Oximetry at admission as a predictor of tomographic and functional impairment after 3-6 months in hospitalized patients with COVID-19.

OBJECTIVE: To investigate characteristics that may be associated with radiologic and functional findings following discharge in patients with severe coronavirus disease 2019 (COVID-19). METHODS: This single-center, prospective, observational cohort study comprised patients aged >18 years who were hospitalized with COVID-19 pneumonia, between May and October 2020. After 3 to 6 months of discharge, patients were clinically evaluated and underwent spirometry, a 6-minute walk test (6MWT), and chest computed tomography (CT). Statistical analysis was performed using association and correlation tests. RESULTS: A total of 134 patients were included (25/114 [22%] were admitted with severe hypoxemia). On the follow-up chest CT, 29/92 (32%) had no abnormalities, regardless of the severity of the initial involvement, and the mean 6MWT distance was 447 m. Patients with desaturation on admission had an increased risk of remaining CT abnormalities: patients with SpO2 between 88 and 92% had a 4.0-fold risk, and those with SpO2 < 88% had a 6.2-fold risk. The group with SpO2 < 88% also walked shorter distances than patients with SpO2 between 88 and 92%. CONCLUSION: Initial hypoxemia was found to be a good predictor of persistent radiological abnormalities in follow-up and was associated with low performance in 6MWT.

A review of the effect of skin pigmentation on pulse oximeter accuracy.

Objective. Pulse oximetry is a non-invasive optical technique used to measure arterial oxygen saturation (SpO2) in a variety of clinical settings and scenarios. Despite being one the most significant technological advances in health monitoring over the last few decades, there have been reports on its various limitations. Recently due to the Covid-19 pandemic, questions about pulse oximeter technology and its accuracy when used in people with different skin pigmentation have resurfaced, and are to be addressed.Approach. This review presents an introduction to the technique of pulse oximetry including its basic principle of operation, technology, and limitations, with a more in depth focus on skin pigmentation. Relevant literature relating to the performance and accuracy of pulse oximeters in populations with different skin pigmentation are evaluated.Main Results. The majority of the evidence suggests that the accuracy of pulse oximetry differs in subjects of different skin pigmentations to a level that requires particular attention, with decreased accuracy in patients with dark skin.Significance. Some recommendations, both from the literature and contributions from the authors, suggest how future work could address these inaccuracies to potentially improve clinical outcomes. These include the objective quantification of skin pigmentation to replace currently used qualitative methods, and computational modelling for predicting calibration algorithms based on skin colour.

Invited Commentary: Undiagnosed and Undertreated-the Suffocating Consequences of the Use of Racially Biased Medical Devices During the COVID-19 Pandemic.

While medical technology is typically considered neutral, many devices rely upon racially biased algorithms that prioritize care for White patients over Black patients, who may require more urgent medical attention. In their accompanying article, Sudat et al. (Am J Epidemiol. 2023;XXX(XX):XXX-XXX) document striking inaccuracies in pulse oximeter readings among Black patients, with significant clinical implications. Their findings suggest that this resulted in racial differences in delivery of evidence-based care during the coronavirus disease 2019 (COVID-19) pandemic, affecting admissions and treatment protocols. Despite the medical community's growing awareness of the pulse oximeter's significant design flaw, the device is still in use. In this article, I contextualize Sudat et al.'s study results within the larger history of racial bias in medical devices by highlighting the consequences of the continued underrepresentation of diverse populations in clinical trials. I probe the implications of racially biased assessments within clinical practice and research and illustrate the disproportionate impact on patients of color by examining 2 medical tools, the pulse oximeter and pulmonary function tests. Both cases result in the undertreatment and underdiagnosis of Black patients. I also demonstrate how the social underpinnings of racial bias in medical technology contribute to poor health outcomes and reproduce health disparities, and propose several recommendations for the field to rectify the harms of racial bias in medical technology.

Effectiveness and safety of pulse oximetry in remote patient monitoring of patients with COVID-19: a systematic review.

