Expiratory Flow-volume Research Articles

Peripheral airway obstruction in primary pulmonary hypertension

Background: As there is controversy about changes in lung function in primary pulmonary hypertension (PPH), lung mechanics were assessed with a focus on expiratory airflow in relation to pulmonary haemodynamics....

Clinical, radiological and functional follow-up after surgical decompression of double aortic arch.

Double aortic arch (DAA) is a congenital vascular anomaly that causes tracheal and oesophageal compression. It requires surgical intervention in patients with severe symptoms. To evaluate the clinical, radiological and functional follow-up after surgical relief of the compression. Ten children (seven boys) with DAA were operated on at a mean age of 1.3 years (range 0.2-7.5). At a mean age of 10.1 years (range 5-18 years), a follow-up study was performed that included clinical, radiological and functional parameters. Seven children reported only mild respiratory symptoms and some trouble with swallowing. Preoperative fluoroscopy with spot images showed the mean tracheal diameter at the level of stenosis to be 37+/-23% of the maximal diameter. At the time of follow-up, this was 70+/-13%. The mean of the oesophageal diameter was 39+/-20% preoperatively and 47+/-16% postoperatively. Maximal expiratory flow volume (MEFV) curves of seven children showed typical characteristics of intrathoracic upper airway obstruction. Mean peak expiratory flow was significantly reduced (77+/-10% of predicted, P<0.0001). Bronchial hyper-reactivity, tested by methacholine challenge, was found in two patients. There was marked relief of clinical symptoms after surgical decompression of DAA in all patients. In spite of this, radiological narrowing of trachea and oesophagus persisted and lung function results were abnormal at long-term follow-up.

Lung function at one month of age as a risk factor for infant respiratory symptoms in a high risk population

Background: Abnormal premorbid lung function is a risk factor for subsequent wheezing in children with one or no atopic parent. This study was undertaken to establish whether early lung function...

Artificial Neural Network based Approach for Diagnosis of Respiratory System using Model based Parameters of Maximum Expiratory Flow-Volume Curve

Artificial Neural Network based Approach for Diagnosis of Respiratory System using Model based Parameters of Maximum Expiratory Flow-Volume Curve

Association of tobacco smoke exposure and respiratory syncitial virus infection with airways reactivity in early childhood.

Exposure to infectious agents and environmental tobacco smoke are thought to induce bronchial hyperresponsiveness (BHR). This study was undertaken to determine the effects of passive exposure to tobacco smoke and respiratory syncitial virus (RSV) lower respiratory infection (LRI) during infancy on the occurrence of BHR in the first 2 years of life. Eighty-six cases of documented RSV (mean age, 188 days) and 78 controls (mean age, 162 days) were enrolled from the clinic and in-patient service of a single hospital. None had a history of prior LRI. Subjects were studied at 6-month intervals up to 19 months of age with a standardized respiratory illness and parental smoking questionnaire, partial expiratory flow-volume curves by the "hug" (rapid thoracic compression) technique, and methacholine challenge. Exposure to maternal and paternal cigarette smoking, maternal history of asthma, and mold exposure were associated with decreased levels of length-corrected maximal flow at functional residual capacity (V'(maxFRC)). RSV-LRI was not related to V'(maxFRC). After adjustment of V'(maxFRC) for these factors, V'(maxFRC) was a significantly and positively correlated with a methacholine concentration provoking a 40% fall in V'(maxFRC) (PC40) and negatively correlated with dose-response slope. After adjustment for V'(maxFRC), there were no independent effects of tobacco smoke exposure or RSV-LRI on methacholine responses. These data do not support a role for RSV as a risk factor for airways reactivity in childhood and indicate that exposure to tobacco smoke affects airways reactivity through its effects on airways.

