Evaluation of acoustic rhinometry and posterior rhinomanometry as tools for inhalation challenge studies

Reproducibility of Acoustic Rhinometry in the Investigation of Occupational Rhinitis

Background

To diagnose occupational rhinitis, it is mandatory to conduct an objective assessment of changes in nasal patency during specific inhalation challenge (SIC). The reproducibility of acoustic rhinometry measurements in the setting of occupational challenges has never been examined. This study assessed the reproducibility of acoustic rhinometry during SIC investigation of occupational rhinitis.

Methods

Twenty-four subjects underwent acoustic rhinometry measurements during SIC investigation of occupational rhinitis. Subjects attended 3–6 days of SIC within a week by means of a realistic or closed-circuit apparatus methodology

Results

All of the within-day intraclass correlation coefficients (ICCs) for nasal volume (2–5 cm) and minimum cross-sectional area (MCA) based on a different number of measurements (2–7) were above 0.85; all of the coefficients of variation (CVs) for the same parameters were low (below 10%). The between-day CVs based on different numbers of SIC sessions ranged from 8.0 to 8.8% and from 6.8 to 8.8% for nasal volume and MCA, respectively. The between-day ICCs ranged from 0.80 to 0.88 and from 0.83 to 0.94 for nasal volume and MCA, respectively.

Conclusion

Acoustic rhinometry showed good within- and between-day reproducibility and can be recommended for the objective monitoring of nasal patency during SIC investigating occupational rhinitis.

The relationship between nasal resistance to airflow and the airspace minimal cross-sectional area

The relationship between nasal resistance (R) and airspace minimal cross-sectional area (mCSA) remains unclear. After the introduction of acoustic rhinometry, many otolaryngologists believed that mCSA measurements would correlate with subjective perception of nasal airway obstruction (NAO), and thus could provide an objective measure of nasal patency to guide therapy. However, multiple studies reported a low correlation between mCSA and subjective nasal patency, and between mCSA and R. This apparent lack of correlation between nasal form and function has been a long-standing enigma in the field of rhinology. Here we propose that nasal resistance is described by the Bernoulli Obstruction Theory. This theory predicts two flow regimes. For mCSA>Acrit, the constriction is not too severe and there is not a tight coupling between R and mCSA. In contrast, when mCSAAcrit (estimated to be 0.37cm(2)), this theory suggests that airway constrictions are rarely an exclusive contributor to nasal resistance, which may explain the weak correlation between mCSA and subjective nasal patency.

Assessment of nasal obstruction: correlation between subjective and objective techniques

BACKGROUND

Nasal sensation of airflow describes the perception of the passage of air through the nose. Nasal obstruction can be assessed using subjective techniques (symptom scores and visual analogue scales [VAS]) and objective techniques (anterior rhinomanometry [RMN], acoustic rhinometry [AR], and peak nasal inspiratory flow [PNIF]). Few studies have evaluated the correlation between these techniques.

OBJECTIVE

The primary objective of our study was to determine the degree of correlation between subjective and objective techniques to assess nasal obstruction.

MATERIALS AND METHODS

Nasal obstruction was assessed using a symptom score, VAS, RMN, AR (minimal cross-sectional area [MCSA] and volume), and PNIF in 184 volunteer physicians. Spearman's rho was recorded. Correlations were considered weak if r ≤ 0.4, moderate if 0.4 < r < 0.8, and strong if r > 0.8.

RESULTS

Mean (SD) age was 37.1 (6.9) years (range, 25-56 years); 61% were women. We found a strong correlation (r > 0.8; p = 0.001) between the different parameters of RMN and a moderate correlation between symptom score and VAS (r = 0.686; p = 0.001) and between MCSA and RMN (resistance) (r = 0.496; p = 0.001) and PNIF (r = 0.459; p = 0.001). The correlations were weak or non-significant for the remaining comparisons.

CONCLUSION

Nasal obstruction can be assessed using subjective and objective approaches. The correlations between objective techniques were moderate to strong. In addition, between subjective techniques we reported a moderate correlation. Finally, the correlations between the subjective and objective techniques were weak and absent. These findings suggest that each of the techniques assesses different aspects of nasal obstruction, thus making them complementary.

Intersession repeatability of acoustic rhinometry measurements in healthy volunteers

Objectives

Acoustic rhinometry is a rapid, reliable and non-invasive technique for the evaluation of conditions associated with impaired nasal patency. This study aimed to examine the intersession repeatability of acoustic rhinometry measurements of unilateral and combined nasal parameters in a group of healthy volunteers.

