CLT Wound Healing & Tissue Repair 2 — Questions and Answers
Question 1: The Arndt-Schulz law as applied to photobiomodulation states that:
- Higher doses always produce better therapeutic outcomes
- Low doses stimulate, moderate doses inhibit, and very high doses destroy (Correct answer)
- Light therapy is only effective when applied continuously
- Wavelength determines effectiveness more than dose
Correct answer: Low doses stimulate, moderate doses inhibit, and very high doses destroy
The Arndt-Schulz law (biphasic dose response) states that low doses of light stimulate biological processes, moderate doses inhibit them, and very high doses can cause damage.
Question 2: Light therapy is generally CONTRAINDICATED when applied over which of the following?
- Diabetic foot ulcers
- Pressure ulcers
- Active malignancies within the treatment area (Correct answer)
- Post-surgical wounds
Correct answer: Active malignancies within the treatment area
Light therapy is contraindicated over active cancer sites because photobiomodulation could potentially stimulate tumor cell growth and proliferation.
Question 3: What is the primary mechanism by which 630–660 nm red light promotes fibroblast activity in wound healing?
- Direct destruction of bacteria in the wound
- Thermal heating that activates heat-shock proteins
- Photon absorption by cytochrome c oxidase increasing ATP and cellular metabolism (Correct answer)
- Ultraviolet induction of vitamin D synthesis
Correct answer: Photon absorption by cytochrome c oxidase increasing ATP and cellular metabolism
Red light (630–660 nm) is absorbed by cytochrome c oxidase, boosting mitochondrial ATP production, which provides the energy fibroblasts need for collagen synthesis and proliferation.
Question 4: Near-infrared light (800–1000 nm) penetrates deeper than red light primarily because:
- NIR has higher photon energy
- NIR has lower absorption by water and hemoglobin, allowing deeper penetration (Correct answer)
- NIR triggers melanin production which guides light downward
- NIR wavelengths are reflected by the stratum corneum
Correct answer: NIR has lower absorption by water and hemoglobin, allowing deeper penetration
NIR light (800–1000 nm) has lower absorption by chromophores like water and hemoglobin compared to visible red light, allowing it to penetrate deeper into tissues.
Question 5: When applying photobiomodulation to a wound, the recommended treatment area should include:
- The wound edges only, not the center
- Surrounding healthy tissue only
- The wound bed and surrounding perilesional tissue (Correct answer)
- Only the area with the deepest tissue involvement
Correct answer: The wound bed and surrounding perilesional tissue
Optimal wound healing with photobiomodulation requires treating both the wound bed (to stimulate repair cells) and the perilesional tissue (to improve circulation and tissue support from the edges).
Question 6: Which of the following best describes the concept of 'fluence' in photobiomodulation wound treatment?
- The color of light used for a given treatment
- The rate at which photons are delivered per unit area per second
- The total energy delivered per unit area, measured in J/cm² (Correct answer)
- The distance between the light source and wound
Correct answer: The total energy delivered per unit area, measured in J/cm²
Fluence (energy density) is the total light energy delivered per unit area, measured in joules per square centimeter (J/cm²), and is a critical dosimetry parameter for effective wound healing treatments.
Question 7: Photodynamic therapy (PDT) reduces biofilm formation in chronic wounds primarily through which mechanism?
- Thermal destruction of the biofilm matrix
- Photosensitizer activation generating reactive oxygen species that destroy bacteria (Correct answer)
- UV-induced sterilization of the wound surface
- Mechanical disruption via light pressure
Correct answer: Photosensitizer activation generating reactive oxygen species that destroy bacteria
PDT uses photosensitizers activated by specific wavelengths to generate reactive oxygen species that destroy bacterial biofilms without causing significant harm to surrounding tissue.
CLT Wound Healing & Tissue Repair 2
The Arndt-Schulz law as applied to photobiomodulation states that: