Tidal Breathing Method Research Articles

Standard technical specifications for methacholine chloride (Methacholine) bronchial challenge test (2023)

Standard technical specifications for methacholine chloride (Methacholine) bronchial challenge test (2023)

Use of a Nasal Cannula as a Preoxygenation Adjunct: A Randomized Crossover Study.

Preoxygenation prior to induction of general anesthesia is intended to increase the oxygen reserve in the lungs. This technique delays the onset of hypoxemia during the placement of the tracheal tube. To observe the benefits of oxygen through nasal cannula when used as an adjunct during preoxygenation. We enrolled 30 healthy volunteers and conducted a sequence of six preoxygenation tests. These included 3-minute tidal volume breathing and 8 vital capacity breaths, with and without oxygen flowing through the nasal cannula as an adjunct. Subjects were kept at a supine position with a face mask on their faces. Their baseline vitals were measured and end-tidal O2 (ETO2) was recorded at the end of each test. The comfort of each technique was also assessed. When comparing the efficacy of the two preoxygenation methods, we found that the addition of oxygen through the nasal cannula improved the efficacy of preoxygenation with both the 3-minute tidal volume breathing method and the 8 vital capacity method (p < 0.001). The three-minute tidal volume breathing technique had higher end-tidal oxygen when compared to the eight vital capacity breaths. The administration of oxygen through a nasal cannula during preoxygenation improves the efficacy of preoxygenation in healthy volunteers. Tidal volume breathing for three minutes achieves a higher end-tidal oxygen concentration compared to eight vital capacity breaths over one minute.

THE RELATIONSHIP AMONG BRONCHIAL HYPERSENSITIVITY, BRONCHIAL HYPER REACTIVITY, AND BRONCHIAL HYPERRESPONSIVENESS IN ASTOGRAPH

Bronchial hyperresponsiveness testing is useful for diagnosing and predicting the risk of bronchial asthma attacks. The Astograph is a tidal breathing method often used in as bronchial provocation testing in Japan. The minimum methachorine dose (Dmin) indicates bronchial sensitivity and is used mainly as an index of bronchial hyperresponsiveness. However, Dmin does not measured hyperresponsiveness, it cannot be compared directly with PC20 in standard methods using FEV1. We investigated the relationship among sensitivity, reactivity, and hyperresponsiveness with the Astograph. We recruited 142 patients with confirmed or suspected bronchial asthma from outpatient clinic at St. Marianna University School of Medicine, Yokohama City Seibu Hospital. We calculated Dmin, SGrs/Grscont, PD35Grs, and PD15Grs compared them as bronchial hyperresponsiveness indices. Subjects had suspected asthma (n=103), or required assessment of asthma remission (n=39). There were significant relationships between logDmin and logPD35Grs (r=0.838, p<0.001), and between parameters and SGrs/Grscont (log PD35Grs r=-0.504, p<0.001, strong, logDmin: r=-0.191, p=0.023, weaker). Among subjects positive for hypersensitivity, (Dmin<10), 38 (36.5%) showed negative hyperresponsiveness (PD35Grs>25). PD15Grs was a strongly and significantly correlated with Dmin and PD35Grs. The ROC curve to detect PD35Grs<25, showed that the cutoff of PD15Grs was 10.7 (AUC 0.983, sensitivity 0.984, specificity 0.905). In Astograph, evaluation of bronchial hyperresponsiveness, we focused on relationship differences between sensitivity and reactivity, and hyperresponsiveness. We revealed the usefulness of the PD15Grs evaluation method.

Exhaled-breath Temperature And Spirometer Airflow Dynamics Following Cold-water Ingestion In Healthy Subjects

