HK1078755B - Method and device for diagnosis using an oscillating airflow - Google Patents

Description

Method and apparatus for diagnosis using oscillating airflow

The present invention relates to the examination of the human upper respiratory tract, and in particular to an apparatus and method for use in the determination of the function and status of the sinuses, and for use as an aid in the diagnosis of various diseases of the human upper respiratory tract.

Background

The paranasal sinuses are cavities in the bones of the surrounding face of the nose that communicate with the nasal cavity through narrow ostia (ostia). The sinus mucosa is connected to the mucosa of the nasal cavity. The maxillary sinus is the largest of these cavities. The opening on the inner side wall of the maxillary sinus is communicated with the middle nasal passage. Sinus ostial obstruction is the major pathogenesis of sinusitis.

The gaseous Nitric Oxide (NO) is released in the human respiratory tract. Most of the NO found in exhaled breath comes from the nasal airways and can be measured non-invasively using different sampling techniques. It is known that large amounts of NO production occur in the paranasal sinuses, where inducible NO synthase is continuously expressed in epithelial cells. NO is also released from other sources in the nose, such as the nasal mucosa. However, the relative supply of different NO sources in the upper respiratory tract to NO found in nasal gas is difficult to estimate. The sinuses communicate with the nasal cavity through sinus ostia, and the rate of gas exchange in these cavities depends, for example, on the size of the ostia. An open ostium is necessary for the maintenance of sinus integrity. Blockage of the ostia, for example caused by virus-induced mucoma, will result in reduced oxygen pressure, mucosal edema, decreased mucociliary transport and eventual bacterial colonization. Early studies showed that nasal NO levels were significantly reduced in respiratory diseases affecting the sinuses, such as Primary Ciliary Dyskinesia (PCD) and Cystic Fibrosis (CF). In healthy sinuses, the NO concentration is very high, sometimes exceeding 20 ppm.

Sinusitis is a very common disease that afflicts many people and is socially costly. In the united states, the prevalence of self-reported chronic rhinosinusitis is approximately 12% of the population. A number of problems are involved in the diagnosis and treatment of this disease. For example, headache, rhinorrhea, and nasal congestion are the most common, but these symptoms are not necessarily indicative of sinusitis. Therefore, the true incidence of sinusitis is low.

Proper ventilation of the sinuses is essential to the integrity of the sinuses. Indeed, blockage of the ostium is considered to be a key factor in the pathogenesis of sinusitis. This obstruction may be mechanical or mucosal, i.e. septum curvature, nasal polyposis, allergic rhinitis or most commonly acute viral infection. The basic principle of treatment is to cure any existing infection and to promote sinus ventilation (drainage) during and after treatment to prevent relapse. In the medical treatment of acute infectious sinusitis, the use of antibiotics remains a fundamental (kernerstone) treatment. Moreover, medical interventions with nasal mucosal decongestants and surgical therapies are also frequently used in the prevention and treatment of chronic rhinosinusitis for the purpose of facilitating sinus ventilation.

Prior Art

Us patent 6142952 describes a method and apparatus for detecting and diagnosing airway obstruction. The invention of the' 952 patent is directed to measuring pressure and flow data of pressurized breathable gas provided to the airway of a patient by using an oscillating element or a pressurized probe signal. The gas is supplied by an interface comprising a mask and a flexible hose, an oscillating element or a pressurized probe signal being coupled to a frequency generator via a loudspeaker. The pressure and flow of breathable gas in the interface is measured or sampled to learn the nature of the patient's airway.

An experimental model for studying gas exchange through the maxillary sinus ostium has been developed (Aust, R. and Drettner, B., Uppsala J Med Sci, 79; 177-. In their article, Aust and Drettner first mention previously known methods, including those to be used for pO₂A small electrode was measured and introduced into the maxillary sinus and the oxygen content in the sinus was continuously recorded. Aust and Drettner instead developed an experimental model using a rubber nose molded from a cadaver and represented the maxillary sinus with a nitrogen-filled syringe. Airflow through the nasal model was generated by the respirator and the pressure change in the syringe was recorded. As a measure of gas exchange, the oxygen content in the injector was measured. In all model trials, the breathing rate was constant, however the volume of the syringe and the diameter of the junction between the nasal model and the syringe could vary. The volume of the syringe represents the volume of the maxillary sinus and the diameter of the junction represents the diameter of the ostium. The results show that gas exchange depends on the diameter of the ostium.

In another article (Aust, R. and Drettner, B., Acta Otolaryng 78: 432-. This method is based on measuring the increase in pressure in the maxillary ostium with an open ostium, caused by the airflow introduced into the sinus by the cannula inserted into the sinus through the lower nasal passage.

Early studies of methods of maxillary ostia patency still relied on recording pressure in the nasolacrimal duct and maxillary sinus during breathing, insufflation and inspiration.

One non-invasive test is the 133-xenon removal (washout) technique, in which a mixture of air and 133-xenon is blown into the nasal cavity (Paulsson et al, Ann. Otol. Rhinol. Layngol., 2001; 110: 667-74). The elevated pressure achieved by the subject blowing a balloon causes the gas to enter the sinuses. The clearance of 133-xenon was monitored with a scintillation camera capable of Single Photon Emission Computed Tomography (SPECT). The elimination half-life was used as a measure of sinus ventilation.