The COVID-19 pandemic has led health systems to increase the use of tools for monitoring and triaging patients remotely. In this systematic review, we aim to assess the effectiveness and safety of pulse oximetry in remote patient monitoring (RPM) of patients at home with COVID-19. We searched five databases (MEDLINE, Embase, Global Health, medRxiv, and bioRxiv) from database inception to April 15, 2021, and included feasibility studies, clinical trials, and observational studies, including preprints. We found 561 studies, of which 13 were included in our narrative synthesis. These 13 studies were all observational cohorts and involved a total of 2908 participants. A meta-analysis was not feasible owing to the heterogeneity of the outcomes reported in the included studies. Our systematic review substantiates the safety and potential of pulse oximetry for monitoring patients at home with COVID-19, identifying the risk of deterioration and the need for advanced care. The use of pulse oximetry can potentially save hospital resources for patients who might benefit the most from care escalation; however, we could not identify explicit evidence for the effect of RPM with pulse oximetry on health outcomes compared with other monitoring models such as virtual wards, regular monitoring consultations, and online or paper diaries to monitor changes in symptoms and vital signs. Based on our findings, we make 11 recommendations across the three Donabedian model domains and highlight three specific measurements for setting up an RPM system with pulse oximetry.

A whole healthcare system mortality review of the second wave COVID-19 pandemic response, were lessons learned?

We previously reported a study of features of emergency healthcare response to COVID-19 that could be modified to mitigate against future excess deaths. Here we determined what themes persisted in later waves. This was an expert panel review of all components of care delivered to COVID-19 patients who died (primary and secondary care, community services, NHS 111 and 999, COVID oximetry at home, virtual wards). 174 deaths were included. 5% were deemed >50% avoidable, 75% included avoidability themes. Contact with primary care remains mostly via telephone, creating diagnostic risk. Patient decision to avoid healthcare contact was common. Recommendations include: better utilisation of home monitoring in future pandemics; improved avoidance of nosocomial spread; patients be encouraged to seek medical advice earlier.

Update on the management of acute respiratory failure using non-invasive ventilation and pulse oximetry.

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2023. Other selected articles can be found online at  https://www.biomedcentral.com/collections/annualupdate2023 . Further information about the Annual Update in Intensive Care and Emergency Medicine is available from  https://link.springer.com/bookseries/8901 .

Parental home-based pulse oximetry monitoring for adults with intellectual disabilities at risk of serious respiratory problems including COVID-19: a brief report.

BACKGROUND: People with intellectual disabilities (ID) are at high risk of developing respiratory health issues. The COVID-19 pandemic has compounded this, with serious consequences, and for some, death. Despite home-based oxygen saturation monitoring being recommended for people with ID, there is a stark lack of evidence in the literature on its feasibility. METHOD: We conducted 3-day baseline home-based oxygen saturation monitoring, using pulse oximeters, with eight parents of nine adults with ID in Scotland. Two eligible parents also completed a further 2 weeks of monitoring, and returned an evaluation questionnaire on its feasibility. RESULTS: Baseline mean readings for eight adults with ID were within the normal range (%Sp02  ≥ 95), and for another one 94%. Fluctuations over the 3-day assessment period were experienced by six of these individuals. However, these variations were within limits which are not dangerous (lowest reading 92%), implying that parental home-based pulse oximetry monitoring is likely to be safe for adults with ID. The two parents who completed the evaluation found home-based pulse oximetry monitoring to be easy/very easy to do, and effective/very effective. CONCLUSIONS: This is the first research study, albeit with a very small sample, to report on the potential feasibility of parental home-based pulse oximetry monitoring for adults with ID. Home-based pulse oximetry monitoring appears to be safe in adults with ID at risk of developing serious respiratory problems, and not difficult for their parents to do. There is an urgent need to replicate this work, using a larger sample, to promote home-based respiratory health monitoring more widely for people with ID.

Pulse Oximeters and Violation of Federal Antidiscrimination Law.

This Viewpoint discusses how some pulse oximeters can provide incorrect oxygen saturation data for dark-skinned patients compared with light-skinned patients, describes the reasons that biased oximeters remained in use, and highlights why a rule recently proposed by the US Department of Health and Human Services may bring about needed change in the use of pulse oximetry for patients with dark skin.