Lung function in children with Duchenne's muscular dystrophy

Duchenne's muscular dystrophy (DMD), characterized by gradually developing muscular weakness, leads to respiratory symptoms and reduced lung function. We aimed to assess lung function in 25 patients with DMD in relationship to age and muscular function. The 25 boys, mean age 13 years, comprized patients in southern Norway with DMD, taking part in an epidemiological follow-up study. None had chronic respiratory disease. Lung function was measured by maximum expiratory flow–volume loops and whole body plethysmography, and repeated after 1 year (n=14). Lung function was reduced compared to predicted values for healthy children. Forced expiratory volume in 1 sec (FEV1)% predicted and forced vital capacity (FVC)% predicted correlated (significantly) inversely to age. FEV1and FVC decreased annually 5·61 and 4·2% of predicted, respectively. Absolute values of FVC (litres) and FEV1(l sec−1) increased until mean age 14 years, decreasing thereafter. Values in % predicted decreased steadily throughout the age range (6–19 years). Lung function correlated closely to upper limb muscle function.

Respiratory findings in livestock farmworkers.

In this cross-sectional study, the prevalence of acute and chronic respiratory symptoms and lung function were investigated in 236 (169 male and 67 female) livestock farmworkers raising domestic animals, including cattle and horses. The prevalence of acute and chronic respiratory symptoms was recorded by administering a modified version of the British Medical Research Council questionnaire on respiratory symptoms. Lung function was measured by recording the maximum expiratory flow-volume curves from which the forced vital capacity, the one-second forced expiratory volume, and the maximum expiratory flow rates at 50% and the last 25% were measured. There was a significantly higher prevalence of almost all chronic respiratory symptoms in farmers compared with controls: highest among men for chronic cough (27.2%) and highest among women for dyspnea (28.3%). Typical symptoms of occupational asthma were diagnosed in 3.6% of the male and 1.5% of the female livestock farmers. A logistic regression analysis performed on chronic respiratory symptoms of livestock workers indicate significant effects of smoking (P < 0.001) on all symptoms except occupational asthma. A large number of male and female livestock farmworkers complained of acute work-related symptoms: highest for dry cough (52.2%) and shortness of breath (44.9%). Lung function data among these workers demonstrated a trend toward lower lung function in general. Multivariate analysis of lung function parameters indicate significant effects of length of employment and smoking in male and length of employment in female livestock farmworkers. The data suggest that employment in livestock farming may be associated in a dose-dependent manner with the development of acute and chronic respiratory symptoms and lung function changes.

Ventilatory defect in coal workers with simple pneumoconiosis: early detection of functional abnormalities.

Airway obstruction is a prominent feature in coal workers' pneumoconiosis (CWP). However, many patients with CWP have even demonstrated a normal forced vital capacity (FVC) and forced expiratory volume in 1s (FEV1). The purpose of this study was to evaluate the ventilatory defect by spirometry and search for parameters, other than FVC and FEV1, suitable for early detection of pulmonary impairment in CWP. A sample of 227 coal miners was selected from the medical clinics of two teaching hospitals. Maximal expiratory flow volume measurement and determination of functional residual capacity (FRC) and residual volume (RV) were carried out with an automated plethysmograph. The prevalence of airway obstruction (FEV1/FVC < 70%) in this sample of miners was 52.9% (120/227). There was a progression of functional impairment with the transition from category 0 to categories 2 and 3, no matter what the miners smoking habits. All of the 107 non-obstructed miners had a normal FVC and FEV1. However, the mean values for FEF25-75% (mean forced expiratory flow during the middle half of FVC) and Vmax50 (maximal expiratory flow rate at 50% FVC) were abnormally low, and RV was already elevated, in those non-obstructed subjects with category 1 simple pneumoconiosis. A borderline abnormally elevated FRC in the miners with radiological category 3 of CWP was also noted. We conclude that the Vmax50, FEF25-75%, and RV appeared to be the discriminative indices for detecting early ventilatory defect in non-obstructed patients with simple CWP. Further studies is still needed to clarify the cause of small airway dysfunction.

