Ulrich Timm

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.

Current Possibilities for Detection of Loosening of Total Hip Replacements and How Intelligent Implants Could Improve Diagnostic Accuracy

Where pain is experienced following a total hip replacement (THR), there needs to be clarification as to whether the cause is due to an infected or mechanically loose THR. The major complication after implantation of a THR is aseptic loosening, caused by stress shielding and wear-particle induced osteolysis with an incidence of 75 % (Malchau et al., 2002). A further prevalent reason for implant loosening is a sepsis due to infection of the periprosthetic membrane. The optimal management in case of hip pain is an often discussed controversy. Currently, several diagnostic methods are used to identify the loosening status of the THR and to establish a basis for revision management. All these techniques are based on imaging methods. An overview of the main imaging methods used is given in figure 1. Although the devices and technology are highly developed, a 100 % diagnostic accuracy is not available (Temmerman et al., 2005). Plain radiographs are mainly used to identify the loosening status of a THR and most decisions on how to treat disorders after THR can be made (Ostlere & Soin, 2003). The time period between e.g. the onset of an infection and the possibility to identify any changes within the THR can be very long (Itasaka et al., 2001). Hence, in early loosening diagnosis, identifying radiolucent lines or increased uptake in radionuclide scanning can be very complex owing to the difficulty with excluding loosening (Love et al., 2001; Udomkiat et al., 2001). Therefore, surgeons cannot verify the actual loosening status accurately until the point of surgical intervention. Thus, the surgeon carries the risk of revising a sufficiently integrated THR. A major clinical problem in diagnosing loosening of a THR is to identify the moment where revision surgery is required. Loosening of THR should be diagnosed precisely and early in order to avoid massive osteolysis of the femur.

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.

A New Approach for Diagnostic Investigation of Total Hip Replacement Loosening

Diagnosis of total hip replacement (THR) loosening using imaging often fails to provide reliable results. New implants instrumented with sensors shall conform to this challenge. Therefore, a novel concept of an in vivo sensor was tested. This simple mechano-acoustical sensor is integrated inside the total hip stem and enables detection of osseous fixation. The sensor is excited by an external coil and impinges inside the THR. The spring-back of the sensor can be detected by an extracorporeal coil, while the structure-borne sound is measured with a vibration sensor placed at the patient’s leg. Experiments of a THR with one integrated sensor showed the possibility to differentiate between well fixed and loosened implants. The presented in vivo sensor system has a promising potential to detect loosening and to analyze osseointegration.