Page 55 - Effects of radiotherapy and hyperbaric oxygen therapy on oral microcirculation Renee Helmers

HBOT and vascular regeneration in oral mucosal flaps
INTRODUCTION
Chronic wounds are common and persistent health problems with significant
economic burden and impact on patient quality of life.12 Most chronic wounds
emerge as a consequence of arterial, venous and microvascular diseases,
linked to diabetes, sustained pressure (decubitus), and therapeutic irradiation
for malignant tumors. Poor blood supply and low oxygen tension (pO2) due
to decreased vascularity produce chronic hypoxia, a condition that is clinically
difficult to control and may compel a wound to succumb to infection, which in 3 turn could result in tissue necrosis and sepsis.18,21,24,25 Hyperbaric oxygen (HBO)
is thought to promote angiogenesis by restoring oxygen tensions in the injured tissues and thereby establish proper oxygen delivery necessary for repair and regeneration.8,19,22 Although HBO is used as an adjunct to conventional medical treatments for management of chronic wounds, the validity of hyperbaric oxygen therapy (HBOT) for clinical use remains controversial. One of the indications for HBOT is for the treatment of osteoradionecrosis (ORN) of the jaw in head and neck oncology patients who undergo postirradiation tooth extractions. Evidence-based studies show that the incidence of ORN is 2-18% in patients who receive tooth extractions after radiotherapy.17 Interestingly, despite improving a variety of conditions that otherwise fail with conventional therapeutic approaches, the mechanisms of action associated with the benefits obtained using HBOT in preventing and/or treating ORN remain largely unknown.6
Research directed at evaluating wound healing responses to HBOT have generated numerous studies that investigated tissue vitality by assessing wound blood perfusion status using laser Doppler flowmetry (LDF), laser Doppler imaging (LDI), and intravital microscopy (IVM).11,20,22,28,29 Interestingly, even with many studies using well recognized and accepted diagnostic instruments, most techniques are only able to quantify a particular parameter (e.g. circulatory flux or blood flow) and are unable to provide information on vascular morphology and angioarchitecture. To this end, we used sidestream dark-field (SDF) imaging, a commercially available handheld video microscopy system that enabled direct noninvasive observations and quantifications of tissue subsurface microcirculation.10 Embodied into a portable handheld device, SDF imaging provides a way of quantifying functional anatomic changes in vivo without the use of contrast enhancement agents and destructive
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