Assessment of accuracy of two pulse oximeters in infants with cyanotic and acyanotic congenital heart diseases.

BACKGROUND: Peripherally measured oxygen saturation (SpO2) may often differ from arterial oxygen saturation (SaO2), measured by co-oximetry, especially within the lower range of oxygen saturations. This can potentially impact clinical decisions and therapy in children with congenital heart disease, as critical hypoxemia might remain unnoticed. AIMS: Our aim was to investigate the accuracy of two different pulse oximeters compared to SaO2 in infants with congenital heart diseases. METHODS: Simultaneous recordings of SpO2, measured by two different pulse oximeters (Philips IntelliVue X3 Monitor and Nellcor™ OxiMax™), were compared to SaO2 obtained by arterial blood gas analysis. RESULTS: A total of 153 measurements were performed in 44 infants with arterial oxygen saturation between 70 and 100%. We divided the measurements into 3 subgroups: group 1-SaO2 70.0%-85.0%, group 2-SaO2 85.1%-94.0%, group 3-SaO2 >94.1%. For Philipps, the median bias was 5.3 (IQR: 2.6-8.7) %, 2.3 (IQR: 0.9-6.0) % and 1.1 (IQR: -0.8-2.4) % in group 1, 2 and 3, respectively. For OxiMax™, the median bias was 2.7 (IQR: 0.5-5.1) %, 0.2 (IQR: -0.9-2.6) % and -0.5 (IQR: -1.3-0.6) % in group 1, 2 and 3, respectively. Regarding the accuracy of these oximeters, as evaluated with the Accuracy root mean squared index (Arms), it was 9.8 versus 4.5% in group 1, 4.5 versus 2.9% in group 2 and 2.4 versus 1.9% in group 3 for Philipps and OxiMax™, respectively. CONCLUSIONS: In lower range saturations between 70% and 85% the accuracy of both pulse oximeters exceeded the threshold of ≤3% recommended by the Food and Drug Administration (FDA). Therefore, peripheral pulse oximetry within the lower range of oxygen saturations should be interpreted with caution in infants with congenital heart diseases, taking into consideration its limitations. Direct co-oximetry should be the preferred method to support clinical decisions in children with cyanotic congenital heart diseases.

History and Social Implications of the Pulse Oximeter.

The pulse oximeter is a portable, bedside tool that allows for the measurement of oxygen saturation in a patient's red blood cells. The technology is based on oxygenated and deoxygenated hemoglobin absorbing light at different wavelengths. The device calculates the ratio of oxygenated to deoxygenated hemoglobin in the blood, and an algorithm produces a percentage oxygen saturation value. Due to its portability and ease of use, it is a ubiquitous medical tool that is commonly used in medical practice. This paper reviews the history and evolution of this tool, and the scientific laws behind oximetry. It also introduces the importance of the pulse oximeter and its basic functions. In addition, the limitations of pulse oximetry are discussed, especially as they pertain to pigmented skin.

Pulse oximetry in pediatric care: Balancing advantages and limitations.

BACKGROUND: Pulse oximetry has become a cornerstone technology in healthcare, providing non-invasive monitoring of oxygen saturation levels and pulse rate. Despite its widespread use, the technology has inherent limitations and challenges that must be addressed to ensure accurate and reliable patient care. AIM: To comprehensively evaluate the advantages, limitations, and challenges of pulse oximetry in clinical practice, as well as to propose recommendations for optimizing its use. METHODS: A systematic literature review was conducted to identify studies related to pulse oximetry and its applications in various clinical settings. Relevant articles were selected based on predefined inclusion and exclusion criteria, and data were synthesized to provide a comprehensive overview of the topic. RESULTS: Pulse oximetry offers numerous advantages, including non-invasiveness, real-time feedback, portability, and cost-effectiveness. However, several limitations and challenges were identified, including motion artifacts, poor peripheral perfusion, ambient light interference, and patient-specific factors such as skin pigmentation and hemoglobin variants. Recommendations for optimizing pulse oximetry use include technological advancements, education and training initiatives, quality assurance protocols, and interdisciplinary collaboration. CONCLUSION: Pulse oximetry is crucial in modern healthcare, offering invaluable insights into patients' oxygenation status. Despite its limitations, pulse oximetry remains an indispensable tool for monitoring patients in diverse clinical settings. By implementing the recommendations outlined in this review, healthcare providers can enhance the effectiveness, accessibility, and safety of pulse oximetry monitoring, ultimately improving patient outcomes and quality of care.