Invasive tests are potentially painful for the patient and are cumbersome to perform.

They are therefore unsuitable for use in daily clinical practice. A simple non-invasive test that can be used to measure ostium patency is most useful. Such a test can help identify patients at risk of developing sinusitis. It can also be used to monitor the effect of surgical or medical interventions for the prevention of sinusitis.

Summary of The Invention

The above problems are solved by the instrument of the present invention for use in the examination of the condition of the upper airways of a person, in particular of the sinus or sinuses of a person, wherein the instrument comprises means for generating and/or maintaining an oscillating airflow acting on the upper airways or parts thereof, and the instrument is adapted to be connected to means for measuring and recording the concentration and/or flow of gas present in the exhaled air of a person. Another aspect of the invention is a method of facilitating examination of the upper respiratory tract of a human, particularly in the testing of the condition of one or more sinuses of a human, wherein the concentration and/or flow rate of at least one gaseous component in nasally exhaled air is determined and recorded in the presence and absence of an oscillating airflow. Other features and associated advantages of the invention will be apparent from the description, examples and claims, which are incorporated herein by reference.

Brief Description of Drawings

The invention will be disclosed in more detail in the following description and examples, with reference to the accompanying drawings,

wherein

Figure 1 shows the initial trace of NO during a single breath of nasal exhalation, either in humming (a) or silent (b);

figure 2 shows the effect of repetitive beeping on nasal NO output. 5 consecutive exhalations were performed at 5-second intervals under buzzer conditions. A progressive decrease in NO levels was observed after each action before plateau was reached;

figure 3 shows nasal NO output measured at baseline during silent expiration, immediately after repeated silent nasal expiration, and immediately after repeated beeping action (five consecutive 10s nasal exhalations upon beeping). P 0.002 compared to baseline, n 6;

FIG. 4 shows the change in nasal NO output (%) following topical nasal application of an NO synthase inhibitor (L-NAME). The subject breathed silently or in a whining breath. (. p ═ 0.002, n ═ 6).

Figure 5 shows the effect of silent nasal exhalations or buzzes on nasal NO output in control and patients with nasal polyposis.

Fig. 6 is a graphical representation of a sinus (G), sinus ostium (syringe tip), and nasal cavity (C) trial model. A denotes a flow/pressure meter, B denotes a flow resistor, D denotes a noise generator (rubber duck buzzer), E denotes a display, and F denotes an NO analyzer.

FIG. 7 shows the effect of ostium size on sinus gas exchange in an experimental model. In either the silent (underfill) or the audible (underfill) condition, the subject is tested for one exhalation at a fixed flow rate (0.2L/sec). Calculating sinus gas exchange by measuring NO in the injector immediately before and after each exhalation;

figure 8 shows the effect of three different beeping frequencies on NO levels in the sinus/nose model. In the model, the subject exhales through the mouth at a fixed flow rate of 0.2L/s, with an NO concentration of 8ppm and a resistance of 1cmH₂O and the sinus ostia size is 1.9 mm.

Detailed Description

The inventors have unexpectedly found that the presence of an oscillating airflow greatly increases nasal NO release in healthy subjects. This increase appears to reflect an increase in NO supply from the paranasal sinuses. Nasal NO measurement in the presence of oscillating airflow is a simple non-invasive test that can give valuable information about the condition of the upper respiratory tract, such as NO production in the sinuses and ostial function.

In the studies, air was oscillated by an external oscillating airflow or by a human generated beep, which appeared to increase the exchange of gas between the sinuses and nasal cavity. This was also confirmed in the two-chamber model system, where the oscillating airflow obtained by the buzzing simulation caused a large increase in NO level. The volume of the syringe, the concentration of NO and the diameter of the syringe tip (representing the sinus ostium) were selected to simulate the physiological values of these parameters. The normal size of the ostium is about 2.4 mm. Interestingly, NO levels were found to be highly dependent on syringe tip diameter. This shows that the increase in nasal NO during humming in vivo and in the presence of oscillating airflow is dependent on sinus ostia size. Also sinus NO concentration and buzzing frequency show the effect on sinus ventilation. Some other factors may also affect the rate of exchange between the two chambers.

Unexpectedly, topical administration of a NOS inhibitor in the nose reduced nasal NO output by more than 50% during silent breathing, but had NO effect on the increase in nasal NO during humming. This again confirms the assumption that this increase is due to increased ventilation of the sinuses which the local nasal spray cannot reach. The inventors cannot exclude that the buzzing increased NO release also comes from other sources in the nose. For example, oscillating gas flow may generally increase the release of dissolved NO in epithelial cells and liquid linings (linnings). However, as shown in the test below, the proposed method may start with repeated beeps to empty the sinuses, followed immediately by silent nasal exhalations and NO measurements. Thus sinus supply of nasal exhaled NO will be minimized, which will help reveal changes in nasal mucosal NO output.