Atypical expiratory flow volume curve in an asthmatic patient with vocal cord dysfunction

Vocal cord dysfunction can coexist with or masquerade as asthma. Vocal cord dysfunction, when coexistent with asthma, contributes substantially to the refractory nature of the respiratory problem. To report a case of an asthmatic patient with vocal cord dysfunction and a previously unreported unique expiratory flow volume curve. A 16-year-old female, known to have asthma, developed increased frequency of her asthma exacerbations. Spirometry, during symptoms, showed an extrathoracic airway obstruction with a reproducible unique abrupt drop and rise in the expiratory flow volume loop. Laryngoscopy showed adduction of the vocal cords during inspiration and expiration. We report a unique expiratory flow volume curve in an asthmatic with vocal cord dysfunction that resolved with panting maneuvers. Speech and psychological counseling helped prevent future attacks.

An Isoflow-Volume Technique for Assessing Airway Dynamics in Children and Adults

Background: We propose a new approach to the measurement of small airway function as an alternative to recordings of maximal expiratory flow-volume (MEFV) curves. Objectives: A newly developed technique to record isoflow-volume (IFV) curves to be tested against maximal respiratory flow curves. Methods: An isoflow whistle (IFW; Iflopen^®) measures the length of a constant expiration after full inspiration. The note of the whistle enables a subject to generate an even expiration, and the isoflow maintenance times at 1 l·s^–1 (IFMT₁) and 2 l·s^–1 (IFMT₂) are recorded. The accuracy and reproducibility of the IFV technique were evaluated in 17 healthy adults (age 17–55 years) and in 14 asthmatic children (age 6–14 years). Comparisons with standard lung function parameters, such as forced expiratory volume in 1 s (FEV₁), maximal expiratory flow at 50% (MEF₅₀) and 25% (MEF₂₅) vital capacity and peak expiratory flow (PEF), obtained with a Wright^® Peakflow Meter were undertaken in 102 healthy (aged 8–14 years) and 101 asthmatic children (aged 6–17 years). A bronchial challenge test was performed in 13 asthmatic children. Results: The expired volume measured by the IFW showed an acceptable agreement with that of a pneumotachograph (mean error of 4.32% for IFMT₁ and 5.93% for IFMT₂). In healthy and in asthmatic children, the correlations between FEV₁ and IFMT₁ or IFMT₂ (r = 0.92 and 0.94, respectively) were found to be greater than that between FEV₁ and PEF (r = 0.68). During bronchial challenge tests in 13 asthmatic children, the FEV₁ decreased to 69% of baseline and IFMT₁ to 58% of baseline. Conclusions: The IFV technique accurately measured airway obstruction and closely followed changes in standard parameters of the MEFV curve.

Peak Expiratory Flow(PEF) Measured by Peak Flow Meter and Correlation Between PEF and Other Ventilatory Parameters in Healthy Children

Background : In diagnosis or monitor of the airway obstruction in bronchial asthma, the measurement of in the standard method because of its reproducibility and accuracy. But the measurement of peak expiratory flow(PEF) by peak flow meter is much simpler and easier than that of especially in children. Yet there have been still no data of the predicted normal values of PEF measured by peak flow meter in Korean children. This study was conducted to provide equations to predict the normal value of PEF and correlation between PEF and in healthy children. Method : PEF was measured by MiniWright peak flow meter, and the forced expiratory volume and the maximum expiratory flow volume curves were measured by Microspiro HI 501(Chest Co.) in 346 healthy children(age:5-16 years, 194 boys and 152 girls) without any respiratory symptoms during 2 weeks before the study. The regression equations for various ventilatory parameters according to age and/or height, and the regression equations of by PEF were derived. Results : 1. The regression equation for PEF(L/min) was: age(year)+height(cm)-263() in boys, and age(year)+height(cm)-293() in girls. 2. The value of FEFmax(L/sec) derived from the maximum expiratory flow volume curves was multiplied by 60 to compare with PEF(L/min), and PEF was faster by 125 L/min in boys and 118 L/min in girls, respectively. 3. The regression equation for (ml) by PEF(L/min) was:PEF-550() in boys, and PEF-146 () in girls, respectively. Conclusion : This study provides regression equations predicting the normal values of PEF by age and/or height in children. And the equations for , a gold standard of ventilatory function, was predicted by PEF. So, in taking care of children with airway obstruction, PEF measured by the peak flow meter can provide useful information.

