Continuous assessment of nasal airflow resistance by adaptive modeling.

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

Spirometer calibration checks: is 3.5% good enough?

BACKGROUND: Current standards for spirometry require daily calibration checks to come within 3.5% of the inserted volume but do not require evaluation of trends over time. We examined the current guidelines and candidate quality control rules to determine the best method for identifying spirometers with suboptimal performance. METHODS: Daily calibration checks on seven volume spirometers recorded over 4 to 11 years were reviewed. Current guidelines and candidate quality control rules were applied to determine how well each detected suboptimal spirometer performance. RESULTS: Overall, 98% of 7,497 calibration checks were within 3.5%. However, based on visual inspection of calibration check data plots, spirometers 3 and 5 demonstrated systematic sources of error, drift, and bias. The +/- 3.5% criteria did not identify these spirometers. The application of +/- 2% criteria identified these spirometers (9% out-of control values in spirometers 3 and 5 vs < 5% in other spirometers). A rule stipulating out-of-control conditions when four consecutive checks exceeded 1% deviation identified suboptimal spirometers (14% and 20% out-of-control values) but maintained low error detection rates in other spirometers (< or = 2%). Other candidate rules were less effective or required longer times to error detection. CONCLUSIONS: The current recommendation that calibration checks come within +/- 3.5% of the inserted volume did not detect subtle errors. Alternative candidate rules were more effective in detecting errors and maintained low overall error-detection rates. Our findings emphasize the need for laboratories to systematically review calibration checks over time and suggest that more stringent guidelines for calibration checks may be warranted for volume spirometers. Although our general approach may also be appropriate for flow-type spirometers, the details are likely to differ since flow-type spirometers are a much more varied category of equipment.

Technical and functional assessment of 10 office spirometers: A multicenter comparative study.

STUDY OBJECTIVES: To investigate the technical properties and user friendliness of 10 office spirometers devoted for use in general practice, and to compare the results with standard diagnostic spirometers. DESIGN: Multicenter study. SETTING: Ten spirometer models were tested independently in three pulmonary function laboratories and by three general practitioners (GPs). MEASUREMENTS: The laboratories studied the technical quality of the office spirometers in terms of precision and agreement with standard spirometers, whereas the three GPs assessed their user friendliness. The spirometers tested were as follows: Spirobank (Medical International Research; Rome, Italy); Simplicity (Puritan Bennett; Pleasanton, CA); OneFlow (Clement Clarke International; Harlow, Essex, UK); Datospir 70 (Sibelmed; Barcelona, Spain); Datospir 120 (Sibelmed); SpiroPro (SensorMedics; Yorba Linda, CA); EasyOne (NDD; Zurich, Switzerland); MicroLoop (Micro Medical; Chatham, Kent, UK); SpiroStar (Medikro; Kuopio, Finland); and Pneumotrac (Vitalograph; Maids Moreton, Buckingham, UK). FVC and FEV1 were measured in 399 subjects. User friendliness was assessed by the three GPs using a questionnaire. RESULTS: The precision of FEV1 of the office and standard spirometers was comparable, but three office spirometers had > 200 mL limits of precision for FVC. Some devices presented a proportional difference on the FEV1 with standard spirometers, underestimating the small values. The limits of agreements between standard and some office spirometers for FEV1/FVC ratio was > 10%. The overall user friendliness was estimated as good. CONCLUSIONS: The global quality and user friendliness of several office spirometers make them acceptable for the detection of COPD, although differences between the laboratory and some of the office spirometers values suggest that the misclassification rates may be increased when using some models of office spirometers.

Use of pocket-sized turbine spirometer in monitoring exercise-induced bronchospasm and bronchodilator responses in children.