Based on the above findings, both corroborated in vivo studies and in experimental devices, the inventors have provided an apparatus for use in upper respiratory examinations, in particular for monitoring the condition of one or more sinuses of a person, wherein said apparatus comprises means for generating and/or maintaining an oscillating airflow having a frequency, duration and flow rate sufficient to increase the ventilation of the sinuses, said apparatus being adapted to be connected to means for monitoring and recording the concentration and/or flow rate of a gas present in the exhaled air of said person. In a particular embodiment of the invention, the gas is endogenous NO.

In this context, the term "upper respiratory tract" is to be understood as referring to the respiratory tract located above the vocal cords, including the paranasal sinuses, nasal cavity, nasopharynx, upper pharynx, oropharynx, oral cavity and lower pharynx.

In this context, the term "nasal airways" is to be understood as referring to the airways from the nostrils to the nasopharynx.

In this context, the term "endogenous gas" is to be understood as referring to a gas produced in the human body.

In this context, an upper respiratory condition is to be considered to include the absence or presence of the following: inflammatory conditions, respiratory tract infections, common cold, tumors, drug related effects, anatomical abnormalities, ostial patency of sinuses, sinus size, biochemical condition of sinuses, sinusitis affecting one or more sinuses, the location of said sinusitis, the risk of developing sinusitis, the bacterial state of sinuses, or especially combinations thereof, which apparatus is useful in the diagnosis of sinus conditions, such as the presence or absence of pathological conditions affecting sinuses, and the location thereof, such as Primary Ciliary Dyskinesia (PCD) and Cystic Fibrosis (CF), nasal polyposis, allergic rhinitis, inflammatory conditions of the upper respiratory tract, common cold, or combinations thereof.

According to particular embodiments of the present invention, the means for generating and/or maintaining an oscillating airflow sufficient to enhance sinus ventilation is a means for electronically or mechanically generating the airflow.

Preferably, the device is adapted for unilateral measurement, i.e. measuring the effect of the oscillating airflow on the gas exhaled through the nose in one naris. This may be achieved by using nasal plugs, by blocking one nostril when measurements are taken in the other nostril, or by blocking the other nostril when using a mask.

According to another embodiment, the means for generating and/or maintaining an oscillating airflow is a means capable of recording the duration, frequency and/or volume of the oscillating airflow generated by the patient, e.g. by a beeping action, comprising a feedback mechanism, e.g. indicating to said patient that a predetermined required duration, frequency, flow and/or volume has been reached.

According to a particular embodiment of the invention, the oscillating airflow is oscillated at a frequency of 1-1000Hz, preferably 10-1000Hz, more preferably 100-1000Hz, and most preferably 100-500 Hz.

In accordance with another embodiment of the present invention, the oscillating airflow oscillates at a frequency near the resonance frequency of the paranasal sinuses.

According to another embodiment of the invention, the air stream is inhaled from the upper respiratory tract and the aspirator is connected to a sound generator causing the air to oscillate.

According to a preferred embodiment of the invention, said apparatus is adapted to be connected to means for detecting and recording the concentration and/or flow of a first gas present in the expired air of a person and to means for supplying to said person a second respiratory gas containing no or only trace and/or known amounts of said first gas. Most preferably, the first gas is nitric oxide and the second gas is nitric oxide-free gas suitable for inhalation. An example of such an instrument is the NIOX ® NO analyzer (Aerocrine AB, Solna, Sweden).

The concentration and/or flow of other gases, endogenous or exogenous, may also be detected. Examples of such gases include Nitric Oxide (NO), nitrogen, oxygen, carbon dioxide, carbon monoxide and suitable inert gases such as argon or xenon.

Further embodiments include means for analyzing the NO time profile, i.e. a plot of concentration plotted against time and/or flow rate. This analysis will give information about the dynamics of the sinuses and is expected to make it possible to distinguish between degree and type of congestion, sinus volume, ostium diameter and to elucidate the potential pathology of sinus problems occurring in each particular patient examined. The absolute amount of exhaled gas (e.g., NO), and its changes over time, such as increases, decreases, associated peaks, slopes, and plateaus, will show anatomical and physiological differences. Additional or more accurate information can be obtained using patient data collected from many patients, or data collected from measurements made on the same patient at different times or with oscillating gas flows of different frequencies, flows and durations. Using this approach, the following anatomical and physiological differences may be shown:

sinus ostia size/patency

Volume of sinus

Sinus NO production

-NO absorption

The invention also provides a method of examining the condition of the upper respiratory tract of a human, in particular the sinus or sinuses of a human, wherein the concentration and/or flow of at least one gas component in the gas exhaled through the nose is determined and recorded in the presence and absence of an oscillating gas flow.

According to a particular embodiment of the invention, the oscillating airflow in the inspection method has an oscillation frequency of 1-1000Hz, preferably 10-1000Hz, more preferably 100-1000Hz, most preferably 100-500 Hz.

According to another embodiment of the invention, the oscillating airflow is oscillated at a frequency near a resonance frequency of the paranasal sinuses during the examination.

