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The reduction of rhinitis symptoms by nasal filters during naturalexposure to ragweed and grass pollen Background: Prototype nasal filters were developed to collect inhaled pollen.
This study evaluated the efficacy of the filters for prevention of rhinitis symp- toms during acute outdoor pollen exposure.
Methods: A randomized double-blind design was used. Subjects (n ¼ 46) with a 1Woolcock Institute of Medical Research, Royal history of autumn exacerbation of rhinitis and positive skin test to ragweed, Prince Alfred Hospital, University of Sydney, New Bermuda and/or Bahia grass wore either active or placebo nasal filters for 2 h in autumn in a park containing these species. Major and Total Symptoms scores Department of Rural Health, University of Sydney were recorded at 0, 30, 60, 90 and 120 min.
and Northern Rivers Area Health Service, LismoreNew South Wales, Australia Results: Subjects wearing active nasal filters had significantly reduced scores, atall time-points compared with placebo group (all P < 0.05). Of 14 individualsymptoms measured, seven were significantly reduced (number of sneezes, runnynose, itchy nose, sniffles, itchy throat; itchy eyes and watery eyes) and anotherthree showed a trend towards lower severity. The nasal filters also enabled the Key words: allergen avoidance; nose filter; prevention.
resolution of existing symptoms. Maximal difference in symptoms was seenimmediately after subjects had spent 20 min sitting beside a large patch of Conclusion: This is the first clinical trial of a nasal filter. The results suggest it has potential for enhancing rhinitis management during acute allergen Avoidance of allergens is advocated as the first step in management of allergic rhinitis, and as an adjunct to medications (1, 2). It is recognized, however, thatavoidance of pollens and fungal spores is difficult to The nasal filter is shown in Fig. 1. The airflow resistance and cap- achieve because of their ubiquitous nature (1). Facemasks ture efficiencies for ragweed (Ambrosia artemisiifolia), Bermuda provide personal protection; however, they are only used grass (Cynadon dactylon) and Bahia grass (Paspalum notatum) by 1% of people (3). While the mainstay of rhinitis pollen (Greer Laboratories Inc., Lenoir, NC) were measured at flowrates of 4.6, 10.3, 21.7 and 32.5 l/min as previously described (4).
management is pharmacotherapy, 74% of people reportthat medications do not adequately control their symp-toms, and 65% report avoiding some medications The study utilized a double-blind placebo-controlled design. The We have previously described nasal filters, worn inside study was approved by the Human Ethics Committee of Northern the nose that collect inhaled particles using the principle Rivers Area Health Service, and subjects gave written informed of impaction (4). They are easy to breathe through, and consent. Eligible subjects were over 16 years old, had a history of have a high capture efficiency for particles above 8 lm in rhinitis exacerbation in the autumn and were skin prick test-positive diameter (4), which includes all pollens (5). Given the to mixed ragweed, Bermuda grass and/or Bahia grass (Table 1).
prevalence of allergic rhinitis, the level of dissatisfaction Exclusion criteria were: complete nasal obstruction, recent sinusitis,history of severe asthma exacerbations, or use of nasal steroids/ with current medications and lack of acceptance of an antihistamines/systemic decongestants within the last month. The effective method to prevent exposure outdoors, we tested study location was a semirural park with abundant flowering Bahia a prototype nasal filter to determine if it would reduce and Bermuda grasses and ragweed. Prior to arriving at the park symptoms of allergic rhinitis during high natural expo- subjects wore disposable dust-masks to reduce the development of baseline symptoms. Subjects were randomly allocated to one of Self-assessed rhinitis symptoms and peak nasal inspiratory flowwere recorded at baseline and at 30 min intervals during thechallenge. Self-recorded symptoms were combined into twocomposite variables: Major Symptom Complex (MSC) and TotalSymptom Complex (TSC) severity scores (6–8). To ensure that atleast moderate levels of ragweed pollen exposure were experi-enced by all participants, each group sat beside a large patch ofragweed for 20 min, during the period 30–60 min after filterinsertion.
