Jens Kraitl

An optical device to measure blood components by a photoplethysmographic method

The development of the photometric device described here is based on the realization of a photoplethysmography measurement device developed for the German Space Agency DLR. It is well known in biomedical engineering that pulsatile changes of blood volume in tissue can be observed by measuring the transmission or the reflection of light (Roberts 1982 Trans. Inst. Meas. Control 4 101–6). The non-invasive multi-spectral method described here is based on the radiation of monochromatic light, emitted by laser diodes in the range 600–1400 nm, through an area of skin on the finger. After interaction with the tissue the transmitted light is detected non-invasively by photo-diodes. The method makes use of the intensity fluctuations caused by the pulse wave. The ratio between the peak to peak pulse amplitudes measured at different wavelengths and its dependence on the optical absorbability characteristics of human blood yields information on the blood composition. Deferrals between the proportions of haemoglobin and water in the intravasal volume should be detected photo-electrically by signal-analytic evaluation of the signals. The computed coefficients are used for the measurement and calculation of the arterial oxygenic saturation (SaO2) and the relative haemoglobin concentration change. Results of clinical measurements are presented for a deoxygenation study with ICG-bolus injection (indocyanine green).

Non-invasive continuous online hemoglobin monitoring system

The Hemoglobin (Hb) concentration in human blood is an important parameter to evaluate the physiological condition. A hemoglobin test reveals how much hemoglobin is to be found in the blood. With this information anemia (a low hemoglobin level) and polycythemia vera (a high hemoglobin level) can be a diagnosed and monitored. It is also possible to observe postoperative bleedings and autologous retransfusions. Currently, invasive methods are used to measure the Hb concentration. For this purpose blood is taken and analyzed. The disadvantage of this method is the delay between the blood collection and its analysis, which does not allow real-time monitoring of patients in critical situations. The non-invasive method, discussed in this paper, allows pain free online monitoring of patients with minimum risk of infection. Real-time data monitoring facilitates immediate clinical reaction to the measured data.

Non-invasive measurement of blood components

NIR-spectroscopy and Photoplethysmography (PPG) is used for a measurement of blood components. The absorption-coefficient of blood differs at different wavelengths. This fact is used to calculate the optical absorbability characteristics of blood which is yielding information about blood components like hemoglobin (Hb) and arterial oxygen saturation (SpO2). The measured PPG time signals and the ratio between the peak to peak pulse amplitudes are used for a calculation of these parameters. The newly developed optical sensor system uses up to five wavelengths in the range of 600 nm to 1400 nm for a measurement of the hemoglobin concentration, oxygen saturation and pulse. This non-invasive multi-spectral measurement method was tested with prototype-devices based on radiation of monochromatic light emitted by laser diodes and by using light emitting diodes (LED) through an area of skin on the finger. The sensors assembled in this investigation are fully integrated into wearable finger clips.

Optical sensor technology for a noninvasive continuous monitoring of blood components

NIR-spectroscopy and Photoplethysmography (PPG) is used for a measurement of blood components. The absorptioncoefficient of blood differs at different wavelengths. This fact is used to calculate the optical absorbability characteristics of blood which is yielding information about blood components like hemoglobin (Hb), carboxyhemoglobin (CoHb) and arterial oxygen saturation (SpO2). The measured PPG time signals and the ratio between the peak to peak pulse amplitudes are used for a measurement of these parameters. Hemoglobin is the main component of red blood cells. The primary function of Hb is the transport of oxygen from the lungs to the tissue and carbon dioxide back to the lungs. The Hb concentration in human blood is an important parameter in evaluating the physiological status of an individual and an essential parameter in every blood count. Currently, invasive methods are used to measure the Hb concentration, whereby blood is taken from the patient and subsequently analyzed. Apart from the discomfort of drawing blood samples, an added disadvantage of this method is the delay between the blood collection and its analysis, which does not allow real time patient monitoring in critical situations. A noninvasive method allows pain free continuous on-line patient monitoring with minimum risk of infection and facilitates real time data monitoring allowing immediate clinical reaction to the measured data.

Sensor system for non-invasive optical hemoglobin determination

The Hemoglobin (Hb) concentration in human blood is an important parameter to evaluate the physiological condition. A hemoglobin test reveals how much hemoglobin can be found in the blood. With this information anemia (a low hemoglobin level) and polycythemia vera (a high hemoglobin level) can be a diagnosed and monitored. It is also possible to observe imminent postoperative bleedings and autologous retransfusions. Currently, invasive methods are used to measure the Hb concentration. For this purpose blood is taken and analyzed. The disadvantage of this method is the delay between the blood collection and its analysis, which does not allow a real-time patient monitoring in critical situations. A non-invasive method allows pain free online patient monitoring with minimum risk of infection and facilitates real time data monitoring allowing immediate clinical reaction to the measured data.

