[Results of measurements of maximal midexpiratory flow rate in healthy persons].
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Adult↗
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[Comparative study of maximal midexpiratory flow rate in normal smoking and non-smoking subjects].
MMF is considered one of the most sensitive parameter to point out initial decay of small airways that should appear prematurely in smokers as compared with non smokers. To verify the above we tested male subjects apparently free from any respiratory disease. They were classed into two groups of equal number: the first group of smokers, the second one of non smokers. We did not find any statistically significant difference between the two groups: this is probably due to the young age of the subjects and consequently to the relative short period of exposure to tobacco smoke.
Forced Expiratory Flow Rates↗
[Effect of breathing low density gas on the maximal midexpiratory flow rate in patients with bronchial asthma].
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Adult↗
Obstructive pulmonary function defects among Taiwanese firebrick workers in a 2-year follow-up study.
The purpose of the study was to follow up an earlier observation of pulmonary function among workers employed in firebrick-manufacturing factories. A 2-year follow-up study of pulmonary function among 442 workers in 30 firebrick-manufacturing factories was designed. Excluding 79 workers with a history of other occupational dust exposure, changes in pulmonary function of 291 firebrick workers were compared with pulmonary function in 72 control subjects over a period of 2 years. Baseline pulmonary function values (i.e., forced expiratory volume in 1 second [FEV1]/forced vital capacity [FVC] and forced expiratory flow after 50% of vital capacity has been expelled [FEF50%] in smoking firebrick workers, and FEV1/FVC and FEF75% in nonsmoking firebrick workers) were significantly lower than those in the comparison group. The statistical method for repeated measurements was used for comparison of the difference between follow-up and baseline lung function. There was no significant difference in FVC and FEV1 changes between firebrick workers and those in the comparison group during the 2-year follow-up period. The decreases in FEV1/FVC, peak expiratory flow rate, maximal midexpiratory flow, and FEF50% in the firebrick workers were significantly greater than in the comparison group, after adjustment for smoking status. The FEV1, maximal midexpiratory flow, FEF50%, and FEF75% also showed a dose-response relationship with job titles. The decrement of pulmonary function in the 2-year follow-up period was the worst in burning work, followed by crushing and molding. The results show that workers in firebrick-manufacturing factories with exposure to silica-containing dusts may contract obstructive pulmonary function defects.
Adult↗
Influence of second-order data filtering on common forced expiration indices.
Forced expiratory manoeuvres are extensively recorded using flow meters coupled to pressure transducers, which usually behave like second-order filters. To assess what should be the dynamic characteristics of such equipment for accurate determination of common forced expiration indices, 125 curves were obtained from 25 healthy subjects in the best technical conditions. The flow-time curves were then submitted to various degrees of second-order filtering, and the indices derived from filtered and unfiltered curves were compared. Considering that experimental error is acceptable if it does not exceed 20% of the normal interindividual variability for 95% of the curves, the following conclusion was drawn; with an optimal damping ratio (r) of 0.7, forced expiratory volume in one second, maximum midexpiratory flow rate and maximal expiratory flow at 25% of the forced vital capacity (MEF25) are still correctly measured when the resonant frequency (fn) is as low as 3 Hz. The corresponding figures are 5 Hz for MEF50, 20 Hz for peak expiratory flow rate and above 20 Hz for MEF75. Higher values of fn are usually required when r is higher or lower than 0.7.
Adult↗
Pulmonary infection with Mycobacterium avium-intracellulare leads to air trapping distal to the small airways.
