Monte Carlo simulation of the effect of melanin concentration on light-tissue interactions in transmittance and reflectance finger photoplethysmography.

Photoplethysmography (PPG) uses light to detect volumetric changes in blood, and is integrated into many healthcare devices to monitor various physiological measurements. However, an unresolved limitation of PPG is the effect of skin pigmentation on the signal and its impact on PPG based applications such as pulse oximetry. Hence, an in-silico model of the human finger was developed using the Monte Carlo (MC) technique to simulate light interactions with different melanin concentrations in a human finger, as it is the primary determinant of skin pigmentation. The AC/DC ratio in reflectance PPG mode was evaluated at source-detector separations of 1 mm and 3 mm as the convergence rate (Q), a parameter that quantifies the accuracy of the simulation, exceeded a threshold of 0.001. At a source-detector separation of 3 mm, the AC/DC ratio of light skin was 0.472 times more than moderate skin and 6.39 than dark skin at 660 nm, and 0.114 and 0.141 respectively at 940 nm. These findings are significant for the development of PPG-based sensors given the ongoing concerns regarding the impact of skin pigmentation on healthcare devices.

Oxygenation saturation index in neonatal hypoxemic respiratory failure.

BACKGROUND: This study aimed to assess the validity of the oxygenation saturation index (OSI) and the ratio of oxygen saturation to the fraction of inspired oxygen (FIO2) (S/F ratio) with percutaneous oxygen saturation (OSISpO2 and the Sp/F ratio) and to evaluate the correlation between these values and the oxygen index (OI). It also determined their cut-off values for predicting OI in accordance with neonatal hypoxic respiratory failure severity. METHODS: We reviewed the data of 77 neonates (gestational age 31.7 ± 6.1 weeks; birthweight, 1768 ± 983 g) requiring invasive mechanical ventilation between 2013 and 2020, 1233 arterial blood gas samples in total. We calculated the OI, OSISpO2, OSI with arterial oxygen saturation (SaO2) (OSISaO2), Sp/F ratio, and the ratio of SaO2 to FIO2 (Sa/F ratio). RESULTS: The regression and Bland-Altman analysis showed good agreement between OSISpO2 or the Sp/F ratio and OSISaO2 or the Sa/F ratio. Although a significant positive correlation was found between OSISpO2 and OI, OSISpO2 was overestimated in SpO2 > 98% with a higher slope of the fitted regression line than that below 98% of SpO2. Furthermore, receiver-operating characteristic curve analysis using only SpO2 ≤ 98% samples showed that the optimal cut-off points of OSISpO2 and the Sp/F ratio for predicting OI were: OI 5, 3.0 and 332; OI 10, 5.3 and 231; OI 15, 7.7 and 108; OI 20, 11.0 and 149; and OI 25, 17.1 and 103, respectively. CONCLUSION: The cut-off OSISpO2 and Sp/F ratio values could allow continuous monitoring for oxygenation changes in neonates with the potential for wider clinical applications.

Pro-Con Debate: Universal Versus Selective Continuous Monitoring of Postoperative Patients.

In this Pro-Con commentary article, we discuss use of continuous physiologic monitoring for clinical deterioration, specifically respiratory depression in the postoperative population. The Pro position advocates for 24/7 continuous surveillance monitoring of all patients starting in the postanesthesia care unit until discharge from the hospital. The strongest arguments for universal monitoring relate to inadequate assessment and algorithms for patient risk. We argue that the need for hospitalization in and of itself is a sufficient predictor of an individual's risk for unexpected respiratory deterioration. In addition, general care units carry the added risk that even the most severe respiratory events will not be recognized in a timely fashion, largely due to higher patient to nurse staffing ratios and limited intermittent vital signs assessments (e.g., every 4 hours). Continuous monitoring configured properly using a "surveillance model" can adequately detect patients' respiratory deterioration while minimizing alarm fatigue and the costs of the surveillance systems. The Con position advocates for a mixed approach of time-limited continuous pulse oximetry monitoring for all patients receiving opioids, with additional remote pulse oximetry monitoring for patients identified as having a high risk of respiratory depression. Alarm fatigue, clinical resource limitations, and cost are the strongest arguments for selective monitoring, which is a more targeted approach. The proponents of the con position acknowledge that postoperative respiratory monitoring is certainly indicated for all patients, but not all patients need the same level of monitoring. The analysis and discussion of each point of view describes who, when, where, and how continuous monitoring should be implemented. Consideration of various system-level factors are addressed, including clinical resource availability, alarm design, system costs, patient and staff acceptance, risk-assessment algorithms, and respiratory event detection. Literature is reviewed, findings are described, and recommendations for design of monitoring systems and implementation of monitoring are described for the pro and con positions.

