An Optical Fiber Photoplethysmographic System for Central Nervous System Tissue (original) (raw)
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Preliminary evaluation of a new fibre-optic cerebral oximetry system
A new system for measuring the oxygen saturation of blood within tissue has been developed, for a variety of patient monitoring applications. A particular unmet need is in the central nervous system, and this project aims to devise a means for measuring blood oxygen saturation in the brain tissue of patients recovering from neurosurgery or head injury. Coupling light sources and a photodetector to optical fibres results in a probe small enough to pass through a cranial bolt of the type already in use for intra-cranial pressure monitoring. The development and evaluation of a two-wavelength fibre-optic reflectance photoplethysmography (PPG) system are described. It was found that good quality red and near-infrared PPG signals could be obtained from the finger using a fibre-optic probe. Experiments were conducted to find the inter-fibre spacings that yield signals most suitable for calculating oxygen saturation. Reliable signals could be obtained for inter-fibre spacings between 2 mm and 5 mm, the latter being the size of the maximum aperture in the cranial bolt. A preliminary measurement from human brain tissue is also presented.
Cerebral Arterial Oxygen Saturation Measurements Using a Fiber-Optic Pulse Oximeter
Background A pilot investigation was undertaken to assess the performance of a novel fiber-optic cerebral pulse oximetry system. A fiber-optic probe designed to pass through the lumen of a cranial bolt of the type used to make intracranial pressure measurements was used to obtain optical reflectance signals directly from brain tissue. Methods Short-duration measurements were made in six patients undergoing neurosurgery. These were followed by a longer duration measurement in a patient recovering from an intracerebral hematoma. Estimations of cerebral arterial oxygen saturation derived from a frequency domain-based algorithm are compared with simultaneous pulse oximetry (SpO 2) and hemoximeter (SaO 2) blood samples. Results The short-duration measurements showed that reliable photoplethysmographic signals could be obtained from the brain tissue. In the long-duration study, the mean (±SD) difference between cerebral oxygen saturation (ScaO 2) and finger SpO 2 (in saturation units) was-7.47(±3.4)%. The mean (±SD) difference between ScaO 2 and blood SaO 2 was-7.37(±2.8)%. Conclusions This pilot study demonstrated that arterial oxygen saturation may be estimated from brain tissue via a fiber-optic pulse oximeter used in conjunction with a cranial bolt. Further studies are needed to confirm the clinical utility of the technique.
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.
Measurements of cerebral arterial oxygen saturation using a fiber-optic pulse oximeter
2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2009
This pilot investigation was undertaken to assess the performance of a novel fiber-optic cerebral pulse oximetry system. A fiber-optic probe designed to pass through the lumen of a cranial bolt of the type used to make intracranial pressure measurements was used to obtain optical reflectance signals directly from the brain tissue. Preliminary results from seven patients measured in the operating theatre and ITU are presented. Estimations of cerebral arterial oxygen saturation derived from a frequency domain-based algorithm are compared with pulse oximetry (SpO 2) and hemoximeter (SaO 2) blood samples. The mean (±SD) difference between cerebral oxygen saturation (ScaO 2) and finger SpO 2 (in saturation units) was-7.47(±3.4)%. The mean (±SD) difference between ScaO 2 and blood SaO 2 was-7.37(±2.8)%.
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.
Journal of Lasers, Optics & Photonics, 2016
In this paper, the design and development of dual wavelength noninvasive fiber optic probe based oxyhemoglobin sensor has been presented. This instrument can be used for real time monitoring contents in the blood. It is well known that in blood, the oxygen is carried by the hemoglobin. It uses the dual wavelength spectroscopy which can be performed on blood to determine the oxyhemoglobin saturation. The two sources used are of wavelength 632.8 nm and 830 nm. Two probes containing a bundle of fibers are designed out of which two are source fiber and one is detector fiber. Two finger holders are also designed to prevent any variation in intensity due to finger movement. The backscattered intensity and transmitted intensity of red light and near infrared light are measured. With the help of the ratio of the backscattered intensities and transmitted intensities of red light and near infrared light, oxyhemoglobin saturation is determined.
Photoplethysmographic measurements from the esophagus using a new fiber-optic reflectance sensor
2011
A prototype fiber-optic reflectance-mode pulse oximetry sensor and measurement system is developed for the purposes of estimating arterial oxygen saturation in the esophagus. A dedicated probe containing miniature right-angled glass prisms coupled to light sources and a photodetector by means of optical fibers is designed and used to record photoplethysmographic (PPG) signals from the esophageal epithelium in anesthetized patients. The probe is inserted simply by an anesthesiologist in all cases, and signals are recorded successfully in all but one of 20 subjects, demonstrating that esophageal PPG signals can be reliably obtained. The mean value of the oxygen saturation recorded from the esophagus for all subjects is 94.0 ± 4.0%. These results demonstrate that SpO 2 may be estimated in the esophagus using a fiber-optic probe.
Feasibility study of a fiber-optic system for invasive blood pressure measurements
Catheterization and Cardiovascular Interventions, 2002
A comparative study was conducted to evaluate the feasibility of a fiber-optic sensor in invasive blood pressure measurements. Static and wide-bandwidth stimuli were offered to the fiber-optic, Millar, Baxter, and Sentron devices to measure static transfer function and transient response. Animal experiments focused on offset drift, dynamic accuracy, and electromagnetic sensitivity. Compared to the Millar, Sentron, and Baxter devices, the fiber-optic sensor had a near-identical static transfer function. Gain and offset errors were < 3.4% and < 0.25%, respectively. Hysteresis nonlinearity was < 0.1%. The dynamic accuracy of the fiber-optic system matched that of the Millar and Sentron systems. Time delay was < 1 msec. Maximum rate of change was > 30,000 mm Hg/sec and bandwidth was 0 -150 Hz minimum. Offset drift was 0.6 ؎ 0.03 mm Hg. Application of diathermy highlighted the fiber-optic sensor's excellent electromagnetic disturbance rejection. The fiber-optic system appears to be a reliable, high-fidelity pressure monitor in demanding clinical environments. Cathet Cardiovasc Intervent 2002;57:272-276.
Photoplethysmographic sensors for perfusion measurements in spinal cord tissue
Journal of Physics: Conference Series, 2011
Sensors for recording photoplethysmographic signals from the nervous tissue of the spinal cord are described. The purpose of these sensors is to establish whether perfusion is compromised in various states of injury which occur in certain animal models of spinal cord injury, for example compression injury. Various measures of perfusion are applicable such as the amplitude of the photoplethysmograph signal and the oxygen saturation, measured using a dual wavelength configuration. Signals are usually compared to baseline measurements made in uninjured subjects. This paper describes two types of probe, one based on optical fibres, and one in which optotes are placed in direct contact with the tissue surface. Results from a study based on a compression model utilising a fibreoptic sensor are presented.