Physiological fluctuations in nasal resistance may interfere with nasal monitoring in the nasal provocation test

Dynamic Changes in Heart Rate Variability and Nasal Airflow Resistance during Nasal Allergen Provocation Test

Allergic rhinitis is a major chronic respiratory disease and an immunoneuronal disorder. We aimed at providing further knowledge on the function of the neural system in nasal allergic reaction. Here, a method to assess simultaneously the nasal airflow resistance and the underlying function of autonomic nervous system (ANS) is presented and used during the nasal provocation of allergic and nonallergic subjects. Continuous nasal airflow resistance and spectral heart rate variability parameters show in detail the timing and intensity differences in subjects' reactions. After the provocation, the nasal airflow resistance of allergic subjects showed a positive trend, whereas LF/HF (Low Frequency/High Frequency) ratio and LF power showed a negative trend. This could imply a gradual sympathetic withdrawal in allergic subjects after the allergen provocation. The groups differed significantly by these physiological descriptors. The proposed method opens entirely new opportunities to research accurately concomitant changes in nasal breathing function and ANS.

Acoustic impedance rhinometry (AIR): a technique for monitoring dynamic changes in nasal congestion

We describe a simple and inexpensive method for monitoring nasal air flow resistance using measurement of the small-signal acoustic input impedance of the nasal passage, similar to the audiological measurement of ear drum compliance with acoustic tympanometry. The method requires generation of a fixed sinusoidal volume-velocity stimulus using ear-bud speakers, and an electret microphone to monitor the resultant pressure fluctuation in the nasal passage. Both are coupled to the nose via high impedance silastic tubing and a small plastic nose insert. The acoustic impedance is monitored in real-time using a laptop soundcard and custom-written software developed in LabView 7.0 (National Instruments). The compact, lightweight equipment and fast time resolution lends the technique to research into the small and rapid reflexive changes in nasal resistance caused by environmental and local neurological influences. The acoustic impedance rhinometry technique has the potential to be developed for use in a clinical setting, where the need exists for a simple and inexpensive objective nasal resistance measurement technique.

Diagnostic value of outcome measures following allergen exposure in an environmental challenge chamber compared with natural conditions

BACKGROUND

Efficacy testing of drugs in seasonal allergic rhinitis (SAR) is often disturbed by seasonal variations of environmental allergens, and assessment of onset and duration of action is hardly possible under natural conditions. Allergen provocation in an environmental challenge chamber (ECC) can be of added value in this respect. However, the specificity, sensitivity, and reproducibility of outcome measures under both settings are unclear.

OBJECTIVE

The aim of this study was to investigate and compare the diagnostic value (specificity, sensitivity, and reproducibility) of clinical end-points and biomarkers both following allergen provocation in an ECC and under natural conditions.

METHODS

Sixty adult patients with SAR to grass and 60 healthy subjects were exposed twice to grass pollen in an ECC and observed twice during the pollen season. Symptoms, nasal flow, as well as exhaled and nasal nitric oxide (NO) were investigated.

RESULTS

The total nasal symptom score (TNSS) in the ECC had the best reproducibility (intraclass correlation coefficient ICC=0.86) and sensitivity/specificity [area under receiver operating characteristic curve (AUC)=0.99] of all measures. Symptoms in season also had good sensitivity/specificity but were far less reproducible. Nasal flow in the ECC had good sensitivity/specificity but reproducibility was limited. NO measurements showed good reproducibility but sensitivity/specificity were limited, except for exhaled NO in season (AUC=0.75).

CONCLUSION

The high reproducibility and sensitivity/specificity in the ECC suggests that TNSS is a valuable outcome measure. While exhaled NO can be considered to monitor airway inflammation, nasal NO appears to be unspecific.

