Comparison of Helzel and OxyLite Systems in the Measurements of Tumor Partial Oxygen Pressure (pO₂)

Abstract

It has been demonstrated in both experimental and human malignancies that hypoxic tumor cells are linked with aggressive disease phenotype. One of the methods to identify these cells is by direct physical measurement of tumor pO 2 . This study compared pO 2 values measured with two systems, the Helzel Hypoximeter (successor of the polarographic Eppen-dorf electrode) and the OxfordOptronix OxyLite (fiber-optic probe), in R3327-AT and R3327-AT/tkeGFP tumors. Partial oxygen pressure was measured in individual tumors with either system or in the same tumor with both systems. The similarities and discrepancies in pO 2 measurements between the two systems were also investigated when tumor-bearing animals were breathing pure oxygen. Our data showed a considerable heterogeneity in pO 2 values in each tumor using both the Helzel and OxyLite systems. Similar results were obtained with both systems for the mean and median pO 2 values, and the distributions of pO 2 values within the interval 0 < pO 2 < 40 mmHg (the range important for defining tumor hypoxia) were found to be statistically equivalent However, the frequencies of high pO 2 values (>40 mmHg) and zero values measured by the two systems were statistically significantly different.

Enzyme-induced posterior vitreous detachment in the rat produces increased lens nuclear pO2 levels

“…The manufacturer of the probe has stated that pO 2 measurements are insensitive to sample viscosity, and McNulty et al (2004) have also found this to be true for protein concentrations up to at least 30% (the highest value tested by the researchers, and the protein concentration that exists in the lens). Other investigators have used the fiber optic fluorescence probe to measure pO 2 levels in solid tissues such as kidney and tumors, and found the results to be comparable with those obtained with other O 2 -measuring instruments (Leong et al, 2008; Seddon et al, 2001; Wen et al, 2008). …”

A method for measuring brain partial pressure of oxygen in unanesthetized unrestrained subjects: The effect of acute and chronic hypoxia on brain tissue PO2

“…The probes are pre-calibrated by Oxford Optronics in solutions of multiple temperatures and PO 2 values. Although factors such as pH sensitivity have not been measured, the in vivo results compare favorably with electrode measurements of PO 2 , even in tumors where pH can vary considerably (Seddon et al, 2001; Wen et al, 2008). The chronically implantable fiber optic probe was constructed by Oxford Optronics based on a design supplied by Dr. Dunn.…”

Hypoxia as a Biomarker and for Personalized Radiation Oncology

“…Unlike the Eppendorf histogram electrode, these do not consume oxygen with each measurement; thus; continuous observations of oxygenation status in the same tumour region is possible (Griffiths and Robinson 1999). Preclinical studies comparing the commercially available Oxford-Optronix OxyLite sensor with the polarographic techniques (Collingridge et al 1997;Braun et al 2001;Seddon et al 2001;Wen et al 2008), or classical paired survival curve estimates of radiobiological hypoxia (Urano et al 2002), reported similarities and differences depending on the tissue type, tumour size or the changes observed using various modifiers of tumour hypoxia. Although fibre optic probes have the potential to not only measure the pretreatment level of tumour hypoxia, but also to monitor tumour oxygenation status continuously during and after treatment, there has as yet been no clinical application in cancer.…”