Project description:Current methods of measuring heart rate (HR) and oxygen levels (SPO2) require physical contact, are individualised, and for accurate oxygen levels may also require a blood test. No-touch or non-invasive technologies are not currently commercially available for use in healthcare settings. To date, there has been no assessment of a system that measures HR and SPO2 using commercial off-the-shelf camera technology that utilises R, G, B, and IR data. Moreover, no formal remote photoplethysmography studies have been performed in real-life scenarios with participants at home with different demographic characteristics. This novel study addresses all these objectives by developing, optimising, and evaluating a system that measures the HR and SPO2 of 40 participants. HR and SPO2 are determined by measuring the frequencies from different wavelength band regions using FFT and radiometric measurements after pre-processing face regions of interest (forehead, lips, and cheeks) from colour, IR, and depth data. Detrending, interpolating, hamming, and normalising the signal with FastICA produced the lowest RMSE of 7.8 for HR with the r-correlation value of 0.85 and RMSE 2.3 for SPO2. This novel system could be used in several critical care settings, including in care homes and in hospitals and prompt clinical intervention as required.
Project description:ImportancePulse oximetry guides triage and therapy decisions for COVID-19. Whether reported racial inaccuracies in oxygen saturation measured by pulse oximetry are present in patients with COVID-19 and associated with treatment decisions is unknown.ObjectiveTo determine whether there is differential inaccuracy of pulse oximetry by race or ethnicity among patients with COVID-19 and estimate the association of such inaccuracies with time to recognition of eligibility for oxygen threshold-specific COVID-19 therapies.Design, setting, and participantsThis retrospective cohort study of clinical data from 5 referral centers and community hospitals in the Johns Hopkins Health System included patients with COVID-19 who self-identified as Asian, Black, Hispanic, or White.ExposuresConcurrent measurements (within 10 minutes) of oxygen saturation levels in arterial blood (SaO2) and by pulse oximetry (SpO2).Main outcomes and measuresFor patients with concurrent SpO2 and SaO2 measurements, the proportion with occult hypoxemia (SaO2<88% with concurrent SpO2 of 92%-96%) was compared by race and ethnicity, and a covariate-adjusted linear mixed-effects model was produced to estimate the association of race and ethnicity with SpO2 and SaO2 difference. This model was applied to identify a separate sample of patients with predicted SaO2 levels of 94% or less before an SpO2 level of 94% or less or oxygen treatment initiation. Cox proportional hazards models were used to estimate differences by race and ethnicity in time to recognition of eligibility for guideline-recommended COVID-19 therapies, defined as an SpO2 level of 94% or less or oxygen treatment initiation. The median delay among individuals who ultimately had recognition of eligibility was then compared.ResultsOf 7126 patients with COVID-19, 1216 patients (63 Asian [5.2%], 478 Black [39.3%], 215 Hispanic [17.7%], and 460 White [37.8%] individuals; 507 women [41.7%]) had 32 282 concurrently measured SpO2 and SaO2. Occult hypoxemia occurred in 19 Asian (30.2%), 136 Black (28.5%), and 64 non-Black Hispanic (29.8%) patients compared with 79 White patients (17.2%). Compared with White patients, SpO2 overestimated SaO2 by an average of 1.7% among Asian (95% CI, 0.5%-3.0%), 1.2% among Black (95% CI, 0.6%-1.9%), and 1.1% among non-Black Hispanic patients (95% CI, 0.3%-1.9%). Separately, among 1903 patients with predicted SaO2 levels of 94% or less before an SpO2 level of 94% or less or oxygen treatment initiation, compared with White patients, Black patients had a 29% lower hazard (hazard ratio, 0.71; 95% CI, 0.63-0.80), and non-Black Hispanic patients had a 23% lower hazard (hazard ratio, 0.77; 95% CI, 0.66-0.89) of treatment eligibility recognition. A total of 451 patients (23.7%) never had their treatment eligibility recognized, most of whom (247 [54.8%]) were Black. Among the remaining 1452 (76.3%) who had eventual recognition of treatment eligibility, Black patients had a median delay of 1.0 hour (95% CI, 0.23-1.9 hours; P = .01) longer than White patients. There was no significant median difference in delay between individuals of other racial and ethnic minority groups and White patients.Conclusions and relevanceThe results of this cohort study suggest that racial and ethnic biases in pulse oximetry accuracy were associated with greater occult hypoxemia in Asian, Black, and non-Black Hispanic patients with COVID-19, which was associated with significantly delayed or unrecognized eligibility for COVID-19 therapies among Black and Hispanic patients. This disparity may contribute to worse outcomes among Black and Hispanic patients with COVID-19.