Continuous assessment of nasal airflow resistance by adaptive modeling

A method to assess nasal airflow resistance is presented that provides a continuous resistance value and applies a novel minimally obtrusive measurement technique. Instead of calculating the resistance once for each breathing cycle conventionally, it is calculated for each signal sample at any sampling frequency. The continuous pressure recording is produced with a nasopharyngeal catheter inserted 8 cm deep along the floor of the other nasal cavity and the flow recording is produced with respiratory effort bands. A least-mean-square (LMS) extension for the resistance model of Broms is developed that dynamically adapts to the time-varying characteristics of the nasal functioning and produces the continuous resistance values. Experimental results are shown that demonstrate the uniqueness and applicability of the new technique in assessing quickly changing resistance in a histamine/xylometatsolin challenges, the differences between normal and symptomatic patients, and the effect of nasal treatment of patients.

Bilateral nasal allergen provocation monitored with acoustic rhinometry. Assessment of both nasal passages and the side reacting with greater congestion: relation to the nasal cycle

BACKGROUND

The effect of bilateral nasal provocation on nasal mucosa measured with the use of acoustic rhinometry (AR) can be assessed for both nasal passages or for the side responding with greater congestion. Assessment of changes in nasal congestion during the nasal provocation test (NPT) can be affected by the nasal cycle (NC). The aim of this study was to find out the most accurate method to evaluate changes observed during bilateral nasal provocation.

METHODS

Cross-sectional areas (CSA) at the level of inferior nasal turbinate (CSA-2) were recorded by AR in 26 volunteers with allergic rhinitis during the NC for 5-7 h and subsequently during NPT. The risk of spontaneous total and unilateral CSA-2 decrease was established. Sensitivity of the NPT assessment for the total CSA-2 and for the side responding with greater congestion was evaluated at chosen thresholds. These thresholds were selected in a way that the risk levels of spontaneous decrease of unilateral and total CSA-2 were equal.

RESULTS

The assessment of the total CSA-2 was found to be more sensitive than the assessment of the side responding with greater congestion. The highest sensitivity and specificity of the test was achieved by using a combination of both assessments. Optimum thresholds of the CSA-2 decrease for assessment at 15 min after provocation, with this method, were 27% and 40% for the side responding with greater congestion and for the total CSA-2, respectively.

CONCLUSIONS

Recognition of the risk of spontaneous unilateral and total CSA-2 decreases enables introduction of combined assessment of bilateral NPT. This assessment seems to be the most accurate method for evaluation of the test results.

Atypical nasal challenges in patients with idiopathic rhinitis: more evidence for the existence of allergy in the absence of atopy?

BACKGROUND

The pathophysiology of idiopathic rhinitis is unknown although evidence is accumulating to suggest that many patients may have a localized form of allergic rhinitis in the absence of other atopic symptoms and markers. This study compares detailed nasal challenge results obtained from patients with idiopathic rhinitis to those of atopic and normal controls.

METHODS

Patients with idiopathic rhinitis (n = 23), perennial allergic rhinitis (n = 8) and normal controls (n = 8) underwent a normal saline challenge to exclude hyper-reactivity and then bilateral nasal allergen challenges. Nasal patency was assessed by anterior active rhinomanometry.

RESULTS

All of the patients with atopic rhinitis demonstrated positive bilateral allergen challenges. All normal control subjects had bilateral negative challenges. Two patients in the idiopathic group tested positively to saline and were excluded from further study with 62% of the remainder testing positive to allergens. Of the idiopathic patients testing positive, 85% were sensitive to house dust mite.

CONCLUSION

A significant proportion of patients with idiopathic rhinitis have positive nasal challenges, the vast majority to house dust mite allergen. These findings add to the weight of evidence that suggests 'localized allergy' may exist in the absence of systemic atopic markers.

Reliable and reproducible anterior active rhinomanometry for the assessment of unilateral nasal resistance

Unilateral nasal resistance is now thought to be more important than total resistance in promoting obstructive symptoms. We assessed the reproducibility of anterior active rhinomanometry in measuring unilateral nasal resistance. Ten baseline readings of unilateral nasal resistance were made over a 30-min period in seven healthy subjects (14 nostrils) using anterior active rhinomanometry performed according to the International Committee for the Standardization of Rhinomanometry (ICSR) guidelines. Baseline readings revealed that measurements using anterior active rhinomanometry had an unacceptably high coefficient of variation (19%-60%). With a more time-consuming revised protocol involving multiple recordings and the identification and exclusion of erroneous data, coefficients of variation of 7%-15% were obtained. We conclude that single anterior active rhinomanometry readings are potentially prone to large errors and each researcher using such equipment must satisfy his/herself that their methodology has an acceptable coefficient of variation in their hands. The ICSR guidelines are not always sufficient to allow reproducible measurement and specially designed protocols may be necessary to produce reliable results.

