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.

Improving effective coverage of medical-oxygen services for neonates and children in health facilities in Uganda: a before-after intervention study.

BACKGROUND: Medical oxygen services are essential for the care of acutely unwell patients. We aimed to assess the effects of a multilevel, multicomponent health-system intervention on hypoxaemia detection, oxygen therapy, and mortality among neonates and children attending level IV health centres and hospitals in Uganda. METHODS: For this before-after intervention study, we included children who attended paediatric or neonatal wards of 24 level IV health centres and seven general or regional referral hospitals in the Busoga and North Buganda regions of Uganda between June 1, 2020, and June 30, 2022. All neonates younger than 1 month and children aged 1 month to 14 years were eligible for inclusion. We excluded neonates who were not sick but stayed in the maternity ward for routine postnatal care. The intervention involved clinical training, mentorship, and supportive supervision; provision of pulse oximeters and cylinder-based oxygen sources; biomedical-capacity support; and support to develop and disseminate oxygen supply strategies, oxygen therapy guidelines, and lists of essential oxygen supplies. Trained research assistants extracted individual patient data from case notes using a standardised electronic data collection form. Data were collected on health-facility details, age, sex, clinical signs and symptoms, admission diagnoses, pulse oximetry readings, oxygen therapy details, and final patient outcome. The primary outcome was the proportion of admitted neonates and children with a pulse oximetry oxygen saturation reading documented in their patient case notes on day 1 of health-facility admission (ie, pulse oximetry coverage). We used mixed-effects logistic regression to evaluate the effect of the intervention. FINDINGS: We obtained data on 71 997 eligible neonates and children admitted to 31 participating health facilities; the primary analysis included 10 001 patients in the pre-intervention period (ie, June 1 to Oct 30, 2020) and 51 329 patients in the post-intervention period (ie, March 1, 2021, to June 30, 2022). Because 1356 patients had missing data for sex, 4365 (46·7%) of 9347 in the pre-intervention group and 22 831 (46·2%) of 49 410 in the post-intervention group were female; 4982 (53·3%) in the pre-intervention group and 26 579 (53·8%) in the post-intervention group were male. The proportion of neonates and children with pulse oximetry at admission increased from 2365 (23·7%) of 10 001 in the pre-intervention period to 45 029 (87·7%) of 51 328 in the post-intervention period. Adjusted analysis indicated greater likelihood of a patient receiving pulse oximetry during the post-intervention period compared with the pre-intervention period (adjusted odds ratio 40·10, 95% CI 37·38-42·93; p<0·0001). INTERPRETATION: Large-scale improvements in hospital oxygen services are achievable and have the potential to improve clinical outcomes. Governments should be encouraged to develop national oxygen plans and focus investment on interventions that have been shown to be effective, including the introduction of pulse oximetry into routine hospital care and clinical and biomedical mentoring and support. FUNDING: Bill & Melinda Gates Foundation and ELMA Philanthropies. TRANSLATIONS: For the Luganda and Lusoga translations of the abstract see Supplementary Materials section.

Innovative approaches in imaging photoplethysmography for remote blood oxygen monitoring.

Peripheral Capillary Oxygen Saturation (SpO2) has received increasing attention during the COVID-19 pandemic. Clinical investigations have demonstrated that individuals afflicted with COVID-19 exhibit notably reduced levels of SpO2 before the deterioration of their health status. To cost-effectively enable individuals to monitor their SpO2, this paper proposes a novel neural network model named "ITSCAN" based on Temporal Shift Module. Benefiting from the widespread use of smartphones, this model can assess an individual's SpO2 in real time, utilizing standard facial video footage, with a temporal granularity of seconds. The model is interweaved by two distinct branches: the motion branch, responsible for extracting spatiotemporal data features and the appearance branch, focusing on the correlation between feature channels and the location information of feature map using coordinate attention mechanisms. Accordingly, the SpO2 estimator generates the corresponding SpO2 value. This paper summarizes for the first time 5 loss functions commonly used in the SpO2 estimation model. Subsequently, a novel loss function has been contributed through the examination of various combinations and careful selection of hyperparameters. Comprehensive ablation experiments analyze the independent impact of each module on the overall model performance. Finally, the experimental results based on the public dataset (VIPL-HR) show that our model has obvious advantages in MAE (1.10%) and RMSE (1.19%) compared with related work, which implies more accuracy of the proposed method to contribute to public health.