Project description:BackgroundIntermittent measurement of respiratory rate via observation is routine in many patient care settings. This approach has several inherent limitations that diminish the clinical utility of these measurements because it is intermittent, susceptible to human error, and requires clinical resources. As an alternative, a software application that derives continuous respiratory rate measurement from a standard pulse oximeter has been developed. We sought to determine the performance characteristics of this new technology by comparison with clinician-reviewed capnography waveforms in both healthy subjects and hospitalized patients in a low-acuity care setting.MethodsTwo independent observational studies were conducted to validate the performance of the Medtronic Nellcor Respiration Rate Software application. One study enrolled 26 healthy volunteer subjects in a clinical laboratory, and a second multicenter study enrolled 53 hospitalized patients. During a 30-minute study period taking place while participants were breathing spontaneously, pulse oximeter and nasal/oral capnography waveforms were collected. Pulse oximeter waveforms were processed to determine respiratory rate via the Medtronic Nellcor Respiration Rate Software. Capnography waveforms reviewed by a clinician were used to determine the reference respiratory rate.ResultsA total of 23,243 paired observations between the pulse oximeter-derived respiratory rate and the capnography reference method were collected and examined. The mean reference-based respiratory rate was 15.3 ± 4.3 breaths per minute with a range of 4 to 34 breaths per minute. The Pearson correlation coefficient between the Medtronic Nellcor Respiration Rate Software values and the capnography reference respiratory rate is reported as a linear correlation, R, as 0.92 ± 0.02 (P < .001), whereas Lin's concordance correlation coefficient indicates an overall agreement of 0.85 ± 0.04 (95% confidence interval [CI] +0.76; +0.93) (healthy volunteers: 0.94 ± 0.02 [95% CI +0.91; +0.97]; hospitalized patients: 0.80 ± 0.06 [95% CI +0.68; +0.92]). The mean bias of the Medtronic Nellcor Respiration Rate Software was 0.18 breaths per minute with a precision (SD) of 1.65 breaths per minute (healthy volunteers: 0.37 ± 0.78 [95% limits of agreement: -1.16; +1.90] breaths per minute; hospitalized patients: 0.07 ± 1.99 [95% limits of agreement: -3.84; +3.97] breaths per minute). The root mean square deviation was 1.35 breaths per minute (healthy volunteers: 0.81; hospitalized patients: 1.60).ConclusionsThese data demonstrate the performance of the Medtronic Nellcor Respiration Rate Software in healthy subjects and patients hospitalized in a low-acuity care setting when compared with clinician-reviewed capnography. The observed performance of this technology suggests that it may be a useful adjunct to continuous pulse oximetry monitoring by providing continuous respiratory rate measurements. The potential patient safety benefit of using combined continuous pulse oximetry and respiratory rate monitoring warrants assessment.