PURPOSE: Ingesting cold-water evokes decreases in spirometric indices of pulmonary function. However, given that most commercial spirometers assume an exhaled-breath temperature (EBT) of 37 °C, a cold-water-induced decrease in EBT may influence the accuracy of flow-volume measurements. Accordingly, the aims of this study were: i) to assess whether cold-water ingestion was sufficient to reduce EBT in healthy subjects; and ii) to model the influence of EBT on pneumotachograph airflow dynamics. METHODS: Ten healthy, recreationally-active adults (5 male, 5 female), with normal pulmonary function, volunteered to participate (age=36±7 y; mass=87.4±31.8 kg; stature=1.74±0.8 m). In a randomized crossover design, subjects consumed either 1000 mL of refrigerated water (2.1±0.64 °C) or water at room temperature (19.4±0.5 °C), with exhaled-breath temperature assessed (via the tidal breathing method) at baseline and at 5, 10, 15, and 30 min post-ingestion. The influence of exhaled-breath temperature on the measurement characteristics of a non-heated pneumotachograph, was modelled using computational fluid dynamics (CFD). RESULTS: Baseline EBT was not different between the two conditions (33.8±0.4 vs. 33.7±0.54 °C; p=0.269, d=0.25). Following the ingestion of cold-water, EBT fell below baseline and remained so until the final measure at 30 min (p<0.01). When compared to water at room temperature, EBT was significantly lower following the ingestion of cold-water at 5 min (31.7±1.1 vs. 33.0±0.9 °C; p<0.001, d=1.34), 10 min (32.6±0.6 vs. 33.2±0.6 °C; p<0.001, d=1.06), and 15 min post-ingestion (32.5±0.6 vs. 33.3±0.5 °C; p<0.001, d=1.46). A mean decrease in EBT of 2.1 °C (as observed acutely following cold-water ingestion) was modelled to under-predict flow by 0.84% and volume by 0.78%. CONCLUSIONS: Cold-water reduces exhaled-breath temperature for at least 30 min post-ingestion, and to a greater extent than water at room-temperature. The mean decrease in EBT resulted in a negligible effect on calculated flow-volume variables. Accordingly, a measured change in lung function that follows cold-water ingestion likely has a physiological explanation which warrants further study. These data may also have implications for the clinical assessment of EBT in monitoring pathological processes of the airway.

Methacholine Challenge Testing: A Novel Method for Measuring PD20

New guidelines for methacholine challenge testing recommend reporting the test outcome as dose rather than concentration. Jet nebulizers have historically been used for methacholine challenge testing, but much of the weight loss, often (incorrectly) referred to as aerosol output, is actually evaporation. The Wright nebulizer is well characterized and still widely used, but its availability is unclear, and it is nondisposable. We developed a novel method using a vibrating mesh nebulizer (Solo). This method was compared with the standard 2-min tidal breathing method using the Wright nebulizer. Repeatability within and between nebulizers was also tested. Fifteen patients with mild asthma completed four methacholine challenges (two with the Solo vibrating mesh nebulizer and two with the Wright jet nebulizer). Challenges with the same nebulizer were 24h apart, and challenges between nebulizers were separated by 1week. Standard 2-min tidal breathing methods were used with the Wright nebulizer. For the Solo nebulizer, the tidal breathing method was modified by nebulizing to completion 0.5mL of doubling concentrations of methacholine at 5-min intervals. Geometric mean methacholine doses required to cause a 20%fall in FEV1 were similar (96 vs110 μg; P > .05); methacholine concentrations that caused a 20%fall in FEV1 were significantly lower with the vibrating mesh nebulizer (0.48 vs4.4mg/mL; P< .001). Repeatability of methacholine doses required to cause a 20%fall in FEV1 within and between nebulizers was excellent (intraclass correlation coefficient > 0.92). We have developed a novel, simple, repeatable method for conducting methacholine challenges using new nebulizer technology. Importantly, the method meets recommendations set out in the new guidelines. ClinicalTrials.gov; No.: 02965482; URL: www.clinicaltrials.gov.

Does diurnal variation in cough reflex testing exist in healthy young adults?

The aim of this study was to investigate whether diurnal variation in cough reflex sensitivity exists in healthy young adults when a tidal-breathing method is used. Fifty-three participants (19–37 years) underwent cough reflex testing on two occasions: once in the morning (between 9 am – midday) and once in the afternoon (between 2–5 pm). The order of testing was counter-balanced. Within each assessment, participants inhaled successively higher citric acid concentrations via a facemask, with saline solution randomly interspersed to control for a placebo response. The lowest concentration that elicited a reflexive cough response was recorded. Morning cough thresholds (mean=0.6mol/L) were not different from afternoon cough thresholds (mean=0.6mol/L), p=0.16, T=101, r=−0.14. We found no evidence of diurnal variability in cough reflex testing. There was, however, an order effect irrespective of time of day, confirming that healthy participants are able to volitionally modulate their cough response.

