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PubMed2005

Mechanical impedance of the respiratory tract in divers before and after simulated deep dives.

Previous studies have inconsistently shown changes in expiratory flows and volumes as well as diffusion capacity of the lungs after single dives and several diving related occupational conditions were considered as possible underlying factors. In this study mechanical impedance of the airways was measured before and after simulated dives to non-invasively determine whether there is evidence for lung function impairment due to hyperbaric exposure. Thirty-three healthy male divers employing air self-contained underwater breathing apparatus were randomly assigned to dry and wet chamber dives in a cross-over design to 600 kPa ambient pressure (total duration 43 min, bottom time 15 min, water temperature 24 degrees C). Immediately before and after diving, oscillometric parameters-e. g. resistance and reactance of the respiratory tract-were measured at defined frequencies (5, 20 Hz). Spirometry was carried out as well (FVC, FEV(1), MEF 25-75). No significant changes between post-exposure values and baseline values were detected by respiratory impedance and spirometry. Diving in accordance to diving regulations and without excessive workload is not a source for acute obstructive lung function changes as the obtained oscillometric data suggested. Moreover this study could not confirm changes in spirometry after simulated diving exposure.

Adult↗
PubMed2001

Static lung compliance as an index of early pulmonary disease in systemic sclerosis.

Pulmonary function abnormalities constitute the most important cause of morbidity and mortality in patients with systemic sclerosis (SSc). A restrictive ventilatory defect with a reduction in pulmonary carbon monoxide diffusion capacity (DLCO) is the commonest finding. Static lung compliance (Cst) is perhaps the most sensitive parameter for the detection of abnormal pulmonary mechanics. We compared the results of Cst and DLCO in patients with SSc and normal spirometry to identify early pulmonary disease. Sixteen of 50 patients had normal spirometry, eight of whom had abnormal Cst. Four of them also had a reduced DLCO. Two patients had abnormal DLCO but their Cst was normal. One of them had pulmonary hypertension on echocardiography. We conclude that Cst was helpful in diagnosing early pulmonary abnormality in 50% of patients with normal spirometry. Among these patients Cst was a better index of abnormality than DLCO.

Adult↗
PubMed2005

[The diagnosis of COPD].

Lung function testing (spirometry) is crucial for the diagnosis of COPD, as irreversible airway obstruction is the main feature of chronic airway inflammation. Spirometry not only is essential in making the diagnosis but also in grading the disease according to FEV1 measurements. Therapeutic interventions and prognostic evaluations are made according to the grading of the disease. Diagnostic procedures aim to evaluate symptoms and disability in the course of COPD. The most important influence on the course of the disease are acute exacerbations. The diagnosis of acute exacerbations is based on clinical observations of sputum production, cough and dyspnoea. Grading of exacerbations according to the severity of symptoms is important for the treatment and in particular for the need of hospitalisation. Exclusion of other lung diseases with similar symptoms necessitates a number of other examinations. Optimal treatment of COPD needs clinical and objective documentation of the course of the disease. Not only spirometry but also quantification of clinical symptoms and exercise capacity measurements are appropriate approaches to follow this chronic disease.

Blood Gas Analysis↗
PubMed1993

Childhood asthma: diagnosis and treatment.