According to another embodiment of the invention, in the examination method a flow of air is inhaled from the upper respiratory tract and the aspirator is connected to a sound generator causing an oscillation of the air.

According to a particular embodiment of this method, the condition of the upper respiratory tract includes the absence or presence of: an inflammatory condition, a respiratory infection, a common cold, a tumor, a drug-related effect, an anatomical abnormality, a sinus ostial opening, a sinus size, a biochemical state of the sinus, sinusitis affecting one or more sinuses, a location of said sinusitis, a risk of developing sinusitis, a bacteriological state of a sinus, or a combination thereof. The present invention is particularly useful for detecting sinus conditions, such as the presence or absence of pathological conditions affecting the sinuses, such as Primary Ciliary Dyskinesia (PCD) and Cystic Fibrosis (CF), nasal polyposis, allergic rhinitis, inflammatory conditions of the upper respiratory tract, the common cold, or a combination thereof. The present invention thus provides methods for use in the diagnosis of any of these or related conditions/diseases.

According to another particular embodiment of this method, the condition of the upper respiratory tract is determined on at least two occasions, before or after administration, or before or after a therapeutic intervention is performed, and the result is used to evaluate the effect of said drug or intervention.

The oscillating airflow necessary for measurement can be obtained by causing a person performing a test or examination to simulate the oscillating airflow generated by a buzzer by generating the oscillating airflow. In this case it may be necessary to include a feedback function, i.e. to record the duration, frequency, flow and/or volume of this oscillating airflow generated by the patient and to prompt the patient when a preset required duration, frequency, flow and/or volume has been reached.

The oscillating airflow may also be generated manually and act directly on the upper airway or a part thereof, such as the sinus or sinuses.

According to a particular embodiment of the method according to the invention, the concentration and/or flow of a first gas present in the expired breath of a person is determined while a second breathing gas is provided to said person which does not contain or only contains traces and/or known amounts of said first gas. Preferably, the first gas is nitric oxide and the second gas is a nitric oxide free gas suitable for inhalation. An example of an instrument suitable for performing these functions is NIOX^®NO analyzer (Aerocrine AB, Solna, Sweden).

The method also includes determining the concentration and/or flow of other gases, endogenous or exogenous. Examples of such gases include Nitric Oxide (NO), nitrogen, oxygen, carbon dioxide, carbon monoxide and suitable inert gases such as argon.

A further embodiment comprises the step of analyzing the NO time profile, i.e. a plot of concentration versus time and/or flow rate. This analysis will give information about the dynamics of the sinuses and is expected to make it possible to distinguish between degree and type of congestion, sinus volume, ostium diameter and to elucidate the potential pathology of sinus problems occurring in each particular patient examined. The absolute amount of exhaled gas (e.g., NO), and its changes over time, such as increases, decreases, associated peaks, slopes, and plateaus, will show anatomical and physiological differences. Additional or more accurate information can be obtained using patient data collected from many patients, or data collected from measurements made on the same patient at different times or with oscillating gas flows of different frequencies, flows and durations. Using this approach, the following anatomical and physiological differences may be shown:

sinus ostia size (open case)

Volume of sinus

Sinus NO production

-NO absorption

Using the two-chamber model, in vivo measurements in the presence of oscillating airflow and measurements during silent nasal exhalation yielded a comparison of the curves. It can be seen that in the two-chamber model, the concentration of NO decreased because NO new NO was produced in the syringe simulating the sinus (results not shown). In vivo experiments, the curves show similar increases and peaks (fig. 1), although these values vary among patients tested. However, due to the supplementation of NO in the sinuses, the reduction was less and there was a variation between subjects in the slope of the curve and the plateau values reached.

This test has the obvious advantages of being non-invasive, rapid and objective. It is also of interest to study whether measurements during humming can be used to get more information on the condition of the upper airways and e.g. to better distinguish between patients with nasal disease and healthy control nasal NO release. The sputum disease includes, for example, CF, PCD, nasal polyposis, and allergic rhinitis.

Examples

1. In vivo measurements

1.1 healthy controls

Characterization of nasal NO during buzzing

Ten healthy, non-smoking volunteers (age 25-47 years, 6 males) were recruited without any history of allergy, nasal disease, asthma or any other chronic lung disease. Using chemiluminescent systems (NIOX)^®Aerocircle AB, stockholm, sweden) measures respiratory NO output, and this system is designed to comply with ATS guidelines for exhaled NO (american third society, am J Respir Crit Care Med 1999; 160: 2104-17). The analyzer was calibrated with a standard gas mixture of NO (987ppb, AGA AB, sweden). NO levels were measured during a single exhalation of the mouth and nose. Nasal measurements were performed with a close fitting mask covering the nose and oral exhalations were performed using a mask. The subject inhales via noseNO air to start each action and exhale at a fixed flow rate (0.2L/s) for 10 seconds either silently or under nasal beeping or mouth sounding conditions. The fixed flow rate is achieved by a dynamic flow restrictor in an analytical system that is integrated with a computerized visual feedback display of the flow. Dynamic flow restrictors use a flexible membrane valve to mechanically regulate flow rate and maintain exhalation at 0.20L/s, over a wide range of exhalation pressures with minimal variation.

