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Journal ArticleDOI

Pulse oximetry: understanding its basic principles facilitates appreciation of its limitations.

01 Jun 2013-Respiratory Medicine (Respir Med)-Vol. 107, Iss: 6, pp 789-799
TL;DR: Pulse oximetry has revolutionized the ability to monitor oxygenation in a continuous, accurate, and non-invasive fashion but many providers do not know the basic principles behind its mechanism of function, so this review discusses the various conditions that can cause spurious readings and the mechanisms underlying them.
About: This article is published in Respiratory Medicine.The article was published on 2013-06-01 and is currently open access. It has received 435 citations till now.
Citations
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Journal ArticleDOI
TL;DR: This work has devised a novel method of cancelling out aliased frequency components caused by artificial light flicker, using auto-regressive (AR) modelling and pole cancellation, and has been able to construct accurate maps of the spatial distribution of heart rate and respiratory rate information from the coefficients of the AR model.
Abstract: Remote sensing of the reflectance photoplethysmogram using a video camera typically positioned 1 m away from the patient's face is a promising method for monitoring the vital signs of patients without attaching any electrodes or sensors to them. Most of the papers in the literature on non-contact vital sign monitoring report results on human volunteers in controlled environments. We have been able to obtain estimates of heart rate and respiratory rate and preliminary results on changes in oxygen saturation from double-monitored patients undergoing haemodialysis in the Oxford Kidney Unit. To achieve this, we have devised a novel method of cancelling out aliased frequency components caused by artificial light flicker, using auto-regressive (AR) modelling and pole cancellation. Secondly, we have been able to construct accurate maps of the spatial distribution of heart rate and respiratory rate information from the coefficients of the AR model. In stable sections with minimal patient motion, the mean absolute error between the camera-derived estimate of heart rate and the reference value from a pulse oximeter is similar to the mean absolute error between two pulse oximeter measurements at different sites (finger and earlobe). The activities of daily living affect the respiratory rate, but the camera-derived estimates of this parameter are at least as accurate as those derived from a thoracic expansion sensor (chest belt). During a period of obstructive sleep apnoea, we tracked changes in oxygen saturation using the ratio of normalized reflectance changes in two colour channels (red and blue), but this required calibration against the reference data from a pulse oximeter.

381 citations

Journal ArticleDOI
TL;DR: An ultraflexible near-IR responsive skin-conformal photoplethysmogram sensor based on a bulk heterojunction photovoltaic active layer containing regioregular polyindacenodithiophene-pyridyl[2,1,3]thiadiazole-cyclopentadityiophene (PIPCP) is reported.
Abstract: Flexible organic optoelectronic devices simultaneously targeting mechanical conformability and fast responsivity in the near-infrared (IR) region are a prerequisite to expand the capabilities of practical optical science and engineering for on-skin optoelectronic applications. Here, an ultraflexible near-IR responsive skin-conformal photoplethysmogram sensor based on a bulk heterojunction photovoltaic active layer containing regioregular polyindacenodithiophene-pyridyl[2,1,3]thiadiazole-cyclopentadithiophene (PIPCP) is reported. The ultrathin (3 µm thick) photodetector exhibits unprecedented operational stability under severe mechanical deformation at a bending radius of less than 3 µm, even after more than 103 bending cycles. Deliberate optimization of the physical dimensions of the active layer used in the device enables precise on/off switching and high device yield simultaneously. The response frequency over 1 kHz under mechanically deformed conditions facilitates conformal electronic sensors at the machine/human interface. Finally, a mechanically stretchable, flexible, and skin-conformal photoplethysmogram (PPG) device with higher sensitivity than those of rigid devices is demonstrated, through conformal adherence to the flexuous surface of a fingerprint.

161 citations

Journal ArticleDOI
TL;DR: The present review will focus on definition, various causes, mechanisms, and approach of hypoxemia in human.
Abstract: Oxygen is an essential element for life and without oxygen humans can survive for few minutes only. There should be a balance between oxygen demand and delivery in order to maintain homeostasis within the body. The two main organ systems responsible for oxygen delivery in the body and maintaining homeostasis are respiratory and cardiovascular system. Abnormal function of any of these two would lead to the development of hypoxemia and its detrimental consequences. There are various mechanisms of hypoxemia but ventilation/perfusion mismatch is the most common underlying mechanism of hypoxemia. The present review will focus on definition, various causes, mechanisms, and approach of hypoxemia in human.

161 citations


Cites background from "Pulse oximetry: understanding its b..."

  • ...Oxy-hemoglobin (O2Hb) and deoxy-hemoglobin (HHb) differentially absorb red and near-infrared (IR) light.[108]...