Methods

Twenty healthy volunteers were studied. In each subject, acoustic rhinometry measurements were performed on five consecutive days, with multiple recordings. Five clinically relevant parameters were measured in each session and the intersession repeatability of these measurements was expressed in terms of mean coefficient of variation, intraclass correlation coefficient and inter-item correlations.

Results

Intraclass correlation coefficients showed a high, and greater repeatability over time for all the combined (mean) values compared to the unilateral values. All intraclass correlations for combined values were ≥0.80 confirming almost perfect agreement. All intraclass correlations and inter-item correlations were associated with P<0.001. The mean coefficient of variation was low (<10%) for all but the proximal minimum cross sectional area (MCA1) measurements.

Conclusion

Acoustic rhinometry provides highly repeatable measurements of nasal patency, which is best for combined (mean) nasal parameters. This property makes it suitable for use in the diagnosis and follow-up of conditions associated with nasal obstruction, either structural or functional.

Correlation between acoustic rhinometry and subjective nasal patency during nasal challenge test in subjects with suspected occupational rhinitis; a prospective controlled study

OBJECTIVES

To assess the correlation between acoustic rhinometry and visual analogue scale endpoints in the context of nasal challenge with occupational agents.

DESIGN

Prospective controlled study.

SETTING

University teaching hospital.

PARTICIPANTS

Sixty-seven subjects with a history of work-related rhinitis and asthma symptoms.

MAIN OUTCOMES MEASURES

Subjects underwent nasal challenge with control and specific agent on consecutive days. Nasal congestive response to challenge was monitored by acoustic rhinometry and visual analogue scale.

RESULTS

Results showed no correlation between visual analogue scale and acoustic rhinometry measurements at baseline on the control (r=-0.13, P=0.3) and active (r=0.14, P=0.2) challenge days. No correlation was found between acoustic rhinometry and visual analogue scale when analysing all measurements obtained at all times after challenge with the control and active agent (control: r=0.09, P=0.04; active: r=0.001, P=0.9). The correlation between acoustic rhinometry and visual analogue scale was good and significant (r=-0.62, P=<0.01) when the analysis was restricted to cases showing a decrease in nasal volume>40% from baseline values.

CONCLUSIONS

We showed that the correlation between acoustic rhinometry and subjective nasal patency was poor on steady conditions. However, a significant correlation was observed in those cases showing a greater nasal congestive response after challenge measured by acoustic rhinometry.

Assessment of Upper Respiratory Tract and Ocular Irritative Effects of Volatile Chemicals in Humans

Accurate assessment of upper respiratory tract and ocular irritation is critical for identifying and remedying problems related to overexposure to volatile chemicals, as well as for establishing parameters of irritation useful for regulatory purposes. This article (a) describes the basic anatomy and physiology of the human upper respiratory tract and ocular mucosae, (b) discusses how airborne chemicals induce irritative sensations, and (c) reviews practical means employed for assessing such phenomena, including psychophysical (e.g., threshold and suprathreshold perceptual measures), physiological (e.g., cardiovascular responses), electrophysiological (e.g., event-related potentials), and imaging (e.g., magnetic resonance imaging) techniques. Although traditionally animal models have been used as the first step in assessing such irritation, they are not addressed here since (a) there are numerous reviews available on this topic and (b) many rodents and rabbits are obligate nose breathers whose nasal passages differ considerably from those of humans, potentially limiting generalization of animal-based data to humans. A major goal of this compendium is to inform the reader of procedures for assessing irritation in humans and to provide information of value in the continued interpretation and development of empirical databases upon which future reasoned regulatory health decisions can be made.