Nasal NO output during humming was calculated by subtracting the values obtained during silent nasal exhalations as described earlier (Lundberg et al, Thorax 1999; 54: 947-. During the last 80% of expiration, NO release was calculated as mean output (n 1/min).

To investigate whether beeps can deplete the NO source, subjects performed five consecutive beeps at different time intervals (5 seconds, 1 minute, and 3 minutes) between each beep. Repeated silent nasal exhalations were also performed at 5 second intervals. Based on the results obtained from the continuous beeping action (see below), all other beeps in this study were followed by a 3 minute silent period.

Effect of NO synthase inhibition

Nasal and oral NO measurement baselines were established during beeping and silent exhalation in six subjects. NG-L-arginine methyl ester (L-NAME) (Sigma, Poole, UK.) in 2.5ml of physiological saline was then delivered randomly through both nostrils by a jet nebulizer (Devilbis, Somerset, PA, USA) 15mg (2.2mM) of solution or saline alone and NO measurement repeated for 20 minutes after application of the solution.

Influence of flow, pressure and frequency during humming

To compare the results obtained with the above model with the in vivo situation, we performed additional experiments on five subjects. They are asked to be at no resistance or at 50cmH₂O L^-1 s^-1Under resistance at two fixed flow rates (0.20 and 0.25L/s) with silent or nasal beeping orBreath was sequentially for 10 seconds under mouth-sounding conditions. Then a nasal beep is performed at three different sound frequencies. The frequency was recorded using a microphone attached to the neck of the subject. During full expiration, NO output is calculated from the average concentration.

Results

In all buzzing experiments, a progressive decrease was observed after the initial NO peak (fig. 1). The total nasal NO output increased during humming (from 471 + -73 nL/min during silent expiration to 2233 + -467 nL/min during humming; P < 0.001) when compared to silent expiration (FIG. 1). During silent expiration, the expired NO through the mouth is 144 + -20 nL/min, and during buzzer, the expired NO through the mouth is 152 + -20 nL/min (P is 0.22).

The NO output measured during 5 single breath beeps was very similar at 3 minute intervals during each beep, indicating less than 15% variability in the individual. At 1 minute intervals, the inter-individual variability was close to 70%. At 5 second intervals, NO progressively decreased after each stroke until a plateau of 571 ± 88 nL/min was reached, compared to a level of 2233 ± 467 nL/min with p ═ 0.002 (fig. 2) during the first beep. For all subjects, a low plateau was reached within four nasal beep maneuvers. In contrast, five consecutive silent nasal exhalations at 5 second intervals did not affect NO output (fig. 3). However, the silent nasal NO output recorded immediately after repeated beeping events was lower than the basal silent NO of all subjects (261 ± 33 nL/min vs 384 ± 39 nL/min; p ═ 0.021). Silent nasal NO decreases were significantly different, between 5-50%, after consecutive beeps. After topical application of L-NAME, the silently exhaled nasal NO levels decreased by more than 50%, from 392. + -. 33 nL/min to 194. + -. 24 nL/min; p is 0.002 (fig. 4). In contrast, the increase in NO output induced by beeping was unaffected (2417 ± 894 nL/min before L-NAME administration versus 2368 ± 811 nL/min after L-NAME administration, p ═ 0.77).

An increase in expiratory rate from 0.20 to 0.25L/s during a beep resulted in a higher nasal NO output (increase from 807 + -172 to 1074 + -197 nL/min, p < 0.05).

Changes in beep frequency also affect nasal NO output. NO levels were 940. + -. 77 nL/min at 130Hz, 807. + -.77 nL/min at 150Hz and 719. + -.58 nL/min at 450Hz (p < 0.05). During the beeping, the higher the nasal pressure, the higher the NO output (from 1cm H)₂O807 + -77 nL/min to 10cm H₂At O, 932. + -. 26 nL/min, p > 0.05).

1.2 sinus volume

The preliminary study included two healthy subjects, whose sinus volumes were pre-recorded. Levels of NO exhaled through the nose were determined during silent breathing and during humming using the standardized chemiluminescent system described above (NIOX ®, aerocine AB, solana, stockholm). The NO values recorded during silent breathing are very similar. The peak NO values for subjects with larger sinus volume (about 1500ppb) were much higher than the peak NO values for subjects with smaller sinus volume (300 ppb). Subjects with larger sinus volumes had slower reduction in NO values. These results indicate that analysis of the peaks, slopes and plateau values gives information on the anatomical and physiological characteristics of the upper respiratory tract, especially the sinuses. (results not shown)

1.3 sinus problem correlation

Ten healthy non-smoking subjects (age 25-52 years, 5 males) without any history of allergy or chronic respiratory disease and 10 patients with chronic sinusitis and nasal polyposis (age 30-56 years, 5 males) participated in this study. At the time of the study, none of the control groups had any progressive respiratory infection. Patients have been listed on the waiting list for sinus surgery. All patients had bilateral polyps and completely opaque sinuses as per the previous CT scan. All patients were treated with nasal corticosteroids, three patients had concomitant asthma and four patients were intolerant to aspirin. NO in a single breath of the nose was measured using a chemiluminescent system, developed in accordance with the principles of ATS guidelines for exhaled NO measurement (aerocircle AB, stockholm, sweden). The nose was covered with a close fitting mask and the subject was allowed to exhale through the nose at a fixed flow rate (0.10l/s) for 10 seconds, with no sound or beeping, with the mouth closed. During the last 80% of expiration, NO levels were calculated as mean output (nl/min). Expiratory flow rate was monitored and changes were minimized (< 0.02 l/s).

