Water-filtered infrared-A (wIRA) in acute and chronic wounds

Abstract

Water-filtered infrared-A (wIRA), as a special form of heat radiation with a high tissue penetration and a low thermal load to the skin surface, can improve the healing of acute and chronic wounds both by thermal and thermic as well as by non-thermal and non-thermic effects. wIRA increases tissue temperature (+2.7 degrees C at a tissue depth of 2 cm), tissue oxygen partial pressure (+32% at a tissue depth of 2 cm) and tissue perfusion. These three factors are decisive for a sufficient supply of tissue with energy and oxygen and consequently also for wound healing and infection defense. wIRA can considerably alleviate pain (without any exception during 230 irradiations) with substantially less need for analgesics (52-69% less in the groups with wIRA compared to the control groups). It also diminishes exudation and inflammation and can show positive immunomodulatory effects. The overall evaluation of the effect of irradiation as well as the wound healing and the cosmetic result (assessed on visual analogue scales) were markedly better in the group with wIRA compared to the control group. wIRA can advance wound healing (median reduction of wound size of 90% in severely burned children already after 9 days in the group with wIRA compared to 13 days in the control group; on average 18 versus 42 days until complete wound closure in chronic venous stasis ulcers) or improve an impaired wound healing (reaching wound closure and normalization of the thermographic image in otherwise recalcitrant chronic venous stasis ulcers) both in acute and in chronic wounds including infected wounds. After major abdominal surgery there was a trend in favor of the wIRA group to a lower rate of total wound infections (7% versus 15%) including late infections following discharge from hospital (0% versus 8%) and a trend towards a shorter postoperative hospital stay (9 versus 11 days). Even the normal wound healing process can be improved. The mentioned effects have been proven in six prospective studies, with most of the effects having an evidence level of Ia/Ib.wIRA represents a valuable therapy option and can generally be recommended for use in the treatment of acute as well as of chronic wounds.

Keywords: absent expenditure of material; acute wounds; chronic venous stasis ulcers of the lower legs; chronic wounds; contact-free method; energy supply; immunomodulatory effects; infection defense; inflammation; infrared thermography; infrared-A radiation; oxygen supply; problem wounds; prospective, randomized, controlled, double-blind studies; quality of life; reduction of pain; thermal and non-thermal effects; thermic and non-thermic effects; thermographic image analysis; tissue blood flow; tissue oxygen partial pressure; tissue temperature; visual analogue scales (VAS); water-filtered infrared-A (wIRA); wound exudation; wound healing; wound infections.

Figure 1. Spectral solar irradiance outside the atmosphere and on the surface of the Earth at sea level,

in both cases with the sun at the zenith and for a mean Earth-sun distance. Shaded areas indicate absorption before reaching the surface of the Earth at sea level due to the atmospheric constituents shown (from [1], [58], adapted from [59]). For comparison of Figures 1 and 3: 1000 W · m^–2 · µm^–1 = 100 mW · cm^–2 · µm^–1 = 1 mW · cm^–2 · (10 nm)^–1

Figure 2. Cross-section of a water-filtered infrared-A radiator (Hydrosun, Müllheim, Germany)

The whole incoherent non-polarized broadband radiation of a 3000 Kelvin halogen bulb is passed through a cuvette containing water, which absorbs or decreases the undesired wavelengths within the infrared region (most parts of infrared-B and -C and the absorption bands of water within infrared-A). The water is hermetically sealed within the cuvette. A fan provides air cooling of the cuvette to prevent the water from boiling. (from [1])

Figure 3. Comparison of the spectra of the sun on the surface of the Earth at sea level and of a water-filtered infrared-A radiator

Spectral solar irradiance on the surface of the Earth at sea level (with the sun at the zenith and for a mean Earth-sun distance) as in Fig. 1 (from [1], adapted from [58]) and spectral irradiance of a water-filtered infrared-A radiator (Hydrosun^® radiator 501 with 10 mm water cuvette and orange filter OG590) at approximately 210 mW/cm² (= 2.1 · 10³ W/m²) total irradiance (from [1], [4]). The spectrum of the sun at sea level includes ultraviolet radiation (UV, <400 nm), visible light (VIS, 380–780 nm), and infrared radiation (IR, >780 nm). The spectrum of the water-filtered infrared-A radiator includes only visible light (VIS) and infrared radiation (IR); the visible part depends on the color filter used; the wIRA radiator does not emit ultraviolet radiation (UV). Both spectra show the decreased irradiances of the absorption bands of water.

Figure 4. Comparison of irradiation with water-filtered infrared-A and with conventional infrared

Thermographical comparison of skin surface temperatures in the lumbar region 12 minutes after commencement of irradiation with water-filtered infrared-A (left) and conventional infrared (right) with the same irradiance: the skin surface temperature is higher in the case of irradiation with conventional infrared (presented in the thermography), while the temperature at 1 cm tissue depth is higher when irradiating with water-filtered infrared-A (from [1], [20]). Water-filtered infrared-A thus leads to a high tissue penetration combined with a low thermal load to the skin surface.

Figure 5. Example of an irradiation of a wound with a water-filtered infrared-A radiator

(published with kind approval of Prof. James Mercer, Tromsø/Norway) (from [1], [23])

Figure 6. Decrease of postoperative pain during irradiation in the group with water-filtered infrared-A (wIRA) and visible light (VIS) and in the control group with only visible light (VIS) (Study Heidelberg)

assessed with a visual analogue scale; given as minimum, percentiles of 25, median, percentiles of 75, and maximum (box and whiskers graph with the box representing the interquartile range), from [2], adapted from [19]). During 230 single irradiations with wIRA(+VIS) the pain decreased without any exceptions, while pain remained unchanged in the control group (p<0.000001 for any single documented day as well as for all the days).