Adenosine dry powder inhalation for bronchial challenge testing, part 2: Proof of concept in asthmatic subjects

Adenosine is an indirect stimulus to assess bronchial hyperresponsiveness (BHR2BHR: Bronchial hyperresponsiveness.2) in asthma. Bronchial challenge tests are usually performed with nebulised solutions of adenosine 5′-monophosphate (AMP3AMP: Adenosine 5′-monophosphate.3). The nebulised AMP test has several disadvantages, like long administration times and a restrictive maximum concentration that does not result in BHR in all patients. In this study, we investigated the applicability of dry powder adenosine for assessment of BHR in comparison to nebulised AMP. Dry powder adenosine was prepared in doubling doses (0.01–80mg) derived from the nebulised AMP test with addition of two higher doses. Five asthmatic subjects performed two bronchial challenge tests, one with nebulised AMP following the 2-min tidal breathing method; the second with dry powder adenosine administered with an investigational inhaler and single slow inhalations (inspiratory flow rate 30–40L/min). All subjects reached a 20% fall in FEV14FEV1: Forced expiratory volume in 1s.4 with the new adenosine test (PD205PD20: Provocative dose causing a 20% fall in the forced expiratory volume in 1s (FEV1).5) compared to four subjects with the AMP test (PC206PC20: Provocative concentration causing a 20% fall in the forced expiratory volume in 1s (FEV1).6). Dry powder adenosine was well tolerated by all subjects and better appreciated than nebulised AMP. In conclusion, this new bronchial challenge test appears to be a safe and convenient alternative to the nebulised AMP test to assess BHR in asthmatic subjects.

Developing Alternative Delivery Systems for Methacholine Challenge Tests

The two American Thoracic Society recommended aerosol delivery devices for methacholine challenge testing are both obsolete and often very difficult to acquire, leading to the test being done with a number of nonstandardized nebulizers. Of the two recommended devices, one is the English Wright nebulizer used in the 2-min tidal breathing method, and the other is the DeVilbiss 646 nebulizer used in the five-breath dosimeter method. The purpose of this study was to evaluate the in vitro performance of potential alternative devices that would be economically viable and would minimize environmental contamination. One device was the disposable breath-actuated AeroEclipse(®) II BAN as a potential delivery system for the 2-min tidal breathing, and the second was the automated system by VIASYS as an alternative to either the 2-min tidal breathing or the five-breath dosimeter method. A breath simulator mimicked an adult or small child breathing pattern, and a slow inhalation for the five-breath method was generated by a spirometry calibration syringe. Methacholine (Provocholine™) was eluted from filters at the "mouth" and assayed by high-pressure liquid chromatography. In 12 sec, the AeroEclipse II BAN would be expected to have a pulmonary deposition equivalent to the 2-min tidal breathing with the English Wright, whereas the VIASYS system would take approximately 40 sec for the equivalent delivery. The per-breath delivery of the VIASYS and the DeVilbiss 646 was approximately the same, whereas one breath from the AeroEclipse II BAN was the equivalent of five from the DeVilbiss 646. These data will allow for planning in vivo studies to develop methacholine challenge protocols using modern aerosol delivery systems.

Reference values of exhaled nitric oxide in healthy children 1–5 years using off‐line tidal breathing

Measurement of the fraction of exhaled nitric oxide (FeNO) is a useful test to diagnose and/or monitor eosinophilic airway inflammation. The off-line tidal breathing method is used for measurements in young children, but reference values for preschool children are scarce. The objective of this study was to establish reference values for FeNO in healthy children 1-5 years old. We included 51 healthy children (23 males), mean age 32.5 months, from the general population and measured FeNO, using an off-line tidal breathing method with a chemiluminescence analyzer. The method proved feasible in 100% of the children. Geometric mean FeNO was 7.1 parts per billion (ppb), 95% confidence interval 2.8-11.5 ppb, with the 95th percentile 22.6 ppb. No significant difference was found between boys and girls, and no correlations were observed between FeNO and age, height, or weight. This study demonstrates that the off-line tidal breathing method is feasible to measure FeNO in preschool children and provides reference values of FeNO in healthy children 1-5 years of age.