Novel multi wavelength sensor concept to detect total hemoglobin concentration, methemoglobin and oxygen saturation

The paper will describe the novel multi-wavelength photometric device OxyTrue Hb® which is capable to measure the hemoglobin (Hb) and methemoglobin (MetHb) concentration non-invasively. Clinic trails in blood donation centers and during the dialysis are done to prove and demonstrate the performance of the system. The results are compared to the gold standard, the BGA measurement.

Non-invasive measurement of blood and tissue parameters based on VIS-NIR spectroscopy

Currently, invasive methods are used to measure the hemoglobin concentration and the most hemoglobin-derivatives, whereby blood is taken from the patient and subsequently analyzed. The noninvasive method presented here allows pain free continuous on-line patient monitoring with minimum risk of infection and facilitates real time data monitoring allowing immediate clinical reaction to the measured data. Visible and near infrared (VIS-NIR) spectroscopy in combination with photo-plethysmography (PPG) is used for a detection of human tissue properties and the measurement of hemoglobin concentration in whole blood and hemoglobin derivatives. The absorption, scattering and the anisotropy of blood and tissue is a function of the irradiated wavelengths. This fact is used to calculate the optical absorbability characteristic of blood and tissue which is yielding information about blood components like hemoglobin-concentration (cHb), carboxyhemoglobin (COHb) and arterial oxygen saturation (SaO2). The ratio between the PPG peak to peak pulse amplitudes for each wavelength is used in combination with a dynamic spectrum extraction. The prediction of the bloodand tissue-parameters is based on a Principal Component Regression (PCR) method. The non-invasive sensor system is calibrated with a lab based artificial blood circulatory system and with data from clinical studies.

Non-invasive sensor for an in vivo hemoglobin measurement

NIR-spectroscopy and Photoplethysmography (PPG) is used for a measurement of blood components. The absorption-coefficient of blood differs at different wavelengths. This fact is used to calculate the optical absorbability characteristics of blood which is yielding information about blood components like hemoglobin (Hb) and arterial oxygen saturation (SpO2). The measured PPG time signals and the ratio between the peak to peak pulse amplitudes are used for a calculation of these parameters. The newly developed optical sensor systems use up to five wavelengths in the range of 600nm to 1400nm for a measurement of the hemoglobin concentration, oxygen saturation and pulse. This noninvasive multi-spectral measurement method was tested with prototype-devices based on radiation of monochromatic light emitted by laser diodes and by using light emitting diodes (LED) through an area of skin on the finger. The sensors assembled in this investigation are fully integrated into wearable finger clips.

Photometric sensor system for a non-invasive real-time hemoglobin monitoring

Hemoglobin (Hb) is an important component of red blood cells. The primary function of Hb is the transport of oxygen from the lungs to the tissue and carbon dioxide back to the lungs. The Hb concentration in human blood is an important parameter in evaluating the physiological status of an individual and an essential parameter in every blood count. Invasive methods are used to measure the Hb concentration, whereby blood is taken from the patient and subsequently analyzed. Apart from the discomfort of drawing blood samples, an added disadvantage of this method is the delay between the blood collection and its analysis, which does not allow real time patient monitoring in critical situations. A non-invasive method allows pain free continuous on-line patient monitoring with minimum risk of infection and facilitates real time data monitoring allowing immediate clinical reaction to the measured data.

Pulse spectroscopy system for non-invasive real-time monitoring of the heart beat volume

The left-ventricular stroke volume is an important direct indicator of the heart efficiency and perfusion of the vessels. Currently a valid measurement of the beat volume can only be implemented by invasive measurements procedures at the hospitals worldwide. Arterial catheterization is limited to intensive care unit (ICU) usage, costly and potential risky. Some available noninvasive methods yield rather an ability to track relative changes. Values delivered by these techniques are highly subjective and controversial. Enhanced pulse spectroscopy and advances in digital signal processing allow reliable measurement of the changes in peripheral blood volume with subsequent estimation of the cardiac output (CO). The aim of the current work was to design a continuous nonivasive system for the absolute monitoring of the heart beat volume (HBV). And eventually prove the validity of this new method by comparing with the standard invasive technique. It was a first trial to achieve a noninvasive measurement of the HBV by the instrumentality of a standard pulse oximeter, advanced signal processing algorithm and single individual calibration. Software algorithm has been tested on ten patients with various disorders of the cardiovascular system. The real-time absolute references of the HBV were obtained via PiCCO catheterization system (Pulsion Medical Systems, Munich, Germany) on the femoral arteries for three patients. Technology presented in this paper faces clinical needs in intensive care unit, internal medicine unit, operative, postoperative and patient recovery areas. The medical relevance of these devices is high.