Pulse oximetry of body cavities and organs (original) (raw)
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A new, continuous method of monitoring splanchnic organ oxygen saturation (SpO 2) would make the early detection of inadequate tissue oxygenation feasible, reducing the risk of hypoperfusion, severe ischaemia, and, ultimately, death. In an attempt to provide such a device, a new fibre optic based reflectance pulse oximeter probe and processing system were developed followed by an in vivo evaluation of the technology on seventeen patients undergoing elective laparotomy. Photoplethysmographic (PPG) signals of good quality and high signal-to-noise ratio were obtained from the small bowel, large bowel, liver and stomach. Simultaneous peripheral PPG signals from the finger were also obtained for comparison purposes. Analysis of the amplitudes of all acquired PPG signals indicated much larger amplitudes for those signals obtained from splanchnic organs than those obtained from the finger. Estimated SpO 2 values for splanchnic organs showed good agreement with those obtained from the finger fibre optic probe and those obtained from a commercial device. These preliminary results suggest that a miniaturized 'indwelling' fibre optic sensor may be a suitable method for pre-operative and post-operative evaluation of splanchnic organ SpO 2 and their health.
Pulse Oximetry for the Measurement of Oxygen Saturation in Arterial Blood
2021
The method of photoplethysmography (PPG) detailed in Chapters 1 and 2 gained enormous prominence due to the development of pulse oximetry. In pulse oximetry, the fact that hemoglobin bound with oxygen (called oxyhemoglobin) and hemoglobin without oxygen (deoxy-hemoglobin or reduced hemoglobin) absorb/reflect light differently is exploited in ascertaining, noninvasively, oxygen saturation in arterial blood. Most pulse oximeters that are in existence today use a couple of PPGs obtained using red and infrared wavelength light sources and calculate oxygen saturation in arterial blood using the red and IR PPGs and an empirical equation. This chapter details the development of pulse oximetry. It describes in detail a couple of novel methods of oxygen saturation calculation using the red and IR PPGs. The methods presented here do not need any calibration to be performed. 3.1 Physiological Signals for Diagnostics Dynamic and static measurements on the physical, electrical, chemical and acoustic signals of a human body will help ascertain its health [1-3]. Whenever a person is affected by a disease or gets injured, one or more of these physical, electrical, chemical and acoustic signals change. However, these physical, electrical, chemical and acoustic signals also change day to day due to natural variations in the life cycle. Moreover, the changes in these signals are a complex combination of different parameters. Hence it is very difficult to delineate the functioning or malfunctioning of the underlying biological parts or processes directly from these signals. The four traditional vital signs, namely, the pulse rate, the respiratory rhythm (and sound), the body temperature and the blood pressure are normally used by medical practitioners all over the globe to assess a patient's state of health. In the modern times, a fifth vital signal, namely, the oxygen saturation in blood has also gained importance. Today any patient with coronary or pulmonary problems must be evaluated for the oxygen
The principal advantage of optical sensors for medical applications is their intrinsic safety since there is no electrical contact between the patient and the equipment. (An added bonus is that they are also less suspect to electromagnetic interference). This has given rise to a variety of optical techniques to monitor physiological parameters: for example, the technique of Laser Doppler velocimetry to measure red blood cell velocity. However, in this lecture course we will concentrate on the technique of pulse oximetry for the non−invasive measurement of arterial oxygen saturation in the blood (although a second use of the technology will be discussed right at the end of the course). For patients at risk of respiratory failure, it is important to monitor the efficiency of gas exchange in the lungs, ie how well the arterial blood is oxygenated (as opposed to whether or not air is going in and out of the lungs). Preferably, such information should be available to clinicians of a continuous basis (rather than every few hours). Both of these requirements can be met non−invasively 2 with the technology of pulse oximetry. The technique is now well established and is in regular clinical use during anaesthesia and intensive care (especially neonatal intensive care since many premature infants undergo some form of ventilator therapy). Pulse oximetry is also being used in the monitoring of pulmonary disease in adults and in the investigation of sleep disorders.
Blood Oxygen Level Measurement with a chest-based Pulse Oximetry Prototype System
This paper presents a prototyped novel chest-based Pulse Oximetry system, and reports on test results from comparative trials with a commercially available fingerbased Pulse Oximetry system using several human subjects. The system was iteratively optimized through adjustment of optical component alignment (angular position, component distance, photosensitive area etc.) and through fine-tuning of LED intensity and receiver sensitivity. This work is significant and timely as it provides compelling evidence that SpO 2 measurements from the chest offer a genuine commercial solution for bedside and ambulatory vital-signs monitoring.
