The pulse oximetry is a non-invasive method to monitor the oxygen saturation and is clinically used for many years. However this technology has some limitations. In case of the presence of dysfunctional hemoglobin derivatives as carboxyhemoglobin (COHb) or methemoglobin (MetHb) the readings of the pulse oximeter are distorted. This erroneous diagnosis of the patient’s status can result in a life threatening situation. This paper will describe a sensor system for noninvasive determination of carboxy- and methemoglobin.
This paper will describe a novel multi-wavelength photometric method to measure carboxyhemoglobin (COHb) and methemoglobin (MetHb) concentration non-invasively.
COHb and MetHb are so called dysfunctional hemoglobin derivatives and they are not able to carry oxygen. Standard pulse oximeters are only able to measure two derivatives, namely oxyhemoglobin (O2Hb) and deoxyhemoglobin (HHb) but the presence of other derivatives in the blood may distort the readings. The paper presents a new approach of a noninvasive sensor system to measure COHb and MetHb and the validation in vivo and in vitro.
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.
During the perioperative period, which includes the period before surgery and after surgery (postoperative), it is essential to measure diagnostic parameters such as: blood oxygen saturation; hemoglobin (Hb) concentration; and pulse rate. The Hb concentration in human blood is an important parameter to evaluate the physiological condition of an individual, as Hb is the oxygen carrying component of red blood cells. By determining the Hb concentration, it is possible, for example, to observe intraoperative or postoperative bleeding, and use this information as a trigger for autologous/ allogenic blood transfusions. In blood donation center it is also an essential parameter for the decision regarding the acceptance of the donor.
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.
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.
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