To clarify the structure and function of the airways in Mycobacterium avium-intracellulare (MAI) infection, we performed pulmonary function tests and high-resolution computed tomography (HRCT) of the thorax in female patients 61 +/- 9 yr of age (n = 12) with pulmonary MAI infection without predisposing lung disease and compared their data with those of normal female volunteers 54 +/- 8 yr of age (n = 9). We calculated the E/I ratio, i.e., the average ratio of HRCT number at full expiration to that at full inspiration, as an index for the evaluation of air trapping distal to the small airways. Patients showed significant increases in residual volume and slope of phase III (DeltaN2) of the single-breath nitrogen test, and significant decreases in flow at 50 and 25% of FVC, suggesting hyperinflation and obstruction of the small airways. HRCT of patients revealed the small nodules and ectasis of bronchioles and small bronchi located mainly in segments (S) S2, S3, S4, and S5. The E/I ratio was significantly elevated in patients, and especially higher in the upper lung field than in the lower lung field, suggesting air trapping distal to the small airways. The difference of E/I ratio between the upper and lower field is probably related to the segmental distribution of CT abnormalities. These findings suggest that MAI infection can lead to air trapping distal to the small airways.
Airway Obstruction↗
A new simple spirometric index for use with bronchial provocation tests.
Spirometric indices such as the forced expiratory volume in one second (FEV1), the maximal expiratory flow rate (MEFR) and the maximal midexpiratory flow rate (MMFR) can be criticized for use with bronchial provocation tests since they are either partly effort-dependent or dependent on the forced vital capacity (FVC). These criticisms can be avoided by the use of a new index corresponding to the volume of air expired in one second starting at 75% of the control FVC, called the (FEV1)-25. This study was performed to evaluate the relative sensitivity of the (FEV1)-25 and the classical FEV1 in detecting airway obstruction caused by an inhaled carbachol aerosol in 20 asthmatic subjects. The mean fall in (FEV1)-25 of 46% following carbachol inhalation compared with a mean fall in FEV1 of 35% indicates that, in addition to its theoretical advantages, the (FEV1)-25 is a sensitive index for use with bronchial provocation tests.
Adolescent↗
[The effect of inhaled nitric oxide and helium-oxygen mixture on the pulmonary function of asthmatics].
OBJECTIVE: To investigate the effect of inhaled nitric oxide (NO) combined with helium-oxygen mixture on the pulmonary function of asthmatics. METHODS: 18 asthmatic patients were included in this study. The patients were divided into two groups randomly. One group of patients inhaled 100 ppm NO combined with helium-oxygen mixture, the other group inhaled 40 ppm NO-containing helium-oxygen mixture. Pulmonary function was examined intermittently during the study process and compared with that of the patients treated with salbutamol. RESULTS: It is shown that inhalation of helium-oxygen mixture improved the forced vital capacity, forced expiratory volume during the first 1.0 second (FEV(1)), peak expiratory flow rate (PEFR) and maximal midexpiratory flow rate (MMEF) significantly as compared with inhalation of air. Although salbutamol inhalation improved FEV(1) and MMEF, the effect was weaker than helium-oxygen mixture inhalation. However the effect of helium-oxygen mixture lasted only one minute. Inhalation of 100 ppm NO with helium-oxygen mixture only slightly improved FEV(1) and PEFR as compared with inhalation of helium-oxygen mixture. 40 ppm NO with helium-oxygen mixture did not influence the pulmonary function in the asthmatic patient as compared with helium-oxygen mixture alone. CONCLUSION: It is suggested that inhalation of helium-oxygen mixture can improve the pulmonary function of asthmatic patients significantly. However, inhalation of NO exerts a weak bronchodilatory effect.
Administration, Inhalation↗
Cold air inhalation challenge in the diagnosis of asthma in children.
A study was designed to determine the usefulness of cold air inhalation challenge testing in children with asthma and to determine the magnitude and duration of the response. A total of 17 children with asthma, mean age 11.7 years (range 6 to 16 years) and eight nonasthmatic children, mean age 11.5 years (range 7 to 15 years) were studied. The average response to isocapneic hyperventilation with cold air in the asthmatic children was a decrease in vital capacity of 10%, a decrease in forced expiratory volume in 1 second (FEV1) of 19%, a decrease in peak flow rate (PFR) of 24%, and a decrease in maximal midexpiratory flow rate (MMFR) of 36%. This was significantly different from the response to the same level of hyperventilation with warm, fully saturated air. The response to isocapneic hyperventilation with cold air in nonasthmatic children was significantly different from the asthmatic children's response with a mean decrease in vital capacity of 0.9%, a decrease in forced expiratory volume in 1 second of 2.5%, a decrease in peak flow rate of 7%, and a decrease in maximal midexpiratory flow rate of 10%. The response in the asthmatic children occurred four to eight minutes after challenge and resolved in eight to 12 minutes. Although the response was highly significant, none of the children developed respiratory distress. It was concluded that isocapneic hyperventilation with cold air is a safe and simple test for diagnosing asthma in children.