Project description:For critically ill adults, oxygen saturation is continuously monitored using pulse oximetry (Spo2) as a surrogate for arterial oxygen saturation (Sao2). Skin pigmentation may affect accuracy of Spo2 by introducing error from statistical bias, variance, or both. We evaluated relationships between race, Spo2, Sao2, and hypoxemia (Sao2 < 88%) or hyperoxemia (Pao2 > 150 mm Hg) among adults receiving mechanical ventilation in a medical ICU.DesignSingle-center, observational study.SettingMedical ICU at an academic medical center.PatientsCritically ill adults receiving mechanical ventilation from July 2018 to February 2021, excluding patients with COVID-19, with race documented as Black or White in the electronic medical record, who had a pair of Spo2 and Sao2 measurements collected within 10 minutes of each other.InterventionsNone.MeasurementsWe included 1,024 patients with 5,557 paired measurements within 10 minutes, of which 3,885 (70%) were within 1 minute. Of all pairs, 769 (14%) were from Black patients and 4,788 (86%) were from White patients. In analyses using a mixed-effects model, we found that across the range of Spo2 values of 92-98%, the associated Sao2 value was approximately 1% point lower for Black patients compared with White patients. Among patients with a Spo2 value between 92% and 96%, Black patients were more likely to have both hypoxemia (3.5% vs 1.1%; p = 0.002) and hyperoxemia (4.7% vs 2.4%; p = 0.03), compared with White patients.ConclusionsAmong patients with a measured Spo2 of 92-96%, greater variation in Sao2 values at a given Spo2 resulted in a higher occurence rate of both hypoxemia and hyperoxemia for Black patients compared with White patients.
Project description:Development of unconventional technologies for wireless collection, storage and analysis of quantitative, clinically relevant information on physiological status is of growing interest. Soft, biocompatible systems are widely regarded as important because they facilitate mounting on external (e.g. skin) and internal (e.g. heart, brain) surfaces of the body. Ultra-miniaturized, lightweight and battery-free devices have the potential to establish complementary options in bio-integration, where chronic interfaces (i.e. months) are possible on hard surfaces such as the fingernails and the teeth, with negligible risk for irritation or discomfort. Here we report materials and device concepts for flexible platforms that incorporate advanced optoelectronic functionality for applications in wireless capture and transmission of photoplethysmograms, including quantitative information on blood oxygenation, heart rate and heart rate variability. Specifically, reflectance pulse oximetry in conjunction with near-field communication (NFC) capabilities enables operation in thin, miniaturized flexible devices. Studies of the material aspects associated with the body interface, together with investigations of the radio frequency characteristics, the optoelectronic data acquisition approaches and the analysis methods capture all of the relevant engineering considerations. Demonstrations of operation on various locations of the body and quantitative comparisons to clinical gold standards establish the versatility and the measurement accuracy of these systems, respectively.
Project description:Pulse wave transit time (PWTT) is the time difference between the occurrence of an R-wave on an electrocardiogram and the detection of pulsatile signals on a pulse oximeter, which reflects changes in blood pressure (BP) corresponding to the vessel wall compliance. However, the factors affecting PWTT variability have not been determined. Thus, we investigated the BP changes associated with variations in PWTT and identified the clinical characteristics associated with these variations. Data related to 605 cases of dental procedures performed under intravenous conscious sedation from April 2020 to November 2021 were collected, and 485 cases were enrolled. Heart rate, systolic blood pressure before and after local anesthesia (LA) administration, and crest and trough PWTT waves during LA administration were recorded. Thereafter, PWTT variability was calculated; cases were divided into two groups: large PWTT variability (LPV, n = 357) and small PWTT variability (SPV, n = 128). The index of large PWTT variability could not detect changes in BP. Logistic regression analysis revealed that factors, such as LA use, age, hypertension, and dental treatment phobia were associated with PWTT variability. The use of epinephrine more than 36.25 µg in each LA resulted in PWTT variability of more than 15 ms.