Impact of Skin Pigmentation on Pulse Oximetry Blood Oxygenation and Wearable Pulse Rate Accuracy: Systematic Review and Meta-Analysis.

BACKGROUND: Photoplethysmography (PPG) is a technology routinely used in clinical practice to assess blood oxygenation (SpO2) and pulse rate (PR). Skin pigmentation may influence accuracy, leading to health outcomes disparities. OBJECTIVE: This systematic review and meta-analysis primarily aimed to evaluate the accuracy of PPG-derived SpO2 and PR by skin pigmentation. Secondarily, we aimed to evaluate statistical biases and the clinical relevance of PPG-derived SpO2 and PR according to skin pigmentation. METHODS: We identified 23 pulse oximetry studies (n=59,684; 197,353 paired SpO2-arterial blood observations) and 4 wearable PR studies (n=176; 140,771 paired PPG-electrocardiography observations). We evaluated accuracy according to skin pigmentation group by comparing SpO2 accuracy root-mean-square values to the regulatory threshold of 3% and PR 95% limits of agreement values to +5 or -5 beats per minute (bpm), according to the standards of the American National Standards Institute, Association for the Advancement of Medical Instrumentation, and the International Electrotechnical Commission. We evaluated biases and clinical relevance using mean bias and 95% CI. RESULTS: For SpO2, accuracy root-mean-square values were 3.96%, 4.71%, and 4.15%, and pooled mean biases were 0.70% (95% CI 0.17%-1.22%), 0.27% (95% CI -0.64% to 1.19%), and 1.27% (95% CI 0.58%-1.95%) for light, medium, and dark pigmentation, respectively. For PR, 95% limits of agreement values were from -16.02 to 13.54, from -18.62 to 16.84, and from -33.69 to 32.54, and pooled mean biases were -1.24 (95% CI -5.31 to 2.83) bpm, -0.89 (95% CI -3.70 to 1.93) bpm, and -0.57 (95% CI -9.44 to 8.29) bpm for light, medium, and dark pigmentation, respectively. CONCLUSIONS: SpO2 and PR measurements may be inaccurate across all skin pigmentation groups, breaching U.S. Food and Drug Administration guidance and industry standard thresholds. Pulse oximeters significantly overestimate SpO2 for both light and dark skin pigmentation, but this overestimation may not be clinically relevant. PRs obtained from wearables exhibit no statistically or clinically significant bias based on skin pigmentation.

Racial Biases Associated With Pulse Oximetry: Longitudinal Social Network Analysis of Social Media Advocacy Impact.

BACKGROUND: Pulse oximetry is a noninvasive method widely used in critical care and various clinical settings to monitor blood oxygen saturation. During the COVID-19 pandemic, its application for at-home oxygen saturation monitoring became prevalent. Further investigations found that pulse oximetry devices show decreased accuracy when used on individuals with darker skin tones. This study aimed to investigate the influence of X (previously known as Twitter) on the dissemination of information and the extent to which it raised health care sector awareness regarding racial disparities in pulse oximetry. OBJECTIVE: This study aimed to explore the impact of social media, specifically X, on increasing awareness of racial disparities in the accuracy of pulse oximetry and to map this analysis against the evolution of published literature on this topic. METHODS: We used social network analysis drawing upon Network Overview Discovery and Exploration for Excel Pro (NodeXL Pro; Social Media Research Foundation) to examine the impact of X conversations concerning pulse oximetry devices. Searches were conducted using the Twitter Academic Track application programming interface (as it was known then). These searches were performed each year (January to December) from 2012 to 2022 to cover 11 years with up to 52,052 users, generating 188,051 posts. We identified the nature of influencers in this field and monitored the temporal dissemination of information about social events and regulatory changes. Furthermore, our social media analysis was mapped against the evolution of published literature on this topic, which we located using PubMed. RESULTS: Conversations on X increased health care awareness of racial bias in pulse oximetry. They also facilitated the rapid dissemination of information, attaining a substantial audience within a compressed time frame, which may have impacted regulatory action announced concerning the investigation of racial biases in pulse oximetry. This increased awareness led to a surge in scientific research on the subject, highlighting a growing recognition of the necessity to understand and address these disparities in medical technology and its usage. CONCLUSIONS: Social media platforms such as X enabled researchers, health experts, patients, and the public to rapidly share information, increasing awareness of potential racial bias. These platforms also helped connect individuals interested in these topics and facilitated discussions that spurred further research. Our research provides a basis for understanding the role of X and other social media platforms in spreading health-related information about potential biases in medical devices such as pulse oximeters.

