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Nasal prongs (NP) connected to a pressure transducer have been suggested as a useful alternative for measuring nasal flow in sleep apnea/hypopnea patients. However, flow measured with NP is expected to be nonlinear. The aim of the present study was to analyze and correct the nonlinearity of nasal flow measurements with NP (VNP). Nasal flow was simultaneously measured with a pneumotachograph (PNT; V) and (NP; VNP) in six healthy subjects during 60 s of breathing at different tidal volumes. Nonlinearity of VNP was assessed by fitting separately, for inspiration and expiration, a Rorher-model equation (VNP x K1 x V + K2 x V2). In addition, we fitted the data to a simpler nonlinear quadratic model (P = K x V2). The main findings were: (1) an excellent fit of the Rorher equation to measured data in all cases; (2) although differences in the Rorher equation coefficients between inspiration and expiration were …