Results

During silent exhalation, nasal NO was similar for control and patient (189. + -.27 nl/min vs 162. + -.22 nl/min). During humming, control nasal NO increased 7-fold (to 1285 + -189 nl/min), but remained completely unchanged in patients (169 + -21 nl/min, FIG. 5).

It shows that there is NO increase in nasal NO during humming in patients with sinusitis at all. The most likely explanation is the lack of an airway between the sinuses and nasal cavity. Interestingly, during this study, one patient underwent surgery, after two weeks, when nasal NO increases during humming nearly reached normal levels (data not shown).

2. Biventricular model study-sinus/nasal model

Description of the model

NO output was measured in a two-chamber model simulating the nasal cavity and one sinus (fig. 6). The syringe (representing the sinus) was filled with various concentrations of NO gas (AGA AB, sweden) from 2 to 10ppm and horizontally connected to a plastic cylinder (representing the nasal cavity) by means of a Luer fitting. The diameter of the syringe tip (representing the sinus ostium) was 0.8-4.0 mm. The volume of the syringe is 5-20 ml. Distal opening of cylinder (nasal cavity) or 50cmH₂O L^-1 s^-1The Hans Rudolph resistor thus producing 1 or 10cmH₂Cylinder pressure of O. Flow and pressure were measured by linear pneumotachymeter (hans Rudolph inc). The resulting NO levels were measured by a fast response chemiluminescence system (aerocircle AB, stockholm, sweden) at the distal end of the cylinder. The signals output from these devices are connected to a computer-based system (aerokrine NO, aerokrine AB, stockholm, sweden) to obtain the instantaneous flow, pressure on a screenNO concentration and NO output.

Artificial generation of buzzes in a model

The pressurized NO-free air was set to produce three different flow rates (0.20, 0.25 and 0.30L/s). Air was passed through a plastic cylinder (nasal cavity), or via a rubber duck horn (Hudson & Co, UK) which produced a pulsating air flow, or via a rubber duck horn without a sound producing membrane (silent control). Three duckling sounds (120, 200 and 450Hz) with different fundamental frequencies were used. NO was measured over a ten second period and all experiments were repeated five times. In an additional experiment, turbulence was created by passing pressurized NO-free air through a plastic mesh attached to a cylinder and measuring NO as described above. The test was carried out without a sound generating device.

In further experiments, we investigated the effect of three different beeping frequencies (120, 200 and 450Hz) on NO output from sinuses with different resonance frequencies.

Human beeps in a model

In the same model, oral exhalations by the subject through the cylinder also produced pulsatile airflow with two fixed flow rates (0.20 or 0.25L/s) and three different frequencies (130, 150 or 450Hz) with or without sound. Oral NO output was subtracted from total breath (10 seconds) to calculate NO output. All experiments were repeated 5 times. To estimate the gas exchange rate between the two chambers, we also measured the remaining NO concentration in the injector at the end of each experiment.

Artificial and human beep frequency measurement

The audio signal was obtained by TCM110 Tiepin electret condenser microphone placed on the plastic cylinder in the model (fig. 6) and recorded directly on PC by soundwell signal workstation. The fundamental frequency is extracted by its Corr module, which calculates the autocorrelation of the audio signal in two adjacent time windows. The mean fundamental frequency and standard deviation were then determined from their histogram moduli.

The resonant frequencies of the model systems were calculated according to Durrant and Lovirinic (Bases of Hearing Science, 3 rd edition, Williams and Wilkins, Baltimore, 1995: 60).

Results

In the standard settings of the model, we used a fixed flow rate of 0.2L/s, NO concentration of 8ppm, 1cmH₂Pressure of O, syringe volume of 15ml, sinus ostia size of 1.9mm and buzzer frequency of 200 Hz. The resonant frequency of this system was calculated to be 200 Hz. When one parameter in the experiment was changed, all other values remained constant.

In all experiments with this model, both manual and human beeps caused an increase in NO output compared to silent expiration. When artificial beeping was used in the model, the NO output increased > 10-fold, from 23.7 + -0.1 nL/min at silent airflow to 295 + -4.5 nL/min during beeping (p < 0.05). When the subject buzzed in the model, NO output increased from 27.7. + -. 0.1nL/min at silent expiration to 175. + -. 8nL/min (p < 0.05). When turbulent flow was used, NO difference in NO output was seen in the model compared to non-turbulent flow (25.2. + -. 0.2nL/min and 23.7. + -. 0.1nL/min, respectively).