Interference in Pulse Oximetry in a Neonate with Bronze Baby Syndrome.

Reliable estimation of pulse oximetry (SpO2) is indispensable in a neonatal intensive care setting. Along with clinical examination, SpO2 is a validated non-invasive correlate of PaO2 to dictate the level of respiratory support. Any alterations that may interfere with this correlation pose significant challenges and lead to inadvertent over- or under-treatment. The authors report a case with an unusual discrepancy between SpO2 and PaO2 in a neonate with jaundice who developed bronze baby syndrome while receiving phototherapy. A review of similar previous reports suggests that abnormal pigment accumulation in bronze baby syndrome may render pulse oximetry transiently unreliable.

Dual-ratio approach to pulse oximetry and the effect of skin tone.

Significance: Pulsatile blood oxygen saturation ( SpO 2 ) via pulse oximetry is a valuable clinical metric for assessing oxygen delivery. Individual anatomical features, including skin tone, may affect current optical pulse oximetry methods. Aim: We developed an optical pulse oximetry method based on dual-ratio (DR) measurements to suppress individual anatomical confounds on SpO 2 . Approach: We designed a DR-based finger pulse oximeter, hypothesizing that DR would suppress confounds from optical coupling and superficial tissue absorption. This method is tested using Monte Carlo simulations and in vivo experiments. Results: Different melanosome volume fractions in the epidermis, a surrogate for skin tone, cause changes in the recovered SpO 2 on the order of 1% in simulation and in vivo. Different heterogeneous pulsatile hemodynamics cause greater changes on the order of 10% in simulations. SpO 2 recovered with DR measurements showed less variability than the traditional single-distance (SD) transmission method. Conclusions: For the models and methods considered here, SpO 2 measurements are strongly impacted by heterogeneous pulsatile hemodynamics. This variability may be larger than the skin tone bias, which is a known confound in SpO 2 measurements. The partial suppression of variability in the SpO 2 recovered by DR suggests the promise of DR for pulse oximetry.

Reliability of Digital Artery Palpation and Pulse Oximetry Waveform As Alternatives to Radial Pulse in the Assessment of Upper Limb Injuries.

INTRODUCTION: Radial pulse palpation is widely accepted as a gold standard clinical method to assess distal vascular perfusion of the upper limb. In some instances, the radial pulse may not be accessible due to splints, casts, or swelling, or the injury may be at the level or distal to the radial artery. Here, the authors assess two alternative methods of assessing perfusion of the hand more distally: palpation of the digital pulse and pulse oximetry (PO) waveform. METHODS: Twenty-four healthy adult volunteers (48 hands) were assessed by two assessors. Digital artery pulses were palpated, and ease of location was recorded. A brachial cuff pressure was inflated to 20 mmHg above systolic pressure to occlude distal perfusion. Radial pulse, digital artery pulse, and PO waveform were monitored as the brachial cuff pressure was deflated in 5 mmHg increments to ascertain when each returned and compare the reliability of these tests to the gold standard of the radial pulse. RESULTS: The digital artery pulse was easily located in 20/24 participants, most reliably over the proximal phalanx of the index finger. With occlusion of the brachial artery, no distal pulses could be felt, and PO showed no waveform. As the brachial artery cuff pressure was incrementally deflated, the digital pulse returned with the same cuff pressure or a lower cuff pressure than the radial pulse in all cases, suggesting a high positive predictive value of radial pulse presence. PO waveform returned at a higher cuff pressure or with the same cuff pressure as the return of the radial pulse, suggesting a higher sensitivity than radial pulse palpation in assessing hand perfusion. CONCLUSION: Digital pulse palpation can be used as a surrogate method of assessing hand perfusion. When present, it can be assumed a radial pulse is present due to a high positive predictive value and no false positives seen in any participant. When absent, further investigation is required. The PO waveform was found to be more sensitive than digital or radial pulse palpation as a measure of distal perfusion, with a return of waveform prior to palpable pulses. This likely represents a more accurate clinical test of distal perfusion and can be relied upon even when pulses are not palpable.