Adolescent↗
Lung function of school children with low levels of alpha1-antitrypsin and tobacco smoke exposure.
Exposure to environmental tobacco smoke (ETS) and other air pollutants has been associated with small decrements in lung function. The susceptibility to pollution exposure may, however, vary substantially between individuals. Children with an impaired protease-antiprotease balance may be particularly vulnerable. Therefore this study aimed to investigate the effects of ETS exposure on children with reduced levels of alpha1-antitrypsin (alpha1-AT). Random samples of school children (aged 9-11 yrs) (n=3,526) were studied according to the International Study of Asthma and Allergies in Childhood (ISAAC) phase II protocol, including parental questionnaires, pulmonary function and allergy testing. Blood samples were obtained to measure plasma levels of alpha1-AT and to genotype for pleomorphic protein inhibitor (Pi)Z and PiS alleles. Children with low levels of alpha1-AT (< or = 116 mg x dL(-1)) showed significant, albeit small decrements in baseline lung function. When exposed to ETS, pronounced decrements of pulmonary function, particularly in measures of mid- to end-expiratory flow rates, were seen in these children as compared to exposed children with normal levels of alpha1-AT. The mean levels of % predicted+/-SE in both groups were: maximum expiratory flow at 50% of vital capacity 79.4+/-7.2 versus 99.0+/-1.5, maximum expiratory flow at 25% of vital capacity 67.4+/-10.0 versus 100.3+/-2.1, maximal midexpiratory flow 73.7+/-8.6 versus 99.9+/-1.7. These findings suggest that school children with low levels of alpha1-antitrypsin are at risk of developing pronounced decrements in pulmonary function, particularly if they are exposed to environmental tobacco smoke. Parents of children with heterozygous alpha1-antitrypsin deficiency resulting in significantly reduced blood concentrations should be advised to prevent their children from being exposed to environmental tobacco smoke and dissuade them from taking up smoking.
Child↗
An assessment of cardiorespiratory adjustments of asthmatic adults to exercise.
The cardiorespiratory adjustments of asthmatic adults to submaximal and maximal workloads were investigated. Cardiorespiratory variables were measured every 2 min during exercise and at the end of maximal physical effort. Exercise-induced asthma (EIA) occurred in all asthmatic subjects while normal subjects maintained normal spirometry. The results suggest that asthmatic adults have no cardiac reserve or oxygen delivery limitations. They work under less efficient ventilatory conditions at submaximal workloads and have a significantly lower functional work capacity. The high degree of correlation between preexercise maximal midexpiratory flow rate (MMF) and maximum O2 consumption (max Vo2) suggests that the smaller airways contribute significantly to the observed abnormalities. We recommend that evaluation of antiasthmatic medications in exercise-induced asthma should take into consideration their effect upon smaller airways and cardiorespiratory variables.
Adult↗
Five cross-sectional studies of grain elevator workers.