This discussion of asthma management should be regarded as providing guidelines, not dogma. The underlying principles of asthma management include recognition of the variability of the disease and the importance of the underlying inflammatory condition. Clinical assessment is not enough and objective monitoring with PEFR or spirometry provides important data. The treatment protocols require individualization. It is important that the patient and family are team members working together with the medical staff toward a goal of good asthma management. In the discussion of the management of asthma, much emphasis was placed on spirometry and home measurement of PEFR. Office use of spirometry is now the norm for asthma management. Providing asthmatic patients with peak flow meters and instructions in their use is part of the routine care of asthma. Instruction of the patient and family in the proper use of medications is paramount. The MDI devices need to be prescribed with careful instructions regarding their use. When the patient comes in for follow-up, part of the examination should include the patient's demonstration of how he uses this device. Discussion of the proper and safe use of bronchodilators is important. Overuse of inhaled bronchodilators may be a reflection of increasing asthma or, at the very least, evidence that the patient does not understand appropriate treatment of asthma. If a patient is dependent on regular use of an inhaled beta agent, it is likely that he would benefit from therapy directed at the underlying inflammation of asthma. The patient and the family should understand the purpose of each medication, the side effects, and the risks and benefits of their use. In particular, if steroid medications are necessary, the reasons for their use should be explained. Carefully matching the severity of the asthma with the therapeutic protocols provides an organized approach to asthma treatment. Avoiding triggers of asthma and controlling the environmental exposure to potential triggers leads to lower medication requirements and less lability. Offering the family written instructions to cope with changes in the child's condition, based on assessment of clinical and PEFR observations, allows them more autonomy and comfort in the day-to-day care of the asthmatic child.

Adolescent↗
PubMed2005

Hyperpolarized HHe 3 MRI of the lung in cystic fibrosis: assessment at baseline and after bronchodilator and airway clearance treatment.

RATIONALE AND OBJECTIVES: The purpose of this study is to determine hyperpolarized helium 3 (HHe) magnetic resonance (MR) findings of the lung in patients with cystic fibrosis (CF) compared with healthy subjects and determine whether HHe MR can detect changes after bronchodilator therapy or mechanical airway mucus clearance treatment. MATERIALS AND METHODS: Thirty-one subjects, 16 healthy volunteers and 15 patients with CF, underwent HHe lung ventilation MR imaging and spirometry at baseline. Eight patients with CF then were treated with nebulized albuterol, after which a follow-up HHe MR scan was obtained. Subsequently, recombinant human deoxyribonuclease (DNase) treatment and chest physical therapy were performed in these eight subjects, followed by a third HHe MR scan. For each MR study, the number of ventilation defects was scored by a human reader. RESULTS: Patients with CF had significantly more HHe MR ventilation defects per image than healthy subjects (mean, 8.2 defects in patients with CF vs 1.6 defects in healthy subjects; P < .05). Even the four subjects with CF with a normal forced expiratory volume in 1 second had significantly more ventilation defects than healthy subjects (mean, 6.5 defects in these patients with CF; P = .0002). After treatment with albuterol, there was a small, but statistically significant, decrease in number of ventilation defects (mean, 9.6-8.0 defects; P = .025). After DNase and chest physical therapy, there was a trend toward increasing ventilation defects (mean, 8.3 defects; P = .096), but with a residual net improvement relative to baseline. CONCLUSION: In patients with CF, HHe MR ventilation defects correlate with spirometry, change with treatment, and are elevated in number in patients with CF with normal spirometry results. Thus, HHe MR appears to possess many of the characteristics required of a biomarker for pulmonary CF and may be useful in the evaluation of CF pulmonary disease severity or progression.

Administration, Inhalation↗
PubMed2006

The diagnostic accuracies of chronic obstructive pulmonary disease (COPD) in general practice: The results of the MAGIC (Manchester Airways Group Identifying COPD) study.

BACKGROUND: Although it is generally accepted that chronic obstructive pulmonary disease (COPD) is underdiagnosed, there is little objective information concerning the size of the problem in the UK. METHOD: Patients from two general practices were offered spirometry if they were aged 30 or older, had reported ever smoking in one of four postal respiratory surveys (1993-2001), and/or reported four or more symptoms or risk factors in 2001 indicating likely obstructive airways disease. RESULTS: Of 2646 subjects invited, 871 attended and 825 had adequate spirometry results for analysis. In all, 163 patients had spirometrically-confirmed COPD; 103 of these (63.2%) had no recorded COPD in their practice records, including 14 out of 31 (45.2%) whose spirometry results classified them as having severe or very severe COPD. CONCLUSION: This study found a considerable under-recording of COPD in two general practices. This may be due to a combination of administrative and diagnostic problems (including the under-use of spirometers), and a reluctance of patients to present with their symptoms. These results have important implications in terms of unmet need and resource utilisation.