Utility of saturation trends to predict successful weaning of nasal CPAP in very preterm neonates - A prospective study.

BACKGROUND: There is no objective criteria to wean CPAP in preterm neonates. We aimed to assess the accuracy of 'saturation trends' to predict successful CPAP discontinuation. METHODS: We included very preterm neonates who required CPAP. Index tests were 'saturation trends'. Outcome was successful CPAP discontinuation, defined as baby stable in room air for 72 h. RESULTS: We had 120 neonates with mean±SD gestation 28.6±1.8 weeks. 96 (80%) neonates had successful discontinuation and 24 (20%) failed. Neonates with successful discontinuation had significantly greater 'saturation trends' during 24 h before discontinuing CPAP compared to those who failed [64.3 (48.1-83.7) vs. 47.3 (23.0-65.0), p = 0.001]. Saturations > 95% while on CPAP with 21% FiO2 for > 60% time had 63% sensitivity and 70% specificity to predict successful CPAP discontinuation. CONCLUSION: 'Saturation trends' is a readily available objective parameter that can be used to guide weaning CPAP in preterm neonates.

Impact of the Menstrual Cycle on the Cardiovascular and Ventilatory Responses During Exercise in Normoxia and Hypoxia.

Citherlet, Tom, Antoine Raberin, Giorgio Manferdelli, Nicolas Bourdillon, and Grégoire P Millet. Impact of the menstrual cycle (MC) on the cardiovascular and ventilatory responses during exercise in normoxia and hypoxia. High Alt Med Biol. 00:00-00, 2024. Introduction: Ovarian hormones influence several physiological functions in women. This study investigated how the hormonal variations across the menstrual cycle (MC) impact cardiovascular and ventilatory responses during rest and moderate exercise in normobaric hypoxia. Methods: Thirteen eumenorrheic women were tested during the early follicular (Fol1), late follicular (Fol2), and mid-luteal (Lut3) phases with measurement of hormonal levels. Heart rate (HR) variability, blood pressure, and baroreflex sensitivity (BRS) were evaluated at rest in normoxia. Ventilation (VE), peripheral oxygen saturation, and HR were monitored at rest and during moderate-intensity cycling exercise in hypoxia (FiO2 = 14%). Results: Despite expected hormone level variations, no significant changes were observed across the MC in HR variability (root mean square of successive differences; 64 (95% confidence interval [47, 81]) at Fol1, 54 [42, 66] at Fol2, 60 [44, 77] ms at Lut3), blood pressure (mean blood pressure; 85 [79, 90]), 87 [81, 93]), 84 [77, 92] mmHg), BRS (26 [17, 36], 28 [20, 35], 23 [17, 29] ms/mmHg), VE (rest: 8.9 [7.9, 9.8], 9.5 [9.0, 9.9], 9.0 [8.1, 9.9]; exercise: 53 [41, 66], 51.1 [36.4, 65.7], 54.4 [34.0, 74.8] l/min), peripheral oxygen saturation (rest: 89.8 [87.4, 92.1], 91.9 [88.7, 95.0], 90.2 [87.8, 92.6]; exercise: 80.5 [77.4, 83.5], 84.4 [80.4, 88.3], 81.9 [78.3, 85.4] %) HR (rest: 69.7 [60.2, 79.1], 70.8 [63.2, 78.3], 70.5 [64.0, 77.0]; exercise: 148 [136, 160], 146 [132, 161], 146 [132, 160] bpm), and cycling efficiency (0.17 [0.16, 0.18], 0.17 [0.13, 0.21], 0.16 [0.15, 0.18] %) (all p > 0.05). Discussion: From a practical point of view, there is no strong evidence of any usefulness of monitoring hormonal variations and the MC phases for women exercising in hypoxia.

