Page 145 - Effects of radiotherapy and hyperbaric oxygen therapy on oral microcirculation Renee Helmers

Radiotherapy (RT) plays an important part in the treatment of head and neck cancer patients. A late side effect of RT is the progressive process of reduced blood flow and fibrosis of the irradiated tissues, which can result in a compromised healing tendency. In an advanced stage this can lead to necrosis of soft tissue and bone (osteoradionecrosis). This process can emerge several months to years after radiotherapy, either spontaneously or after surgery or wounding. The patient’s health status and the amount of radiation dose influence the risk of late side effects. However, based on the previous, it is not possible to fully predict which individual patient will develop osteoradionecrosis over time.
Hyperbaric oxygen therapy (HBOT) is used both preventively and curatively to support healing in irradiated tissue. Previous research has shown that hyperbaric oxygen promotes blood flow in irradiated tissues. However, the precise working mechanism and the type of patients that benefit from therapy remains unclear.
Previous studies have shown that microcirculation assessment is of additional value in diagnosing diseases and predicting their course. With the use of “handheld vital microscopy” (HVM), an imaging technique in the form of a hand-held microscope, it is possible to image the microcirculation down to the level of the red blood cells and to assign a value to the density, diameter, blood flow and shape of the capillaries. The studies in this thesis were performed with the use of this technique.
Chapters 2 and 3 describe experimental studies which demonstrate that
the effect of HBOT can be measured in the oral microcirculation directly
(in a hyperbaric tank) and over time. It was observed that the direct effect
of hyperbaric oxygen in the microcirculation (decrease in vessel density) is immediatelyrestoreduponreturntonormalpressureandoxygen(chapter 2).
The usual vasoconstriction in response to higher oxygen tension was not 8 observed under pressure in this experiment. This aberrant vascular response
under pressure could facilitate oxygen transport to hypoxic tissues (e.g. chronic wound, irradiated tissue). In chapter 3, an experimental wound healing model investigates the effects of hyperbaric oxygen on the duration of wound healing in the mouth using repeated microcirculation measurements. A faster healing
Summary - Samenvatting
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