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

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.

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

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) (ICC_2,1) 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.

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).

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.