In a large general population-based sample of young adults, PNIF was highly reproducible and closely related to the signs of rhinitis, as determined by clinical examination. The PNIF provides information that is qualitatively different to that provided by symptom scores and may be useful to measure the extent of nasal obstruction.

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Persistent bronchodilatation induced by regular agonist administration may allow an Background -Regular, inhaled 2 agonists may increase airway responsiveness in increased allergen load to reach the airways. 4 Alternatively, tachyphylaxis of receptors presasthmatic subjects. The mechanism is not known but may be via an increase in airway ent on mast cells may reduce their stabilising effect and allow inflammatory mediator release inflammation. A study was undertaken to examine the effect of regular inhaled sal-in response to a lesser stimulus than is normally required. 6butamol on airway responsiveness to methacholine and hypertonic saline, on Methacholine and histamine act directly on airway smooth muscle to cause bronchothe maximal response plateau to methacholine, and on inflammatory cells in in-constriction which is related to thickening of the airway wall, smooth muscle contraction, duced sputum in rhinitic non-asthmatic subjects.and lung elastic recoil. 7 Hypertonic saline is believed to cause bronchoconstriction inMethods -Thirty subjects with a baseline maximal response plateau of >15% fall in directly by the release of inflammatory mediators from airway mast cells and possibly forced expiratory volume in one second (FEV 1 ) entered a randomised, placebo airway nerves, 8 and may therefore be a marker of inflammatory processes. Inhalation of hypercontrolled, parallel trial consisting of two weeks run in, four weeks of treatment, and tonic saline is also the basis of techniques which induce sputum for cytological examination.9 two weeks washout. Methacholine challenges were performed at the beginning of Although the sensitivity of the airways is a useful indicator of the degree of airway rethe run in period, before treatment, after treatment, and after washout. Hypertonic sponsiveness, the maximal extent of airway narrowing has been recognised as an important saline challenges were performed before and after treatment and induced sputum measurement in recent years. Maximal airway narrowing can be assessed during bronchial samples were collected for differential cell counting.challenge by increasing the dose of inhaled stimulus until the forced expiratory volume Results -There was no change in airway responsiveness, maximal response plateau in one second (FEV 1 ) ceases to decrease in response to further provocation, producing a to methacholine, or in induced sputum eosinophils or mast cells. The maximum plateau.10 It has been suggested that the maximal response plateau may be an index of fall in FEV 1 after hypertonic saline increased in the salbutamol group (median greater clinical relevance than airway sensitivity as it is a reflection of the potential severity of change 6.0%, interquartile range (IQR) 11.0) but did not change in the placebo an exacerbation of asthma. 11The aim of this study was to determine if group (median change 1.3%, IQR 5.5). Conclusions -Regular inhaled salbutamol regular treatment with a agonist (salbutamol) increases airway sensitivity to direct and infor four weeks inc...

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