Pulse oximetry for the prediction of acute mountain sickness: A systematic review.

Acute mountain sickness (AMS) causes serious illness for many individuals ascending to high altitude (HA), although preventable with appropriate acclimatisation. AMS is a clinical diagnosis, with symptom severity evaluated using the Lake Louise Score (LLS). Reliable methods of predicting which individuals will develop AMS have not been developed. This systematic review evaluates whether a predictive relationship exists between oxygen saturation and subsequent development of AMS. PubMed, PubMed Central, MEDLINE, Semantic Scholar, Cochrane Library, University of Birmingham Library and clinicaltrials.gov databases were systematically searched from inception to 15 June 2023. Human studies involving collection of peripheral blood oxygen saturation ( S p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ ) from healthy lowlanders during ascent to HA that evaluated any relationship between S p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ and AMS severity were considered for eligibility. Risk of bias was assessed using a modified Newcastle-Ottawa Tool for cohort studies (PROPSPERO CRD42023423542). Seven of 980 total identified studies were ultimately included for data extraction. These studies evaluated S p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ and AMS (via LLS) in 1406 individuals during ascent to HA (3952-6300 m). Risk of bias was 'low' for six and 'moderate' for one of the included studies. Ascent profiles and S p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ measurement methodology varied widely, as did the statistical methods for AMS prediction. Decreasing oxygen saturation measured with pulse oximetry during ascent shows a positive predictive relationship for individuals who develop AMS. Studies have high heterogeneity in ascent profile and oximetry measurement protocols. Further studies with homogeneous methodology are required to enable statistical analysis for more definitive evaluation of AMS predictability by pulse oximetry.

Newborn pulse oximetry screening coverage in a nationwide complex survey sample: An assessment of a congenital heart disease early detection program at the regional level in Brazil.

OBJECTIVES: To estimate the coverage of newborn pulse oximetry screening (POS) in Brazil, as well as identifies associated factors and the proportion of positive screening results. METHODS: Coverage was estimated based on the most recent National Health Survey (2019). Adjusted marginal prevalence ratios were estimated via poisson regression model with robust variance. RESULTS: The POS coverage was 66.3 % (95 %CI: 65.5-67.1; N = 3,140,023) and was higher in children born in privately funded hospitals (PFHs) than in the Unified Health System (SUS): 78.1 % (76.7-79.5) versus 61.1 % (60.2-62.1). In the North region, the POS coverage in PFHs (64.9 %, 59.7-70.1) was lower than that in the South (82.5 %, 79.4-85.6) and the Southeast (81.5 %, 79.3-83.6); it was even lower in SUS in the North (44.0 %; 42.4-45.6). After a federal ordinance providing financial resources to postscreening diagnostic, the screening coverage in SUS increased from 57.6 % (56.2-59.1) to 64.6 % (63.3-65.9). The proportion of positive screening tests was 9.2 % (8.9-9.5) in SUS and 7.8 % (7.3-8.3) in PFHs, of which 40.8 % (40.5-41.1) underwent complementary exams in SUS and 57.2 % (56.7-57.7) in PFHs. In the multivariate model, the main independent predictors of POS were the coverage of other newborn screening tests. CONCLUSIONS: Inequalities were found between major regions and healthcare systems. Government financial incentives have reduced this inequality, although the percentage of postscreening complementary exams remains insufficient and unequal. The main independent predictors of screening prevalence were those related to the organization of health services.