Pulse Oximetry Improves COVID-19 Screening Sensitivity by Detecting Asymptomatic and Afebrile Infections in a Case Control Study.

SARS-CoV-2 has spread quickly despite the implementation of various strategies to limit the spread of the disease. Current screening procedures are unable to detect asymptomatic infections. This study reports the prevalence of abnormal vital signs among incarcerated individuals with asymptomatic infections and proposes an enhanced screening algorithm that may detect asymptomatic infections. A case control study used a retrospective electronic chart review of COVID-19 infected people and matched controls housed in one Federal Bureau of Prisons institution. Data were collected on age, body mass index, medical history, temperature, blood oxygen saturation (SpO2), and symptoms. Fifty-seven laboratory-confirmed COVID-19 infections and 81 confirmed controls were identified. Asymptomatic infections were present in 35/57 people (61%) with a group minimum SpO2 94.4% (standard deviation [SD] 1.4) and a maximum oral temperature of 99.19°F (SD 0.36). An enhanced screening algorithm that uses pulse oximetry yields a sensitivity of 84.2%, 95% confidence interval [72.1-92.5]. Among asymptomatic people, there is a high prevalence of abnormal SpO2 and temperature measurements. A screening algorithm that uses both of these measures can detect asymptomatic infections with a low false positive rate.

Overestimation of Oxygen Saturation Measured by Pulse Oximetry in Hypoxemia. Part 1: Effect of Optical Pathlengths-Ratio Increase.

On average, arterial oxygen saturation measured by pulse oximetry (SpO2) is higher in hypoxemia than the true oxygen saturation measured invasively (SaO2), thereby increasing the risk of occult hypoxemia. In the current article, measurements of SpO2 on 17 cyanotic newborns were performed by means of a Nellcor pulse oximeter (POx), based on light with two wavelengths in the red and infrared regions (660 and 900 nm), and by means of a novel POx, based on two wavelengths in the infrared region (761 and 820 nm). The SpO2 readings from the two POxs showed higher values than the invasive SaO2 readings, and the disparity increased with decreasing SaO2. SpO2 measured using the two infrared wavelengths showed better correlation with SaO2 than SpO2 measured using the red and infrared wavelengths. After appropriate calibration, the standard deviation of the individual SpO2-SaO2 differences for the two-infrared POx was smaller (3.6%) than that for the red and infrared POx (6.5%, p < 0.05). The overestimation of SpO2 readings in hypoxemia was explained by the increase in hypoxemia of the optical pathlengths-ratio between the two wavelengths. The two-infrared POx can reduce the overestimation of SpO2 measurement in hypoxemia and the consequent risk of occult hypoxemia, owing to its smaller increase in pathlengths-ratio in hypoxemia.

Inverse association between blood pressure and pulse oximetry accuracy: an observational study in patients with suspected or confirmed COVID-19 infection.

BACKGROUND: Pulse oximeters are a standard non-invasive tool to measure blood oxygen levels, and are used in multiple healthcare settings. It is important to understand the factors affecting their accuracy to be able to use them optimally and safely. This analysis aimed to explore the association of the measurement error of pulse oximeters with systolic BP, diastolic BP and heart rate (HR) within ranges of values commonly observed in clinical practice. METHODS: The study design was a retrospective observational study of all patients admitted to a large teaching hospital with suspected or confirmed COVID-19 infection from February 2020 to December 2021. Data on systolic and diastolic BPs and HR levels were available from the same time period as the pulse oximetry measurements. RESULTS: Data were available for 3420 patients with 5927 observations of blood oxygen saturations as measured by pulse oximetry and ABG sampling within 30 min. The difference in oxygen saturation using the paired pulse oximetry and arterial oxygen saturation difference measurements was inversely associated with systolic BP, increasing by 0.02% with each mm Hg decrease in systolic BP (95% CI 0.00% to 0.03%) over a range of 80-180 mm Hg. Inverse associations were also observed between the error for oxygen saturation as measured by pulse oximetry and with both diastolic BP (+0.03%; 95% CI 0.00% to 0.05%) and HR (+0.04%; 95% CI 0.02% to 0.06% for each unit decrease in the HR). CONCLUSIONS: Care needs to be taken in interpreting pulse oximetry measurements in patients with lower systolic and diastolic BPs, and HRs, as oxygen saturation is overestimated as BP and HR decrease. Confirmation of the oxygen saturation with an ABG may be appropriate in some clinical scenarios.

