Finger Versus Earlobe Pulse Oximetry During the 6-Minute Walk Test in Interstitial Lung Disease (OXISITE-ILD)

A Prospective, Multicenter, Observational Method-Comparison Study of Finger Versus Earlobe Pulse Oximetry for Oxygen Saturation During the Six-Minute Walk Test in Patients With Interstitial Lung Disease (OXISITE-ILD)

The OXISITE-ILD study is a prospective, multicenter, observational study designed to evaluate the agreement between finger (digital) and earlobe (auricular) pulse oximetry for measuring oxygen saturation (SpO2) during the six-minute walk test (6MWT) in patients with interstitial lung disease (ILD). In routine clinical practice, exercise SpO2 is usually measured at the finger; however, the finger reading can be unreliable in some patients, and there is currently no recommendation on the best sensor location in ILD. This study compares the two sensor locations, recorded at the same time, and evaluates whether any disagreement changes how exercise desaturation is classified and whether ambulatory oxygen is indicated.

All patients undergoing a 6MWT as part of routine ILD care are included consecutively to ensure a pragmatic, real-world representation of the ILD population. The primary objective is to measure the agreement between the two locations in the lowest SpO2 reached during the test, including the size and direction of any difference. Secondary objectives include the reclassification of patients at the clinical desaturation thresholds, the comparison between autoimmune and non-autoimmune ILD, the rate of invalid readings at each location, and the clinical, vascular and functional factors associated with disagreement.

Study Overview

• Status: Recruiting
• Conditions: Interstitial Lung Disease (ILD); Idiopathic Pulmonary Fibrosis (IPF); Progressive Pulmonary Fibrosis; Interstitial Lung Disease Due to Connective Tissue Disease (Disorder); Connective Tissue Disease-Associated Interstitial Lung Disease
• Intervention / Treatment: Other: Dual-site pulse oximetry (finger and earlobe)

Detailed Description

OXISITE-ILD is a prospective, consecutive, multicenter, observational, cross-sectional method-comparison (agreement) study.

Each participant is assessed once, during a single 6MWT performed as part of routine care. SpO2 and heart rate are recorded simultaneously at the finger and at the earlobe with two pulse oximeters, at eight timepoints: baseline, each of minutes 1 to 6, and after a 2-minute recovery. The paired heart rate at each timepoint is used as a signal-quality control, so that agreement is assessed only on simultaneous, valid readings. In some participants, an arterial blood gas or a nailfold capillaroscopy may also be performed to help interpret the difference between locations.

A minimum of 100 participants is planned at the coordinating center, sufficient on its own for the primary objective; recruitment may be extended at the coordinating center and at the collaborating centers as the study requires. The participation of collaborating centers is opportunistic and adds precision, subgroup analyses, and external validity.

• Study Type: Observational
• Enrollment (Estimated): 100

Contacts and Locations

• Study Contact: Name: Jaume Bordas-Martinez, Ph.D.; M.D.; Phone Number: 938 42 50 00; Email: jbordas@fphag.org

Study Locations

• Spain
  • Spain
    • Granollers, Spain, Spain, 08402
      • Recruiting
      • Hospital de Granollers

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Consecutive adults with a confirmed diagnosis of interstitial lung disease (ILD), either newly diagnosed or under follow-up, attending the ILD/pulmonary fibrosis units of the participating centres and undergoing a clinically indicated 6-minute walk test. Patients with or without prior oxygen therapy are enrolled consecutively, and baseline oxygen status (none, exertional only, or at rest) is recorded. Each patient is assessed on a single occasion, consistent with the cross-sectional design.

