Low intensity laser therapy (LILT) is currently undergoing investigation as a treatment for chronic wounds. Although the intended target is the wound bed and surrounding skin, wound bacteria are also exposed and hence subject to LILT, thus a good understanding of the effects of LILT on bacterial growth is essential for prescribing safe and effective laser therapy for wounds. The present work examines the effects of 810 nm laser on bacterial growth. The objectives were: 1. to determine an effective combination of radiation parameters leading to bacterial inhibition, or alternatively 2. to determine which combination of laser parameters produce the least stimulation of bacterial growth.
Purpose: To determine the effect of low intensity laser therapy (LILT) on healing of infected skin wounds in the rat. Methods: Wounds on the dorsum of Sprague-Dawley rats (14 per group) were inoculated or sham-inoculated with P. aeruginosa. Wounds were irradiated or sham-irradiated three times weekly from Day 1-19 using 635nm or 808nm diode lasers at radiant exposure of 1 or 20 J/cm2 delivered in continuous wave (CW) or at an intensity modulation frequency of 3800Hz. Wound area and bacterial growth were evaluated three times weekly. Results: CW 808 nm (1 and 20 J/cm2) irradiation generally delayed healing in acute wounds. However, from Day 10 onwards CW 808 nm (1 J/cm2 and 20 J/cm2) and 808 nm 3800 Hz (1 J/cm2) irradiation improved healing in inoculated wounds. Healing in acute wounds improved using 635 nm irradiation at low radiant exposure (1 J/cm2); however, using 635 nm irradiation at high radiant exposure (20 J/cm2) delayed healing. Bacterial balance in wounds was significantly altered using 635 nm (20 J/cm2) and CW 808 nm irradiation (1 and 20 J/cm2). Conclusion: Clearing wounds of normal flora was not associated with improved healing. Proliferation of staphylococcal species in wounds was associated with delayed healing.
Purpose: To examine factors that affect penetration of phototherapy. Methods: Age, sex, height, and weight were recorded; skin color, skinfold thickness, and light transmission through a skinfold were measured over biceps and triceps muscles, and at the anterior waistline. Light was generated using two 23-diode LED arrays at 840 nm and 660 nm with surface area of 7 cm2. Photon irradiation was measured using an Optical Power Meter consisting of a 1x1-cm2 light detector placed in the centre of the illuminated 7 cm2 spot. Transmission was measured using three skin-diode coupling conditions. Results: Penetration of LED irradiation increased when diodes were coupled to skin with pressure. Red light attenuated more rapidly than infrared light and the attenuation of red light increased as skin color darkened. Penetration of red and infrared light decreased as the amount of subcutaneous fat increased. There were gender effects on penetration of infrared light at normal and low BMI values. Conclusions: When using divergent light sources for phototherapy, radiant exposure should take into account individual physical characteristics, irradiation wavelength and diode configuration of the laser therapy system.
Conference Committee Involvement (1)
Therapeutic Laser Applications and Laser-Tissue Interactions
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