Adult↗
PubMed2006

Chronic obstructive pulmonary disease in Brazilian primary care: Diagnostic competence and case-finding.

AIMS: The developing world is particularly at risk of an increasing health burden due to an increased prevalence of Chronic Obstructive Pulmonary Disease (COPD) secondary to increasing tobacco consumption. However, research is scarce. The objectives of this study were to assess the current competence for diagnosing COPD in primary care in a resource-limited setting in Brazil, and to develop a local patient profile for case-finding. METHODS: 34 general practitioners (GPs) in five areas of northern Brazil recruited adult patients with principal complaints of cough and/or shortness of breath who then had spirometry (n = 142). RESULTS: For the dichotomous variable 'COPD' the degree of agreement between GP diagnosis (n = 64, 18.3%) and spirometric outcome (n = 36, 25.4%) was poor, with Kappa = 0.055 (SE 0.087) and DOR = 1.35. False-positive and false-negative diagnosis proportions were 19.8% and 75%, respectively. Independent risk factors were 'smoking history of more than five pack years' and 'presence of both dyspnoea and cough'. It requires the testing of 2.2 smokers with more than five pack years to detect one patient at risk. CONCLUSIONS: COPD is a common yet underdiagnosed disease in Brazilian primary care. Spirometry improves diagnostic competence and case-finding substantially. If applied in a pre-selected high-risk population, we believe spirometry can be a cost-effective diagnostic tool for case-finding in the resource-limited setting. This study provides important baseline information for effective guideline implementation.

Adolescent↗
PubMed2005

Changes in peak expiratory flow and respiratory strength during the menstrual cycle.

This study evaluated the spirometry and respiratory static pressures in 17 young women, twice a week for three successive ovulatory menstrual cycles to determine if such variables changed across the menstrual, follicular, periovulatory, early-to-mid luteal and late luteal phases. The factors phases of menstrual cycle and individual cycles had no significant effect on the spirometry variables except for peak expiratory flow (PEF) and respiratory static pressures. Significant weak positive correlations were found between the progesterone:estradiol ratio and PEF and between estrogen and tidal volume (r = 0.37), inspiratory time (r = 0.22), expiratory time (r = 0.19), maximal inspiratory pressure (r = 0.25) and maximal expiratory pressure (r = 0.20) and for progesterone and maximal inspiratory pressure (r = 0.32) during the early-to-mid luteal phase. Although most parameters of the spirometry results did not change during the menstrual cycle, the correlations observed between sexual hormones and respiratory control variables suggest a positive influence of sexual female hormones controlling the thoracic pump muscles in the luteal phase.

Adult↗
PubMed2006

Comparison of FEV6 and FVC for detection of airway obstruction in a community hospital pulmonary function laboratory.

