-
Scientific Reports Sep 2022In patients with kidney failure treated by hemodialysis, intradialytic arterial oxygen saturation (SaO) time series present intermittent high-frequency high-amplitude...
In patients with kidney failure treated by hemodialysis, intradialytic arterial oxygen saturation (SaO) time series present intermittent high-frequency high-amplitude oximetry patterns (IHHOP), which correlate with observed sleep-associated breathing disturbances. A new method for identifying such intermittent patterns is proposed. The method is based on the analysis of recurrence in the time series through the quantification of an optimal recurrence threshold ([Formula: see text]). New time series for the value of [Formula: see text] were constructed using a rolling window scheme, which allowed for real-time identification of the occurrence of IHHOPs. The results for the optimal recurrence threshold were confronted with standard metrics used in studies of obstructive sleep apnea, namely the oxygen desaturation index (ODI) and oxygen desaturation density (ODD). A high correlation between [Formula: see text] and the ODD was observed. Using the value of the ODI as a surrogate to the apnea-hypopnea index (AHI), it was shown that the value of [Formula: see text] distinguishes occurrences of sleep apnea with great accuracy. When subjected to binary classifiers, this newly proposed metric has great power for predicting the occurrences of sleep apnea-related events, as can be seen by the larger than 0.90 AUC observed in the ROC curve. Therefore, the optimal threshold [Formula: see text] from recurrence analysis can be used as a metric to quantify the occurrence of abnormal behaviors in the arterial oxygen saturation time series.
Topics: Humans; Oximetry; Oxygen; Polysomnography; Sleep Apnea Syndromes; Sleep Apnea, Obstructive
PubMed: 36163364
DOI: 10.1038/s41598-022-20493-0 -
Anaesthesia Jun 2017
Topics: Anesthesiology; Cost-Benefit Analysis; Developing Countries; Humans; Malawi; Oximetry
PubMed: 28439874
DOI: 10.1111/anae.13897 -
Advanced Science (Weinheim,... May 2021For wearable electronics/optoelectronics, thermal management should be provided for accurate signal acquisition as well as thermal comfort. However, outdoor solar energy...
For wearable electronics/optoelectronics, thermal management should be provided for accurate signal acquisition as well as thermal comfort. However, outdoor solar energy gain has restricted the efficiency of some wearable devices like oximeters. Herein, wireless/battery-free and thermally regulated patch-type tissue oximeter (PTO) with radiative cooling structures are presented, which can measure tissue oxygenation under sunlight in reliable manner and will benefit athlete training. To maximize the radiative cooling performance, a nano/microvoids polymer (NMVP) is introduced by combining two perforated polymers to both reduce sunlight absorption and maximize thermal radiation. The optimized NMVP exhibits sub-ambient cooling of 6 °C in daytime under various conditions such as scattered/overcast clouds, high humidity, and clear weather. The NMVP-integrated PTO enables maintaining temperature within ≈1 °C on the skin under sunlight relative to indoor measurement, whereas the normally used, black encapsulated PTO shows over 40 °C owing to solar absorption. The heated PTO exhibits an inaccurate tissue oxygen saturation (StO) value of ≈67% compared with StO in a normal state (i.e., ≈80%). However, the thermally protected PTO presents reliable StO of ≈80%. This successful demonstration provides a feasible strategy of thermal management in wearable devices for outdoor applications.
Topics: Body Temperature Regulation; Cold Temperature; Humans; Monitoring, Physiologic; Oximetry; Oxygen; Signal Processing, Computer-Assisted; Skin Temperature; Wireless Technology
PubMed: 34026462
DOI: 10.1002/advs.202004885 -
Journal of Biomedical Optics Jul 2022Pulse oximetry is widely used in clinical practice to monitor changes in arterial oxygen saturation (SpO2). However, decreases in SpO2 can be delayed relative to the...
SIGNIFICANCE
Pulse oximetry is widely used in clinical practice to monitor changes in arterial oxygen saturation (SpO2). However, decreases in SpO2 can be delayed relative to the actual clinical event, and near-infrared spectroscopy (NIRS) may detect alterations in oxygenation earlier than pulse oximetry, as shown in previous cerebral oxygenation monitoring studies.
AIM
We aim to compare the response of transcutaneous muscle NIRS measures of the tissue saturation index with pulse oximetry SpO2 during hypoxia.
APPROACH
Episodes of acute hypoxia were induced in nine anesthetized Yucatan miniature pigs. A standard pulse oximeter was attached to the ear of the animal, and a transcutaneous NIRS sensor was placed on the hind limb muscle. Hypoxia was induced by detaching the ventilator from the animal and reattaching it once the pulse oximeter reported 70% SpO2.