For field studies of asthma, portable hand-held pulmonary function testing devices are required. Other than for peak flow measurements, little has been done to validate their use in children. Fifty children aged 5-15 years having asthma symptoms were examined using an exercise challenge (8 min free running outdoors) and a bronchodilation test (salbutamol inhalation at a dose of 0.15 mg/kg). Pulmonary function was measured with a turbine spirometer, with a Wright peak flow meter (WPEF) and with a flow-volume spirometer (FVS). A fall of 15% or more in peak expiratory flow associated with wheezing or cough was considered diagnostic for bronchial hyper-responsiveness to exercise (BHRE). A rise of 15% or more from baseline in peak expiratory flow after salbutamol inhalation was considered as a positive bronchodilator response (BDR). BHRE was present in 16 children (32%). Using the limit of a 15% or greater fall in FEV1, turbine spirometry identified 12 as BHRE-positive and no additional cases, giving a sensitivity of 75% and a specificity of 100%. The turbine spirometer showed lower FEV1 values than the FVS, the difference increasing with airway obstruction. BDR was positive in eight children (16%). Using the limit of a 10% or greater rise in FEV1, turbine spirometry was positive in six cases. FEV1 measured by turbine spirometry could not be used interchangeably with conventional FVS. However, the turbine spirometer offers the possibility to measure FEV1 repeatedly in field conditions, such as during exercise challenges outdoors.

Evaluation of an electronic hand-held spirometer in patients with asthma.

In this pilot study we assessed patient compliance and acceptability of data recorded in the home environment by asthmatics using a Vitalograph 2110 spirometer which measures peak expiratory flow rate (PEFR) and forced expiratory volume in 1 s (FEV1). This meter automatically time and date stamps all measurements and can also assess the technical acceptability of results. Data are uploaded to a personal computer for review and analysis. We recruited 30 patients (10 male and 20 female, age range 21-72 years) from the chest clinic at Guy's Hospital (n = 20) and from a GP clinic (n = 10). Patients were asked to record spirometry data using the meter at set times (8.00 a.m. and 8.00 p.m.) for 2 weeks. The spirometer incorporated an alarm to remind patients to take measurements. All patients completed the study. Mean (SD) compliance with spirometer use was 100.8% (49.9%). Nineteen patients had a compliance rate of between 80% and 120% of expected use. Timing of recordings was compared with the scheduled times of 8.00 a.m. and 8.00 p.m. Values recorded with +/- 2 h were judged as acceptable. For morning recordings 67.4% of all values and for evening recordings 71.7% of all values met this criterion. Technical acceptability of spirometry data was also assessed by using quality assurance criteria recorded by the spirometer. Valid tests were performed for 75.2% of all recordings. Twenty-two patients performed valid tests for 80-100% of the time. We suggest that the use of an electronic meter in the home environment is practical and is likely to generate more accurate and reliable data.

A device for sampling of human alveolar breath for the measurement of expired volatile organic compounds.

This report describes the development of a portable spirometer capable of collecting primarily alveolar breath into 1.8-L canisters for subsequent gas chromatographic/mass spectrometric (GC/MS) analysis. Based on CO2 measurements, greater than 97% of the breath collected is alveolar in origin. Sample collection takes place in approximately two minutes. Clean air for inhalation is provided by two organic vapor respirator cartridges. Studies of the breakthrough volume of test compounds at both the 5- and 50-micrograms/m3 levels indicate that each cartridge filter can be used to sample over 300 L of air and that this volume is not altered by intermittent use and storage of the filter for up to five days. In experiments designed to mimic human breathing, recoveries of test compounds through the device at the 5-mu/m3 level ranged from 87 to 112%. Essentially no volatile organic compound (VOC) memory (i.e., adsorption carryover by the device) was measured at the 50-micrograms/m3 level. The data suggest that the device can be used successfully for organic compounds with volatilities greater than that of p-dichlorobenzene.

[Electronic spirometry]. / Elektronische Spirometrie.

Electronic spirometry on the basis of forced expiration and flow-volume-curve possess many advantages for the detection of ventilatory alterations in human lung.