An oesophageal pulse oximetry system utilising a fibre-optic probe
Journal of Physics: Conference Series, 2009
A dual-wavelength fibre-optic pulse oximetry system is described for the purposes of estimating oxygen saturation (SpO 2) from the oesophagus. A probe containing miniature right-angled glass prisms was used to record photoplethysmographic (PPG) signals from the oesophageal wall. Signals were recorded successfully in 19 of 20 patients, demonstrating that PPG signals could be reliably obtained from an internal vascularised tissue site such as the oesophageal epithelium. The value of the mean oxygen saturation recorded from the oesophagus was 94.0 ± 4.0%. These results demonstrate that SpO 2 may be estimated in the oesophagus using a fibre-optic probe.
Development of a medical fiber-optic oxygen sensor based on optical absorption change
IEEE Transactions on Biomedical Engineering, 1992
A new fiber-optic oxygen sensor has been developed for use in medical applications. The sensor's viologen indicator becomes strongly absorbant after brief UV stimulation, and then returns to the transparent state. The rate of indicator return to transparency is proportional to the local oxygen concentration. Indicator absorbance is monitored with a red LED and receiving photodiode, and absorbance data are. processed by a dedicated CPU. The solid-state sensor system has performance comparable to existing oxygen measurement techniques, and may be applicable for both in vitro and in vivo oxygen measurements.
A prototype device for standardized calibration of pulse oximeters
Journal of clinical monitoring and computing, 2000
To develop and test a method for standardized calibration of pulse oximeters. A novel pulse oximeter calibration technique capable of simulating the behavior of real patients is discussed. It is based on an artificial finger with a variable spectral-resolved light attenuator in conjunction with an extensive clinical database of time-resolved optical transmission spectra of patients fingers in the wavelength range 600-1000 nm. The arterial oxygen saturation of the patients at the time of recording was derived by analyzing a corresponding blood sample with a CO-oximeter. These spectra are used to compute the modulation of the light attenuator which is attached to the artificial finger. This calibration method was tested by arbitrarily playing back recorded spectra to pulse oximeters and comparing their display to the value they displayed when the spectra were recorded. We were able to demonstrate that the calibrator could generate physiological signals which are accepted by a pulse ox...
Pulse oximetry: fundamentals and technology update
Medical Devices: Evidence and Research, 2014
Oxygen saturation in the arterial blood (SaO 2) provides information on the adequacy of respiratory function. SaO 2 can be assessed noninvasively by pulse oximetry, which is based on photoplethysmographic pulses in two wavelengths, generally in the red and infrared regions. The calibration of the measured photoplethysmographic signals is performed empirically for each type of commercial pulse-oximeter sensor, utilizing in vitro measurement of SaO 2 in extracted arterial blood by means of co-oximetry. Due to the discrepancy between the measurement of SaO 2 by pulse oximetry and the invasive technique, the former is denoted as SpO 2. Manufacturers of pulse oximeters generally claim an accuracy of 2%, evaluated by the standard deviation (SD) of the differences between SpO 2 and SaO 2 , measured simultaneously in healthy subjects. However, an SD of 2% reflects an expected error of 4% (two SDs) or more in 5% of the examinations, which is in accordance with an error of 3%-4%, reported in clinical studies. This level of accuracy is sufficient for the detection of a significant decline in respiratory function in patients, and pulse oximetry has been accepted as a reliable technique for that purpose. The accuracy of SpO 2 measurement is insufficient in several situations, such as critically ill patients receiving supplemental oxygen, and can be hazardous if it leads to elevated values of oxygen partial pressure in blood. In particular, preterm newborns are vulnerable to retinopathy of prematurity induced by high oxygen concentration in the blood. The low accuracy of SpO 2 measurement in critically ill patients and newborns can be attributed to the empirical calibration process, which is performed on healthy volunteers. Other limitations of pulse oximetry include the presence of dyshemoglobins, which has been addressed by multiwavelength pulse oximetry, as well as low perfusion and motion artifacts that are partially rectified by sophisticated algorithms and also by reflection pulse oximetry.