RESULTS
Twenty-four episodes of acute hypoxia were analyzed. Upon the start of hypoxia, the transcutaneous NIRS measures changed in 5.3 ± 0.4 s, whereas the pulse oximetry measures changed in 14.9 ± 1.0 s (p < 0.0001).
CONCLUSIONS
Transcutaneous muscle NIRS can detect the effects of hypoxia significantly sooner than pulse oximetry in the Yucatan miniature pig. A transcutaneous NIRS sensor may be used as an earlier detector of oxygen saturation changes in the clinical setting than the standard pulse oximeter.
Topics: Animals; Hypoxia; Oximetry; Oxygen; Spectroscopy, Near-Infrared; Swine; Swine, Miniature
PubMed: 35879816
DOI: 10.1117/1.JBO.27.7.077001 -
Current Eye Research Dec 2013To demonstrate the feasibility of fundus camera guided photoacoustic ophthalmoscopy (PAOM) system and its multimodal imaging capabilities.
PURPOSE
To demonstrate the feasibility of fundus camera guided photoacoustic ophthalmoscopy (PAOM) system and its multimodal imaging capabilities.
METHODS
We integrated PAOM and a fundus camera consisting of a white-light illuminator and a high-sensitivity, high-speed CCD. The fundus camera captures both retinal anatomy and PAOM illumination at the same time to provide a real-time feedback when we position the PAOM illuminating light. We applied the integrated system to image rat eyes in vivo and used full-spectrum, visible (VIS), and near infrared (NIR) illuminations in fundus photography.
RESULTS
Both albino and pigmented rat eyes were imaged in vivo. During alignment, different trajectories of PAOM laser scanning were successfully visualized by the fundus camera, which reduced the PAOM alignment time from several minutes to 30 s. In albino eyes, in addition to retinal vessels, main choroidal vessels were observed using VIS-illumination, which is similar to PAOM images. In pigmented eyes, the radial striations of retinal nerve fiber layer were visualized by fundus photography using full-spectrum illumination; meanwhile, PAOM imaged both retinal vessels and the retinal pigmented epithelium melanin distribution.
CONCLUSIONS
The results demonstrated that PAOM can be well-integrated with fundus camera without affecting its functionality. The fundus camera guidance is faster and easier comparing with our previous work. The integrated system also set the stage for the next-step verification between oximetry methods based on PAOM and fundus photography.
Topics: Albinism; Animals; Feasibility Studies; Fundus Oculi; Lasers; Ophthalmoscopy; Oximetry; Photoacoustic Techniques; Photography; Pigmentation; Rats; Rats, Long-Evans; Rats, Sprague-Dawley; Retina
PubMed: 24131226
DOI: 10.3109/02713683.2013.815219 -
Journal of Healthcare Engineering 2013This paper presents opto-physiological (OP) modeling and its application in cardiovascular assessment techniques based on photoplethysmography (PPG). Existing contact... (Review)
Review
This paper presents opto-physiological (OP) modeling and its application in cardiovascular assessment techniques based on photoplethysmography (PPG). Existing contact point measurement techniques, i.e., pulse oximetry probes, are compared with the next generation non-contact and imaging implementations, i.e., non-contact reflection and camera-based PPG. The further development of effective physiological monitoring techniques relies on novel approaches to OP modeling that can better inform the design and development of sensing hardware and applicable signal processing procedures. With the help of finite-element optical simulation, fundamental research into OP modeling of photoplethysmography is being exploited towards the development of engineering solutions for practical biomedical systems. This paper reviews a body of research comprising two OP models that have led to significant progress in the design of transmission mode pulse oximetry probes, and approaches to 3D blood perfusion mapping for the interpretation of cardiovascular performance.
Topics: Humans; Image Processing, Computer-Assisted; Models, Cardiovascular; Monte Carlo Method; Oximetry; Photoplethysmography; Reproducibility of Results; Signal Processing, Computer-Assisted; Skin Physiological Phenomena
PubMed: 24287429
DOI: 10.1260/2040-2295.4.4.505 -
Anaesthesia Mar 1991There is no absolute reference for oxygen saturation, although multiwavelength in vitro oximeters are accepted as the 'gold standard'. Regardless of whether fractional... (Comparative Study)
Comparative Study Review
There is no absolute reference for oxygen saturation, although multiwavelength in vitro oximeters are accepted as the 'gold standard'. Regardless of whether fractional or functional saturation is used by manufacturers to calibrate their oximeters, evaluation against fractional saturation is recommended since this is the clinically relevant variable. The use of standard notation and comparisons based on bias and precision is recommended. The accuracy of pulse oximetry is intrinsically limited by the use of only two wavelengths, and is dependent on the initial calibration population. The empirical algorithms used to convert the signal to its 'readout value' and the quality control of hardware may both be important sources of variability between oximeters. Change in blood temperature may introduce errors in pulse oximeter and in vitro oximeter saturation readings, but these will be clinically insignificant. Changes in blood pH should not decrease pulse oximetry accuracy.