The Performance of Critical Congenital Heart Disease Screening in Rural Versus Urban Locations in the Northwest United States.

Objectives: Pulse oximetry screening of newborns detects critical congenital heart disease (CCHD). Rural birth location is known to affect timing and management of when infants with CHD undergo surgery, but its association with CCHD screening is unknown. We assess the relationship between rural location and postnatal CCHD diagnosis and describe lesion-specific modes of diagnosis. Study design: Data were abstracted from medical records at 2 cardiac surgery centers in Washington state. Infants with CCHD, defined as CHD requiring either cardiac intervention or resulting in death at <1 month of age, born between July 2015 and June 2020, were included and classified by method of identification. Patient home ZIP codes were used to determine rural location. Results: We included 561 newborns with CCHD; 35% were diagnosed postnatally. Predominant postnatal mechanisms of identification (n = 194) included symptomatic before CCHD screening period (56%), CCHD screening (22%), and symptomatic after false-negative screen (15%). Postnatal diagnosis rate increased with degree of ruralness (48% in small rural/isolated regions vs 32% in urban regions; P = .01) and incidence of undiagnosed CCHD at birth increased with lower nursery levels (5.5/10 000 live births in nursery level 1 vs 2.1/10 000 live births in level 4). Conclusions: CCHD screening identifies 22% of postnatally diagnosed CCHD and 7% of cases overall in our region. Postnatal diagnosis is more common in rural regions. The incidence of undiagnosed CCHD at birth increases with decreasing nursery levels. This study supports the value of CCHD screening in routine newborn care, especially in rural areas and hospitals with lower nursery levels.

Development and external validation of a novel modality for rapid recognition of aortic dissection based on peripheral pulse oximetry waveforms.

BACKGROUND: Aortic dissection (AD) is a life-threatening cardiovascular emergency that is often misdiagnosed as other chest pain conditions. Physiologically, AD may cause abnormalities in peripheral blood flow, which can be detected using pulse oximetry waveforms. PURPOSE: This study aimed to assess the feasibility of identifying AD based on pulse oximetry waveforms and to highlight the key waveform features that play a crucial role in this diagnostic method. METHODS: This prospective study employed high-risk chest pain cohorts from two emergency departments. The initial cohort was enriched with AD patients (n = 258, 47% AD) for model development, while the second cohort consisted of chest pain patients awaiting angiography (n = 71, 25% AD) and was used for external validation. Pulse oximetry waveforms from the four extremities were collected for each patient. After data preprocessing, a recognition model based on the random forest algorithm was trained using patients' gender, age, and waveform difference features extracted from the pulse oximetry waveforms. The performance of the model was evaluated using receiver operating characteristic (ROC) curve analysis and decision curve analysis (DCA). The importance of features was also assessed using Shapley Value and Gini importance. RESULTS: The model demonstrated strong performance in identifying AD in both the training and external validation sets. In the training set, the model achieved an area under the ROC curve of 0.979 (95% CI: 0.961-0.990), sensitivity of 0.918 (95% CI: 0.873-0.955), specificity of 0.949 (95% CI: 0.912-0.985), and accuracy of 0.933 (95% CI: 0.904-0.959). In the external validation set, the model attained an area under the ROC curve of 0.855 (95% CI: 0.720-0.965), sensitivity of 0.889 (95% CI: 0.722-1.000), specificity of 0.698 (95% CI: 0.566-0.812), and accuracy of 0.794 (95% CI: 0.672-0.878). Decision curve analysis (DCA) further showed that the model provided a substantial net benefit for identifying AD. The median mean and median variance of the four limbs' signals were the most influential features in the recognition model. CONCLUSIONS: This study demonstrated the feasibility and strong performance of identifying AD based on peripheral pulse oximetry waveforms in high-risk chest pain populations in the emergency setting. The findings also provided valuable insights for future human fluid dynamics simulations to elucidate the impact of AD on blood flow in greater detail.

Peripheral perfusion index of pulse oximetry in adult patients: a narrative review.