Alternative consent methods used in the multinational, pragmatic, randomised clinical trial SafeBoosC-III.

BACKGROUND: The process of obtaining prior informed consent for experimental treatment does not fit well into the clinical reality of acute and intensive care. The therapeutic window of interventions is often short, which may reduce the validity of the consent and the rate of enrolled participants, to delay trial completion and reduce the external validity of the results. Deferred consent and 'opt-out' are alternative consent methods. The SafeBoosC-III trial was a randomised clinical trial investigating the benefits and harms of cerebral oximetry monitoring in extremely preterm infants during the first 3 days after birth, starting within the first 6 h after birth. Prior, deferred and opt-out consent were all allowed by protocol. This study aimed to evaluate the use of different consent methods in the SafeBoosC-III trial, Furthermore, we aimed to describe and analyse concerns or complaints that arose during the first 6 months of trial conduct. METHODS: All 70 principal investigators were invited to join this descriptive ancillary study. Each principal investigator received a questionnaire on the use of consent methods in their centre during the SafeBoosC-III trial, including the possibility to describe any concerns related to the consent methods used during the first 6 months of the trial, as raised by the parents or the clinical staff. RESULTS: Data from 61 centres were available. In 43 centres, only prior informed consent was used: in seven, only deferred consent. No centres used the opt-out method only, but five centres used prior and deferred, five used prior, deferred and opt-out (all possibilities) and one used both deferred and opt-out. Six centres applied to use the opt-out method by their local research ethics committee but were denied using it. One centre applied to use deferred consent but was denied. There were only 23 registered concerns during the execution of the trial. CONCLUSIONS: Consent by opt-out was allowed by the protocol in this multinational trial but only a few investigators opted for it and some research ethics boards did not accept its use. It is likely to need promotion by the clinical research community to unfold its potential.

Race and Pulse Oximetry in Infants With Single Ventricles Undergoing Stage 1 Palliation.

This cross-sectional study investigates perioperative oxygen saturation differences in Black and White infants with single ventricles undergoing stage 1 palliation.

Impaired retinal oxygen metabolism and perfusion are accompanied by plasma protein and lipid alterations in recovered COVID-19 patients.

The aim of the present study was to investigate retinal microcirculatory and functional metabolic changes in patients after they had recovered from a moderate to severe acute COVID-19 infection. Retinal perfusion was quantified using laser speckle flowgraphy. Oxygen saturation and retinal calibers were assessed with a dynamic vessel analyzer. Arterio-venous ratio (AVR) was calculated based on retinal vessel diameter data. Blood plasma samples underwent mass spectrometry-based multi-omics profiling, including proteomics, metabolomics and eicosadomics. A total of 40 subjects were included in the present study, of which 29 had recovered from moderate to severe COVID-19 within 2 to 23 weeks before inclusion and 11 had never had COVID-19, as confirmed by antibody testing. Perfusion in retinal vessels was significantly lower in patients (60.6 ± 16.0 a.u.) than in control subjects (76.2 ± 12.1 a.u., p = 0.006). Arterio-venous (AV) difference in oxygen saturation and AVR was significantly lower in patients compared to healthy controls (p = 0.021 for AVR and p = 0.023 for AV difference in oxygen saturation). Molecular profiles demonstrated down-regulation of cell adhesion molecules, NOTCH3 and fatty acids, and suggested a bisphasic dysregulation of nitric oxide synthesis after COVID-19 infection. The results of this study imply that retinal perfusion and oxygen metabolism is still significantly altered in patients well beyond the acute phase of COVID-19. This is also reflected in the molecular profiling analysis of blood plasma, indicating a down-regulation of nitric oxide-related endothelial and immunological cell functions.Trial Registration: ClinicalTrials.gov ( https://clinicaltrials.gov ) NCT05650905.

Feasibility and acceptability of remotely monitoring spirometry and pulse oximetry as part of interstitial lung disease clinical care: a single arm observational study.

