Page 66 - Effects of radiotherapy and hyperbaric oxygen therapy on oral microcirculation Renee Helmers

Chapter 3
al. obtained from an ischemic ear model in rabbits that showed an increase in blood vessel count associated with HBO compared to ischemic controls.30 In an irradiated rabbit model Marx et al. determined an eight- to ninefold increased vascular density after HBOT by histological analysis.13 Analogous to increasing anatomical components, Sheikh et al. reported restored tissue functionality for the first time by demonstrating elevated wound bed perfusion after HBOT on full-thickness dermal wounds in mice.22 Interestingly, Sheikh and co-workers reported a significant increase in perfusion in their HBO group on day 10, three days after the very last hyperbaric session on day 7. Although, the present study used a different wound model, our results demonstrate a similar trend in wound blood circulation restoration indicated by augmented expression in tissue vascularity between days 7, 9, and 11 in the HBOT group. In another study using LDF, it was reported that acute HBOT on ischemic rat skin flaps improves perfusion by stimulating the microcirculation.29 Subsequent HBOT investigations later demonstrated elevated blood perfusion in healing tissue of a mandibular bone defect in rats and acceleration of neovascularization in impaired wound models using IVM in mice.11,20 However, despite positive results using HBOT to improve tissue vascularization and microperfusion, contradicting results associated with HBO still persist. One example of such contradictory results was reported in a study using LDI, in which no significant improvement in blood flow patterns between HBO group and controls was found.28 However, there is very little experimental evidence regarding wound microperfusion restoration after injuries. Although previous dermal perfusion studies were performed using LDI and LDF, observations of microcirculatory angioarchitecture and hemodynamics has as yet not been observed in vivo after HBOT. Moreover, laser Doppler techniques though useful in detecting the absence or presence of blood flow, the data obtained using LDF or LDI cannot be attributed to specific microvascular networks nor can they reveal angioarchitecture or angiomorphology.
As HBO increases the amount of oxygen dissolved in blood plasma (pO2), higher oxygen tensions can be obtained in injured tissues and in ischemic wounds.26 When a higher pO is measured in tissue adjacent to an ischemic
2
wound, an accelerated wound healing was observed.4,23 In vitro HBO
experiments have been shown to accelerate enzymatic processes that among others improve cellular response and proliferation.24 New fibroblasts in a wound require sufficient oxygen for sequential synthesis and maturation of collagen to support blood vessel proliferation.9,18
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