Five cross-sectional studies were conducted on grain workers in all the terminal elevators in British Columbia, Canada, at 3-year intervals from 1976 to 1988. Civic workers were studied in the same manner as a referent group. The studies consisted of questionnaires, spirometry using the same spirometers, allergy skin tests, and measurement of dust concentration by personal sampling. Although the dust concentration in the elevators was reduced progressively over the years, grain workers had more respiratory symptoms and lower lung function compared with the civic workers in each of the five cross-sectional studies. Exposure to grain dust was associated with significant reduction in forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) but not in maximal midexpiratory flow rate or FEV1/FVC, suggesting reduction in volume which may be due to lesions in the lung parenchyma or in the small airways. Cigarette smoking was associated with significant reduction in FEV1, maximal midexpiratory flow rate, and FEV1/FVC due to airflow obstruction, but had no influence on FVC. Workers who took part in all five surveys tended to be a "healthier" selected group, but the grain workers still had lower lung function compared with the civic workers. This study confirmed previous findings that grain dust has adverse effects on the lungs. Cross-sectional study of the grain elevator workers proved to be a consistent and useful method to evaluate occupational health hazards.
Adult↗
Comparison of an electronic spirometer with a pediatric Wright Peak Flow Meter and their relationship to clinical symptomatology in asthmatic children.
To evaluate the correlations between the Wright Peak Flow Meter and an Electronic Spirometer with clinical symptomatology in chronic asthmatic chidlren, objective measurements of Peak Flow (PF) on both electronic (Vanguard Electric Spirometer) and mechanical (Wright Peak Flow Meter) Spirometers, Forced Vital Capacity (FVC), Forced, Expiratory Volune 1/2 second (FEV 0.5), Forced Expiratory Volume 1/2 per cent (FEV 0.5%), AND Maximal Midexpiratory Flow Rate (MMEFR) were obtained. Subjective observations of clinical wheezing were recorded immediately before each flow rate by trained nurses. PF determinations of both the mechanical and electronic spirometers were in close agreement. PF on the electronic spirometer correlated best with clinical wheezing in this study. The MMEFR calculated from the electronically produced graphys had the nex best coefficient of corelation. These were followed by the PF measured mechanically on the WPFM.
Adolescent↗
Upper respiratory tract infections and airway reactivity in normal and asthmatic subjects.
To assess the effect of an upper respiratory tract infection (URTI) on airway reactivity, histamine inhalation tests (HITs) were performed prospectively in 44 nonsmoking asthmatic (14) and nonasthmatic (30) volunteers. Fifteen of the subjects developed an URTI during the following 4 months. Pulmonary function-forced expiratory volume in one second (FEV1), maximal midexpiratory flow rates (MMEFR) and maximal flow at 50% vital capacity (V50), and HITs, were studied at onset and 2, 3, and 4 wk after infection. There were no significant changes in pulmonary function during the total study period. For the 15 subjects, the mean provocative concentration of histamine causing a 20% fall in FEV1, (PC20H) was 8.73 mg/ml prior to onset of URTI, and at 1, 2, 3, and 4 wk after URTI was 7.97, 8.68, 8.13, and 8.61 mg/ml. These were not significantly different for the group as a whole, nor for the subgroups of asthmatics and nonasthmatics. Small changes in PC20H outside the normal range of variability occurred in 5 of 15 subjects. These were short-lived and no predictive factor for change in PC20H was identified in this group. Thus, URTI was not associated with significant changes in PC20H in this group of asthmatic and nonasthmatic subjects.
Adult↗
Environmental exposure to tobacco smoke and lung function in young adults.
The relationship between lung function and environmental exposure to tobacco smoke (passive smoking) was studied in 293 nonsmoking young men and women, 15 to 35 yr of age. A self-administered mailed questionnaire was used to assess the lifetime environmental exposure to cigarette smoke at home and at work for each subject. Lung function information used here had been gathered in the course of a previous study of the determinants of lung function in early adulthood. In men, maximal midexpiratory flow rate (FEF25-75) decreased in relation to an index of cumulative lifetime environmental exposure to tobacco smoke at home, after taking into account the effects of cumulative exposure at work as well as age, height, body size, respiratory pressures, and cooking fuels used at home. The components of this exposure index most closely related to the reduction in FEF25-75 were maternal smoking habits and exposure to second-hand smoke during childhood. In women, the diffusing capacity of the lung (DLCO) decreased in relation to cumulative exposure to tobacco smoke at work, after accounting for the effects of cumulative lifetime exposure at home and the other factors mentioned above. These findings contribute to the gathering evidence that environmental exposure to tobacco smoke is harmful to respiratory health, and suggest that the effects are not insignificant. For instance, the FEF25-75 of a young man 20 yr of age who had never smoked and always lived at home would be 800 ml less if both his parents smoked than if they did not.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Lung growth and airway function after lobectomy in infancy for congenital lobar emphysema.
