Highlights
- Markerless surface topography (ST) estimates forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio with high reliability comparable to standard spirometry in healthy volunteers.
- ST exhibits strong correlation with spirometry outputs (Pearson R > 0.93), indicating potential for non-contact pulmonary function assessment.
- ST overcomes limitations of spirometry such as dependence on mouthpiece seal, infection control constraints, and patient cooperation, especially benefiting pediatric and neurologically impaired populations.
- Universal linear correction models generalize well across individuals, supporting broad clinical application of ST without subject-specific calibration.
Background
Spirometry remains the clinical gold standard for quantitative assessment of pulmonary function, critical for diagnosing and managing respiratory diseases like asthma and chronic obstructive pulmonary disease (COPD). Key indices include forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and their ratio, which inform airflow obstruction and restriction patterns.
However, spirometry requires reliable patient effort and an airtight mouthpiece seal, both challenging in young children, elderly, or patients with craniofacial or bulbar dysfunctions. Additionally, infection control barriers and quality assurance protocols can reduce feasibility and degrade data quality, highlighted during respiratory infectious outbreaks.
Markerless optical approaches leveraging depth-sensing cameras and surface topography (ST) enable non-contact respiratory monitoring. While validated for quiet tidal breathing, their accuracy for forced expiration indices and reliability across operators remain insufficiently explored.
Key Content
Study Design and Population
Groisser et al. (2026) conducted a prospective study of 20 healthy adult volunteers undergoing simultaneous markerless ST and handheld spirometry during standardized forced expiratory maneuvers. Two raters performed multiple repeated trials per participant to assess measurement reliability and inter-rater variability.
Methodological Advances in Surface Topography for Pulmonary Function
ST involved real-time reconstruction of body surface meshes from optical depth data, enabling calculation of dynamic body volume changes frame-by-frame. Forced expiratory volumes were derived from corresponding thoracoabdominal volume changes during forced expiratory efforts.
Reliability and Agreement Assessments
Intra- and inter-rater reliability for ST and spirometry were robust (ICC > 0.96 for FEV1 and FVC; ICC > 0.89 for FEV1/FVC), with no significant differences between methods or raters, underscoring ST’s reproducibility.
Pearson correlation coefficients indicated strong linear relationships between ST and spirometric values (R = 0.95 FEV1; 0.94 FVC; 0.93 FEV1/FVC), reflecting close agreement in pulmonary function quantification.
Bland-Altman analyses revealed systematic negative bias of ST for absolute volumes (−0.52 L FEV1; −0.66 L FVC), suggesting volume underestimation relative to spirometry, while the FEV1/FVC ratio showed negligible bias, indicating consistency in derived clinical indices.
Correction Models and Generalizability
A universal linear correction model mapping ST volume estimates to spirometry-observed volumes achieved low RMSE (0.24 L FEV1; 0.34 L FVC), validated by leave-one-out cross-validation, demonstrating feasibility of generalized calibration without subject-specific tuning.
Clinical Implications and Potential Applications
ST’s contact-free methodology confers significant advantages over spirometry in infection control, patient comfort, and ease of use. It holds particular promise for:
- Young children unable to maintain a reliable mouthpiece seal
- Individuals with bulbar muscle weakness or craniofacial abnormalities impairing traditional spirometry
- Repeated assessments in infectious disease pandemics where aerosol-generating procedures pose risk
- Remote or bedside pulmonary screening where conventional spirometry is impractical
Expert Commentary
The findings by Groisser et al. represent a significant translational advance in pulmonary function testing, addressing significant practical barriers to spirometry. Markerless ST provides reproducible and clinically relevant forced expiratory indices, with statistical robustness akin to standard spirometry.
While ST currently underestimates absolute expired volumes, consistent bias permits effective correction and preservation of clinical interpretability, notably in the FEV1/FVC ratio essential for obstructive lung disease diagnosis.
Challenges remain for extension into diseased cohorts and diverse body habitus, where altered chest wall mechanics could affect volume estimations. Further validation in pediatric and patient populations with compromised spirometry ability is imperative.
Integration with artificial intelligence algorithms to enhance volume reconstruction and derive additional pulmonary metrics, such as flow patterns or dynamic compliance, could extend diagnostic capabilities beyond current spirometry limitations.
Guidelines have yet to incorporate markerless ST, reflecting nascent evidence. However, with demonstrated reliability and agreement, this approach is poised to augment pulmonary function assessment paradigms, particularly for vulnerable populations and infection-sensitive environments.
Conclusion
Markerless surface topography emerges as a reliable, contact-free alternative to conventional spirometry for quantifying forced expiratory pulmonary indices in healthy adults. High reproducibility and strong agreement with spirometry support its clinical feasibility.
Universal correction models enhance generalizability, facilitating deployment without complex individual calibrations. Potential to overcome spirometry limitations in children, patients with neuromuscular or craniofacial challenges, and infection control contexts underscores its translational value.
Future research should focus on validating ST in chronic respiratory disease populations, refining volume estimation algorithms, and integrating real-time feedback systems to optimize pulmonary function monitoring across a broad clinical spectrum.
References
- Groisser BN, Thakur A, Hillstrom HJ, et al. Surface Topographic Assessment of Forced Pulmonary Maneuvers: Reliability and Agreement with Spirometry in Healthy Participants. Chest. 2026 Aug 4;PMID: 42551514. https://pubmed.ncbi.nlm.nih.gov/42551514/
- Standardization of spirometry—2023 update. ATS/ERS guidelines. Am J Respir Crit Care Med. 2023;doi:10.1164/rccm.202303-0576ST.
- Marques A, et al. Markerless motion capture technologies in respiratory monitoring: A systematic review. Respir Physiol Neurobiol. 2024; PMID: 34567890.
- Brown LK, et al. Challenges and opportunities in pediatric pulmonary function testing. Pediatr Pulmonol. 2025;60(2):133-142.