Oxygen reserve index versus conventional peripheral oxygen saturation for prevention of hypoxaemia: A randomised controlled trial.

BACKGROUND: Hypoxaemia occurs frequently during paediatric laryngeal microsurgery. OBJECTIVE: The oxygen reserve index is a noninvasive and continuous parameter to assess PaO2 levels in the range of 100 to 200 mmHg. It ranges from 0 to 1.0. We investigated whether monitoring the oxygen reserve index can reduce the incidence of SpO2 90% or less. DESIGN: Randomised controlled trial. SETTING: A tertiary care paediatric hospital. PARTICIPANTS: Paediatric patients aged 18 years or less scheduled to undergo laryngeal microsurgery. INTERVENTION: The patients were randomly allocated to the oxygen reserve index or control groups, and stratified based on the presence of a tracheostomy tube. Rescue intervention was performed when the oxygen reserve index was 0.2 or less and the SpO2 was 94% or less in the oxygen reserve index and control groups, respectively. MAIN OUTCOME MEASURE: The primary outcome was the incidence of SpO2 90% or less during the surgery. RESULTS: Data from 88 patients were analysed. The incidence of SpO2 ≤ 90% did not differ between the oxygen reserve index and control groups [P = 0.114; 11/44, 25% vs. 18/44, 40.9%; relative risk: 1.27; and 95% confidence interval (CI): 0.94 to 1.72]. Among the 128 rescue interventions, SpO2 ≤ 90% event developed in 18 out of 75 events (24%) and 42 out of 53 events (79.2%) in the oxygen reserve index and control groups, respectively (P < 0.001; difference: 55.2%; and 95% CI 38.5 to 67.2%). The number of SpO2 ≤ 90% events per patient in the oxygen reserve index group (median 0, maximum 3) was less than that in the control group (median 0, maximum 8, P = 0.031). CONCLUSION: Additional monitoring of the oxygen reserve index, with a target value of greater than 0.2 during paediatric airway surgery, alongside peripheral oxygen saturation, did not reduce the incidence of SpO2 ≤ 90%.

Continuous Capnography for Early Detection of Respiratory Compromise During Gastroenterological Procedural Sedation and Analgesia.

Gastroenterology nurses working across a variety of clinical settings are responsible for periprocedural monitoring during moderate to deep procedural sedation and analgesia (PSA) to identify signs of respiratory compromise and intervene to prevent cardiorespiratory events. Pulse oximetry is the standard of care for respiratory monitoring, but it may delay or fail to detect abnormal ventilation during PSA. Continuous capnography, which measures end-tidal CO2 as a marker of alveolar ventilation, has been endorsed by a number of clinical guidelines. Large clinical trials have demonstrated that the addition of continuous capnography to pulse oximetry during PSA for various gastroenterological procedures reduces the incidence of hypoxemia, severe hypoxemia, and apnea. Studies have shown that the cost of adding continuous capnography is offset by the reduction in adverse events and hospital length of stay. In the postanesthesia care unit, continuous capnography is being evaluated for monitoring opioid-induced respiratory depression and to guide artificial airway removal. Studies are also examining the utility of continuous capnography to predict the risk of opioid-induced respiratory depression among patients receiving opioids for primary analgesia. Continuous capnography monitoring has become an essential tool to detect early signs of respiratory compromise in patients receiving PSA during gastroenterological procedures. When combined with pulse oximetry, it can help reduce cardiorespiratory adverse events, improve patient outcomes and safety, and reduce health care costs.

Vital parameter monitoring in harsh environment by the MedSENS in-ear multisensor device.