Figure 7. Required dose of analgesics of the subgroups with water-filtered infrared-A (wIRA) and visible light (VIS) in relation to the control subgroups with only visible light (VIS) (medians of the control subgroups = 100) (Study Heidelberg)

(given as minimum, percentiles of 25, median, percentiles of 75, and maximum (box and whiskers graph with the box representing the interquartile range), adapted from [2], data taken from [19]). The required dose of analgesics was 52–69% lower (median differences) in the subgroups with wIRA(+VIS) compared to the control subgroups with only VIS.

Figure 8. Subcutaneous oxygen partial pressure at a tissue depth of 2 cm on the postoperative days 2 and 10 in the group with water-filtered infrared-A (wIRA) and visible light (VIS) and in the control group with only visible light (VIS) (Study Heidelberg)

(given as minimum, percentiles of 25, median, percentiles of 75, and maximum (box and whiskers graph with the box representing the interquartile range); adapted from [2], [19]). During irradiation with wIRA(+VIS), the subcutaneous oxygen partial pressure rose markedly by more than 30%, whereas it remained unchanged in the control group.

Figure 9. Subcutaneous temperature at a tissue depth of 2 cm on the postoperative days 2 and 10 in the group with water-filtered infrared-A (wIRA) and visible light (VIS) and in the control group with only visible light (VIS) (Study Heidelberg)

(given as minimum, percentiles of 25, median, percentiles of 75, and maximum (box and whiskers graph with the box representing the interquartile range); adapted from [2], [19]). During irradiation with wIRA(+VIS) the subcutaneous temperature rose markedly by approximately 2.7°C, whereas it remained unchanged in the control group.

Figure 10. Relative change of wound area in severely burned children as a function of duration of treatment (in days) in the group with water-filtered infrared-A (wIRA) and visible light (VIS) and in the control group with only visible light (VIS) (Study Kassel)

(given as minimum, percentiles of 25, median, percentiles of 75, and maximum (box and whiskers graph with the box representing the interquartile range), adapted from [2]). The figure presents the data from those 10+10 = 20 children (out of 21+24 = 45 children), who had second degree, type a burns (not second degree, type b burns) and were consequently treated non-surgically until complete cutaneous regeneration occurred including irradiation (starting on the day of the burn, until complete reepithelialization) with wIRA(+VIS) or with only VIS (control group). Patients in the group with wIRA showed a markedly faster reduction of wound area compared to the control group: a median reduction of wound size of 50% was reached in the group with wIRA already after 7 days compared to 9 days in the control group, a median reduction of wound size of 90% was achieved in the group with wIRA already after 9 days compared to 13 days in the control group.

Figure 11. Example of a rapid improvement with wIRA in a severely burned child (Study Kassel)

Left: 1 day after the burn, right: only 30 hours later than shown on the left side (from [2]).

Figure 12. Example of a successful treatment of recurrent wound seromas with wIRA

A 64 year-old female patient had relapsing wound seromas and wound hematomas (without infection) after a hip operation (replacement of the acetabulum part of a 15 year-old endoprosthesis) even after an additional operation with the sole intention of stopping the wound seromas and after approximately 8 aspirations of seroma fluid (up to approximately 90 mL within one aspiration) within 2 months, and a third operation was seriously considered: Figure A shows the sonographic state. At that time, wIRA(+VIS) irradiation was commenced, beginning with 30 minutes twice per day and increasing up to 3 times one hour per day. Within a few days the seroma no longer increased as usual; after approximately one week a slight decrease of seroma size was noticed clinically (Figure B). Figure C shows reduced seroma size after 18 days and Figure D after 29 days. After approximately 2 months the seroma had resolved completely (both clinically and sonographically) without any aspiration of seroma fluid or operation since commencement of wIRA(+VIS) irradiation (sonographic pictures published with kind approval of Dr. Michael Paulus, Herzogenaurach, Germany) (from [2]).

Figure 13. Example of the healing process of a chronic venous stasis ulcer of the lower leg under therapy with wIRA (Study Tromsø/Hillerød)

(28 times 30 minutes irradiation with water-filtered infrared-A (wIRA) and visible light (VIS) within 52 days = approximately 7 weeks) with normal view, thermographic image, and temperature profile across the ulcer, in each case to the left before therapy and to the right after completion of the course of therapy. The arrow in the thermographic image - taken after completion of the course of therapy - points to the place where the wound has been. Diameter of the red circles: 16 mm. (Study of the University of Tromsø/Norway and the Hospital in Hillerød/Denmark) (adapted from [3], [4], [23])

Figure 14. Example of the healing process of a chronic venous stasis ulcer of the lower leg under therapy with wIRA

88 year-old woman with an infected (lightly malodorous) crustaceous ulcer (of the right distal medial lower leg), which had persisted for 13 months and had increased despite conservative dermatological therapy including local antisepsis, systemic antibiotic, and non-adhesive wound dressing up to 10 cm in diameter. Chronic venous insufficiency with marked stasis-related edemas of the lower legs and extensive stasis dermatitis, diabetes mellitus type II (orally treated), slightly overweight, and decreased amount of daily motion. Under irradiation with wIRA(+VIS) 30 minutes once daily, compression therapy, local antisepsis, non-adhesive wound dressing and the possibility of ending the systemic antibiotic therapy, a complete wound closure was achieved within 4½ months: initial findings, result after 3½ months, result after 4½ months (healed) (adapted from [3], [4])