Home monitoring by pulse oximetry of primary care patients with COVID-19: a pilot randomised controlled trial.

BACKGROUND: Pulse oximetry as a home or remote monitoring tool accelerated during the pandemic for patients with COVID-19, but evidence on its use is lacking. AIM: To assess the feasibility of home monitoring by pulse oximetry of patients aged ≥40 years with cardiovascular comorbidity and moderate-to-severe COVID-19. DESIGN AND SETTING: A primary care-based, open, pilot randomised controlled trial, with nested process evaluation, was undertaken in the Netherlands. METHOD: From November 2020 to June 2021, eligible patients presenting to one of 14 participating Dutch general practices were randomly allocated to regular measurement of peripheral oxygen saturation (at least three SpO2 measurements per day for 14 days) with a validated pulse oximeter or usual care. RESULTS: All 41 participants (21 intervention, 20 usual care) completed the 45-day follow-up period. Overall, the intervention group performed 97.6% of protocolised measurements; the median daily measurement per participant was 2.7 (interquartile range 1-4). Hypoxemia (SpO2 <94%) was reported in 10 participants (in 52 measurements); of those, six consulted the GP as instructed. Participants reported a high feeling of safety (0-100 visual analogue scale): 71.8 for the intervention group versus 59.8 for the control (P = 0.09). Primary care consultations were similar across groups: 50 for the intervention versus 51 for the control. Eleven visits by 10 participants were made to the emergency department (eight from the intervention group versus three from usual care), of which six participants were hospitalised (five intervention versus one usual care). No participants were admitted to the intensive care unit or died during follow-up. CONCLUSION: Home monitoring of patients with moderate-to-severe COVID-19 by pulse oximetry appeared feasible; adherence was high, patients reported a high feeling of safety, while the number of primary care consultations remained similar to usual care.

Evaluating the impact of a pulse oximetry remote monitoring programme on mortality and healthcare utilisation in patients with COVID-19 assessed in emergency departments in England: a retrospective matched cohort study.

BACKGROUND: To identify the impact of enrolment onto a national pulse oximetry remote monitoring programme for COVID-19 (COVID-19 Oximetry @home; CO@h) on health service use and mortality in patients attending Emergency Departments (EDs). METHODS: We conducted a retrospective matched cohort study of patients enrolled onto the CO@h pathway from EDs in England. We included all patients with a positive COVID-19 test from 1 October 2020 to 3 May 2021 who attended ED from 3 days before to 10 days after the date of the test. All patients who were admitted or died on the same or following day to the first ED attendance within the time window were excluded. In the primary analysis, participants enrolled onto CO@h were matched using demographic and clinical criteria to participants who were not enrolled. Five outcome measures were examined within 28 days of first ED attendance: (1) Death from any cause; (2) Any subsequent ED attendance; (3) Any emergency hospital admission; (4) Critical care admission; and (5) Length of stay. RESULTS: 15 621 participants were included in the primary analysis, of whom 639 were enrolled onto CO@h and 14 982 were controls. Odds of death were 52% lower in those enrolled (95% CI 7% to 75%) compared with those not enrolled onto CO@h. Odds of any ED attendance or admission were 37% (95% CI 16% to 63%) and 59% (95% CI 32% to 91%) higher, respectively, in those enrolled. Of those admitted, those enrolled had 53% (95% CI 7% to 76%) lower odds of critical care admission. There was no significant impact on length of stay. CONCLUSIONS: These findings indicate that for patients assessed in ED, pulse oximetry remote monitoring may be a clinically effective and safe model for early detection of hypoxia and escalation. However, possible selection biases might limit the generalisability to other populations.

