Page 27 - Effects of radiotherapy and hyperbaric oxygen therapy on oral microcirculation Renee Helmers

Hyperoxia-driven microvascular changes
INTRODUCTION
It is generally acknowledged that hyperoxia and hyperbaric oxygen therapy
(HBOT) can promote metabolic resuscitation,34,47 angiogenesis,18,20,42
and regulate tissue perfusion37,48 by restoring oxygen tensions in tissues 2 distressed by ischemic injuries or poor vasculature. Recanalization of oxygen
establishes sufficient oxygen availability necessary for sustaining repair
and regeneration.39,41 However, research-based evidence in support of the
beneficial effects associated with hyperoxia and hyperbaric oxygen (HBO) have
been controversial. For example, breathing high oxygen concentrations has
been associated with adverse events such as elevated reactive oxygen species
(ROS),8,46 altered cellular metabolic25,37,38 and rheological properties,1,50 activation
of coagulation,27,30,32,35 endothelial dysfunction7 and vasoconstriction.37,48 While
it is plausible that mutual advantages and disadvantages associated with
hyperoxia may yield ultimately beneficial therapeutic effects, the net result
depends on what the treatment strategy demands for achieving a desired
therapeutic outcome.
Intrabarochamber measurements (HBOm) of microhemodynamic responses in oral tissues are very limited since data acquisitions involving oxygen rich environments and electrical equipment remain a safety and technical challenge. Most studies report data obtained before and after HBOT and few directly from inside the HB tank. To our knowledge laser Doppler flowmetry (LDF),36,44 near- infrared spectroscopy (NIRS),26 and video capillaroscopy (VC)50 have been used inside HBO environments to investigate peripheral cutaneous microcirculation from the posterior region of the medial malleolus (foot), the thenar eminence (thumb), and the nailfold microcirculation respectively. However, the extent of measuring functional vascular changes in specified tissue compartments such as the subepithelial microcirculation of the oral mucosa remains nihil since LDF and NIRS are unable to produce information based on anatomic inspection. VC on the other hand can provide anatomic based information; however, its size and cumbersome setup have hindered its introduction for applications intraorally. In view of this, the evolution and commercialization of technology incorporating optics and spectroscopy into compact handheld instruments today enables the application of sidestream dark-field video imaging (SDFI) for studying the microcirculation in oral tissues. Recently, the influence of HBOT on keratinized oral mucosal flap vascularization was investigated with SDFI for
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