BACKGROUND: Remote monitoring of patient-recorded spirometry and pulse oximetry offers an alternative approach to traditional hospital-based monitoring of interstitial lung disease (ILD). Remote spirometry has been observed to reasonably reflect clinic spirometry in participants with ILD but remote monitoring has not been widely incorporated into clinical practice. We assessed the feasibility of remotely monitoring patients within a clinical ILD service. METHODS: Prospective, single-arm, open-label observational multi-centre study (NCT04850521). Inclusion criteria included ILD diagnosis, age ≥ 18 years, FVC ≥ 50% predicted. 60 participants were asked to record a single spirometry and oximetry measurement at least once daily, monitored weekly by their local clinical team. Feasibility was defined as ≥ 68% of participants with ≥ 70% adherence to study measurements and recording measurements ≥ 3 times/week throughout. RESULTS: A total of 60 participants were included in the analysis. 42/60 (70%) were male; mean age 67.8 years (± 11.2); 34/60 (56.7%) had idiopathic pulmonary fibrosis (IPF), Median ILD-GAP score was 3 (IQR 1-4.75). Spirometry adherence was achieved for ≥ 70% of study days in 46/60 participants (77%) and pulse oximetry adherence in 50/60 participants (83%). Recording ≥ 3 times/week every week was provided for spirometry in 41/60 participants (68%) and pulse oximetry in 43/60 participants (72%). Mean difference between recent clinic and baseline home spirometry was 0.31 L (± 0.72). 85.7% (IQR 63.9-92.6%) home spirometry attempts/patient were acceptable or usable according to ERS/ATS spirometry criteria. Positive correlation was observed between ILD-GAP score and adherence to spirometry and oximetry (rho 0.24 and 0.38 respectively). Adherence of weekly monitoring by clinical teams was 80.95% (IQR 64.19-95.79). All participants who responded to an experience questionnaire (n = 33) found remote measurements easy to perform and 75% wished to continue monitoring their spirometry at the conclusion of the study. CONCLUSION: Feasibility of remote monitoring within an ILD clinical service was demonstrated over 3 months for both daily home spirometry and pulse oximetry of patients. Remote monitoring may be more acceptable to participants who are older or have more advanced disease. TRIAL REGISTRATION: clinicaltrials.gov NCT04850521 registered 20th April 2021.

[Design of Pulse and Respiratory Signals Detection System].

A pulse and respiration synchronous detection system is designed to explore the changes of physiological signals in different situations. The system obtains the corresponding signal through STM32 control pulse and respiratory acquisition circuit, calculates and displays real-time parameters such as heart rate and respiratory rate, and transmits the data to the upper computer for storage in the database. The experimental test results show that the system can monitor pulse and respiratory waveform in different situations, and the waveform is in good condition. Compared with medical pulse oximeter, the error of measured heart rate and blood oxygen concentration is less than 3%, and the error of respiratory rate is less than 5% compared with the actual value, which verifies the accuracy of system signal acquisition. The system is small in size, low in cost, and comfortable to wear, and can be applied in experimental research related to pulse and respiratory signals.

Development of a Web-Based Oxygenation Dashboard for Preterm Neonates: A Quality Improvement Initiative.

BACKGROUND: Preterm neonates are extensively monitored to require strict oxygen target attainment for optimal outcomes. In daily practice, detailed oxygenation data are hardly used and crucial patterns may be missed due to the snapshot presentations and subjective observations. This study aimed to develop a web-based dashboard with both detailed and summarized oxygenation data in real-time and to test its feasibility to support clinical decision making. METHODS: Data from pulse oximeters and ventilators were synchronized and stored to enable real-time and retrospective trend visualizations in a web-based viewer. The dashboard was designed based on interviews with clinicians. A preliminary version was evaluated during daily clinical rounds. The routine evaluation of the respiratory condition of neonates (gestational age < 32 weeks) with respiratory support at the NICU was compared to an assessment with the assistance of the dashboard. RESULTS: The web-based dashboard included data on the oxygen saturation (SpO2), fraction of inspired oxygen (FiO2), SpO2/FiO2 ratio, and area < 80% and > 95% SpO2 curve during time intervals that could be varied. The distribution of SpO2 values was visualized as histograms. In 65% of the patient evaluations (n = 86) the level of hypoxia was assessed differently with the use of the dashboard. In 75% of the patients the dashboard was judged to provide added value for the clinicians in supporting clinical decisions. CONCLUSIONS: A web-based customized oxygenation dashboard for preterm neonates at the NICU was developed and found feasible during evaluation. More clear and objective information was found supportive for clinicians during the daily rounds in tailoring treatment strategies.

[Pulse oximetric saturation/fraction of inspired oxygen and partial pressure of oxygen/fraction of inspired oxygen in diagnosing acute respiratory distress syndrome: which is better?]