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Journal ArticleDOI
TL;DR: Evaluated patient‐reported oxygen saturation (SpO2) using pulse oximetry as a home monitoring tool for patients with initially nonsevere COVID‐19 to identify need for hospitalization.
Abstract: OBJECTIVES: Our objective was to evaluate patient-reported oxygen saturation (SpO2 ) using pulse oximetry as a home monitoring tool for patients with initially nonsevere COVID-19 to identify need for hospitalization. METHODS: Patients were enrolled at the emergency department (ED) and outpatient testing centers. Each patient was given a home pulse oximeter and instructed to record their SpO2 every 8 hours. Patients were instructed to return to the ED for sustained home SpO2 < 92% or if they felt they needed emergent medical attention. Relative risk was used to assess the relation between hospitalization and home SpO2 < 92% in COVID-19-positive patients. RESULTS: We enrolled 209 patients with suspected COVID-19, of whom 77 patients tested positive for COVID-19 and were included. Subsequent hospitalization occurred in 22 of 77 (29%) patients. Resting home SpO2 < 92% was associated with an increased likelihood of hospitalization compared to SpO2 ≥ 92% (relative risk = 7.0, 95% confidence interval = 3.4 to 14.5, p < 0.0001). Home SpO2 < 92% was also associated with increased risk of intensive care unit admission, acute respiratory distress syndrome, and septic shock. In our cohort, 50% of patients who ended up hospitalized only returned to the ED for incidental finding of low home SpO2 without worsening of symptoms. One-third (33%) of nonhospitalized patients stated that they would have returned to the ED if they did not have a pulse oximeter to reassure them at home. CONCLUSIONS: This study found that home pulse oximetry monitoring identifies need for hospitalization in initially nonsevere COVID-19 patients when a cutoff of SpO2 92% is used. Half of patients who ended up hospitalized had SpO2 < 92% without worsening symptoms. Home SpO2 monitoring also reduces unnecessary ED revisits.

130 citations

Journal ArticleDOI
TL;DR: The wearable technologies available for non-invasive monitoring of various parameters concerning an athlete's training and health are discussed and a combination of several wearables is proposed that is most effective for accessing all relevant parameters, disturbing the athlete as little as possible, and optimizing performance and promoting health.
Abstract: Athletes adapt their training daily to optimize performance, as well as avoid fatigue, overtraining and other undesirable effects on their health. To optimize training load, each athlete must take his/her own personal objective and subjective characteristics into consideration and an increasing number of wearable technologies (wearables) provide convenient monitoring of various parameters. Accordingly, it is important to help athletes decide which parameters are of primary interest and which wearables can monitor these parameters most effectively. Here, we discuss the wearable technologies available for non-invasive monitoring of various parameters concerning an athlete's training and health. On the basis of these considerations, we suggest directions for future development. Furthermore, we propose that a combination of several wearables is most effective for accessing all relevant parameters, disturbing the athlete as little as possible, and optimizing performance and promoting health.

126 citations

References
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Journal ArticleDOI
TL;DR: The millimolar absorptivities of the four clinically relevant derivatives of fetal and adult human hemoglobin in the visible and near-infrared spectral range (450-1000 nm) were determined, and spectral absorption curves of similar shape were found.
Abstract: We determined the millimolar absorptivities of the four clinically relevant derivatives of fetal and adult human hemoglobin in the visible and near-infrared spectral range (450-1000 nm). As expected, spectral absorption curves of similar shape were found, but the small differences between fetal and adult hemoglobin absorptivity were important enough that they should be taken into account in multicomponent analysis of hemoglobin derivatives. Common pulse oximeters, however, involving light of 660 and 940 nm, are so insensitive to the presence of fetal hemoglobin that they can be used safely in neonates. The error in pulse oximetry caused by the presence of carboxyhemoglobin is insubstantial, but methemoglobin gives either an understimation or an overestimation at high or low oxygen saturation, respectively, the turning point being near 70% saturation.

661 citations


"Pulse oximetry: understanding its b..." refers background in this paper

  • ...The degree to which HbF affects FO2Hb readings depends on the specific co-oximeter used as different co-oximetermodels often utilize different sets of wavelengths; in addition, HbA and HbF differ in light absorbance (for both O2Hb and HHb) primarily in the 450e650 nm spectral rangeewhich coincides with the wavelengths used by most co-oximeters.(52,53) Although simply adding the fictitious COHb level to O2Hb in an attempt to correct the FO2Hb (provided there is no evidence of hemolysis or CO poisoning that can cause a true increase in COHb) may work for some systems, some cooximeters can correct the readings in the presence of HbF....

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Journal ArticleDOI
TL;DR: From the Division of Pulmonary, Allergy, and Critical Care Medicine and the Hemostasis and Vascular Biology Research Institute, University of Pittsburgh, Pittsburgh, and Children’s Hospital and Research Center at Oakland, Oakland, CA.
Abstract: From the Division of Pulmonary, Allergy, and Critical Care Medicine and the Hemostasis and Vascular Biology Research Institute, University of Pittsburgh, Pittsburgh, (M.T.G.); and Children’s Hospital and Research Center at Oakland, Oakland, CA (E.V.). Address reprint requests to Dr. Gladwin at the Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh, NW 168 Montefiore Hospital, 354 Fifth Ave., Pittsburgh, PA, 15213, or at gladwinmt@upmc.edu.