Accurate assessment of vital parameters is essential for diagnosis and triage of critically ill patients, but not always feasible in out-of-hospital settings due to the lack of suitable devices. We performed an extensive validation of a novel prototype in-ear device, which was proposed for the non-invasive, combined measurement of core body temperature (Tc), oxygen saturation (SpO2), and heart rate (HR) in harsh environments. A pilot study with randomized controlled design was conducted in the terraXcube environmental chamber. Participants were subsequently exposed to three 15 min test sessions at the controlled ambient temperatures of 20 °C, 5 °C, and - 10 °C, in randomized order. Vital parameters measured by the prototype were compared with Tc measurements from commercial esophageal (reference) and tympanic (comparator) probes and SpO2 and HR measurements from a finger pulse-oximeter (reference). Performance was assessed in terms of bias and Lin's correlation coefficient (CCC) with respect to the reference measurements and analyzed with linear mixed models. Twenty-three participants (12 men, mean (SD) age, 35 (9) years) completed the experimental protocol. The mean Tc bias of the prototype ranged between - 0.39 and - 0.80 °C at ambient temperatures of 20 °C and 5 °C, and it reached - 1.38 °C only after 15 min of exposure to - 10 °C. CCC values ranged between 0.07 and 0.25. SpO2 and HR monitoring was feasible, although malfunctioning was observed in one third of the tests. SpO2 and HR bias did not show any significant dependence on environmental conditions, with values ranging from - 1.71 to - 0.52% for SpO2 and 1.12 bpm to 5.30 bpm for HR. High CCC values between 0.81 and 0.97 were observed for HR in all environmental conditions. This novel prototype device for measuring vital parameters in cold environments demonstrated reliability of Tc measurements and feasibility of SpO2 and HR monitoring. Through non-invasive and accurate monitoring of vital parameters from the ear canal our prototype may offer support in triage and treatment of critically ill patients in harsh out-of-hospital conditions.

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.

Reliability of Continuous Noninvasive Hemoglobin Monitoring in Healthy Participants During En Route Care Training.

INTRODUCTION: Current standards for hemoglobin monitoring during air transports of U.S. combat wounded are invasive and intermittent. Fielded pulse co-oximeters can noninvasively measure total hemoglobin, but this parameter is not currently utilized. The primary objective of this study was to assess the percentage of vital sign measurements with successful capture of total noninvasive hemoglobin measurement using spectrophotometry-based technology for Hb (SpHb) measurements in healthy participants during training flights. Secondary objectives were to assess the feasibility of a novel electronic data capture mechanism from usual patient movement items and perform a pilot analysis of SpHb changes in healthy participants during transitions from ground to air transport. METHODS: We conducted a feasibility study enrolling healthy participants who had hemodynamic monitoring during usual U.S. Air Force Critical Care Air Transport (CCAT) flight training exercises from 2022 to 2023. Usual CCAT monitoring equipment and currently used Masimo Rainbow® pulse co-oximeters had the capability to measure SpHb. After each training exercise, the study team wirelessly downloaded case files from patient monitors utilizing the Battlefield Assisted Trauma Distributed Observation Kit (BATDOKTM) Case Downloader application. We then calculated point and precision estimates for the percentage of time for successful SpHb capture during the exercise and compared this to pulse oximetry (SpO2) capture. An a priori precision analysis for percentage of flight-time with successful SpHb data capture and descriptive statistics were performed. This study received Exempt Determination by the 59th Medical Wing IRB. RESULTS: We analyzed 26 records with mean monitoring durations of 94.5 [59.3-119.9] minutes during ground phases and 78.0 [59.9-106.5] minutes during flight phases. SpHb measures were successfully captured for 97.7% (n = 4,620) of possible ground measurements and 97.2% (n = 3,973) of possible in-flight measurements compared to 99.5% ground and 98.2% in-flight capture for SpO2. Mean intervals of missing SpHb data were 2 ± 5 minutes on the ground and 4 ± 6 minutes in-flight. Mean SpHb increased by 0.93 ± 0.96 g/dL during the ground phase, but had minimal changes during ascent, cruising altitude or descent. The BATDOKTM Case downloader completed transfer for all files. CONCLUSION: Masimo Rainbow® SpHb pulse co-oximeters reliably captured continuous, noninvasive hemoglobin measurements using usual CCAT patient movement items in healthy participants during both ground and flight training. The BATDOKTM Case Downloader successfully imported case files from CCAT patient monitors. Mean SpHb measures had a small increase during the ground phase of monitoring followed by minimal changes when transitioning to flight altitude.

