Rhinology,46, 200-203, 2008 *Received for publication: October 26; accepted: March 21, 2008 INTRODUCTION The measurement of nasal patency has long interested rhinolo- gists and respiratory physiologists. In a previous work (1) , study- ing normallevels of Peak Nasal Inspiratory Flow(PNIF), we reported that PNIFis influencedby a number of covariates: SEX,AGE and HEIGHT being the most significant. However, after accounti ng for these vari abl es, there remai ns a large degree of between-patient variability in PNIFlevels. We con- cluded that further variables, such as pulmonary function, may exist which can refine the modelling of data. Theaim of this analysis is to determine whether the measure- ment of the pulmonary ventilatory capacity enables more pre- cise determination of PNIF. Pulmonary ventilatory capacity was testedbythe PeakExpiratory Flow(PEF) using a portable peak flow meter (2) . MATERIALS AND METHODS The protocol for this experiment followscloselythat of an ear- lier study designed to examine the relationship between PNIF andvarious covariates (1) ,but in which the variablePEF was not recorded. Subjects We recruited 112 subjects ranging from 15 to 71 years old. Of these, 6 women were excludedbecause they were taking oral contraceptives, 2 individuals were excludedbecause of α-blocker therapy, 2 because of β-blocker therapy,1because of a mean score >1 on SNOT 20 (Rhinitis Quality of Life questionnaire) (3) ,1because of poor collaboration which did not allow them to achieve a maximal respiratory effort. 100 volunteers were enteredinto the study and none had complaints of nasal block- age, history of asthma or other respiratory symptoms. All were non-smokers, non-asthmatic, without any previous surgery to Aims: Measurement of Peak Nasal Inspiratory Flow (PNIF) seems to be a cheap and easily performed method to assess nasal patency. As demonstrated in a previous work, PNIF is influenced by SEX, AGE and HEIGHT. However there is a large degree of between-patient variability in PNIF levels. The purpose of this analysis is to determine whether the measure- ment of the pulmonary ventilatory capacity, by mean of Peak Expiratory Flow (PEF), enables more precise determination of PNIF. Methods and results: Repeated measurements of PNIF and PEF were performed in 112 vol- unteers. 100 of these fulfilled the study criteria (55 females and 45 males) and all of them were non-smokers, non-asthmatic, without nose and paranasal sinuses problems, with ages ranging from 15 to 71 years. Statistical analysis was undertaken to determine whether a rela- tionship existed between PNIF and age, sex and height, but which also considered PEF. The data from both experiments were analysed together. In both groups there is a clear tendency for PNIF to increase with PEF. As clearly demonstrated in this work the value of PEF is informative in predicting PNIF and that the larger the value of PEF, the larger the value of PNIF. Conclusions: PNIF is a useful method to study nasal patency in both primary and secondary care to aid diagnosis of nasal disease, but low values of PNIF have to be confirmed by a study of the PEF as PNIF low values may be an expression of low ventilatory activity rather than an expression of nasal obstruction. Key words: Peak Nasal Inspiratory Flow, Peak Expiratory Flow, nasal patency, pulmonary ventilatory capacity, age, height, sex. SUMMARY Does peak nasal inspiratory flow relate to peak expiratory flow?* Giancarlo Ottaviano 1 , V alerie J. Lund 2 , Stuart Coles 3 , Alberto Staff ieri 1 , Glenis K. Scadding 4 1 Department of Otolaryngology, Head and Neck Surgery, University of Padua, Padua, Italy 2 Ear Institute, University College of London, London, United Kingdom 3 Department of Statistics, University of Padua, Padua, Italy 4 Royal National Throat, Nose and Ear Hospital, London, United Kingdom