Description

Inclusion Criteria:

• Adults aged 18 years or older
• Confirmed diagnosis of interstitial lung disease (ILD) based on clinical, radiological and/or histological criteria
• Newly diagnosed or under follow-up for ILD
• Physically and cognitively able to perform the 6-minute walk test (6MWT)
• Signed informed consent

Exclusion Criteria:

• Inability to obtain a reliable, stable baseline pulse oximetry reading at the finger and/or the earlobe, preventing a valid paired baseline measurement and the calculation of agreement
• ILD exacerbation, decompensated comorbidity, or acute respiratory infection at the time of the test

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Intervention / Treatment

ILD patients undergoing the 6MWT; Adults with an established diagnosis of interstitial lung disease (ILD) undergoing a six-minute walk test (6MWT) as part of routine care. Each participant is assessed once, with oxygen saturation (SpO2) and heart rate recorded simultaneously at the finger and at the earlobe. Pre-specified subgroups for the analysis are autoimmune-associated versus non-autoimmune ILD.

Other: Dual-site pulse oximetry (finger and earlobe); During a single 6MWT, SpO2 and heart rate are recorded simultaneously at the finger (digital) and the earlobe (auricular) with two pulse oximeters, at eight timepoints (baseline, minutes 1 to 6, and a 2-minute recovery). No treatment is administered and routine clinical management is not modified; the procedure adds the simultaneous earlobe measurement for comparison with the finger.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Intraclass correlation coefficient for agreement in minimum SpO2 between sensor locations	Absolute agreement in minimum SpO2 during the six-minute walk test between the finger and earlobe sensors, quantified with the intraclass correlation coefficient (two-way mixed-effects model, absolute agreement) and its 95% confidence interval. ICC values are interpreted as below 0.50 poor, 0.50 to 0.75 moderate, 0.75 to 0.90 good, and above 0.90 excellent agreement.	Day 1
Bland-Altman agreement in minimum SpO2 between sensor locations	Agreement in minimum SpO2 during the six-minute walk test between the finger and earlobe sensors, assessed with Bland-Altman analysis: mean bias (earlobe minus finger) with its 95% confidence interval and 95% limits of agreement, evaluated against a prespecified clinically acceptable difference of 3 percentage points. The direction of the bias is reported, as the finger is hypothesised to register lower values than the earlobe.	Day 1

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Reclassification of exertional desaturation between sensor locations at SpO2 below 88%	Proportion of participants whose classification of significant exertional desaturation changes between the finger and earlobe sensors at the threshold of minimum SpO2 below 88% (American Thoracic Society indication threshold for ambulatory oxygen). Agreement is assessed with the Cohen kappa coefficient (Landis-Koch interpretation) and the difference in proportions with the McNemar test for paired data. At this threshold the McNemar test and the raw reclassification proportions are the primary read, as kappa can be unstable when prevalence is extreme.	Day 1
Reclassification of exertional desaturation between sensor locations at SpO2 below 90%	Proportion of participants whose classification of significant exertional desaturation changes between the finger and earlobe sensors at the threshold of minimum SpO2 below 90% (British Thoracic Society indication threshold for ambulatory oxygen). Agreement is assessed with the Cohen kappa coefficient (Landis-Koch interpretation) and the difference in proportions with the McNemar test for paired data.	Day 1
Reclassification of exertional desaturation between sensor locations at a fall in SpO2 of 4% or more	Proportion of participants whose classification changes between the finger and earlobe sensors at the prognostic threshold of a fall in minimum SpO2 of 4% or more from baseline. Agreement is assessed with the Cohen kappa coefficient (Landis-Koch interpretation) and the difference in proportions with the McNemar test for paired data.	Day 1
Agreement in minimum SpO2 by autoimmune versus non-autoimmune ILD	Comparison of the agreement between sensor locations (intraclass correlation coefficient and Bland-Altman) in autoimmune-associated ILD versus non-autoimmune ILD, with interstitial pneumonia with autoimmune features (IPAF) described separately. Where sample size permits, agreement is also described, exploratorily and without formal hypothesis testing, by major ILD subtype (for example idiopathic pulmonary fibrosis, hypersensitivity pneumonitis, or connective tissue disease-associated ILD), and by autoimmune subtype (for example systemic sclerosis or rheumatoid arthritis).	Day 1
Rate of invalid or poor-quality readings by sensor location	Comparison, among enrolled participants, of the rate of invalid or poor-quality (low-signal) readings between the finger and earlobe sensors during the six-minute walk test, across the eight measurement timepoints. At each timepoint the paired heart rate from the two sensors is used as a signal-quality control: a discordant heart rate flags poor signal or sensor disconnection and identifies invalid SpO2 readings, so that agreement is assessed only on simultaneous, valid readings. The per-participant difference in the rate of invalid readings between sensor locations is reported with its 95% confidence interval and the McNemar test for paired data.	Day 1
Clinical, vascular and functional predictors of discordance	Clinical, vascular and functional factors associated with discordance between sensor locations, including ILD type (autoimmune-associated versus other), autoimmune subtype (systemic sclerosis versus other), fibrosing versus non-fibrosing ILD, pathological capillaroscopy, Raynaud phenomenon, skin pigmentation, cardiovascular comorbidity, and pulmonary function (FVC and DLCO). For each discordance criterion (SpO2 below 88%, SpO2 below 90%, and a fall of 4% or more) a logistic regression model is fitted with the patient as the unit of analysis, complemented by mixed-effects logistic regression (GLMM) with the measurement timepoint as a predictor and a random intercept per participant. Missing data from incomplete follow-up are handled by maximum likelihood; penalised regression (L1/L2) is considered if events are sparse.	Day 1

