Measuring adult breathing pattern: devices, outcomes, and evidence-a scoping review

To map instruments and protocols used to assess adult breathing pattern (BP), describe the outcomes they yield, appraise reported measurement properties, and identify whether any single modality is "clinically ready." The review asks which instruments and protocols quantify adult BP, which outcomes are reported (e.g., rate, amplitude, I:E ratio, thoracoabdominal mobility), and what evidence exists for reliability, sensitivity, or specificity.

A scoping review, guided by Joanna Briggs Institute methods and reported per PRISMA-ScR, was undertaken. Searches in Scopus, Web of Science, and PubMed were run to 27 Aug 2024 and updated on 21 Aug 2025 with identical strategies. Five reviewers screened records in three stages against predefined eligibility criteria (adult human samples; instrumented BP assessment). Data were charted for population, device and sampling, reference standards, tasks, outcomes, and clinimetric reporting. Thirty-one studies met eligibility.

Evidence (1994-2025; 31 studies) clusters into contact and contactless families: optical/vision and motion capture, respiratory inductance plethysmography and other belts/pressure arrays, wearable inertial sensors, radar, and depth/thermal cameras. Outcomes concentrate on respiratory rate, tidal/volume proxies, and thoraco-abdominal contributions/coordination; fewer studies report event timing, displacement, or phase/asynchrony. Validation is chiefly against spirometry/pneumotachography; agreement for respiratory rate is generally high, while absolute volume agreement varies with calibration and posture. Reliability indices and diagnostic metrics are inconsistently reported. Most samples are small and posture-bound (laboratory or seated/supine), with heterogeneous preprocessing and reference-frame conventions limiting comparability.

Multiple modalities can quantify BP, but no single instrument currently satisfies validity, reliability, responsiveness, interpretability, feasibility, and equity across settings. Near-term use is strongest for respiratory-rate and trend-level expansion under controlled conditions. Progress depends on standardized reference frames for wearables, transparent breath-cycle definitions, cross-instrument calibration against common protocols, and larger real-world studies with systematic reporting.