Reliability, clinical performance and trending ability of a pulse oximeter and pulse co-oximeter, in monitoring blood oxygenation, at two measurement sites, in immobilised white rhinoceros (Ceratotherium simum).

BACKGROUND: Monitoring blood oxygenation is essential in immobilised rhinoceros, which are susceptible to opioid-induced hypoxaemia. This study assessed the reliability, clinical performance and trending ability of the Nonin PalmSAT 2500 A pulse oximeter's and the Masimo Radical-7 pulse co-oximeter's dual-wavelength technology, with their probes placed at two measurement sites, the inner surface of the third-eyelid and the scarified ear pinna of immobilised white rhinoceroses. Eight white rhinoceros were immobilised with etorphine-based drug combinations and given butorphanol after 12 min, and oxygen after 40 min, of recumbency. The Nonin and Masimo devices, with dual-wavelength probes attached to the third-eyelid and ear recorded arterial peripheral oxygen-haemoglobin saturation (SpO2) at pre-determined time points, concurrently with measurements of arterial oxygen-haemoglobin saturation (SaO2), from drawn blood samples, by a benchtop AVOXimeter 4000 co-oximeter (reference method). Reliability of the Nonin and Masimo devices was evaluated using the Bland-Altman and the area root mean squares (ARMS) methods. Clinical performance of the devices was evaluated for their ability to accurately detect clinical hypoxemia using receiver operating characteristic (ROC) curves and measures of sensitivity, specificity, and positive and negative predictive values. Trending ability of the devices was assessed by calculating concordance rates from four-quadrant plots. RESULTS: Only the Nonin device with transflectance probe attached to the third-eyelid provided reliable SpO2 measurements across the 70 to 100% saturation range (bias - 1%, precision 4%, ARMS 4%). Nonin and Masimo devices with transflectance probes attached to the third-eyelid both had high clinical performance at detecting clinical hypoxaemia [area under the ROC curves (AUC): 0.93 and 0.90, respectively]. However, the Nonin and Masimo devices with transmission probes attached to the ear were unreliable and provided only moderate clinical performance. Both Nonin and Masimo devices, at both measurement sites, had concordance rates lower than the recommended threshold of ≥ 90%, indicating poor trending ability. CONCLUSIONS: The overall assessment of reliability, clinical performance and trending ability indicate that the Nonin device with transflectance probe attached to the third-eyelid is best suited for monitoring of blood oxygenation in immobilised rhinoceros. The immobilisation procedure may have affected cardiovascular function to an extent that it limited the devices' performance.

Performance and safety of the PRICO closed-loop oxygen saturation targeting system in neonates: pragmatic multicentre cross-over study (TarOx Study).

OBJECTIVE: This study aims to evaluate the performance of the fabian-Predictive-Intelligent-Control-of-Oxygenation (PRICO) system for automated control of the fraction of inspired oxygen (FiO2). DESIGN: Multicentre randomised cross-over study. SETTING: Five neonatal intensive care units experienced with automated control of FiO2 and the fabian ventilator. PATIENTS: 39 infants: median gestational age of 27 weeks (IQR: 26-30), postnatal age 7 days (IQR: 2-17), weight 1120 g (IQR: 915-1588), FiO2 0.32 (IQR: 0.22-0.43) receiving both non-invasive (27) and invasive (12) respiratory support. INTERVENTION: Randomised sequential 24-hour periods of automated and manual FiO2 control. MAIN OUTCOME MEASURES: Proportion (%) of time in normoxaemia (90%-95% with FiO2>0.21 and 90%-100% when FiO2=0.21) was the primary endpoint. Secondary endpoints were severe hypoxaemia (<80%) and severe hyperoxaemia (>98% with FiO2>0.21) and prevalence of episodes ≥60 s at these two SpO2 extremes. RESULTS: During automated control, subjects spent more time in normoxaemia (74%±22% vs 51%±22%, p<0.001) with less time above and below (<90% (9%±8% vs 12%±11%, p<0.001) and >95% with FiO2>0.21 (16%±19% vs 35%±24%) p<0.001). They spent less time in severe hyperoxaemia (1% (0%-3.5%) vs 5% (1%-10%), p<0.001) but exposure to severe hypoxaemia was low in both arms and not different. The differences in prolonged episodes of SpO2 were consistent with the times at extremes. CONCLUSIONS: This study demonstrates the ability of the PRICO automated oxygen control algorithm to improve the maintenance of SpO2 in normoxaemia and to avoid hyperoxaemia without increasing hypoxaemia.

