| Summary: | We have developed a sensor for monitoring the hemoglobin (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>H</mi><mi>b</mi></mrow></semantics></math></inline-formula>) concentration in the effluent of a continuous bladder irrigation. The <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>H</mi><mi>b</mi></mrow></semantics></math></inline-formula> concentration measurement is based on light absorption within a fixed measuring distance. The light frequency used is selected so that both arterial and venous <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>H</mi><mi>b</mi></mrow></semantics></math></inline-formula> are equally detected. The sensor allows the measurement of the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>H</mi><mi>b</mi></mrow></semantics></math></inline-formula> concentration up to a maximum value of 3.2 g/dL (equivalent to ≈20% blood concentration). Since bubble formation in the outflow tract cannot be avoided with current irrigation systems, a neural network is implemented that can robustly detect air bubbles within the measurement section. The network considers both optical and temporal features and is able to effectively safeguard the measurement process. The sensor supports the use of different irrigants (salt and electrolyte-free solutions) as well as measurement through glass shielding. The sensor can be used in a non-invasive way with current irrigation systems. The sensor is positively tested in a clinical study.
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