A universal way to evaluate the curve in rhinomanometry

Automatic Processing of Nasal Pressure Recordings to Derive Continuous Side-Selective Nasal Airflow and Conductance

Monitoring of nasal airflow and conductance provides crucial insights into the variable nature of the nasal resistance, nasal cycle, and ventilation. We have previously shown that tracking of pressure swings at the entrance of each nasal passage by a dedicated catheter system allows bilateral monitoring of nasal airflow over several hours but requires complex linearization and calibration procedures. Side-selective nasal conductance is derived from linearized and calibrated bilateral nasal pressure swings and corresponding driving pressure, i.e., the transnasal pressure difference derived from an epipharyngeal catheter. Manual analysis of such recordings and computation of instantaneous conductance as the ratio of flow to driving pressure over several hours is extremely tedious, time consuming, and therefore not suitable for routine practice. To address this point, we developed and validated a software for automatic processing of nasal and epipharyngeal pressure recordings as a convenient tool for studying the nasal ventilation. The software applies an eight-parameter logistic model to transform nasal pressure swings into side-selective estimates of airflow that are calibrated and further processed along with epipharyngeal pressure to compute bilateral nasal conductance over consecutive, user-selectable time-segments. Essential processing steps include (1) offset correction, (2) low-pass filtering, (3) cross-correlation, (4) cutting of signals into individual breaths, (5) normalization, (6) ensemble averaging to obtain a mean pressure signal for each nasal side, (7) derivation of airflow, conductance, and further variables. Among four evaluated algorithms for calculation of nasal conductance, the derivative of the airflow-pressure curve according to the mean value theorem agreed closest with the gold standard, i.e., the conductance derived from airflow measured by a pneumotachograph attached to an oral-nasal mask and transnasal pressure. In combination with the nasal catheter system, our novel software represents a valuable tool for use in clinical practice and research to conveniently investigate nasal ventilation and its changes occurring spontaneously or in response to various exposures and therapeutic interventions.

Robust nondimensional estimators to assess the nasal airflow in health and disease

There are significant variations of both human nose shapes and airflow patterns inside nasal cavities, so it is difficult to provide a comprehensive medical identification using a universal template for what otolaryngologists consider normal breathing at rest. In addition, airflow patterns present even more random characteristics in diseased nasal cavities. To give a medical assessment to differentiate the nasal cavities in health and disease, we propose 2 nondimensional estimators obtained from both medical images and computational fluid dynamics. The first mathematical estimator ϕ is a function of geometric features and potential asymmetries between nasal passages, while the second estimator R represents in fluid mechanics terms the total nasal resistance that corresponds to the atmosphere-choana pressure drop. These estimators only require global information such as nasal geometry and magnitudes of flow determined by simulations under laminar conditions. We find that these estimators take low and high values for healthy and diseased nasal cavities, respectively. Our study, based on 24 healthy and 25 diseased Caucasian subjects, reveals that there is an interval of values associated with healthy cavities that clusters in a small region of the plane ϕ-R. Therefore, these estimators can be seen as a first approximation to provide nasal airflow data to the clinician in a noninvasive method, as the computed tomography scan that provides the required images is routinely obtained as a result of the preexisting naso-sinusal condition.

Nasal congestion and airway obstruction: the validity of available objective and subjective measures

Rhinomanometry and acoustic rhinometry provide the best methods for objective assessment of nasal obstruction. Advanced equipment for these methods is now available, and most devices are reliable provided that care is taken to calibrate the device properly and, for rhinomanometers, the user is completely familiar with the mathematical algorithm for resistance used by the accompanying software. Suggestions for improvement in standardization of rhinomanometry are given. Rhinomanometry and rhinometry are both capable of objectively measuring nasal obstruction, but they are complementary methods that assess different nasal attributes, the former being a test of nasal function, and the latter a representation of nasal geometry. Objective methods are strongly recommended for use in the evaluation of pharmacologic agents that are expected to improve nasal airflow. When further studies needed to validate their use for long-term comparisons are done, these methods should find an increasing place in clinical practice.

Evaluation of active anterior and posterior rhinomanometry in normal subjects

In this study active anterior (AAR) and active posterior (APR) rhinomanometry were performed by 100 normal subjects with a Mercury rhinomanometer according to the recommendations of the International Standardization Committee. There was no significant difference between total nasal airway resistance (Rna) values obtained with APR by direct measurement and those calculated from AAR. Mean total Rna was 0.31 Pa/cm3/s (range 0.13-0.84) at a reference pressure of 75 Pa. Measurements by AAR were more reproducible than those by APR, mean intrasubject coefficients of variation were 12 and 16% respectively. This reproducibility was similar to that of lower airways' resistance measurements. Rna values from this population did not conform to a normal Gaussian distribution. Rna was higher during expiration than inspiration and values were higher in women than in men.

Intranasal verapamil in allergen-induced rhinitis

Twenty-six pollen-allergic subjects participated in a double-blind, placebo-controlled trial of the protective effect of the calcium antagonist, verapamil, on allergen-provoked nasal symptoms. Intranasal verapamil, 1 mg. had a weak protective effect in that "tickling score" was 22% lower (P less than 0.01) and the number of sneezes 29% lower (nonsignificant) after verapamil as compared with placebo pretreatment. There were no differences with regard to nasal blockage or discharge. It is concluded that the verapamil spray used, cannot be recommended for clinical trials, but that further investigations of other formulations of calcium antagonist are justified in order to analyse the potential role of this type of drugs in the treatment of allergic rhinitis.