Ambient pollen levels were measured using a Burkard 7-day volu-metric spore trap, running at 10 l/min, located 3.5 m above theground at the challenge site. Individual pollen exposures weremeasured by the number of pollen grains collected on the adhesivecore of the active nasal filters. Samples were stained with Calberla’s Figure 1. The nasal filter prototype is made up of a soft medical solution (9) and ragweed and grass pollen were counted under a grade silicone and has an inner polypropylene core is coated with an adhesive. The placebo filters were of identical externalappearance, but did not have an inner core (inner core has been removed from only one nostril in this picture). To accommodatedifferent sized noses, two sizes of nasal filter were used.
In a questionnaire administered 1 week after the challenge, sub-jects were asked to score their global satisfaction with the nasalfilters.
Table 1. Baseline subject characteristics The primary outcome variables were change in MSC and TSC scores from baseline, using all time-points. Secondary outcome variables were changes from baseline in the individual components of MSC and TSC. Overall differences between groups were exam- Duration of allergic rhinitis, years (range) ined by repeated measures anova, and t-tests were used to analyse differences between treatment groups at each time-point. Differ- ences between groups in the frequency of sensitization were exam- ined by chi-squared test. Statistical significance was defined as In the test rig, pollen capture for Bahia, Bermuda and MSC, Major Symptom Complex, range 0–1360 (number of nose blows, number of ragweed averaged 98% for active and 3.5% for placebo sneezes, runny nose, sniffles, itchy nose and watery eyes); TSC, Total Symptom filters, across the range of flow rates. Airflow resistance, Complex, range 0–2448 (MSC symptoms plus itchy eyes, itchy ears, itchy throat, cough and postnasal drip); SPT-positive ¼ skin prick test weal ‡4 mm2.
* ¼ P < 0.05 between active and placebo groups.
2O/L/s for active and 1.6 cmH2O/L/s for placebo Pollen exposure on the challenge day was measured at 102 grains/2 h from the spore trap, and 68 pollen grains/ eight groups, and each group received either active (n ¼ 22) or person/2 h from the active filters (geometric mean placebo (n ¼ 24) nasal filters (Fig. 1). To eliminate visual unblind-ing: neither participants nor group supervisors (medical students) had previous experience of the nasal filters; the way the filtersworked was not explained to the participants or supervisors; supervisors were blinded to the randomization allocation; withineach group all subjects received the same type of filter; there was no Baseline MSC scores, prior to filter insertion, were 339.8 contact between groups; and the external appearance of the active and 187.3 for the active (n ¼ 22) and placebo (n ¼ 24) and placebo filters, once inserted, was identical.
After baseline assessments, subjects removed the dust-masks filter groups, respectively (P ¼ 0.02). Over the 2-h chal- and placed the nasal filters into their nostrils. Subjects were asked lenge period MSC decreased in the active group and to breathe through the nose for 2 h, while engaging in only mild increased in the placebo group compared with baseline activity (sitting, walking, eating) in a central location in the park.
(Fig. 2), resulting in highly significant differences between Nasal filters for ragweed and grass pollen Time (min)
Figure 2. Mean absolute change in MSC scores between active and placebo nasal filter groups. Overall difference between act-ive and placebo P ¼ 0.0076, repeated measures anova. Error bars are 95% confidence intervals (CIs) for each mean.
#P < 0.001, *P < 0.05 (t-test). MSC ¼ Major Symptom Complex (number of nose blows, number of sneezes, runny nose, sniffles, itchy nose and watery eyes).
–70 –60 –50 –40 –30 –20 –10
% Baseline
Figure 3. Percentage change from baseline in each symptom the groups (overall, P ¼ 0.0076). At 30, 60, 90 and score for active and placebo filter groups at 60 min. *P < 0.05 120 min the net difference in MSC for active compared at 60 min (t-test). Individual symptoms that were significantly with placebo filters were )25, )68, )39 and )50% points reduced by the filters during the 2 h study were: number of respectively. The maximum difference was seen at 60 min, sneezes, runny nose, itchy nose, sniffles, itchy throat, itchy eyes immediately after the 20 min period of sitting beside a large patch of ragweed. Similar differences between activeand placebo filters were seen in TSC scores (data notshown, overall P ¼ 0.023).