The National Lung Health Education Program recommends that primary care providers perform spirometry tests on cigarette smoking patients 45 years or older in order to detect airways obstruction and aid smoking cessation efforts [Ferguson GT, Enright Pl, Buist AS, et al. Office spirometry for lung health assessment in adults: a consensus statement from the national lung education program. Chest 2000; 117: 1146-61]. An abbreviated forced expiratory maneuver that requires exhalation for 6s (FEV6) has recently been proposed as a substitute for forced vital capacity (FVC) to facilitate performance of such spirometry. We set out to assess the accuracy of diagnosis of obstruction and abnormal pulmonary function using FEV6 in comparison to FVC in a community hospital population. One hundred pulmonary function tests performed at a community hospital were randomly selected and retrospectively analyzed. Sixty-three of the 100 tests had satisfactory 6-s expiration and were subject to further analysis. We compared the spirometric interpretation using Morris predictive equations for FEV1/FVC and Hankison predictive equations for FEV1/FVC and FEV1/FEV6. The Hankison set of equations is the only published reference formulas for prediction of FEV6. We found that versus our Morris gold standard, Hankison based FEV1/FVC interpretation was 100% sensitive and 67% specific for the diagnosis of obstruction and 100% sensitive and 65% specific for the diagnosis of any abnormality. The Hankison based FEV1/FEV6 interpretation was 97% sensitive and 47% specific for diagnosing obstruction and 100% sensitive and 50% specific for identifying any abnormality versus the Morris FVC based gold standard. In conclusion, in our hospital based pulmonary function laboratory, FEV6 based interpretation has excellent sensitivity for detection of spirometric abnormalities. However, its moderate specificity may hinder its utility as a screening test. Further testing is necessary to determine its reliability in different patient populations with less highly trained operators.

Adult↗
PubMed2006

Mexican American elders have similar severities of COPD despite less tobacco exposure than European American elders.

INTRODUCTION: Hispanics are the fastest growing ethnicity of the US population and the largest subset includes those of Mexican origin. Hispanics, including Mexican Americans (MAs), consistently report less tobacco exposure than European Americans (EAs), but limited data are available regarding differences in the clinical characteristics, severity of airflow obstruction, and functional status between MAs and EAs with chronic obstructive pulmonary disease (COPD). METHODS: Participants in a community-based study of aging and frailty among MAs and EAs, San Antonio Longitudinal Study of Aging, underwent spirometry. Participants with spirometry values consistent with COPD by Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria are described here. RESULTS: Thirty-four percent (248/721) of the participants who underwent spirometry had evidence of GOLD Stages 1-4 COPD. Significantly more MAs with COPD reported being never smokers compared to EAs with COPD. Among those with COPD who also smoked, MAs reported significantly less tobacco exposure than EAs (15.7 vs. 32.4 pack-years, respectively), but both groups had surprisingly similar severities of airflow obstruction. Additionally, MAs had worse functional status and perceived health than did EAs. CONCLUSIONS: Despite significantly less exposure to tobacco smoke, MAs with COPD had a similar degree of obstruction to airflow compared with EAs with COPD. Healthcare providers should have a high index of suspicion for COPD in MAs who are exposed to even small amounts of cigarette smoke.

Aged↗
PubMed2000

Pulmonary hemodynamics contribute to indicate priority for lung transplantation in patients with cystic fibrosis.

OBJECTIVE: Lung transplantation is a viable option for patients with cystic fibrosis. The current strategy of selection, based on spirometry and deterioration of quality of life, results in a high mortality on the waiting list. We reviewed the case histories of patients with cystic fibrosis accepted for lung transplantation to ascertain whether pulmonary hemodynamics could contribute to predict life expectancy. METHODS: Forty-five patients with cystic fibrosis were accepted: 11 died on the waiting list (group I), 24 underwent transplantation (group II), and 10 are still waiting (group III). During evaluation we recorded spirometry, oxygen requirement, ratio of arterial oxygen tension to inspired oxygen fraction (PaO (2)/FIO (2)), arterial carbon dioxide tension (PaCO (2)), 6-minute walk test results, right ventricular ejection fraction, echocardiography, and pulmonary hemodynamics. We compared data from group I, II, and III patients. A comparison was also made within group II between the data collected at the time of evaluation and at the time of transplantation to quantify the deterioration during the waiting time. RESULTS: The waiting time, spirometry, 6-minute walk test results, and right ventricular ejection fraction did not differ among the three groups. A statistically significant difference was found for PaO (2)/FIO (2), PaCO (2), mean pulmonary artery pressure, cardiac index, pulmonary arterial wedge pressure, and intrapulmonary shunt between groups I and II. Groups I and III showed statistically significant differences for mean pulmonary artery pressure, PaO (2)/FIO (2), and systemic vascular resistance indexed. No differences were observed between groups II and III. The comparison within group II showed a significant deterioration of pulmonary hemodynamics during the waiting time. CONCLUSIONS: Pulmonary hemodynamics are worst in patients dying on the waiting list and deteriorate significantly during the waiting time. They may thus contribute to establish priority for lung transplantation in patients with cystic fibrosis.