Objective monitoring of nasal patency and nasal physiology in rhinitis

Nasal obstruction can be monitored objectively by measurement of nasal airflow, as evaluated by nasal peak flow, or as airways resistance/conductance as evaluated by rhinomanometry. Peak flow can be measured during inspiration or expiration. Of these measurements, nasal inspiratory peak flow is the best validated technique for home monitoring in clinical trials. The equipment is portable, relatively inexpensive, and simple to use. One disadvantage, however, is that nasal inspiratory peak flow is influenced by lower airway as well as upper airway function. Rhinomanometry is a more sensitive technique that is specific for nasal measurements. The equipment, however, requires an operator, is more expensive, and is not portable. Thus, it is applicable only for clinic visit measures in clinical trials. Measurements require patient cooperation and coordination, and not all can achieve repeatable results. Thus, this objective measure is best suited to laboratory challenge studies involving smaller numbers of selected volunteers. A nonphysiological measure of nasal patency is acoustic rhinometry. This sonic echo technique measures internal nasal luminal volume and the minimum cross-sectional area. The derivation of these measures from the reflected sound waves requires complex mathematical transformation and makes several theoretical assumptions. Despite this, however, such measures correlate well with the nasal physiological measures, and the nasal volume measures have been shown to relate well to results obtained by imaging techniques such as computed tomography scanning or magnetic resonance imaging. Like rhinomanometry, acoustic rhinometry is not suitable for home monitoring and can be applied only to clinic visit measures or for laboratory nasal challenge monitoring. It has advantages in being easy to use, in requiring little patient cooperation, and in providing repeatable results. In addition to nasal obstruction, allergic rhinitis is recognized to be associated with impaired mucociliary clearance and altered nasal responsiveness. Measures exist for the monitoring of these aspects of nasal dysfunction. Although measures of mucociliary clearance are simple to perform, they have a poor record of reproducibility. Their incorporation into clinical trials is thus questionable, although positive outcomes from therapeutic intervention have been reported. Measures of nasal responsiveness are at present largely confined to research studies investigating disease mechanisms in allergic and nonallergic rhinitis. The techniques are insufficiently standardized to be applied to multicenter clinical trials but could be used in limited-center studies to gain insight into the regulatory effects of different therapeutic modalities.

Assessment of ocular and nasal irritation in asthmatics resulting from fragrance exposure

BACKGROUND

Many asthmatics report worsening of symptoms following exposure to odours and sensory irritants commonly found in household and cosmetic products. Despite this, little evidence exists to confirm the degree to which such subjective reports are correlated with localized, objective changes in the upper or lower airways following a fragranced product exposure.

OBJECTIVE

Subjective symptom reports were compared to objective measures in mild asthmatics, moderate asthmatics and non-asthmatics following exposure to one of two fragranced household aerosol mixtures and a clean air control condition to determine if asthmatics reported greater subjective symptoms of nasal congestion or exhibited objective measures of elevated ocular irritation and nasal congestion following exposure than did healthy controls.

METHODS

Measures of nasal mucosal swelling, using acoustic rhinometry, and photographic assessments of ocular hyperemia, using macro-photography, were taken before exposure, immediately after an initial 5-min exposure and again following a 30-min exposure to either of two, fragranced aerosol products and a clean air control. Self-reports of nasal patency at each time-point were also obtained.

RESULTS

Although moderate asthmatics tended to report more nasal congestion following fragranced product exposure than did non-asthmatics, no exposure-related changes in ocular redness or nasal mucosal swelling were observed among the three groups. Spirometry readings also failed to show evidence of any exposure-related changes in pulmonary function.

CONCLUSION

Despite claims that exposure to fragranced products may trigger ocular and respiratory symptoms among asthmatics, we found no evidence that 30 min of exposure to one of two fragranced aerosols elicited objective adverse effects in the ocular or nasal mucosa of mild and moderate asthmatics. While physiological mechanisms of fragrance impact may yet be responsible for some of the adverse reports among asthmatics following fragrance exposure, such reports may also reflect a non-physiological locus of symptom perception triggered by other sensory cues.

Upper airway irritation, odor perception and health risk due to airborne chemicals

Chemosensory irritation associated with the manufacture and use of volatile materials has been a public and employee health concern for many years. Because odor properties can often be detected at much lower concentrations than those capable of eliciting upper respiratory tract irritation, confusion between odor and irritation coupled with variability in odor sensitivity and response can produce significant obstacles for evaluating the potential for adverse effects or annoyance from worker and community exposures. Although rigorous research methods have been developed to accurately quantify chemosensory irritation in human evaluations, several important considerations should be included in the design and interpretation of such studies. Specifically, research studies evaluating chemosensory irritation from volatile materials should be capable of (1) distinguishing between the annoyance or concern elicited by odor sensation and that elicited by true sensory irritation, (2) evaluating exposure-related factors that affect odor or irritancy responses, and (3) separating true adverse health effects from those mediated via psychosocial factors. Objective measures of upper respiratory tract irritation onset obtained in conjunction with subjective reports can lend valuable input to the decision process for determining occupational exposure limits. Subjective reports of irritation at low levels that cannot be reconciled with objective measures should prompt a careful investigation into the other factors (e.g. cognitive or emotional) that may be modulating the sensory response. Distinguishing between the exposure that elicits local effects of sensory irritation in the upper respiratory tract and the exposure that elicits self-reports of irritation is a key component in establishing occupational exposure limits that are protective of exposed workers.