Topics: Humans; Hydrogen-Ion Concentration; Oximetry; Oxygen; Oxyhemoglobins; Reference Standards; Signal Processing, Computer-Assisted; Statistics as Topic; Temperature
PubMed: 2014898
DOI: 10.1111/j.1365-2044.1991.tb09410.x -
Journal of Biomedical Informatics Feb 2022Uncontrolled hemorrhage is a leading cause of preventable death among patients with trauma. Early recognition of hemorrhage can aid in the decision to administer blood...
Uncontrolled hemorrhage is a leading cause of preventable death among patients with trauma. Early recognition of hemorrhage can aid in the decision to administer blood transfusion and improve patient outcomes. To provide real-time measurement and continuous monitoring of hemoglobin concentration, the non-invasive and continuous hemoglobin (SpHb) measurement device has drawn extensive attention in clinical practice. However, the accuracy of such a device varies in different scenarios, so the use is not yet widely accepted. This article focuses on using statistical nonparametric models to improve the accuracy of SpHb measurement device by considering measurement bias among instantaneous measurements and individual evolution trends. In the proposed method, the robust locally estimated scatterplot smoothing (LOESS) method and the Kernel regression model are considered to address those issues. Overall performance of the proposed method was evaluated by cross-validation, which showed a substantial improvement in accuracy with an 11.3% reduction of standard deviation, 23.7% reduction of mean absolute error, and 28% reduction of mean absolute percentage error compared to the original measurements. The effects of patient demographics and initial medical condition were analyzed and deemed to not have a significant effect on accuracy. Because of its high accuracy, the proposed method is highly promising to be considered to support transfusion decision-making and continuous monitoring of hemoglobin concentration. The method also has promise for similar advancement of other diagnostic devices in healthcare.
Topics: Hematologic Tests; Hemoglobins; Hemorrhage; Humans; Oximetry
PubMed: 34906736
DOI: 10.1016/j.jbi.2021.103975 -
Minerva Anestesiologica May 2002Pulse-oximeter is described as the most important technological proceeding for monitoring the patients' safety during anesthesia, after surgery and in emergency. This... (Review)
Review
Pulse-oximeter is described as the most important technological proceeding for monitoring the patients' safety during anesthesia, after surgery and in emergency. This opinion was widely confirmed in the 1990s when pulse-oximeter has been definitively introduced in the standard for base monitoring in the OR and has been proposed for routinary use also in the ICU. In this paper we consider the importance, in the cardiovascular, respiratory and brain parameters monitoring, of continuous oximetry of mixed venous blood (SVO2) and blood venous saturation in the internal jugular vein (SjvO2).
Topics: Anesthesia; Critical Care; Humans; Jugular Veins; Monitoring, Intraoperative; Monitoring, Physiologic; Oximetry; Oxygen
PubMed: 12029270
DOI: No ID Found -
NeuroImage Aug 2022Currently, there is great interest in making neuroimaging widely accessible and thus expanding the sampling population for better understanding and preventing diseases....
Currently, there is great interest in making neuroimaging widely accessible and thus expanding the sampling population for better understanding and preventing diseases. The use of wearable health devices has skyrocketed in recent years, allowing continuous assessment of physiological parameters in patients and research cohorts. While most health wearables monitor the heart, lungs and skeletal muscles, devices targeting the brain are currently lacking. To promote brain health in the general population, we developed a novel, low-cost wireless cerebral oximeter called FlexNIRS. The device has 4 LEDs and 3 photodiode detectors arranged in a symmetric geometry, which allows for a self-calibrated multi-distance method to recover cerebral hemoglobin oxygenation (SO) at a rate of 100 Hz. The device is powered by a rechargeable battery and uses Bluetooth Low Energy (BLE) for wireless communication. We developed an Android application for portable data collection and real-time analysis and display. Characterization tests in phantoms and human participants show very low noise (noise-equivalent power <70 fW/√Hz) and robustness of SO quantification in vivo. The estimated cost is on the order of $50/unit for 1000 units, and our goal is to share the device with the research community following an open-source model. The low cost, ease-of-use, smart-phone readiness, accurate SO quantification, real time data quality feedback, and long battery life make prolonged monitoring feasible in low resource settings, including typically medically underserved communities, and enable new community and telehealth applications.
Topics: Brain; Head; Hemoglobins; Humans; Oximetry; Phantoms, Imaging; Wearable Electronic Devices; Wireless Technology
PubMed: 35452803
DOI: 10.1016/j.neuroimage.2022.119216