Acute Respiratory Distress Syndrome (ARDS) is distinguished by hypoxemia, contributing to heightened morbidity, elevated mortality rates, and substantial healthcare expenses, thereby imposing a significant burden on patients and society. Presently, effective treatments for ARDS are lacking, emphasizing the pivotal role of early diagnosis and timely intervention in its successful management. The partial pressure of oxygen/fraction of inspired oxygen (PaO2/FiO2, P/F) has traditionally served as a crucial metric for assessing patient hypoxemia and disease severity. While relatively accurate, its reliance on advanced technical expertise and specific medical equipment conditions constrains its implementation in areas with underdeveloped medical standards, resulting in missed diagnoses and treatments for ARDS patients. Conversely, the Pulse oximetric saturation/fraction of inspired oxygen (SpO2/FiO2, S/F) has garnered increasing attention owing to its straightforward, non-invasive, and sustainable monitoring attributes. This article seeks to meticulously compare the correlation, accuracy, and clinical feasibility of S/F with P/F in ARDS diagnosis, so as to propose diagnostic indicators for more quickly and accurately assessing the oxygenation status of ARDS patients.

Risk factors for collisions attributed to microsleep-related behaviors while driving in professional truck drivers.

Sleep-disordered breathing (SDB) is prevalent among professional drivers. Although SDB is a known risk factor for truck collisions attributed to microsleep-related behaviors at the wheel (TC-MRBs), the usefulness of overnight pulse oximetry for predicting TC-MRBs is debatable. This retrospective study assessed the association between overnight pulse oximetry parameters, the Epworth Sleepiness Scale (ESS), and TC-MRBs, confirmed by dashcam footage. This study included 108 matched professional truck drivers (TC-MRBs: N = 54; non-TC-MRBs: N = 54), with a mean age and body mass index of 41.9 ± 11.3 years and 23.0 ± 3.7 kg/m2, respectively. Night-time drivers, 4% oxygen desaturation index (ODI), and nadir oxygen saturation (SpO2) were associated with TC-MRBs (odds ratio [95% confidence interval]: 25.63 [5.88-111.77], p < 0.0001; 2.74 [1.02-7.33], p = 0.045; and 3.87 [1.04-14.39], p = 0.04, respectively). The area under the curve of 4% ODI and nadir SpO2 for TC-MRBs were 0.50 and 0.57, respectively. In conclusion, night-time driving, 4% ODI, and nadir SpO2 were significantly associated with TC-MRBs in professional truck drivers. However, the sensitivity of overnight pulse oximetry parameters to predict TC-MRBs in a real-world application was poor. Therefore, combining subjective and objective assessments such as dashcam video footage may be needed to achieve high accuracy for predicting TC-MRBs among professional truck drivers.

A Self-Calibrated Single Wavelength Biosensor for Measuring Oxygen Saturation.

Traditional methods for measuring blood oxygen use multiple wavelengths, which produce an intrinsic error due to ratiometric measurements. These methods assume that the absorption changes with the wavelength, but in fact the scattering changes as well and cannot be neglected. We found that if one measures in a specific angle around a cylindrical tissue, called the iso-pathlength (IPL) point, the reemitted light intensity is unaffected by the tissue's scattering. Therefore, the absorption can be isolated from the scattering, which allows the extraction of the subject's oxygen saturation. In this work, we designed an optical biosensor for reading the light intensity reemitted from the tissue, using a single light source and multiple photodetectors (PDs), with one of them in the IPL point's location. Using this bio-device, we developed a methodology to extract the arterial oxygen saturation using a single wavelength light source. We proved this method is not dependent on the light source and is applicable to different measurement locations on the body, with an error of 0.5%. Moreover, we tested thirty-eight males and females with the biosensor under normal conditions. Finally, we show the results of measuring subjects in a hypoxic chamber that simulates extreme conditions with low oxygen.

Characteristics of pulse oximetry and arterial blood gas in patients with fibrotic interstitial lung disease.

BACKGROUND: Fibrotic interstitial lung disease (ILD) is frequently associated with abnormal oxygenation; however, little is known about the accuracy of oxygen saturation by pulse oximetry (SpO2) compared with arterial blood gas (ABG) saturation (SaO2), the factors that influence the partial pressure of carbon dioxide (PaCO2) and the impact of PaCO2 on outcomes in patients with fibrotic ILD. STUDY DESIGN AND METHODS: Patients with fibrotic ILD enrolled in a large prospective registry with a room air ABG were included. Prespecified analyses included testing the correlation between SaO2 and SpO2, the difference between SaO2 and SpO2, the association of baseline characteristics with both the difference between SaO2 and SpO2 and the PaCO2, the association of baseline characteristics with acid-base category, and the association of PaCO2 and acid-base category with time to death or transplant. RESULTS: A total of 532 patients with fibrotic ILD were included. Mean resting SaO2 was 92±4% and SpO2 was 95±3%. Mean PaCO2 was 38±6 mmHg, with 135 patients having PaCO2 <35 mmHg and 62 having PaCO2 >45 mmHg. Correlation between SaO2 and SpO2 was mild to moderate (r=0.39), with SpO2 on average 3.0% higher than SaO2. No baseline characteristics were associated with the difference in SaO2 and SpO2. Variables associated with either elevated or abnormal (elevated or low) PaCO2 included higher smoking pack-years and lower baseline forced vital capacity (FVC). Lower baseline lung function was associated with an increased risk of chronic respiratory acidosis. PaCO2 and acid-base status were not associated with time to death or transplant. INTERPRETATION: SaO2 and SpO2 are weakly-to-moderately correlated in fibrotic ILD, with limited ability to accurately predict this difference. Abnormal PaCO2 was associated with baseline FVC but was not associated with outcomes.