Bronchial hyperresponsiveness in an adult population in Helsinki: decreased FEV1, the main determinant

IntroductionBronchial hyperresponsiveness (BHR) elevates the risk for development of respiratory symptoms and accelerates the decline in forced expiratory volume in the first second (FEV1). We thus aimed to assess the prevalence, determinants and quantity of BHR in Helsinki.ObjectivesThis study involved 292 randomly selected subjects age 26–66 years, women comprising 58%.MethodsFollowing a structured interview, a spirometry, a bronchodilation test, and a skin-prick test, we assessed a bronchial challenge test with inhaled histamine using a dosimetric tidal breathing method. Results included the provocative dose inducing a decrease in FEV1 by 15% (PD15FEV1) and the dose-response slope. For statistical risk factor-analyses, the severity of BHR was considered; PD15 values ≤1.6 mg (BHR) and ≤0.4 mg [moderate or severe BHR (BHRms)] served as cut-off levels.ResultsBHR presented in 21.2% and BHRms in 6.2% of the subjects. FEV1 < 80% of predicted [odds ratio (OR) 4.09], airway obstruction (FEV1/forced vital capacity < 88% of predicted) (OR 4.33) and history of respiratory infection at age <5 (OR 2.65) yielded an increased risk for BHR as ORs in multivariate analysis. For BHRms, the determinants were decreased FEV1 below 80% of predicted (OR 27.18) and airway obstruction (OR 6.16). Respiratory symptoms and asthma medication showed a significant association with BHR.ConclusionsOf the adult population of Helsinki, 21% showed BHR to inhaled histamine. The main determinants were decreased FEV1 and airway obstruction. Quantitative assessment of BHR by different cut-off levels provides a tool for characterization of phenotypes of airway disorders in epidemiologic and clinical studies.Please cite this paper as: Juusela M, Pallasaho P, Sarna S, Piirilä P, Lundbäck B and Sovijärvi A. Bronchial hyperresponsiveness in an adult population in Helsinki: decreased FEV1, the main determinant. Clin Respir J 2013; 7: 34–44.

Cough frequency in health and disease

To the Editor: Chronic cough is a difficult clinical problem, partly because there is an absence of well-validated means to assess cough [1, 2]. We have previously reported that the semi-automated computerised Leicester Cough Monitor detects cough accurately over 6 h and that cough frequency is increased in patients with chronic cough compared to controls [3, 4]. There remains uncertainty on the performance of the system over 24 h and across the range of expected cough frequency in larger populations. We set out to address these questions in healthy adult volunteers and adult volunteers with respiratory disease. 44 healthy volunteers were recruited from those responding to a poster advertisement. All reported no current respiratory symptoms, were nonsmokers with a <5 pack-yr past smoking history and had normal spirometric values, methacholine airway responsiveness and induced sputum inflammatory cell counts. 78 patients with respiratory disease were recruited from respiratory clinics. The diagnostic criteria for the conditions have been described previously [5]. Six current smokers and four males taking angiotensin converting enzyme inhibitors (ACEi) were also recruited. The study was approved by the Leicestershire, Northampton and Rutland Research Ethics Committee. All volunteers underwent spirometry and those with normal spirometry had a methacholine inhalation test using the tidal breathing method. The Leicester Cough Monitor (iRiver iFP-799 mp3 device; iRiver Europe GmbH, Eschborn, Germany and Sennheiser MKE 2–5 field microphone; Sennheiser electronic GmbH & Co. KG, Wedemark, Germany) was attached and recordings obtained and analysed as …

