Page 135 - Effects of radiotherapy and hyperbaric oxygen therapy on oral microcirculation Renee Helmers

The pathophysiological process of LRTI remains a significant clinical problem and an ongoing topic of debate given the different theories discussed in the literature.1,5,8 Progression and degree of LRTI differs per individual and no scoring index based on (vascular) tissue state is available to classify the onset of tissue injury before clinical symptoms emerge. HBOT is being applied prophylactically prior to oral surgery to prevent disturbed healing in IR tissues, without solid evidence from the current literature and based on differing clinical judgement of the treating physican.13 For therapeutic indication, HBOT is administered in cases of tissue necrosis where deterioration is already in a far progressed state and therefore difficult to reverse.
The work presented in this thesis aimed to extend knowledge on development and treatment of LRTI in oral tissue by elucidating the effects of RT and HBOT independently on the oral microcirculation. Additionally, the data aimed to provide more clarity regarding the effects and resuscitating potential of HBOT in previously IR oral tissues in HNCPs. Furthermore, the feasibility of using HVM devices (SDF and CC device) in chairside observation of HNCPs to identify RT and HBOT induced changes in the microcirculation was examined.
NB and HB hyperoxia-driven microcirculatory changes
Supplemental oxygen is administered to treat tissues with inadequate oxygen
saturation levels that are subject to infection or hypoxia due to an underlying
pathology and suffer from compromised microvascular blood perfusion. HBOT
additionally dissolves O2 in blood plasma due to pressure causing a higher
oxygen tension aside from fully saturated hemoglobin in RBCs. The steep O2
gradient next to distressed tissue promotes the forming of new capillaries aiding 7 the vascularization process. An experimental model was developed in which
sublingual microvascular alterations in response to hyperoxia under NB and HB circumstances was described (Chapter 2). SDFI has proven to be a feasible technique for continuous intrabarochamber microcirculation measurements. Furthermore, in healthy subjects the NB/HB hyperoxia-driven changes in the sublingual microcirculation were observed to be reversible and hyperoxic microvascular response (vasoconstriction) seemed absent in HB conditions as blood vessel diameter did not alter compared to NB normoxia. The latter might indicate a beneficial physiological adaptation to maintain optimal tissue perfusion.
General discussion
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