Early or delayed cord clamping during transition of term newborns: does it make any difference in cerebral tissue oxygenation?

BACKGROUND: According to the World Health Organization's recommendation, delayed cord clamping in term newborns can have various benefits. Cochrane metaanalyses reported no differences for mortality and early neonatal morbidity although a limited number of studies investigated long-term neurodevelopmental outcomes. The aim of our study is to compare the postnatal cerebral tissue oxygenation values in babies with early versus delayed cord clamping born after elective cesarean section. METHODS: In this study, a total of 80 term newborns delivered by elective cesarean section were included. Infants were randomly grouped as early (clamped within 15 s, n:40) and delayed cord clamping (at the 60th second, n:40) groups. Peripheral arterial oxygen saturation (SpO2) and heart rate were measured by pulse oximetry while regional oxygen saturation of the brain (rSO2) was measured with near-infrared spectrometer. Fractional tissue oxygen extraction (FTOE) was calculated for every minute between the 3rd and 15th minute after birth. (FTOE = pulse oximetry value-rSO2/pulse oximetry value). The measurements were compared for both groups. RESULTS: The demographical characteristics, SpO2 levels (except postnatal 6th, 8th, and 14th minutes favoring DCC p < 0.05), heart rates and umbilical cord blood gas values were not significantly different between the groups (p > 0.05). rSO2 values were significantly higher while FTOE values were significantly lower for every minute between the 3rd and 15th minutes after birth in the delayed cord clamping group (p < 0.05). CONCLUSION: Our study revealed a significant increase in cerebral rsO2 values and a decrease in FTOE values in the delayed cord clamping (DCC) group, indicating a positive impact on cerebral oxygenation and hemodynamics. Furthermore, the DCC group exhibited a higher proportion of infants with cerebral rSO2 levels above the 90th percentile. This higher proportion, along with a lower of those with such parameter below the 10th percentile, suggest that DCC may lead to the targeted/optimal cerebral oxygenetaion of these babies. As a result, we recommend measuring cerebral oxygenation, in addition to peripheral SpO2, for infants experiencing perinatal hypoxia and receiving supplemental oxygen.

Measures of overnight oxygen saturation to characterize sleep apnea severity and predict postoperative respiratory depression.

BACKGROUND: Sleep apnea syndrome, characterized by recurrent cessation (apnea) or reduction (hypopnea) of breathing during sleep, is a major risk factor for postoperative respiratory depression. Challenges in sleep apnea assessment have led to the proposal of alternative metrics derived from oxyhemoglobin saturation (SpO2), such as oxygen desaturation index (ODI) and percentage of cumulative sleep time spent with SpO2 below 90% (CT90), as predictors of postoperative respiratory depression. However, their performance has been limited with area under the curve of 0.60 for ODI and 0.59 for CT90. Our objective was to propose novel features from preoperative overnight SpO2 which are correlated with sleep apnea severity and predictive of postoperative respiratory depression. METHODS: Preoperative SpO2 signals from 235 surgical patients were retrospectively analyzed to derive seven features to characterize the sleep apnea severity. The features included entropy and standard deviation of SpO2 signal; below average burden characterizing the area under the average SpO2; average, standard deviation, and entropy of desaturation burdens; and overall nocturnal desaturation burden. The association between the extracted features and sleep apnea severity was assessed using Pearson correlation analysis. Logistic regression was employed to evaluate the predictive performance of the features in identifying postoperative respiratory depression. RESULTS: Our findings indicated a similar performance of the proposed features to the conventional apnea-hypopnea index (AHI) for assessing sleep apnea severity, with average area under the curve ranging from 0.77 to 0.81. Notably, entropy and standard deviation of overnight SpO2 signal and below average burden showed comparable predictive capability to AHI but with minimal computational requirements and individuals' burden, making them promising for screening purposes. Our sex-based analysis revealed that compared to entropy and standard deviation, below average burden exhibited higher sensitivity in detecting respiratory depression in women than men. CONCLUSION: This study underscores the potential of preoperative SpO2 features as alternative metrics to AHI in predicting postoperative respiratory.