The peripheral perfusion index (PI) is derived from pulse oximetry and is defined as the ratio of the pulse wave of the pulsatile portion (arteries) to the non-pulsatile portion (venous and other tissues). A growing number of clinical studies have supported the use of PI in various clinical scenarios, such as guiding hemodynamic management and serving as an indicator of outcome and organ function. In this review, we will introduce and discuss this traditional but neglected indicator of the peripheral microcirculatory perfusion. Further clinical trials are required to clarify the normal and critical values of PI for different monitoring devices in various clinical conditions, to establish different standards of PI-guided strategies, and to determine the effect of PI-guided therapy on outcome.

Modification of McGill Oximetry Score in Improving the Diagnostic Capability of Paediatric OSA.

OBJECTIVES: This study aimed to devise a modified oximetry scoring system and calculate its diagnostic accuracy in detecting paediatric obstructive sleep apnoea syndrome (OSAS). STUDY DESIGN: This prospective diagnostic accuracy study was divided into two phases. SETTING: The study was conducted at a quaternary teaching hospital. METHODS: Polysomnograms performed from 1 April 2014 to 31 December 2021 were included. In Phase 1, the parameters of 95 oximetry trend graphs were evaluated, and a modified scoring system was constructed. In Phase 2, the modified scoring system was employed in 272 oximetry trend graphs, and its diagnostic accuracy was determined. A logistic regression model was used to assess the ability of each scoring system to predict paediatric OSAS. RESULTS: A total of 367 patients were recruited. In Phase 1, a four-tier severity classification system was constructed. In Phase 2, its diagnostic accuracy was found to be 53.3% sensitive, 97% specific, with positive predictive value of 98.5% and negative predictive value of 34.6%. The lowest detectable apnoea-hypopnoea index (AHI) was 4.5. The inter-rater reliability calculated was 80%. Logistic regression was applied to assess associations of the modified McGill score (MMS) or McGill oximetry score (MOS) with OSAS. The area under the receiver operating characteristic curve was higher for the MMS than for MOS (0.78 [95% CI 0.73-0.84] vs. 0.59 [95% CI 0.51-0.66]). CONCLUSION: This study demonstrated that our modified scoring system had increased sensitivity at detecting OSAS at a much lower AHI and showed a much greater ability to predict paediatric OSAS.

Ninety years of pulse oximetry: history, current status, and outlook.

Significance: This year, 2024, marks the 50th anniversary of the invention of pulse oximetry (PO), which was first presented by Takuo Aoyagi, an engineer from the Nihon Kohden Company, at the 13th Conference of the Japanese Society of Medical Electronics and Biological Engineering in Osaka in 1974. His discovery and the development of PO for the non-invasive measurement of peripheral arterial oxygenation represents one of the most significant chapters in the history of medical technology. It resulted from research and development efforts conducted by biochemists, engineers, physicists, physiologists, and physicians since the 1930s. Aim: The objective of this work was to provide a narrative review of the history, current status, and future prospects of PO. Approach: A comprehensive review of the literature on oximetry and PO was conducted. Results and Conclusions: Our historical review examines the development of oximetry in general and PO in particular, tracing the key stages of a long and fascinating story that has unfolded from the first half of the twentieth century to the present day-an exciting journey in which serendipity has intersected with the hard work of key pioneers. This work has been made possible by the contributions of numerous key pioneers, including Kurt Kramer, Karl Matthes, Glenn Millikan, Evgenii M. Kreps, Earl H. Wood, Robert F. Show, Scott A. Wilber, William New, and, above all, Takuo Aoyagi. PO has become an integral part of modern medical care and has proven to be an important tool for physiological monitoring. The COVID-19 pandemic not only highlighted the clinical utility of PO but also revealed some of the problems with the technology. Current research in biomedical optics should address these issues to make the technology even more reliable and accurate. We discuss the necessary innovations in PO and present our thoughts on what the next generation of PO might look like.

What Remote PPG Oximetry Tells Us about Pulsatile Volume?

