For diagnostic function tests it must be proven that they are adapted to the physiological task and fulfil the requirements for a measuring tool. Also for the diagnosis of nasal obstruction, the measurement of the nasal volume flow (mass flow, flow) and the narino-choanal differential pressure as well as a reference to the subjective perception of obstruction is necessary. 4-phase rhinomanometry (4PR) and peak nasal inspiratory flow (PNIF) were compared. The reproducibility of the measurements was tested both in vitro and in vivo. For 4PR, the obstructive sensation was measured simultaneously on a visual analogue scale. For 4PR we found a high reproducibility both when using a simulator and in test subjects. After logarithmic transformation of the measured values, there was a high correlation to the subjective values (Weber-Fechner's law). PNIF also shows a high reproducibility, but we consider the method to be completely unsuitable for a nasal function test, as it provokes the elastic nasal closure as when sniffing. A second study investigated the usefulness of the parameters work and performance as nasal function parameters. We showed that these parameters are dependent on the depth of breathing and also on nasal resistance, but found them not to be meaningful as nasal function tests. Both studies included measurement system analysis (MSA) as a method for controlling and evaluating a measurement process. The key statistical methods of MSA include analysis of overall process variability using two-factor variance analysis and R control charts.