Adolescent↗
PubMed2003

Pulmonary function testing in asthma: nursing applications.

Spirometry has become the most widely used assessment of pulmonary function for diagnostic and prognostic purposes. This article reviews the indications for spirometry in persons who have asthma, the parameters measured, acceptable testing techniques, acceptability, quality assurance criteria, and basic interpretation of results in evaluating the person who has asthma. Understanding basic spirometry is an invaluable aid to the nurse and nurse practitioner who provide care to children and adults who have asthma.

Asthma↗
PubMed1985

Assessing severity of adult asthma and need for hospitalization.

Exacerbations of asthma requiring emergency treatment are common but, fortunately, asthma is rarely life threatening. In the course of treating acute asthmatics, however, the question of whether to admit the patient often is raised. With the current costs of hospitalization and morbidity associated with the disease, it is advantageous to be able to separate accurately those who require in-hospital treatment from those who can be treated as outpatients. The choice to hospitalize the asthmatic patient must be based on objective findings, including spirometry alone, spirometry plus history and physical signs, or index scoring (Figure). The best method awaits elucidation by prospective study. The most objective indicator of asthma severity is the indirect measurement of airways obstruction by spirometry, either by FEV1.0 or PEFR. FEV1.0 and PEFR yield comparable results. Simple, inexpensive devices for these measurements are available. An FEV1.0 less than 0.8 to 1.0 L (less than 25% predicted in women and men ages 25 to 65 years) or a PEFR less than 100 L/min (less than 20% predicted in women and men ages 25 to 65 years) accurately indicates a severe asthma exacerbation. The percentage predicted is utilized in those individuals who lack average stature. An increase in FEV1.0 to greater than 1.6 to 2.1 L (greater than 60% predicted) or a PEFR improvement to greater than 300 L/min (greater than 60% predicted) after therapy negates the need for hospitalization. In order to gain such improvement the patient may require approximately four to six hours of outpatient treatment. Some will treat patients for longer periods. Evidence of worsening obstruction or impending respiratory failure during this period mandates admission.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMed2003

[Reliability of chronic obstructive pulmonary disease diagnosis by primary care physicians and pneumologists in Spain. Predictive factors].

OBJECTIVE: The aims of this study were to assess the methods used by primary care physicians and pneumologists to diagnose chronic obstructive pulmonary disease (COPD) in Spain, and to analyze the factors affecting correct diagnosis of the disease. MATERIAL AND METHODS: This observational, descriptive, cross-sectional and multicenter study enrolled a stratified randomized sample from each Spanish region from the practices of primary care physicians and pneumologists. RESULTS: Five hundred sixty-eight (63.2%) of the 898 subjects enrolled had airway obstruction, 92 (10.3%) did not fulfill functional criteria for COPD and 238 (26.5%) did not perform spirometric tests to confirm the diagnosis and establish severity of disease. Primary care physicians classified 29.3% of the patients correctly, whereas pneumologists diagnosed 84.8% correctly. Clinical and/or radiologic criteria were the basis for correct diagnosis in 38.6% of the cases managed by primary care physicians and 10.2% of those treated by pneumologists. Spirometry was available to 49.1% of the primary care physicians and 97.8% of the pneumologists' cases (p < 0.001). Moreover, only 29.9% of the primary care settings had a technician in charge of performing the study, in comparison with 97.8% of the specialized pneumology settings (p < 0.001). The use of spirometry in diagnosing COPD was related to level of patient care (primary or specialized), availability of the test in the primary care setting, place of residence and a patient's situation of temporary absence from work due to COPD. CONCLUSIONS: Many COPD patients are incorrectly diagnosed, particularly in primary care. There are differences in diagnostic procedures at the different levels of patient care. The availability of spirometry is an important factor for correctly diagnosing COPD.