[Peak flow measurement]. / Peak-Flow-Metrie.

Peak flow rate measurements with a simple device are useful in detecting and objective assessment of obstructive airway disease. They are easy to perform and offer a rational basis for antiobstructive treatment.

Inhalation challenge.

Inhalation challenge with methacholine is now a standardized procedure using a drug specifically approved for the purpose of determining the nature and extent of airways hyperreactivity. The methodology described involves the intermittent administration of graduated concentrations of methacholine by aerosol inhalation followed by routine spirometry after each incremental dose thereby enabling the construction of a dose response curve. The PD20FEV1, the provocation dose of agonist necessary for a 20% decrease in FEV1, is interpolated from the curve and is the accepted index of airways sensitivity. Clinically, the procedure has been widely used to implement the diagnosis of asthma in such atypical cases as when the physical exam and pulmonary function tests are equivocal. In such a setting, a positive test often justifies the use of therapeutic bronchodilators whereas a negative test would lead the examiner away from the alternative of hyperactive airways. Other applications include the evaluation of antigen sensitivity for diagnostic and research purposes including occupational asthma, epidemiology, and investigational drug trials.

Computer interpretation of pulmonary function tests.

A computer program for interpretation of pulmonary function tests, including flow-volume loops, lung volumes, and diffusing capacity, is described. Comparisons of data obtained before and after administration of bronchodilators and comparison with previous tests are also available as part of the program. Computer interpretation of pulmonary function testing accelerates the reporting of test data and may have a role in education in the discipline of respiratory medicine and related fields.

[Bonchodynamic tests in the study of bronchial asthma]. / Pruebas broncodinámicas en el estudio del asma bronquial.

One characteristic of chronic obstructive bronchopneumopathies, especially bronchial asthma, is the slowing down of respiratory flow. Spirographic studies are therefore valued highly among specialists in respiratory pathology. All of those working in this field of physiopathology, however, agree that broncodynamic provocation tests are not fully specific for bronchial asthma. One important problem is the difficulty in determining the quantity of product inhaled by the patient, making the test even less precise. With our method, based on the broncotest developed by Piglowski, we are able to determine the quantity of inhaled material with a fairly high degree of accuracy. It thus represents a quantitative study and is much more specific. One hundred patients with bronchial asthma, whose ages ranged from 14 to 60 years, were selected for this study. We found that 100% of them (except for one 16-year-old patient whose case has been commented on) were positive for the acetylcholine aerosol test and for beta-2adrenergics (phenotherol). These results enabled us to establish diagnostic patterns for the severity of bronchial hyperactivity in relation to the number of micrograms needed to provoke a 20% variation in the VEMS. We consider it very important to determine the threshold does of acetylcholine, since it may serve in both diagnosis and prognosis. We believe that this method may represent a new direction in pharmacodynamic examination of asthma patients.

[Elementary precautions necessary for the validity of ventilatory function measurements with electronic spirometers]. / Contraintes élémentaires nécessaires a la validité des mesures de la fonction ventilatoire enregistrée par des "spiromètres secs".

The increase of morbidity rate of chronic bronchitis demonstrates the interest of an early check-up, in the free symptom phase of illness, because obstruction of small bronchii may be reversible, as it has been pointed out by previous longitudinal studies. These finding involve the use of simple devices, easy to manage and rebrabld. The three apparatus have been tested : Ohio 842 spirograph, Oude Delft expirometer and Chemetron Corporation P.F.I., in 165 patients. All of them have been compared to Jaeger spirometer. No good agreement has been found between expirometer, P.F.I. and Jaeger spirometer. But Ohio 842 spirograph values were quiet close to those observed with Jaeger spirometer. Electronic spirometers present a digital display without graphic recording or calibration. It has been difficult to detect errors at a first glance. Mostly they came from non linearity of response of thermistance, irregular expiratory flow, insufficient cooperation of patients.