Environmental priming influences allergen-specific nasal reactivity

BACKGROUND

Preceding mucosal response to one allergen leads to the priming of the nasal mucosal response to another allergen. This study aimed to determine whether environmental allergens, especially ubiquitous animal dander, can induce nasal priming.

METHODS

We investigated 26 grass-pollen-allergic subjects with additional sensitization to other aeroallergens. We performed continuous allergen challenge for 2 h with 1500 Dactylis glomerata pollen/m3 in the Vienna challenge chamber. The nasal flow at 150 Pa was examined, and subjective scores were obtained every 15 min. Statistical analysis was calculated from the area under curve of nasal flow reduction by Student's t-test and the Mann-Whitney U-test. Alpha was 0.05.

RESULTS

In subjects with positive cat-dander RAST (class of > or = 3), besides grass-pollen allergy, the specific nasal allergic reaction to Dactylis challenge was significantly pronounced (P < 0.01), and an earlier onset of reaction was evident. The same results were obtained with additional sensitization to dog dander (P < 0.05). Concomitant sensitization to mugwort also led to escalating symptoms (P < 0.05).

CONCLUSIONS

These results indicate that a specific nasal allergic reaction is augmented by environmental priming caused by ubiquitous animal dander and possibly is influenced by the daily use of spices.

Acoustic rhinometry, rhinomanometry and the amount of nasal secretion in the clinical monitoring of the nasal provocation test

BACKGROUND

The reliable interpretation of the nasal provocation test in allergy diagnosis requires objective and measurable monitoring parameters for clinical practice. The clinical usefulness of the nasal provocation test has been limited by scanty knowledge of the specificity and sensitivity of the test and a lack of reference values.

OBJECTIVE

To test and compare three objective monitoring parameters of a nasal provocation test in occupational allergic rhinitis. To evaluate the magnitude of the nasonasal effects in a unilateral allergen challenge.

METHODS

The monitoring parameters of the nasal reaction were derived from the minimum cross-sectional area on acoustic rhinometry, the nasal resistance on active anterior rhinomanometry and the amount of nasal secretion measured at 15 min intervals for 60 min. Twenty-three bovine-allergic dairy and beef cattle farmers and 19 exposed, non-allergic control subjects were challenged first with a control solution and then with the cow allergen.

RESULTS

All the three monitoring parameters showed high specificity and sensitivity in finding allergic and non-allergic subjects. The secretion parameter was found to be slightly superior to the acoustic rhinometry and rhinomanometry parameters. The side difference in the nasal response between the allergen-challenged and the contralateral diluent-challenged cavity was significant for all the parameters among the allergic subjects. The contralateral secretion amount was 1/3 of the ipsilateral secretion, indicating the magnitude of the contralateral nasonasal reflex. A nasonasal reflex was also noted in the nasal patency monitoring. The coefficient of variation was significantly lower for the acoustic rhinometry than for the rhinomanometry (P=0.0001). The optimal threshold values for a positive test were a secretion amount of 100 mg, a 15% decrease in the minimum cross-sectional area and a 50% increase in the resistance for the observation period of 30 min and correspondingly 210 mg, 30% and 100% for 60 min.

CONCLUSION

The low-pressure aspiration of the nasal secretion from the anterior part of the nasal cavity was found to be a reliable and practical monitoring parameter to be used together with acoustic rhinometry or rhinomanometry in the nasal provocation test for clinical purposes. Although significant nasonasal effects took place in the unilateral allergen challenge, the response was more prominent in the allergen-challenged than in the contralateral diluent-challenged nasal cavity in most allergic subjects.