Pulse Oximetry and Arterial Saturation Difference in Pediatric COVID-19 Patients: Retrospective Analysis by Race.

OBJECTIVES: Pulse oximetry (Sp o2 ) may overestimate arterial oxygen saturation (Sa o2 ) in blood laboratory testing. This study aimed to assess Sp o2 -Sa o2 difference in relation to race (i.e., patient self-reporting as Black or White), occult hypoxemia, and length of stay (LOS) in pediatric patients with COVID-19. DESIGN: Single-center retrospective study in pediatric COVID-19 patients. We used multivariable linear regressions to examine the association between race and oximetry measurements and between occult hypoxemia and LOS. Oximetry bias was defined using Sp o2 and Sa o2 data according to approved comparisons. Occult hypoxemia was defined as Sp o2 greater than 92% and Sa o2 less than 88%. SETTING: Quaternary pediatric hospital. PATIENTS: Pediatric COVID-19 patients admitted to Texas Children's Hospital between May 2020 and December 2021. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: There were 2713 patients with complete physiological data in the analysis. Of the total, 61% were Black, and 39% were White. Oximetry bias was greater in Black compared with White patients ( p < 0.001), and this bias increased as the oxygen saturations decreased ( p < 0.001). Black and White patients had a 12% and 4% prevalence of occult hypoxemia, respectively ( p < 0.001). LOS was not associated with oximetry bias or occult hypoxemia once controlled for the level of support (intensive care, respiratory, circulatory). CONCLUSIONS: We found an oximetry bias in the measurement of Sp o2 with respect to Sa o2 in symptomatic hospitalized pediatric patients with the diagnosis of COVID-19. Furthermore, race is related to an increased oximetry bias. However, we did not find a relationship between oximetry bias and the LOS in the hospital in this cohort of patients.

Prognostication using SpO2/FiO2 in invasively ventilated ICU patients with ARDS due to COVID-19 - Insights from the PRoVENT-COVID study.

BACKGROUND: The SpO2/FiO2 is a useful oxygenation parameter with prognostic capacity in patients with ARDS. We investigated the prognostic capacity of SpO2/FiO2 for mortality in patients with ARDS due to COVID-19. METHODS: This was a post-hoc analysis of a national multicenter cohort study in invasively ventilated patients with ARDS due to COVID-19. The primary endpoint was 28-day mortality. RESULTS: In 869 invasively ventilated patients, 28-day mortality was 30.1%. The SpO2/FiO2 on day 1 had no prognostic value. The SpO2/FiO2 on day 2 and day 3 had prognostic capacity for death, with the best cut-offs being 179 and 199, respectively. Both SpO2/FiO2 on day 2 (OR, 0.66 [95%-CI 0.46-0.96]) and on day 3 (OR, 0.70 [95%-CI 0.51-0.96]) were associated with 28-day mortality in a model corrected for age, pH, lactate levels and kidney dysfunction (AUROC 0.78 [0.76-0.79]). The measured PaO2/FiO2 and the PaO2/FiO2 calculated from SpO2/FiO2 were strongly correlated (Spearman's r = 0.79). CONCLUSIONS: In this cohort of patients with ARDS due to COVID-19, the SpO2/FiO2 on day 2 and day 3 are independently associated with and have prognostic capacity for 28-day mortality. The SpO2/FiO2 is a useful metric for risk stratification in invasively ventilated COVID-19 patients.

COVID-19 Detection Using Photoplethysmography and Neural Networks.

The early identification of microvascular changes in patients with Coronavirus Disease 2019 (COVID-19) may offer an important clinical opportunity. This study aimed to define a method, based on deep learning approaches, for the identification of COVID-19 patients from the analysis of the raw PPG signal, acquired with a pulse oximeter. To develop the method, we acquired the PPG signal of 93 COVID-19 patients and 90 healthy control subjects using a finger pulse oximeter. To select the good quality portions of the signal, we developed a template-matching method that excludes samples corrupted by noise or motion artefacts. These samples were subsequently used to develop a custom convolutional neural network model. The model accepts PPG signal segments as input and performs a binary classification between COVID-19 and control samples. The proposed model showed good performance in identifying COVID-19 patients, achieving 83.86% accuracy and 84.30% sensitivity (hold-out validation) on test data. The obtained results indicate that photoplethysmography may be a useful tool for microcirculation assessment and early recognition of SARS-CoV-2-induced microvascular changes. In addition, such a noninvasive and low-cost method is well suited for the development of a user-friendly system, potentially applicable even in resource-limited healthcare settings.

