A 3D-printed recycled-PET CPAP mask shows no detectable penalty in surface bioburden, pressure tolerance or particle transfer relative to a commercial interface

Abstract

It presents a comparative, matched-pair bench assessment of a fused-deposition-modelled, recycled-polyethylene-terephthalate continuous positive airway pressure mask against a commercially manufactured reference interface. The investigation examines three prespecified endpoints: recoverable bacterial surface burden, mechanical integrity under stepped positive pressure, and visible particle transfer following standardized contact with onion epidermis. Microbiological testing includes twelve matched pairs, with colony counts normalized by sampled area and recovery efficiency. Twelve paired assemblies undergo progressive loading between 4 and 30 cmH₂O, while ten paired specimens contribute calibrated microscopic fields for automated segmentation. Statistical inference operates at the matched-pair level to avoid pseudoreplication, reporting mean differences, 95% confidence intervals, exact sign-flip tests, and Holm-adjusted significance levels. Across the primary outcomes, estimated differences are −0.004 log₁₀ CFU/cm², +0.17 cmH₂O, and −2.9 particles/mm², respectively, without statistically detectable between-interface differences. Secondary analyses characterize unintended leakage, particle morphology, pressure-dependent deformation, sensitivity to background subtraction, and methodological robustness. The discussion distinguishes non-significant findings from demonstrated equivalence and addresses pressure-ceiling censoring, limited sample sizes, optical identification constraints, and absent clinical validation. Because the paper identifies its dataset as simulated, its findings illustrate analytical performance rather than independently substantiated experimental evidence or therapeutic safety