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The goal of this thesis was to develop, characterize, and technically evaluate nonintrusive optical oximeters. Non-intrusive oximeters are oximeters with high level of comfort for the ambulatory patients or in case of application in the operation theater, with quick application and read-out, with no need for fixation and extended measurement period. Two oximeters are presented. The first one functions based on visible light spectroscopy and the second one is a textile based continuous wave (CW) near infrared spectroscopy (NIRS) oximeter. In applications such as flap oximetry (e.g. in reconstructive surgery), skin oximetry, and oximetry of bone or heart, themselves, in open surgeries, a non-intrusive oximeter is required which incorporates a small probe and is capable of local measurement of tissue oxygen saturation (StO2) instantly. We developed a non-intrusive oximetry based on visible light spectroscopy (Oxy VLS), which applies visible light and based on the shape of the absorption spectrum of hemoglobin calculates StO2, oxyhemoglobin concentration ([O2Hb]), deoxyhemoglobin concentration ([HHb]), and reduced scattering coefficient (µ’s). The functionality of the oximeter is demonstrated in a liquid phantom with adjustable StO2. We characterized the oximeter by the influence of scattering and light path as well as total hemoglobin concentration ([tHb]) of tissue and concluded that [tHb] had only marginal effect on the StO2 measured by OxyVLS and the effect of m0 s was less than 10%. We additionally verified a good agreement between [O2Hb], [HHb], and (µ’s) measured by OxyVLS and frequency domain (FD) NIRS oximeters. Moreover, we derived equations for conversion of the results obtained by Oxy VLS in a liquid phantom with adjustable StO2 to Nonin-neonatal, INVOS adult and neonatal, OxyPrem v1.3, and OxiplexTS which are common in research and clinics. Last but not least, we applied OxyVLS as a reference oximeter, in a phantom measurement and quantified the effect of adipose tissue thickness (ATT) on CW-NIRS oximeters. In applications such as muscle oximetry, which is of interest, for example, in patients with high risk of peripheral vascular disease (PVD) or in case of pressure ulcer prevention in paraplegics, long term monitoring of StO2 is required. In such applications, oximetry has to not only protect the health of the patient but also provide a high level of comfort. In paraplegics, for instance, the pressure points from the oximeter’s sensor may increase the risk of pressure ulcer development. In our opinion a textile based CW-NIRS oximeter (TexNIRS) overcomes this issue. We developed and charv acterized sensors and actuators for NIRS on phantoms as well as on a healthy subject. We additionally, evaluated the application and plausibility of the values measured by TexNIRS on 16 legs from 10 healthy subjects by venous occlusion. StO2, venous oxygen saturation (SvO2), oxygen consumption (VO2), blood flow (BF), hemoglobin flow (HF), and change in [O2Hb] and [HHb] due to venous occlusion were plausible and in good agreement with the values reported in the literature.

Non-intrusive tissue oximetry by near infrared and visible light spectroscopy