Automatic COVID-19 severity assessment from HRV.

COVID-19 is known to be a cause of microvascular disease imputable to, for instance, the cytokine storm inflammatory response and the consequent blood coagulation. In this study, we propose a methodological approach for assessing the COVID-19 presence and severity based on Random Forest (RF) and Support Vector Machine (SVM) classifiers. Classifiers were applied to Heart Rate Variability (HRV) parameters extracted from photoplethysmographic (PPG) signals collected from healthy and COVID-19 affected subjects. The supervised classifiers were trained and tested on HRV parameters obtained from the PPG signals in a cohort of 50 healthy subjects and 93 COVID-19 affected subjects, divided into two groups, mild and moderate, based on the support of oxygen therapy and/or ventilation. The most informative feature set for every group's comparison was determined with the Least Absolute Shrinkage and Selection Operator (LASSO) technique. Both RF and SVM classifiers showed a high accuracy percentage during groups' comparisons. In particular, the RF classifier reached 94% of accuracy during the comparison between the healthy and minor severity COVID-19 group. Obtained results showed a strong capability of RF and SVM to discriminate between healthy subjects and COVID-19 patients and to differentiate the two different COVID-19 severity. The proposed method might be helpful for detecting, in a low-cost and fast fashion, the presence and severity of COVID-19 disease; moreover, these reasons make this method interesting as a starting point for future studies that aim to investigate its effectiveness as a possible screening method.

Derivation and external validation of a simple risk score to predict in-hospital mortality in patients hospitalized for COVID-19: A multicenter retrospective cohort study.

ABSTRACT: As severe acute respiratory syndrome coronavirus 2 continues to spread, easy-to-use risk models that predict hospital mortality can assist in clinical decision making and triage. We aimed to develop a risk score model for in-hospital mortality in patients hospitalized with 2019 novel coronavirus (COVID-19) that was robust across hospitals and used clinical factors that are readily available and measured standardly across hospitals.In this retrospective observational study, we developed a risk score model using data collected by trained abstractors for patients in 20 diverse hospitals across the state of Michigan (Mi-COVID19) who were discharged between March 5, 2020 and August 14, 2020. Patients who tested positive for severe acute respiratory syndrome coronavirus 2 during hospitalization or were discharged with an ICD-10 code for COVID-19 (U07.1) were included. We employed an iterative forward selection approach to consider the inclusion of 145 potential risk factors available at hospital presentation. Model performance was externally validated with patients from 19 hospitals in the Mi-COVID19 registry not used in model development. We shared the model in an easy-to-use online application that allows the user to predict in-hospital mortality risk for a patient if they have any subset of the variables in the final model.Two thousand one hundred and ninety-three patients in the Mi-COVID19 registry met our inclusion criteria. The derivation and validation sets ultimately included 1690 and 398 patients, respectively, with mortality rates of 19.6% and 18.6%, respectively. The average age of participants in the study after exclusions was 64 years old, and the participants were 48% female, 49% Black, and 87% non-Hispanic. Our final model includes the patient's age, first recorded respiratory rate, first recorded pulse oximetry, highest creatinine level on day of presentation, and hospital's COVID-19 mortality rate. No other factors showed sufficient incremental model improvement to warrant inclusion. The area under the receiver operating characteristics curve for the derivation and validation sets were .796 (95% confidence interval, .767-.826) and .829 (95% confidence interval, .782-.876) respectively.We conclude that the risk of in-hospital mortality in COVID-19 patients can be reliably estimated using a few factors, which are standardly measured and available to physicians very early in a hospital encounter.