447 citations


"Pulse oximetry: understanding its b..." refers background in this paper

  • ...Complications of sickle cell disease, such as vasoocclusive crisis and acute chest syndrome, are often precipitated or exacerbated by hypoxemia, and can result in a vicious cycle of additional sickling and vasoocclusive crises.(11) Thus, accurate detection of hypoxemia in these patients plays an important role in mitigating further red blood cell sickling....

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Journal ArticleDOI
TL;DR: The principles of pulse oximetry are reviewed, with an eye toward recognizing the limitations of this tool, which include performance limitations in the settings of carboxyhemoglobinemia, methemoglobeinema, motion artifact, hypotension, vasoconstriction, and anemia.
Abstract: The pulse oximeter has become an essential tool in the modern practice of emergency medicine. However, despite the reliance placed on the information this monitor offers, the underlying principles and associated limitations of pulse oximetry are poorly understood by medical practitioners. This article reviews the principles of pulse oximetry, with an eye toward recognizing the limitations of this tool. Among these are performance limitations in the settings of carboxyhemoglobinemia, methemoglobinemia, motion artifact, hypotension, vasoconstriction, and anemia. The accuracy of pulse oximetry is discussed in light of these factors, with further discussion of applications for pulse oximetry in emergency medicine, including both oximetric and plethysmographic operation. The pulse oximeter is an invaluable instrument for emergency medicine practice, but as with any test the data it offers must be critically appraised for proper interpretation and utilization.

423 citations


"Pulse oximetry: understanding its b..." refers background in this paper

  • ...For example, in hypotensive, vasoconstricted patients, ear and forehead probes may be more reliable as these areas are less likely to vasoconstrict than the fingers in response to endogenous and exogenous catecholamines.(3,7) In hypothermia, where there is secondary vasoconstriction, the forehead probe has been shown to be more reliable than the finger probe....

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  • ...It is fortuitous that O2Hb and HHb have significant differences in absorption at red and near-IR light because these two wavelengths penetrate tissues well whereas blue, green, yellow, and far-IR light are significantly absorbed by nonvascular tissues and water.(3) O2Hb absorbs greater amounts of IR light and lower amounts of red light than does HHb; this is consistent with experience e welloxygenated blood with its higher concentrations of O2Hb appears bright red to the eye because it scatters more red light than does HHb....

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Journal ArticleDOI
TL;DR: BleBleile as discussed by the authors explained his approach to the initial assessment of Bobby, a 4;3 (years; months) old child with suspected problems with articulation and phonology. Blei...
Abstract: In the lead article of this forum, Ken Bleile explains his approach to the initial assessment of Bobby, a 4;3 (years; months) old child with suspected problems with articulation and phonology. Blei...

312 citations

Journal ArticleDOI
TL;DR: The pulse oximeter, as the sole indicator of blood oxygenation, should be used with caution in patients with recent carbon monoxide exposure, because transcutaneous PO2 falls linearly as COHb increases, and reaches about one-fifth of its initial value at the highestCOHb levels despite the maintenance of constant arterial PO2.
Abstract: Five dogs were anesthetized, intubated, and ventilated with various mixtures of oxygen, nitrogen, and carbon monoxide. Each dog was monitored with arterial and pulmonary artery catheters, a transcutaneous PO2 analyzer, and two pulse oximeters. An IL-282 Co-oximeter was used to periodically measure arterial oxyhemoglobin (O2Hb) and carboxyhemoglobin (COHb) as percentages of the total hemoglobin. The PaO2, PaCO2, and pHa were measured in the same blood specimens using standard electrodes. When the inspired oxygen concentration was reduced in the absence of COHb, the pulse oximeter saturation (SpO2) estimated O2Hb with reasonable accuracy. COHb levels were then varied slowly from 0-75% in each dog. As the COHb level increased and oxyhemoglobin decreased, both pulse oximeters continued to read an oxygen saturation of greater than 90%, while the actual O2Hb fell below 30%. In the presence of COHb, the SpO2 is approximately the sum of COHb and O2Hb, and, thus, may seriously overestimate O2Hb. The pulse oximeter, as the sole indicator of blood oxygenation, should, therefore, be used with caution in patients with recent carbon monoxide exposure. On the other hand, transcutaneous PO2 falls linearly as COHb increases, and reaches about one-fifth of its initial value at the highest COHb levels despite the maintenance of constant arterial PO2.

246 citations


"Pulse oximetry: understanding its b..." refers background in this paper

  • ...Co-oximeter reports ell as FO2Hb (meaning fractional SaO2 although the term oth functional SaO2 and SpO2 are minimally affected by experimental animals, a SpO2 level of 90% was recorded ation was 30%.(55) Thus, even in significant CO poisoning, ication of oxygenation whereas the O2 carrying capacity is distinction between SaO2 and FO2Hb is illustrated ncluding that because a severely anemic patient has a e blood is adequate....

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