Airway Responses to Deep Inspiration in Asthma by Different Bronchial Challenge

Objective: Deep inspirations (DI) provide physiologic protection against airway narrowing and DI-induced bronchoprotection and bronchodilation are impaired in asthma. Methods: To evaluate effect of DI on airway narrowing during methacholine challenge, we compared the 2 minutes tidal breathing method and the breath dosimeter method. Methacholine challenge in 12 asthmatics and 10 healthy controls was cross-overly performed by two methods. On first visit, a questionnaire for symptoms, allergy skin test, spirometry, and methacholine challenge was performed. On second visit, spirometry and methacholine challenge using the 25 mg/mL at 5 minutes intervals during the 2 minutes tidal breathing method and the ten-breath dosimeter method were performed on two separate days at same time each day. Results: The decreases in forced expiratory volume in one second (FEV1) and forced vital ca pacity during the 2 minutes tidal breathing method and dosimeter method in patients with asthmatics were higher than those in normal controls. The decreases in FEV1 and forced vital capacity during the 2 minutes tidal breathing method were higher than during dosimeter method in both asthmatics and controls. Conclusion: These observations indicate that the continuous generation method produce more bronchoconstriction than the dosimeter method during methacholine challenge and asthmatics had more bronchoconstriction than controls, suggesting inhibition of DI enhance methacholine induced airway narrowing in asthmatics.

Exhaled Nitric Oxide: Offline Tidal Breathing Measurements Are Feasible in Children and Correlate with Online Single Breath Measurements

Fractional exhaled nitric oxide (FENO) measurements are useful in monitoring airway inflammation. Online and offline sampling techniques are well standardized. However, young children are often unable to perform slow vital capacity maneuvers. The aim of this study was to compare a simplified mobile offline tidal breathing method with an online single breath measurement. We performed online and offline FENO measurements in children between 5 and 16 years with respiratory disease. Online measurements were performed by a slow vital capacity maneuver; offline measurements were performed by collecting exhaled air in Mylar balloons during tidal breathing. In 59 children (5.3–16.7 years) able to perform both techniques, a good correlation (0.9348) between offline tidal breathing and online single breath measurement was found over a wide range of values. Offline tidal breathing values correspond to online values. Online single breath FENO values can be predicted from offline tidal breathing FENO values. Offline tidal breathing measurements are highly correlated with online single breath values in children.

The effect of challenge method on methacholine-induced changes in sensitivity and air trapping

The methacholine challenge test performed with the tidal breathing method induces a greater fall in FEV(1) than the dosimeter method; however, the effect of the challenge method on methacholine-induced fall in FVC has not been investigated. To determine the influence of the challenge method on methacholine-induced changes in FEV(1) and FVC. Airway responsiveness to methacholine was determined by dosimeter method and tidal breathing method in 37 subjects with suspected asthma. The dosimeter was modified to deliver an identical volume to that obtained with the tidal breathing method and the same nebulizer model was used for the two challenges. The response was expressed by the provocative concentration of methacholine causing a 20% fall in FEV(1) (PC(20)) and by the percent fall in FVC at the PC(20) value relative to FVC after saline inhalation. The PC(20) values obtained with the tidal breathing method and the dosimeter method were similar, with geometric mean values of 3.15 (95%CI, 1.85-5.34mg/mL) and 2.51 (1.37-4.61mg/mL, P=0.092), respectively. The percent fall in FVC at the PC(20) value obtained with the dosimeter was significantly greater than that obtained with the tidal breathing method, with mean values of 11.8 (95%CI, 10.0-13.5%) and 9.4 (95%CI, 8.1-10.8, P=0.002), respectively. Differences in methacholine PC(20) values obtained with the two challenge methods recommended in guidelines may be overcome by introducing some technical modifications in the dosimeter method. However, the technical factors that affect methacholine sensitivity and air trapping are at least partially different.

The capsaicin cough reflex in patients with symptoms elicited by odorous chemicals

Patients with multiple chemical sensitivity and eczema patients with airway symptoms elicited by odorous chemicals have enhanced cough reflex to capsaicin when applying the tidal breathing method. The aims of the present study were to test whether the capsaicin induced cough reflex was enhanced when applying the single breath inhalation method in similar groups of patients with symptoms related to odorous chemicals e.g. other persons wearing of perfume; and to investigate to what extent the reporting of lower airway symptoms influenced the cough reflex. Sixteen patients fulfilling Cullen's criteria for multiple chemical sensitivity and 15 eczema patients with airway symptoms elicited by odorous chemicals were compared with 29 age-matched, healthy controls. We measured C5--the capsaicin concentration causing five coughs or more--using the single breath inhalation test. No difference was found between groups in age, body mass index or pulmonary function. The median C5 were 129 micromol/L (control group), 48 micromol/L (multiple chemical sensitivity patients), 32 micromol/L (eczema patients). The reporting of lower airway symptoms from odorous chemicals was significantly (p<0.05) correlated to increased cough reflex sensitivity to capsaicin, independent of patient group or co-existence of asthma. The results suggest that the C5 is not reliable for diagnosing MCS but C5 can be used to verify presence of lower airway symptoms related to odorous chemicals.

