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 (SpO). 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, FEV) 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/m, FEV 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 SpO. In 'persistent worsening' participants (n = 11), significant associations included HR variability, nightly RR variability, nightly SpO, 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.