For seven of the 14 individual symptoms, there was a significant reduction in severity and for a further three This is the first reported clinical trial of nasal filters for symptoms there was a consistent trend towards lower the prevention of symptoms of allergic rhinitis. The nasal severity in the active filter group than the placebo group.
filters collect inhaled particles by impaction (4), resulting The strongest effect was seen for the symptoms of sniffles in high capture efficiency for particles above 8 lm and (overall, P ¼ 0.004), rhinorrhea (overall, P ¼ 0.035) and negligible air-flow resistance (4, 10). Most pollen grains itchy nose (overall, P ¼ 0.034), especially at 60 min are above 15 lm in diameter and ragweed, Bermuda and (Fig. 3) where highly significant differences were found.
Bahia pollens which are 18, 28 and 34 lm, respectively During the 2-h challenge period, significant reductions (5) were captured with high efficiency in the nasal filter were also observed in number of sneezes, itchy throat, itchy eyes and watery eyes (P < 0.05, t-test). For number In the clinical trial of natural outdoor pollen exposure, of nose blows, nasal blockage and peak nasal inspiratory the net difference in MSC scores were the result of flow, there was a trend to improvement in the active decreases in symptoms in the active filter group ()18 to group but the differences were not significant. The active )33%) and increases in symptoms in the placebo filter filters did not appear to influence postnasal drip or cough, group (+7 to +35%), with a maximum net difference in while a significant (P < 0.05) increase in itchy ears was MSC of 68% at 60 min. While this study did not compare the efficacy of the filters to rhinitis medications, a surveyof the literature indicates that both the magnitude andonset of symptom reduction with active filters compares very favourably with that from medications (6–8, 11). The Ninety-three percent of subjects said they would be rapid reduction of pre-existing symptoms in the active prepared to wear the filters again, with most people filter group may expand the utility of the filters. In studies prepared to use them in private situations such as around of rhinitis medications, which have used similar acute the house (88%) or in the garden (81%) compared with challenge experiments, there has been a well-recognized visiting friends (46%) or playing golf (33%).
placebo effect (6–8), which was not observed for the placebo filter group, although the low baseline symptoms (12). Conventional allergen avoidance strategies such as may account for this. Of note is the beneficial effect of the mattress encasing, when practiced with high allergen load nasal filters on ocular symptoms (Fig. 3), which is in a normal domestic setting, often appear to fail to consistent with the converse observations of ocular reduce allergens to a level where significant improvement symptoms occurring following direct nasal challenge (1).
in symptoms occur [see meta-analysis (13)]. Additional Although the active nasal filter group had significantly studies are required to examine the feasibility of using the higher baseline symptoms than the placebo group, this nasal filters for longer periods, as would be needed for did not explain the significant reduction in symptoms in the active group. A post hoc analysis of data forindividuals with similar mid-range baseline symptoms inboth groups (n ¼ 10/group) showed a significant reduc- tion in MSC and TSC for the active filter group ()35%),while symptoms in the placebo group increased by Authors thank Prof. John Beard, Northern Rivers University, approximately 28% (P < 0.05). The active and placebo Department of Rural Health, University of Sydney and Mr Mark groups also differed in the prevalence of sensitization to Barlettt, Northern Rivers Area Health Service, for their assistance Bermuda grass (Table 1); however, this was not related in setting up this project. Drs Janet Rimmer, Connie Katelaris andNorbert Berend reviewed the trial protocol. Authors appreciate the to baseline MSC scores (P ¼ 0.89, t-test).
support provided by the NSW Department of State and Regional The nasal filters may also have an application for the Development and Inhalix Pty Ltd. The authors also thank Kath prevention of exposure to perennial allergens, especially O’Driscoll for assistance with recruiting and running the trial and those from house dust mites where the majority of Dr Diana Bass for help with location of a suitable site. Thank you allergen is carried on particles above 10 lm in diameter to all the subjects who volunteered for this study.
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