Reproducibility of acoustic rhinometry and rhinomanometry in normal subjects

The reproducibility of nasal patency measurements was assessed by acoustic rhinometry and active rhinomanometry using previously described Toronto methodologies. Six subjects with normal upper airways were tested with both procedures on six separate occasions within a 2-month period. Topical decongestant was applied to minimize the effects of mucosal variation on the nasal airway. The mean coefficients of variation (mean +/- s.d; %) over time of the measurements were 8.1 +/- 4.1 and 9.7 +/- 5.2 for minimal unilateral cross-sectional area and 4.8 +/- 1.8 and 5.5 +/- 3.5 for nasal volume (0-5 cm) of the right and left sides, respectively. For active rhinomanometry, the mean coefficients of variation (mean +/- s.d.; %) over time of the measurements were 15.9 +/- 7.3, 12.9 +/- 4.6, and 8.5 +/- 2.8 for right, left and combined nasal airflow resistance. The intraclass correlation coefficient was 0.76, 0.70, and 0.96 for right, left, and combined nasal resistance, 0.91 and 0.87 for right and left minimal cross sectional area, and 0.86 and 0.69 for right and left nasal volumes, respectively, also confirming a high level of reproducibility for both methods. In conclusion, performed by an experienced operator under controlled circumstances, the reproducibility of both methods of nasal patency assessment compared favorably with many widely accepted clinical tests.

The value of acoustic rhinometry in assessing nasal responses to cat exposure

BACKGROUND

Acoustic rhinometry (AR) uses sonar principles to map the anatomy of the nasal cavity and has been used in other studies to assess acute airway responses to allergen exposure.

OBJECTIVE

The purpose of this study was to evaluate the utility of AR in assessing acute airway responses to cat allergen exposure by using a well-characterized cat exposure model.

METHODS

Thirty subjects with a history of cat-induced rhinitis and a positive skin prick test response to cat allergen underwent an environmental cat challenge. Of these 30 subjects, 10 also had repeat challenges at lower levels of antigen to determine whether there was a dose response. Five subjects with negative skin test responses to cat were recruited as control subjects. During the 1-hour cat exposure, upper and lower respiratory symptoms were scored every 5 minutes, and spirometry and AR were obtained every 15 minutes.

RESULTS

Although 29 of 30 subjects had changes in AR measurements, no correlations were detected between upper respiratory symptom scores and any of the changes observed in AR. In comparing the baseline challenges with lower antigen level challenges, upper respiratory symptom scores differed significantly (P = .002), whereas AR responses were nearly identical. Subjects without cat allergy did exhibit less response by AR (P = .05 to .13), but the greatest differences remained in the upper respiratory symptoms scores (P < .0001).

CONCLUSION

We conclude that although AR does provide an objective measure of nasal response to allergen exposure, it has significant limitations. These are evidenced by the lack of correlation with symptoms, the inability to measure a dose response, and the changes noted even among the control subjects.

Allergy immunotherapy

Specific immunotherapy for allergy has been used for over eight decades. Despite this history, controversy continues over techniques, indications, and the eventual outcomes. This article reviews immunotherapy techniques available to the various practitioners of allergy care. Safety recommendations, indications for therapy, and available measurements for outcomes are also discussed.

Differential susceptibility to inhaled pollutants: effects of demographics and diseases

Inhaled pollutants and respiratory disease deserve particular attention at a conference focused on susceptibility and environmental risk. Inhaled air contains diverse biological, physical and chemical stressors which may cause upper and lower respiratory inflammation and exacerbate complex polygenic disorders such as asthma and sinusitis. This paper focuses on intrinsic susceptibility factors of demographics and diseases as well as genetic background. The National Health Information Survey shows that acute and chronic respiratory conditions are common at all ages, but their incidence and prevalence vary between age groups. Susceptibility is therefore not a fixed characteristic, but the aggregate effect of changing intrinsic factors such as age and disease. While ethnicity is often cited as a risk factor for disease prevalence or severity, recent research shows that measurable factors such as nasal ellipticity determine exposure-dose relationships, while the imperfect surrogate of ethnicity does not. Studies also show that exposure-dose relationships can be modified by recent exposures, and additional information is clearly needed in this area. We propose that evidence for the genetic contribution to pollutant susceptibility be sought in inter-individual variation in responses of homogenous, well characterized individuals to short term controlled pollutant exposure. Future improvements in risk assessment models will be based on a precise identification of factors that determine exposure-dose relationships, and a mechanistic understanding of the reasons that a demographic factor or disease appears to confer altered susceptibility.