Surface Topographic Assessment of Forced Pulmonary Maneuvers: Reliability and Agreement With Spirometry in Healthy Participants.

BACKGROUND

Spirometry remains the clinical gold standard for measuring pulmonary function such as forced expiratory indices; however, reliance on a mouthpiece seal, quality assurance, and infection control procedures limit feasibility and degrade data quality. Markerless optical approaches (depth cameras and surface topography) show promise in monitoring quiet breathing but often require patient-specific calibration, with limited validation of forced expiratory indices and formal reliability testing.

RESEARCH QUESTION: Can markerless surface topography (ST) provide reliable estimates of FEV1, FVC, and FEV1/FVC comparable with spirometry?

STUDY DESIGN AND

METHODS

Twenty healthy volunteers underwent prospective simultaneous ST and handheld spirometry during standardized forced expiratory maneuvers. Two raters administered multiple trials per patient. Body volume was computed per frame from reconstructed surface meshes. Intrarater and interrater reliability were assessed using intraclass correlation coefficients (ICCs) (ICC2,1) with paired permutation testing for differences. ST-spirometry agreement was evaluated by Pearson correlations and Bland-Altman analysis. Leave-one-out cross validation tested generalizability of a universal linear correction mapping ST volumes to spirometry.

RESULTS

ST and spirometry demonstrated similar reliability for FEV1 (ICC > 0.97), FVC (ICC > 0.96), and FEV1/FVC ratio (ICC > 0.89), with no significant ICC differences between modalities or raters (all P > .10). ST correlated strongly with spirometry (R = 0.95 for FEV1, R = 0.94 for FVC, R = 0.93 for FEV1/FVC ratio). Bland-Altman analysis showed stable negative bias for absolute volumes (FEV1, -0.52 L; FVC, -0.66 L) and negligible bias for FEV1/FVC. Cross validation yielded low root mean square errors (FEV1, 0.24 L; FVC, 0.34 L; FEV1/FVC ratio, 0.025).

INTERPRETATION: Our results show that ST provides contact-free forced expiratory estimates that correlate strongly with spirometry, with comparable reliability. This may benefit populations for whom the spirometer interface is a barrier, including young children and those with bulbar dysfunction or craniofacial abnormalities.