Project description:BackgroundCoarctation of the aorta is a common form of critical congenital heart disease that remains challenging to diagnose prior to clinical deterioration. Despite current screening methods, infants with coarctation may present with life-threatening cardiogenic shock requiring urgent hospitalization and intervention. We sought to improve critical congenital heart disease screening by using a novel pulse oximetry waveform analysis, specifically focused on detection of coarctation of the aorta.Methods and resultsOver a 2-year period, we obtained pulse oximetry waveform data on 18 neonates with coarctation of the aorta and 18 age-matched controls hospitalized in the cardiac intensive care unit at Children's Healthcare of Atlanta. Patients with coarctation were receiving prostaglandin E1 and had a patent ductus arteriosus. By analyzing discrete features in the waveforms, we identified statistically significant differences in the maximum rate of fall between patients with and without coarctation. This was accentuated when comparing the difference between the upper and lower extremities, with the lower extremities having a shallow slope angle when a coarctation was present (p-value 0.001). Postoperatively, there were still differences in the maximum rate of fall between the repaired coarctation patients and controls; however, these differences normalized when compared with the same individual's upper vs. lower extremities. Coarctation patients compared to themselves (preoperatively and postoperatively), demonstrated waveform differences between upper and lower extremities that were significantly reduced after successful surgery (p-value 0.028). This screening algorithm had an accuracy of detection of 72% with 0.61 sensitivity and 0.94 specificity.ConclusionsWe were able to identify specific features in pulse oximetry waveforms that were able to accurately identify patients with coarctation and further demonstrated that these changes normalized after surgical repair. Pulse oximetry screening for congenital heart disease in neonates may thus be improved by including waveform analysis, aiming to identify coarctation of the aorta prior to critical illness. Further large-scale testing is required to validate this screening model among patients in a newborn nursery setting who are low risk for having coarctation.
Project description:Because of the impact of continuous pulse oximetry (CPOX) on the overdiagnosis of hypoxemia in bronchiolitis, the American Academy of Pediatrics and the Choosing Wisely campaign have issued recommendations for intermittent monitoring. Parental preferences for monitoring may impact adoption of these recommendations, but these perspectives are poorly understood. Using this cross-sectional survey, we explored parental perspectives on CPOX monitoring before discharge and 1 week after bronchiolitis hospitalizations. During the 1-week call, half of the participants were randomly assigned to receive a verbal statement on the potential harms of CPOX to determine if conveying the concept of overdiagnosis can change parental preferences on monitoring frequency. An aggregate variable measuring favorable perceptions of CPOX was created to determine CPOX affinity predictors. In-hospital interviews were completed on 357 patients, of which 306 (86%) completed the 1-week follow-up. Although 25% of parents agreed or strongly agreed that hospital monitors made them feel anxious, 98% agreed that the monitors were helpful. Compared to other vital signs, respiratory rate (87%) and oxygen saturation (84%) were commonly rated as "extremely important." Providing an educational statement on CPOX comparatively decreased parental desire for continuous monitoring (40% vs 20%; P < .001). Although there were no significant predictors of CPOX affinity, the effect size of the educational intervention was higher in college-educated parents. Parents find security in CPOX. A brief statement on the potential harms of CPOX use had an impact on stated monitoring preferences. Parental perspectives are important to consider because they may influence the adoption of intermittent monitoring.
Project description:A novel optical sensor probe combining monitoring of blood oxygen saturation (SpO₂) with contact pressure is presented. This is beneficial as contact pressure is known to affect SpO₂ measurement. The sensor consists of three plastic optical fibres (POF) used to deliver and collect light for pulse oximetry, and a fibre Bragg grating (FBG) sensor to measure contact pressure. All optical fibres are housed in a biocompatible epoxy patch which serves two purposes: (i) to reduce motion artefacts in the photoplethysmogram (PPG), and (ii) to transduce transverse loading into an axial strain in the FBG. Test results show that using a combination of pressure measuring FBG with a reference FBG, reliable results are possible with low hysteresis which are relatively immune to the effects of temperature. The sensor is used to measure the SpO₂ of ten volunteers under different contact pressures with perfusion and skewness indices applied to assess the quality of the PPG. The study revealed that the contact force ranging from 5 to 15 kPa provides errors of <2%. The combined probe has the potential to improve the reliability of reflectance oximeters. In particular, in wearable technology, the probe should find use in optimising the fitting of garments incorporating this technology.
Project description:COVID-19 behaves like a heterogeneous disease. Some patients may develop dyspnea-free hypoxemia during its evolution (silent hypoxemia). Pulse oximetry plays a crucial role in detecting hypoxemia in these patients, especially when they remain at home. Patients with SpO2 levels ≤ 92% or desaturations ≥ 3% after exercise test require hospital admission. Progressive saturation declines reaching SpO2 levels < 96% require strict clinical assessment (radiological study, blood test) for which it will be sent to a health center.