not only to evaluate the effectiveness, such as enhancing microcirculation, of FIR in the clinical setting, but also to reveal the latent mechanism experimentally to fit in the last piece of the puzzle into the whole picture.
Acknowledgment
We thank Professor Dr Tse-Hao Ko, Feng-Chia University, for his critical review of the article.
Footnotes
Author Contributions: Dr Lin and Dr Li searched the PubMed database for relevant articles. Dr Lin prepared the initial draft of this article. Final correction was done by Dr Li.
Declaration of Conflicting Interests: The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding: The authors received no financial support for the research, authorship, and/or publication of this article.
Ethical Approval: As this study did not involve animals, ethical approval was not required.
References
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