Effect of ostium size

Ostia diameters of 0.8, 1.29, 1.9, 2.1 and 4.0mm were used. At larger ostium sizes, NO output increased during humming (fig. 7). When the sinus ostium size ratio is 1: 1.6: 2.4: 2.6: 5, the NO output ratios in human and artificial models are 1: 4.5: 6: 14: 30 and 1: 8: 13: 15: 39, respectively. As an estimate of the gas exchange rate in the sinuses, the remaining NO concentration in the injector was measured immediately after expiration (fig. 7). We found that NO concentration in the injector did not change significantly after silent exhalation regardless of sinus ostium size. In contrast, the gas exchange during humming is highly dependent on the sinus ostia size, reaching almost 100% when it is the largest sinus ostia (fig. 7).

Influence of the buzzer frequency

We found that in all experiments, NO output was significantly changed by changing the beep frequency. When the artificial buzzer was used in the model, the NO output was 230. + -. 5.7nL/min at a frequency of 120Hz, 295. + -. 3.4nL/min at a frequency of 200Hz, and 143. + -. 2.0nL/min at a frequency of 450Hz (p < 0.05, FIG. 8).

In the human buzzer model, the NO level is 204 ± 11nL/min at a frequency of 130Hz, 175 ± 8nL/min at a frequency of 150Hz, and 143 ± 2nL/min at a frequency of 450Hz (p < 0.05, n ═ 5). When studying the effect of different beeping frequencies on NO output from injectors with different resonance frequencies, we found that NO output was maximal when the beeping frequency was close to the resonance frequency of a particular sinus (table I).

TABLE I influence of buzzer frequency on NO output (nL/min) when using sinusoids with different resonance frequencies in the model

Buzzing frequency	Sinus resonance frequency
			120Hz	200Hz
	120Hz	1043±10			527±5.8
200Hz			561±8.3	611±7.7
	400Hz	286±6.3			418±8.1

Effect of syringe volume

Tables II and III show the results after beeping when sinus ostia size, NO concentration, flow and resistance were kept constant as per the standard settings. Syringe volumes of 5, 10, 15 and 20ml were used. When the sinus volume ratio is 1: 2: 3: 4, the ratio of NO levels in the artificial buzzer model is 1: 2.5: 5: 7, and the ratio of NO levels in the human buzzer model is 1: 2: 4: 5.5.

Effect of injector NO concentration

Tables II and III show the effect of injector NO concentration during humming. The NO concentrations used were 2, 4, 8 and 10 ppm. When the ratio of the concentration of the injector NO is 1: 2: 4: 5, the ratios of the levels of NO in the artificial and human buzzer models are 1: 2.1: 4: 5.5 and 1: 2: 3: 7, respectively.

Influence of the airflow Rate

The results relating to NO output at different nasal airflow rates during humming are shown in tables II and III. When the ratio of the airflow rates is 1: 1.25: 1.5, the ratios of NO levels in the artificial and human buzzer patterns are 1: 1.25: 1.4 and 1: 1.5: 2, respectively.

Table ii influence of sinus volume, sinus NO concentration and flow rate on NO levels induced by artificial pulsatile airflow in nasal and sinus models (see methods for details). P < 0.05

		Artificial buzzer
			NO output (nL/min)
		Sinus volume		5ml	79±1.0
10ml	159±4.5*
			15ml	295±3.4*
20ml	427±3.7*
			Concentration of NO	2ppm	76±1.5
4ppm	162±2.8*
		8ppm		295±3.4*
10ppm	434±6.1*
		Flow rate		0.20L/s	295±3.4
0.25L/sec	369±5.8*
			0.30L/s	411±7.6*

Table iii influence of sinus volume, sinus NO concentration and flow rate on NO levels induced by pulsatile airflow in the nose and sinus model (see methods for details). P < 0.05

		Human buzzer
			NO output (nL/min)
		Sinus volume		5ml	79±1.0
10ml	87±3.6*
			15ml	175±8.0*
20ml	242±14.7*
			Concentration of NO	2ppm	57±8.1
4ppm	118±14.6*
		8ppm		175±8.0*
10ppm	416±32*
		Flow rate		0.20L/s	175±8.0
0.25L/sec	268±4.8*
			0.30L/s	356±10*

Influence of pressure

In the artificial buzzer model, we found that during buzzer, the NO output increases with higher pressure (from 175 + -8 nL/min to 377 + -22 nL/min). In the human buzzer model, we found that NO output decreased (from 250. + -. 3.4nL/min to 140. + -. 1.9nL/min) when pressure was increased.

3. Statistics of

The NO output for all sampling modes was calculated as the concentration of flow xNO. Two-sided p-value nonparametric statistics were used. Paired data were analyzed using the friedman test and the Wilcoxon test. p values less than 0.05 are considered significant. Results are given as mean ± SEM.

