Exploring Pulse OXimeter Accuracy Across SKin Tones

Study Overview
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Brief Summary
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This study within a trial (SWAT) will be a sub-study of the UK-ROX trial (ISRCTN13384956), which is currently running in intensive care units across the UK. UK-ROX is large-scale randomised controlled trial evaluating conservative oxygen therapy (a target SpO2 of 88-92%) versus usual oxygen therapy in mechanically ventilated adult patients admitted to ICUs in the UK. The purpose of this observational sub-study is to compare pulse oximeter-derived peripheral oxygen saturation (SpO2) values to co-oximeter-derived arterial oxygen saturation (SaO2) measurements from arterial blood gas (ABG) samples, for a range of fingertip pulse oximeters in an ethnically diverse group of adult patients admitted to UK intensive care units (ICUs). Approximately 900 patients will be recruited over 12 month period from 24 sites to provide an anticipated 10,800 paired SpO2 and SaO2 measurements. Patient skin tone will be objectively measured using a handheld spectrophotometer. Data from the sub-study will be used to determine the accuracy of the tested pulse oximeters across a range of skin tones and arterial oxygenation levels.

Detailed Description
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Research question: What is the diagnostic accuracy of different pulse oximeters at peripheral oxygen saturation levels (SpO2) relevant to their use by patients at home and how does this vary in people with darker skin pigmentation? Primary objective: To compare pulse oximeter-derived SpO2 values to co-oximeter-derived arterial oxygen saturation (SaO2) measurements from arterial blood gas (ABG) samples, for a range of fingertip pulse oximeters in an ethnically diverse group of adult patients with a broad spectrum of skin tones admitted to UK intensive care units (ICUs). Design: This study within a trial (SWAT) that will form an observational sub-study of the NIHR HTA funded UK-ROX trial (https://fundingawards.nihr.ac.uk/award/NIHR130508), which is currently running in ICUs across the UK. Twenty four ICUs enrolling patients into the UK-ROX trial trial will be randomly allocated two brands of pulse oximeter to evaluate. Over a period of 24 hours for each participant, SpO2 values from the test pulse oximeters will be compared to simultaneous SaO2 values from ABG samples analysed on a standard ICU ABG co-oximeter machine. Patient skin tone will be objectively measured using a handheld spectrophotometer. The difference between SpO2 and SaO2 will be compared across skin tones and across a range of arterial oxygenation levels. Setting: The UK-ROX trial is large-scale, multi-centre, data-enabled, registry embedded randomised controlled trial (RCT) evaluating conservative oxygen therapy (a target SpO2 of 88-92%) versus usual oxygen therapy in mechanically ventilated adult patients admitted to ICUs in the United Kingdom. Target population: 900 mechanically ventilated adults screened for enrolment into the UK-ROX trial. Primary outcome: The accuracy of SpO2 measurement in the evaluated pulse oximeters, validated against co-oximeter-derived SaO2 ABG sample analysis.

Official Title
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A Study Within a Trial to Determine the Effect of Skin Tone on the Diagnostic Accuracy of Pulse Oximeters

Conditions
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Critical Illness, Hypoxemia

Intervention / Treatment
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* Device: Pulse oximetry
* Device: Spectrophotometry


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria are for those of the main UK-ROX trial: Adult (aged ≥18 years) Receiving invasive mechanical ventilation in the ICU following an unplanned ICU admission OR invasive mechanical ventilation started in the ICU (i.e. the patient was intubated in the ICU). Receiving supplemental oxygen (> 21% oxygen) at the time of enrolment Exclusion Criteria are for those of the main UK-ROX trial: • The clinician considers that one study treatment arm is either indicated or contraindicated. In order in increase the number of patients eligible for this observational diagnostic accuracy study, we will have also received ethical approval to enrol mechanically ventilated adult patients who have been screened for, but not enrolled into, the UK-ROX trial. These may include patients who missed the 12 hour recruitment window for the main trial and patients in whom the clinical team decided that one study treatment arm is either indicated or contraindicated.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Critically ill adults<br>Adult patients admitted to an intensive care unit who require mechanical ventilation and supplemental oxygen | Device: Pulse oximetry<br>* Pulse oximeters will be evaluated against routine arterial blood gas measurements<br>Device: Spectrophotometry<br>* Spectrophotometry will be used to measure skin tone<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Accuracy of SpO2 measurements | Accuracy of SpO2 measurement, validated against co-oximeter derived SaO2 arterial blood gas analysis (calculated as SpO2 minus paired SaO2) | Over 24 hour observation window | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Detection of hypoxaemia | Diagnostic accuracy (area under the receiver operating characteristic curve and sensitivity and specificity at relevant cut-points) for SpO2 as a predictor of SaO2 ≤ 92%. | Over 24 hour observation window | 
| Detection of occult hypoxaemia | The presence of an SaO2 < 88% among participants with a paired SpO2 reading of >92% | Over 24 hour observation window |