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Agreement in SpO2 at additional timepoints	Agreement between sensor locations in SpO2 at baseline, maximum, per-minute intervals during the walk, and recovery, assessed with the intraclass correlation coefficient and Bland-Altman analysis.	Day 1
Quantitative paired difference and Passing-Bablok regression between sensor locations	Exploratory analysis of systematic differences between the finger and earlobe in SpO2. The paired difference (earlobe minus finger) is summarised with its 95% confidence interval (paired t test, or Wilcoxon signed-rank test with a Hodges-Lehmann interval, as appropriate). Passing-Bablok regression is used to detect constant and proportional differences between the two locations, with 95% confidence intervals for the intercept and the slope.	Day 1
Agreement of each sensor location with baseline arterial oxygen saturation	Exploratory comparison of the agreement of finger and of earlobe SpO2 with baseline arterial oxygen saturation, in the subgroup of participants undergoing arterial blood gas sampling.	Day 1
Direct and indirect cost associated with invalid finger readings	Exploratory description of the direct and indirect costs associated with invalid or poor-quality finger readings. No prespecified cost model is applied.	Day 1

Collaborators and Investigators

• Sponsor: Hospital de Granollers
• Investigators: Study Director: Jaume Bordas-Martinez, M.D., Ph.D., Hospital de Granollers

Study record dates

Study Major Dates

• Study Start (Actual): January 13, 2026
• Primary Completion (Estimated): August 1, 2027
• Study Completion (Estimated): December 31, 2027

Study Registration Dates

• First Submitted: June 30, 2026
• First Submitted That Met QC Criteria: July 21, 2026
• First Posted (Actual): July 23, 2026

Study Record Updates

• Last Update Posted (Actual): July 23, 2026
• Last Update Submitted That Met QC Criteria: July 21, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: Six-Minute Walk Test; Systemic Sclerosis; Idiopathic Pulmonary Fibrosis; Pulse Oximetry; Interstitial Lung Disease; SpO2; Oxygen Saturation; Method Comparison; Ambulatory Oxygen; Connective Tissue Disease-ILD; Earlobe Oximetry; Finger Oximetry; Exercise Desaturation; Bland-Altman Analysis
• Additional Relevant MeSH Terms: Connective Tissue Diseases; Respiratory Tract Diseases; Lung Diseases; Skin Diseases; Pulmonary Fibrosis; Skin and Connective Tissue Diseases; Idiopathic Pulmonary Fibrosis; Lung Diseases, Interstitial; Scleroderma, Systemic
• Other Study ID Numbers: OXISITE-ILD

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No