A bimodal feature fusion convolutional neural network for detecting obstructive sleep apnea/hypopnea from nasal airflow and oximetry signals.

The most prevalent sleep-disordered breathing condition is Obstructive Sleep Apnea (OSA), which has been linked to various health consequences, including cardiovascular disease (CVD) and even sudden death. Therefore, early detection of OSA can effectively help patients prevent the diseases induced by it. However, many existing methods have low accuracy in detecting hypopnea events or even ignore them altogether. According to the guidelines provided by the American Academy of Sleep Medicine (AASM), two modal signals, namely nasal pressure airflow and pulse oxygen saturation (SpO2), offer significant advantages in detecting OSA, particularly hypopnea events. Inspired by this notion, we propose a bimodal feature fusion CNN model that primarily comprises of a dual-branch CNN module and a feature fusion module for the classification of 10-second-long segments of nasal pressure airflow and SpO2. Additionally, an Efficient Channel Attention mechanism (ECA) is incorporated into the second module to adaptively weight feature map of each channel for improving classification accuracy. Furthermore, we design an OSA Severity Assessment Framework (OSAF) to aid physicians in effectively diagnosing OSA severity. The performance of both the bimodal feature fusion CNN model and OSAF is demonstrated to be excellent through per-segment and per-patient experimental results, based on the evaluation of our method using two real-world datasets consisting of polysomnography (PSG) recordings from 450 subjects.

Implementation of an arterial blood gas indication algorithm in cardiac surgery.

PROBLEM: Arterial blood gasses (ABGs) account for an estimated 10-20% of all costs during an ICU stay. Non-clinically indicated ABGs increased costs of care, lengths of stay, ventilator days, and line days, increasing the risk of adverse outcomes in already vulnerable critically ill patients. A cardiac surgery intensive care unit (CSICU) within a large urban mid-Atlantic academic medical center accounted for 31% of the entire institution's ABG analyses between 2018-2019, was identified as a top utilizer due to inappropriate ordering practices compared to current guidelines. PURPOSE: The purpose of this quality improvement project was to implement an algorithm using evidence-based guidelines that identified appropriate standardized clinical indications for ABGs, with the intention of reducing non-clinically indicated blood gas analyses orders within the CSICU. Anticipated outcomes of this practice change included decreasing the total volume of ABGs sent, resulting in reduced costs of care, lengths of stay, and improved morbidity and mortality rates. METHODS: An evidence-based ABG indication algorithm was created focusing on acute changes in oxygenation, ventilation, acid base balance; changes in hemodynamics, post-operative baseline, and for patient ABGs to correlate with extra-corporeal membranous oxygenation values. Routine ABGs for monitoring were eliminated. Implementation occurred over fourteen-weeks in the fall of 2020 following staff and provider education. Training emphasized the use of non-invasive monitoring such as pulse-oximetry and capnography. Compliance and gross laboratory totals and indications were obtained from weekly auditing. RESULTS: There was an 8.8% reduction in ABGs obtained and 32% decrease in ABGs per patient day. The most common indications were extra-corporeal membranous oxygenation (ECMO)-correlated ABGs, post-operative, and changes in oxygenation and/or ventilation; 7.8% were non-indicated. CONCLUSIONS: Implementation of an ABG indication algorithm resulted in fewer ABGs sent, mostly due to a reduction in routine monitoring, and ABGs were more likely to be clinically indicated in response to an acute concern. Implementing an ABG indication algorithm is safe, feasible, and can lead to significant cost reductions for the institution.

Using Effect Scores to Characterize Heterogeneity of Treatment Effects.

This JAMA Guide to Statistics and Methods article explains effect score analyses, an approach for evaluating the heterogeneity of treatment effects, and examines its use in a study of oxygen-saturation targets in critically ill patients.