Methacholine challenge – Comparison of an ATS protocol to a new rapid single concentration technique

Bronchial methacholine challenge is well established in asthma diagnostics and research. ATS guidelines propose a five step standard dosimeter (SDM) protocol with incremental concentrations of methacholine to calculate the concentration causing a 20% drop in FEV(1) in an individual (PC(20)FEV(1)). In contrast, the aerosol provocation system (APS) by Viasys automatically determines the administered dose of methacholine by measuring the effective nebulisation time and referring it to drug concentration and nebuliser power. Therefore, it offers a feasible and less time-consuming provocation procedure by applying incremental doses (PD(20)) of methacholine using a single concentration (16mg/mL methacholine, APS-SC). In this study we compared these two methods in 52 young adults (25+/-5.8 years). Following a screening visit, subjects were randomly assigned to undergo either SDM or APS-SC followed by the other method within 1 week. A close correlation between concentration and dosage causing a 20% fall of FEV(1) was found (r=0.69, p<0.001). Using the ATS categorisation of bronchial responsiveness we interpreted the results of the APS-SC method as follows: PD(20) methacholine<0.3mg as "moderate to severe BHR", 0.3 - 0.6mg as "mild BHR", 0.6 - 1.0mg as "borderline BHR", and>1.0mg as "normal bronchial response". We conclude that the five-step APS-SC is a suitable method, providing reliable results. In clinical practice the APS-SC is a timesaving procedure and less prone to errors since only one dilution of methacholine is necessary compared to the SDM.

Two ATS Recommended Protocols for Administration of Methacholine Are Not Equal

Background. The 1999 American Thoracic Society methacholine challenge guidelines stated that the 5-breath dosimeter method of methacholine administration is similar to the 2-minute tidal breath method. Recent data has disputed this assertion. We examined the differences in the diagnosis of asthma using these two methods. Methods. Data were abstracted from a prospectively generated pulmonary function database over 4 years. During the first 2 years the 5-breath dosimeter method was used, and the subsequent 2 years the 2-minute tidal breath method was used. The effect of the delivery technique was assessed by crude and adjusted odds ratios, controlling for known confounders and group differences. Results. A total of 907 subjects underwent methacholine challenge testing during the 4-year study period: 19.3% of the subjects tested with the 5-breath dosimeter method and 31.2% of those tested with the 2-minute tidal breathing method had a PC20 ≤ 8.0 mg/mL (OR 1.90, 95% CI 1.4 to 2.58, p < 0.001). The ability to reliably exclude airway hyper-responsiveness (PC20 > 16.0 mg/mL) was also altered by the differences between the testing techniques. Using the 5-breath dosimeter method, 72.4% of subjects were ruled out for airway hyper-responsiveness, whereas only 59.9% of subjects were ruled out with the 2-minute tidal breathing technique (p < 0.001). Conclusion. The two recommended protocols for the diagnosis of asthma are not equivalent and significantly alter the rate of diagnosis of asthma as well as the severity. The differences were seen across all PC20 levels, from those with strongly positive tests (PC20 ≤ 1.0 mg/mL) as well as those with negative tests for airway hyper-responsiveness (PC20 > 16.0 mg/mL).