Aged↗
PubMed1999

[Comparative study of the efficacy of 2 respiratory physiotherapy protocols for patients with cystic fibrosis].

OBJECTIVE: To compare the short-term efficacy of two respiratory physiotherapy protocols on sputum clearance, lung function and symptoms in patients with cystic fibrosis. Treatment A consisted of diaphragm breathing with incentive spirometry and postural drainage. Treatment B consisted of diaphragm breathing with positive expiratory pressure (PEP-mask) and postural drainage. METHODS: Twenty-seven cystic fibrosis patients in stable condition followed both protocols (A and B) in random order on different days separated by at least 48 hours. After each treatment session the amount of sputum removed was weighed. Lung function variables (FVC, FEV1, FEV1%, MMEFwt-75, MVV and PEF) were measured pre- and posttreatment. PEF was measured with a peak flow meter. The patients later recorded PEF every hour at home and filled in a questionnaire on frequency and intensity of coughing, sputum characteristics, chest discomfort and dyspnea. RESULTS: During treatment A with incentive spirometry, 14.6 +/- 13.7 g of sputum was removed, whereas 9.8 +/- 10.2 g was eliminated during treatment B (p < 0.05). The differences in PEF after treatments A and B in comparison with baseline values were +19.3 l/min and -0.2 l/min, respectively (p < 0.01). PEF stayed high during the afternoon, in comparison with baseline, with treatment A (p < 0.02). After treatment B, no changes in PEF in comparison with baseline were observed (p = 0.49). Neither treatment led to significant differences in symptoms reported on the clinical questionnaire. CONCLUSIONS: Respiratory physiotherapy with incentive spirometry significantly increases sputum clearance in cystic fibrosis patients, with no immediate repercussions on lung function or symptoms.

Adolescent↗
PubMedDate not supplied

[Allergic rhinitis and bronchial hyperreactivity].

BACKGROUND: Bronchial hyperreactivity (BHR) is a characteristic of bronchial asthma. Patients with allergic rhinitis who do not report symptoms of bronchial asthma on spirometry show BHR, which could indicate the presence of subclinical inflammation of the lower respiratory airway. The aim of this study was to investigate whether the patients diagnosed with allergic rhinitis in our unit without symptoms of bronchial asthma had bronchial hyperreactivity and to determine which allergens caused these symptoms in our patients. METHODS AND RESULTS: We performed a retrospective, observational study of patients diagnosed with allergic rhinitis in our Allergy Unit between August 2000 and December 2001. The patients' medical records were reviewed and data on the following were gathered: demographic information, age, sex, rhinitis symptoms (perennial or seasonal), conjunctivitis, atopic dermatitis, bronchitis, sensitization (specific IgE, skin tests, nasal challenge tests), total IgE levels, spirometry performed through stress test (positive with a decrease of FEV1 > 15 % with stress or an increase of FEV1 of 12 % after bronchodilation) and family history of allergic disease. A total of 135 medical records of patients with allergic rhinitis were reviewed. Of these, 68 did not report symptoms of bronchial asthma (35 men and 33 women aged between 4 and 18 years). Most of our patients (50/68) reported perennial asthma and were sensitized to mites (44/68). In 14/68 spirometry was not performed at diagnosis. Stress test was positive in 13/54 (24 %). All patients who showed bronchial hyperreactivity were sensitized to mites and only one of these reported seasonal rhinitis. CONCLUSIONS: According to the latest guidelines on the treatment and control of allergic rhinitis --The Allergic Rhinitis and its Impact on Asthma Workshop Report-- bronchial asthma and allergic rhinitis are distinct manifestations of a single airway and of the same disease. In view of our results, we recommend systematic evaluation of bronchial hyperreactivity in the study protocol of allergic rhinitis in patients who do not report symptoms of bronchial asthma.