While pulse oximetry using remote photoplethysmography (rPPG) is used in medicine and consumer health, sound theoretical foundations for this methodology are not established. Similarly to traditional pulse oximetry, rPPG oximetry uses two wavelengths to calculate the tissue oxygenation using the so-called ratio-of-ratios, R. However, the relationship between R and tissue oxygenation has not been derived analytically. As such, rPPG oximetry relies mostly on empirical methods. This article aimed to build theoretical foundations for pulse oximetry in rPPG geometry. Using the perturbation approach in diffuse approximation for light propagation in tissues, we obtained an explicit expression of the AC/DC ratio for the rPPG signal. Based on this ratio, the explicit expression for "ratio-of-ratios" was obtained. We have simulated the dependence of "ratio-of-ratios" on arterial blood saturation across a wide range (SaO2 = 70-100%) for several commonly used R/IR light sources (660/780, 660/840, 660/880, and 660/940 nm) and found that the obtained relationship can be modeled by linear functions with an extremely good fit (R2 = 0.98-0.99) for all considered R/IR pairs. Moreover, the location of the pulsatile volume can be extracted from rPPG data. From experimental data, we found that the depth of blood pulsations in the human forehead can be estimated as 0.6 mm on the arterial side, which points to the papillary dermis/subpapillary vascular plexus origin of the pulsatile volume.

Monte Carlo simulation of the effect of melanin concentration on light-tissue interactions for transmittance pulse oximetry measurement.

Significance: Questions about the accuracy of pulse oximeters in measuring arterial oxygen saturation ( SpO 2 ) in individuals with darker skin pigmentation have resurfaced since the COVID-19 pandemic. This requires investigation to improve patient safety, clinical decision making, and research. Aim: We aim to use computational modeling to identify the potential causes of inaccuracy in SpO 2 measurement in individuals with dark skin and suggest practical solutions to minimize bias. Approach: An in silico model of the human finger was developed to explore how changing melanin concentration and arterial oxygen saturation ( SaO 2 ) affect pulse oximeter calibration algorithms using the Monte Carlo (MC) technique. The model generates calibration curves for Fitzpatrick skin types I, IV, and VI and an SaO 2 range between 70% and 100% in transmittance mode. SpO 2 was derived by inputting the computed ratio of ratios for light and dark skin into a widely used calibration algorithm equation to calculate bias ( SpO 2 - SaO 2 ). These were validated against an experimental study to suggest the validity of the Monte Carlo model. Further work included applying different multiplication factors to adjust the moderate and dark skin calibration curves relative to light skin. Results: Moderate and dark skin calibration curve equations were different from light skin, suggesting that a single algorithm may not be suitable for all skin types due to the varying behavior of light in different epidermal melanin concentrations, especially at 660 nm. The ratio between the mean bias in White and Black subjects in the cohort study was 6.6 and 5.47 for light and dark skin, respectively, from the Monte Carlo model. A linear multiplication factor of 1.23 and exponential factor of 1.8 were applied to moderate and dark skin calibration curves, resulting in similar alignment. Conclusions: This study underpins the careful re-assessment of pulse oximeter designs to minimize bias in SpO 2 measurements across diverse populations.

Averaging Times for Pulse Oximeter Measurements - A Review of Manuscripts Published in the Top Five Sleep Medicine Journals.

Purpose: Clinical management decisions often rely on a patient's SpO2 level and desaturation rate. Limitations include that measurements depend on the averaging time (AVT) used, which is particularly relevant to sleep medicine, but has yet received little attention. Methods: Cross-sectional review of studies reporting pulse oximeter saturation (SpO2) measurements published in 5 leading sleep medicine journals. All papers published between 2017 and 2023 reporting SpO2 measurements were screened regarding the AVT used. Results: Of 193 papers identified, 151 were included; of these, only 9 studies mentioned the AVT, 4 of these were published in one journal. The AVT ranged from zero (beat-to-beat-mode) to 10s, with 3s being used most often (33.3%), followed by 2s (22.2%). Conclusion: The AVT is only rarely mentioned in sleep medicine papers, despite its influence on sleep study results. Reported AVTs were heterogenous. Further research is warranted to set up guidelines for using or reporting the AVT.