The Role of Exhaled Nitric Oxide in Evaluation of Acute Asthma in a Pediatric Emergency Department

Fractional excretion of nitric oxide (FE(NO)) has been used as a noninvasive marker to assess and manage chronic asthma in adults and children. The aim of this study was to determine the feasibility of obtaining FE(NO) concentrations in children treated in the emergency department (ED) for acute asthma exacerbation and to examine the association between FE(NO) concentrations and other measures of acute asthma severity. This was a cross-sectional study of a convenience sample of children 2-18 years old who were seen in an urban ED for acute asthma exacerbation. Using a tidal breathing method with real-time display, the authors measured FE(NO) concentrations before and 1 hour after the administration of corticosteroids and at discharge from the ED. Outcome measures included pulmonary index score (PIS), hospital admission, and short-term outcomes (e.g., missed days of school). A total of 133 subjects were enrolled. Sixty-eight percent (95% confidence interval [CI] = 60% to 76%) of the subjects provided adequate breaths for FE(NO) measurement. There was no difference in the median initial FE(NO) concentration among subjects, regardless of the severity of their acute asthma. Most subjects showed no change in their FE(NO) concentrations from the start to the end of treatment. FE(NO) concentrations were not significantly associated with other short-term outcomes. Measurement of FE(NO) is difficult for a large proportion of children with acute asthma exacerbation. FE(NO) concentration during an asthma exacerbation does not correlate with other measures of acute severity and has limited utility in the ED management of acute asthma in children.

Differences in the Response to Methacholine Between the Tidal Breathing and Dosimeter Methods: Influence of the Dose of Bronchoconstrictor Agent Delivered to the Mouth

Background It has been postulated that differences in provocative concentration of methacholine causing a 20% fall in FEV 1 (PC 20 ) values between the dosimeter method and tidal breathing method might be due to differences in the dose of agonist delivered to the mouth. The aim of the present study was to determine the influence of the dose of aerosol delivered to the mouth on differences in the response obtained with each challenge method. Methods This study measured airway responsiveness to methacholine by dosimeter method and tidal breathing method in 27 subjects with suspected asthma. The dosimeter was modified to deliver an identical volume to that obtained with the tidal breathing method. Concentration-response curves were characterized by the PC 20 . Results The dosimeter method PC 20 was significantly higher than the tidal breathing method PC 20 , with geometric mean values of 4.03 (95% confidence interval [CI], 1.86 to 8.78 mg/mL) and 2.19 (95% CI, 1.32 to 3.64 mg/mL; p=0.04), respectively. The mean difference in the PC 20 value detected with each method was similar in subjects with tidal breathing method PC 20 values ≥ 2 mg/mL (0.77 doubling concentrations) and in those with PC 20 values Conclusions The tidal breathing method produces PC 20 values significantly lower than a modified dosimeter method, which delivers the same volume of aerosol. These results suggest that the discordant PC 20 values obtained with the two methods are not due to differences in the dose of agonist delivered to the mouth.

Occupational allergy and asthma among salt water fish processing workers.

Fish processing is a common economic activity in Southern Africa. The aim of this study was to determine the prevalence and host determinants of allergic symptoms, allergic sensitization, bronchial hyper-responsiveness and asthma among workers processing saltwater fish. A cross-sectional study was conducted on 594 currently employed workers in two processing plants involved in pilchard canning and fishmeal processing. A modified European Community Respiratory Health Survey (ECRHS) questionnaire was used. Skin prick tests (SPT) used extracts of common airborne allergens, fresh fish (pilchard, anchovy, maasbanker, mackerel, red eye) and fishmeal. Spirometry and methacholine challenge tests (MCTs; tidal breathing method) used ATS guidelines. Work-related ocular-nasal symptoms (26%) were more common than asthma symptoms (16%). The prevalence of atopy was 36%, while 7% were sensitized to fish species and 26% had NSBH (PC(20) < or = 8 mg/ml or > or =12% increase in FEV(1) post-bronchodilator). The prevalence of probable occupational asthma was 1.8% and fish allergic rhino-conjunctivitis 2.6%. Women were more likely to report work-related asthma symptoms (OR = 1.94) and have NSBH (OR = 3.09), while men were more likely to be sensitized to fish (OR = 2.06) and have airway obstruction (OR = 4.17). Atopy (OR = 3.16) and current smoking (OR = 2.37), but not habitual seafood consumption were associated with sensitization to fish. Based on comparison with previous published studies, the prevalence of occupational asthma to salt water fish is lower than due to shellfish. The gendered distribution of work and exposures in fish processing operations together with atopy and cigarette smoking are important determinants of occupational allergy and asthma.