Discussion 4

Large and reproducible increases in nasal NO caused by buzzes on healthy subjects and in nasal and sinus models have been depicted. The beep method gives information about NO from the nose and sinuses and the relative supply of ostia opening. Many factors strongly suggest that the increase in NO seen during humming is due to the rapid clearance of NO accumulated in the paranasal sinuses. The nasal exhalation profile (peak and progressive decline) in the model was very similar to that in the human study, and the factors affecting NO levels were the same. After repeated successive beeps, both the peak and total nasal NO output decreased significantly, and complete recovery was observed after 3 minutes of silence. This mode again demonstrates the idea that beeping empties the sinuses, and silence over time causes NO to accumulate again. Topical administration of a NOS inhibitor (L-NAME) in the nose reduced nasal NO levels by 50% when silent, but had NO effect on the increase during humming. Given that this route of administration affects mainly the nasal mucosa with little access to the sinuses, this also supports the sinus origin of nasal NO during humming.

Sinus ostia size appears to be the most important factor affecting nasal NO increase during humming. Sinus NO concentration and buzzing frequency also affect sinus ventilation. Interestingly, buzzing frequency affected sinus output in both models and healthy volunteers. These preliminary experiments have shown that ventilation of the sinuses in the model is maximal when the buzzing frequency is close to the sinus model resonance frequency.

By observing the residual NO in the injector after a single exhalation in the test, it is evident that buzzing is a very effective means of increasing sinus ventilation. This is also supported by in vivo experiments in which a rapid decrease in NO during humming indicates sinus emptying. These results show that if the subject buzzes, almost all sinus volume is exchanged in one exhalation. Even when a small ostium diameter is used, buzzing is very useful for sinus ventilation in the model used. This suggests that buzzing can help increase sinus ventilation in patients with sinusitis and partial blockage of the ostia.

In this study, silent nasal NO levels decreased by 5-50% shortly after repeated beeps. If we assume that this action effectively empties the sinuses, this decrease can be quite well reflected in the normal sinus to NO supply in the exhaled air through the nose. It is important to note, however, that this assumption is only correct under the precise conditions of the present study. Using the methods described herein, it may be possible to better distinguish sinus NO from nasal mucosal NO release.

While the present invention has been described with respect to the preferred embodiments, which constitute the best modes known to the inventors at the present time, it should be understood that variations and modifications as would be obvious to one skilled in the art may be made without departing from the scope of the invention as set forth in the claims below.

Claims (14)

1. An apparatus for diagnosing a condition of the upper respiratory tract of a human, characterized in that said apparatus comprises means for generating and/or maintaining an oscillating airflow in said upper respiratory tract or a part thereof, and said apparatus is adapted to be connected to means for determining and recording the concentration and/or flow of endogenous NO present in the exhaled breath of said human, wherein the condition of the upper respiratory tract is absent or present: an inflammatory condition, a respiratory infection, a common cold, a tumor, a drug-related effect, an anatomical abnormality, a sinus ostial opening, a sinus size, a biochemical condition of the sinus, sinusitis affecting one or more sinuses, a location of said sinusitis, a risk of developing sinusitis, a microbiological condition of the sinuses, or a combination thereof.

2. An apparatus according to claim 1, wherein the means for generating and/or maintaining an oscillating airflow comprises means for electronically or mechanically generating said airflow.

3. An apparatus according to claim 1, wherein the means for generating and/or maintaining an oscillating airflow comprises means for recording the duration, frequency and/or volume of the oscillating airflow generated by the patient, in connection with means for indicating to said patient that a predetermined required duration, frequency and/or volume has been reached.

4. An apparatus according to claim 1, wherein the oscillating airflow oscillates at a frequency of 1 to 1000 Hz.

5. An apparatus according to claim 1, wherein the oscillating airflow oscillates at a frequency of 10 to 1000 Hz.

6. The apparatus according to claim 1, wherein the oscillating airflow oscillates at a frequency of 100-1000 Hz.

7. The apparatus according to claim 1, wherein the oscillating airflow oscillates at a frequency of 100-500 Hz.

8. An apparatus according to claim 1, wherein the oscillating airflow oscillates at a frequency close to the resonance frequency of the paranasal sinuses.

9. An apparatus according to claim 1 wherein the apparatus comprises means for unilaterally diagnosing an abnormal condition affecting only the right or left hand side of the nasal airway including the paranasal sinuses.

10. Apparatus for diagnosing the condition of the upper airways of a human, characterized in that it comprises means for generating and/or maintaining an oscillating airflow in said upper airways or parts thereof, and means for determining and recording the concentration and/or flow of a first gas present in the exhaled breath of said human, and means for supplying to said human a second respiratory gas which does not contain or contains only minute and/or known amounts of said first gas.

11. An apparatus according to claim 10, wherein said first gas is nitric oxide and said second gas is a nitric oxide-free gas suitable for inhalation.

12. An apparatus according to claim 10, wherein the apparatus is adapted to be connected to a device for measuring and recording the concentration and/or flow rate of the tracer gas.

13. An apparatus according to claim 10, wherein the apparatus is adapted to be connected to a device for measuring and recording the concentration and/or flow rate of a tracer gas, said tracer gas being an endogenous gas.

14. An apparatus according to claim 10, wherein the apparatus is adapted to be connected to a device for measuring and recording the concentration and/or flow rate of a trace gas, the trace gas being an exogenous gas.