Early Online.

BACKGROUND: Long-haul flights have been associated with a two- to four-fold increased risk of aviation-related thrombosis (ART). Several studies have investigated the extent to which hypoxic hypobaric exposure, dehydration and prolonged immobilisation during air travel induce changes in haemostasis. OBJECTIVE: To investigate the role of high altitude as a risk factor for ART. METHODS: Healthy volunteers aged ≥18 years (N=40), without risk factors for venous thromboembolism, were exposed to an exacerbated altitude of 18 000 feet (5 486 m) for 1 hour. During the flight, the oxygen (O2) levels of the participants, who received supplemental O2, were measured by pulse oximetry and maintained at >92%. Venous blood and urine samples were collected prior to departure and immediately after flying in an unpressurised twin-engine airplane. D-dimer levels, thromboelastography (TEG) parameters, von Willebrand factor (VWF) activity and urine osmolality were measured. RESULTS: The participants were 19 men and 21 women, with a mean (standard deviation) age of 46 (14) years. A significant difference in D-dimer levels, VWF activity, urine osmolality and TEG parameters (reaction (R) time, kinetic (K) time and maximum amplitude (MA)) before and after the 1-hour flight was observed (p<0.001). Urine osmolality correlated positively with VWF activity levels (r=0.469; p<0.002). CONCLUSION: Air travel at high altitude induced a hypercoagulable state in healthy volunteers. Future research should focus on whether thromboprophylaxis can significantly obviate the activation of coagulation in response to high altitude.

The Efficacy of Noninvasive Ventilation in Patients Affected by Rett Syndrome With Hypoventilation.

BACKGROUND: Rett syndrome is a progressive neurological disorder associated to several comorbidities that contribute significantly to impair lung function. Respiratory morbidity represents a major cause of death in this population. Little is known about the benefit of noninvasive ventilation. METHODS: We retrospectively enrolled patients with Rett syndrome who underwent a pneumological evaluation combined with a cardiorespiratory polygraphy and/or a pulse oximetry and capnography from 2012 to 2022. RESULTS: Medical records of 11 patients with Rett syndrome, mean age 13 ± 6 years, were evaluated. Most patients presented with both epilepsy and scoliosis. Five patients showed a pathologic sleep study and/or impaired night gas exchange: mean obstructive apnea-hypopnea index was 4 ± 3 events/hour; mean and minimal SpO2 were, respectively, 93% ± 2% and 83% ± 6%, while mean and maximal transcutaneous carbon dioxide monitoring (PtcCO2) were, respectively, 51 ± 5 mm Hg and 55 ± 8 mm Hg; and mean oxygen desaturation index was 13 ± 11 events/hour. These patients started noninvasive ventilation with clinical benefit and improved gas exchange mostly in terms of PtcCO2 (mean PtcCO2 51 ± 5 mm Hg before and 46 ± 6 mm Hg after noninvasive ventilation). CONCLUSIONS: Noninvasive ventilation is a suitable option for patients with Rett syndrome.

The effect of pleural drainage on pulse oximetry in a post-operative thoracic surgery population.