To characterize the outcome of lobectomy in infancy and the low expiratory flows which persist after lobectomy for congenital lobar emphysema, 15 subjects with this history were studied at age 8-30 yr. Total lung capacity was normal in all, but higher values (P < 0.05) were observed in nine subjects with upper lobectomy than in five subjects with right middle lobectomy. Ratio of residual volume to total lung capacity was correlated (P < 0.05) with the amount of lung missing as estimated from normal relative weights of the respective lobes. Xe(133) radiospirometry in eight subjects showed that the operated and unoperated sides had nearly equal volumes at total lung capacity, but that the operated side was larger than the unoperated side at residual volume. Perfusion was equally distributed between the two sides. Similar findings were detected radiographically in four other subjects. Forced expiratory volume in 1 s and maximal midexpiratory flow rate averaged 72 and 45% of predicted, respectively. Low values of specific airway conductance and normal density dependence of maximal flows in 12 subjects suggested that obstruction was not limited to peripheral airways. Pathologic observations at the time of surgery and morphometry of the resected lobes were not correlated with any test of pulmonary function. These data show that lung volume can be completely recovered after lobectomy for congenital lobar emphysema in infancy. The volume increase occurs on the operated side, and probably represents tissue growth rather than simple distension. The response to resection is influenced by the particular lobe resected and may be associated with decreased lung recoil near residual volume. Low expiratory flows in these subjects could be explained by several mechanisms, among which a disproportion between airway and parenchymal growth in infancy (dysanaptic growth) is most compatible with our data.
Adolescent↗
Evaluation of supported upper limb exercise capacity in patients with cystic fibrosis.
Physiological responses to upper limb exercise have not been well documented in patients with cystic fibrosis (CF). This is the first study to quantify ventilatory responses to supported incremental upper limb exercise in this patient group. Twenty-four subjects with CF, with a wide range of pulmonary impairment, and ten normal control subjects were studied. Subjects performed pulmonary function tests and incremental arm and leg exercise to peak work capacity on an arm crank and bicycle ergometer. All subjects performed less work with the arms than legs. At an equivalent oxygen consumption, ventilation was higher for arm work than leg work. This higher ventilation was achieved mainly through a higher frequency of breathing. Only CF subjects with severe pulmonary impairment (FEV1 < 40% predicted, FEF25-75% < 20% predicted) had a reduced arm work capacity compared with control subjects. At peak arm work, these subjects had a mean ventilation to maximum voluntary ventilation ratio (VE/MVV) of 106% +/- 25, while maximum heart rate was less than 80% predicted. Despite the high ventilatory requirement for arm exercise, arm work capacity was well maintained in subjects with CF until severe lung disease impaired the ability to further increase ventilation.
Adolescent↗
Effectiveness of a portable face mask in attenuating exercise-induced asthma.
Recent investigations have demonstrated that exercise-induced asthma (EIA) can be prevented by inspiration of warm, fully humidified air during exercise. We evaluated the success of a surgical face mask, used to retain warm, humidified, expired air, in preventing EIA in ten asthmatic children. subjects underwent six minutes of exercise on a treadmill during two sessions, in one session breathing room air and in another wearing a mask covering the nose and mouth. On the control day, average group forced expiratory volume in 1 s (FEV1) and maximal midexpiratory flow rate (MMEF) decreased from the preexercise baseline value to 66% and 47% of baseline, respectively, at six minutes; on the mask day, FEV1 and MMEF were 91% and 82% of the baseline values (increased in all subjects). A simple face mask may be an inexpensive, nonpharmacologic alternative for alleviation of EIA.
Adolescent↗