Adolescent↗
PubMed2003

Preoperative pulmonary assessment of the older adult.

Postoperative pulmonary complications in the elderly are common and are a significant source of morbidity, mortality, and prolonged length of stay. Risk factors differ from the well-known risk factors for cardiac complications and can be divided into patient- and procedure-related factors. Patient-related factors include COPD, recent cigarette use, poor general health status as defined by Goldman or ASA class, dependent functional status, and laboratory parameters including abnormal chest radiograph, renal insufficiency, and low serum albumin. Age is a minor risk factor when adjusted for comorbidities and confers approximately a two-fold increase in risk. Elderly patients who are otherwise acceptable surgical candidates should not be denied surgery based solely on age and concern for postoperative pulmonary complications. The surgical site is the single most important predictor of pulmonary complications. High-risk surgeries include thoracic, upper abdominal, aortic, neurosurgery, and peripheral vascular. Other procedure-related risk factors include surgery lasting longer than 3 hours, the use of general anesthesia, pancuronium use, and emergency surgery. Clinicians should not recommend routine preoperative spirometry before high-risk surgery because it is no more accurate in predicting risk than clinical evaluation. Patients who might benefit from preoperative spirometry include those who have unexplained dyspnea or exercise intolerance and those who have COPD or asthma in whom uncertainty exists as to the status of airflow obstruction when compared with baseline. After identifying patients at risk for postoperative pulmonary complications, clinicians can recommend strategies to reduce risk throughout the operative period. In addition to minimizing or avoiding the above risk factors, optimization of COPD or asthma, deep breathing exercises, incentive spirometry, and epidural local anesthetics reduce the risk of postoperative pulmonary complications in elderly surgical patients.

Age Factors↗
PubMed1994

Tracheal wheezes during methacholine airway challenge (MAC) in workers exposed to occupational hazards.

Methacholine airway challenge (MAC) is a simple and useful means to assess bronchial hyperreactivity in workers exposed to various occupational hazards. Recently, wheeze detection by tracheal auscultation has been proposed as an indicator of bronchial responsiveness during bronchial provocation test in children. Our aim was to examine the relationship between the appearance of wheezes and the concurrent changes in forced expiratory volume in one second (FEV1) observed during MAC test in adults. Three cumulative doses of a methacholine solution (100 micrograms, 500 micrograms and 1500 micrograms) were inhaled by 45 workers with occupational exposure to flour dust. Spirometry was done using an electronic spirometer. Tracheal sounds were recorded with an electronic stethoscope placed over the anterior cervical triangle, 2 cm above the sternal notch. The amplified sounds were stored on magnetic tape, band-pass filtered (50-2000 Hz), and digitized at a sampling rate of 4096 Hz into a GenRad Vibration Control System. Wheezes were detected by fast Fourier transform (FFT) analysis and their presence compared to a 20% fall in FEV1. A positive MAC test by spirometry was found in 12 subjects whereas wheezes were identified in 14 subjects. Among the wheezing subjects, nine had a positive MAC test (range of fall in FEV1 = 20.6 to 42.3%) and five had a negative one (range of fall in FEV1 = 3.6 to 16.9%). Moreover, no wheezes were found in the remaining three subjects with a positive MAC test (range of fall in FEV1 = 20.7 to 27.4%). Taking a 20% fall in FEV1 as reference, wheezes were 75% sensitive and 84.8% specific to detect airflow obstruction. In conclusion, since it carries a significant although small false-negative rate, the acoustic technique based upon wheeze detection cannot, at the present time, fully replace spirometry during airway challenge testing in subjects with suspected asthma.

Adult↗