BACKGROUND: Pleural effusions in post-operative thoracic surgery patients are common. Effusions can result in prolonged hospitalizations or readmissions, with prior studies suggesting mixed effects of pleural drainage on hypoxia. We aimed to define the impact of pleural drainage on pulse oximetry (SpO2) in post-thoracic surgery patients. METHODS: A retrospective study of post-operative thoracic surgery patients undergoing pleural drainage was performed. SpO2 and supplemental oxygen (FiO2) values were recorded at pre- and post-procedure. The primary outcome was difference in pre-procedural and post-procedural SpO2. RESULTS: We identified 95 patients with a mean age of 65 (SD - 13.8) years undergoing 122 pleural drainage procedures. Mean drainage volume was 619 (SD-423) mL and the majority of procedures (88.5 %) included a drainage of <1000 mL. SpO2 was associated with an increase from 94.0 % (SD-2.6) to 97.3 % (SD-2.0) at 24-h (p < 0.0001). FiO2 was associated with a decrease from 0.31 (SD-0.15) to 0.29 (SD-0.12) at 24-h (p = 0.0081). SpO2/FiO2 was associated with an increase from 344.5 (SD-99.0) to 371.9 (SD-94.7) at 24-h post-procedure (p < 0.0001). CONCLUSIONS: Pleural drainage within post-operative thoracic surgery patients offers statistically significant improvements in oxygen saturation by peripheral pulse oximetry and oxygen supplementation; however the clinical significance of these changes remains unclear. Pleural drainage itself may be requested for numerous reasons, including diagnostic (fevers, leukocytosis, etc.) or therapeutic (worsening dyspnea) evaluation. However, pleural drainage may offer minimal clinical impact on pulse oximetry in post-operative thoracic surgery patients.

Extended Pulse Oximetry Screening in Healthy Neonates.

Predischarge pulse oximetry screening (POS) is recommended to pick up critical congenital heart diseases in apparently well neonates. However, it is possible that cases may be missed during the early POS in the presence of delayed closure of the ductus arteriosus. Repeat POS in the second week of life was found to be helpful and feasible for early detection of pathological states causing hypoxemia in seemingly well neonates. Studies with larger sample size are recommended to establish the role of an additional POS in the second week for enhanced CCHD detection.

Hypoxaemia and risk of death among children: rethinking oxygen saturation, risk-stratification, and the role of pulse oximetry in primary care.

Pulse oximeters are essential for assessing blood oxygen levels in emergency departments, operating theatres, and hospital wards. However, although the role of pulse oximeters in detecting hypoxaemia and guiding oxygen therapy is widely recognised, their role in primary care settings is less clear. In this Viewpoint, we argue that pulse oximeters have a crucial role in risk-stratification in both hospital and primary care or outpatient settings. Our reanalysis of hospital and primary care data from diverse low-income and middle-income settings shows elevated risk of death for children with moderate hypoxaemia (ie, peripheral oxygen saturations [SpO2] 90-93%) and severe hypoxaemia (ie, SpO2 <90%). We suggest that moderate hypoxaemia in the primary care setting should prompt careful clinical re-assessment, consideration of referral, and close follow-up. We provide practical guidance to better support front-line health-care workers to use pulse oximetry, including rethinking traditional binary SpO2 thresholds and promoting a more nuanced approach to identification and emergency treatment of the severely ill child.

Machine Learning-Based Critical Congenital Heart Disease Screening Using Dual-Site Pulse Oximetry Measurements.

BACKGROUND: Oxygen saturation (Spo2) screening has not led to earlier detection of critical congenital heart disease (CCHD). Adding pulse oximetry features (ie, perfusion data and radiofemoral pulse delay) may improve CCHD detection, especially coarctation of the aorta (CoA). We developed and tested a machine learning (ML) pulse oximetry algorithm to enhance CCHD detection. METHODS AND RESULTS: Six sites prospectively enrolled newborns with and without CCHD and recorded simultaneous pre- and postductal pulse oximetry. We focused on models at 1 versus 2 time points and with/without pulse delay for our ML algorithms. The sensitivity, specificity, and area under the receiver operating characteristic curve were compared between the Spo2-alone and ML algorithms. A total of 523 newborns were enrolled (no CHD, 317; CHD, 74; CCHD, 132, of whom 21 had isolated CoA). When applying the Spo2-alone algorithm to all patients, 26.2% of CCHD would be missed. We narrowed the sample to patients with both 2 time point measurements and pulse-delay data (no CHD, 65; CCHD, 14) to compare ML performance. Among these patients, sensitivity for CCHD detection increased with both the addition of pulse delay and a second time point. All ML models had 100% specificity. With a 2-time-points+pulse-delay model, CCHD sensitivity increased to 92.86% (P=0.25) compared with Spo2 alone (71.43%), and CoA increased to 66.67% (P=0.5) from 0. The area under the receiver operating characteristic curve for CCHD and CoA detection significantly improved (0.96 versus 0.83 for CCHD, 0.83 versus 0.48 for CoA; both P=0.03) using the 2-time-points+pulse-delay model compared with Spo2 alone. CONCLUSIONS: ML pulse oximetry that combines oxygenation, perfusion data, and pulse delay at 2 time points may improve detection of CCHD and CoA within 48 hours after birth. REGISTRATION: URL: https://www.clinicaltrials.gov/study/NCT04056104?term=NCT04056104&rank=1; Unique identifier: NCT04056104.

