Continuous characterisation of exacerbation pathophysiology using wearable technologies in free-living outpatients with COPD: a prospective observational cohort study.

Background: The most recent exacerbation of COPD (ECOPD) classification criteria relies in part on changes in respiratory rate (RR), heart rate (HR) and oxygen saturation (SpO₂). Despite this paradigm shift, a thorough understanding of exacerbation patterns is still lacking, as is the identification of physiological exacerbation biomarkers.

Methods: Using a convenience sampling approach, this prospective observational cohort study was conducted between February 2023 and January 2024. Continuous measurements of daytime/overnight respiratory (primary outcome), cardiovascular, autonomic, activity and sleep-related parameters were collected by a wearable biometric wristband and ring over 21 consecutive days in free-living outpatients experiencing and receiving treatment (≤3 days) for a current exacerbation from the home environment. The EXACT-PRO questionnaire served as the validated reference for daily symptom burden and to identify 'recovered' versus 'persistent worsening' participants. Unadjusted and adjusted (for age, sex, FEV₁) linear mixed-effects models were fitted to estimate associations between each physiological parameter with daily EXACT-PRO score (points, pts), in all, 'recovered', and 'persistent worsening' participants. Results are presented as point estimates with 95% CIs.

Findings: In 21 participants with COPD (43% female, mean age 66.8, BMI 27.7 kg/m², FEV₁ 36.3% predicted; 85.7% with GOLD 3-4 disease), significant associations in unadjusted models with daily EXACT-PRO score included RR variability (-1.45 [-2.84, -0.073] pts/breath/min) but not RR, daily step count (-0.56 [-0.82, -0.31] pts/1000 steps), and sleep efficiency (-0.12 [-0.20, -0.037] pts/%asleep). In 'recovered' participants (n = 10), significant associations included nighttime HR, movement intensity and nightly SpO₂. In 'persistent worsening' participants (n = 11), significant associations included HR variability, nightly RR variability, nightly SpO₂, sleep efficiency, and skin temperature. Similar results were found in adjusted models.

Interpretation: This study provides a prospective continuous characterisation of exacerbations of COPD using remotely collected, ambulatory/free-living data. The physiological patterns presented may contribute to the understanding of exacerbations and may enhance the development of effective remote monitoring solutions.

Funding: University hospital (MUHC-CAS) grant.