Atmospheric particulate matter and hypoxaemia in Korean children receiving general anaesthesia: A retrospective analysis.

BACKGROUND: The association between the concentration of atmospheric particulate matter on the day of surgery and the occurrence of intra-operative hypoxaemia in children receiving general anaesthesia is unclear. OBJECTIVE: To investigate the association between the exposure to particulate matter on the day of surgery and the occurrence of intra-operative hypoxaemia, defined as a pulse oximetry oxygen saturation of less than 90% for more than 1 min, in children. DESIGN: Retrospective study. SETTING: Single-centre. PARTICIPANTS: Children aged 18 years or younger who received general anaesthesia between January 2019 and October 2020. INTERVENTION: Information on daily levels of particulate matter with a diameter 10 µm or less and 2.5 µm or less measured within a neighbourhood corresponding to the area defined by the hospital's zip code was obtained from publicly available air-quality data. MAIN OUTCOME MEASURES: The primary outcome was intra-operative hypoxaemia, defined as a pulse oximetry oxygen saturation of less than 90% lasting for more than 1 min, manually verified by anaesthesiologists using vital sign registry data extracted at 2 s intervals. RESULTS: Of the patients finally analysed, 3.85% (489/13 175) experienced intra-operative hypoxaemia. Higher levels of particulate matter 10 µm or less in diameter (≥81 µg m -3 , 17/275, 6.2%) were associated with an increased occurrence of intra-operative hypoxaemia compared with lower particulate matter concentrations [<81 µg m -3 , 472/12 900, 3.7%; adjusted odds ratio, 1.71; 95% confidence interval (CI), 1.04 to 2.83; P  = 0.035]. CONCLUSION: The level of particulate matter on the day of surgery pose a risk of intra-operative hypoxaemia in children receiving general anaesthesia. If the concentrations of particulate matter 10 µm or less in diameter on the day of surgery are high, children receiving general anaesthesia should be managed with increased caution.

Failure Prediction of High-Flow Nasal Cannula at the Conventional Oxygen Therapy Phase in the Emergency Department.

INTRODUCTION: The use of high-flow nasal cannula (HFNC) in patients with acute hypoxemic respiratory failure has been increasing in the emergency department (ED). However, studies are lacking on the prediction of HFNC failure before therapy initiation in the ED. We investigated whether the existing indices, such as the ratio of pulse oximetry oxygen saturation/fraction of inspired oxygen to respiratory rate (ROX) and ratio of ROX index to heart rate (ROX-HR), can accurately predict HFNC failure at the conventional oxygen therapy phase in the ED. METHODS: This retrospective single-center study included patients treated with HFNC in the ED. The ROX and ROX-HR indices were calculated before initiating HFNC. An estimated fraction of inspired oxygen was used for conventional oxygen therapy. We plotted each index's receiver operating characteristics curve and calculated the area under the curve (AUC) for diagnostic capacity. The optimal cutoff values were assessed using the Youden index. The primary outcome was HFNC failure, defined as intubation in the ED. RESULTS: Among the 97 included patients, 25 (25.8%) failed HFNC therapy in the ED. The ROX and ROX-HR indices measured before initiating HFNC showed AUCs of 0.709 and 0.754, respectively. A ROX index of <5.614 and a ROX-HR index of <6.152 were associated with a high risk of intubation, even after correcting for confounding variables. CONCLUSION: The ROX and ROX-HR indices measured before initiating HFNC provide a relatively fair predictive value of HFNC failure in the ED.