Maximal Expiratory Flow Patterns After Single-Lung Transplantation in Patients With and Without Chronic Airways Obstruction

A biphasic-plateau pattern in the maximal expiratory flow-volume (MEFV) curve has been described after single-lung transplantation (SLT) in patients with chronic airways obstruction (CAO). It has been theorized that this pattern is either related to stenosis at the anastomotic or subanastomotic site, or the sum of the airflow contribution from the native lung with airways obstruction and transplanted lung. We analyzed data in 16 patients with CAO who had undergone transplantations (5 men, 11 women; mean age [+/- SD], 53.8 +/- 4.9 years), and 9 patients with pulmonary vascular disease (PVD) without airways obstruction who had undergone transplantations (2 men, 7 women; mean age, 35.4 +/- 11.4 years). In the patients with PVD, there were no significant changes in static or dynamic lung volumes or in the MEFV curve after SLT. In the patients with CAO, indexes of airways obstruction improved significantly after SLT, and the typical biphasic-plateau pattern developed in the MEFV curve. In one patient with CAO who required pneumonectomy of the native lung after SLT, the biphasic pattern was absent. These results support the view that this MEFV pattern is a result of airflow from the native and transplanted lungs in patients with CAO. In addition, the results show that in patients with no prior airways obstruction, SLT does not alter static or dynamic lung volumes or maximal expiratory flow rate.

Effects ofIn Uteroand Environmental Tobacco Smoke Exposure on Lung Function in Boys and Girls with and without Asthma

To investigate whether the effects of in utero exposure to maternal smoking and environmental tobacco smoke (ETS) exposure on lung function vary by sex or asthma status, we examined medical history and tobacco smoke exposure data for 5,263 participants in the Children's Health Study. At study enrollment, parents or guardians of each subject completed a questionnaire, and lung function was measured spirometrically with maximum forced expiratory flow-volume maneuvers. To assess the in utero effects of maternal smoking and ETS exposure on lung function, we used regression splines that accounted for the nonlinear relationship between pulmonary function, height, and age. In utero exposure to maternal smoking was independently associated with deficits in lung function that were larger for children with asthma. Boys and girls with a history of in utero exposure to maternal smoking showed deficits in maximum midexpiratory flow (MMEF) and a decrease in the FEV(1)/FVC ratio. As compared with children without asthma, boys with asthma had significantly larger deficits from in utero exposure in FVC, MMEF, and FEV(1)/FVC, and girls with asthma had larger decreases in FEV(1)/FVC. The effect of ETS exposure varied by children's gender and asthma status. Deficits in flows associated with current ETS exposure were present in children with and without asthma but were significant only among children without asthma. Past ETS exposure was associated with reduced FEV(1), MMEF, and FEV(1)/FVC among boys with asthma. In contrast, past ETS exposure was associated with decreased flow rates in girls without asthma. In summary, both in utero exposure to maternal smoking and ETS exposure were associated with persistent deficits in lung function. The effects of in utero exposure were greatest among children with asthma.

Unsuspected pseudophysiologic emphysema in chronic persistent asthma.

The current literature emphasizes the role of airway remodeling in chronic persistent asthma and its putative effect on causing fixed expiratory airflow limitation. We studied 18 adults with chronic persistent asthma; 12 men, six women, age 59 +/- 15 yr (mean +/- SD) with fixed expiratory airflow obstruction. We measured lung elastic recoil and examined the mechanism of expiratory airflow limitation. Diaphragmatic strength was also measured in six asthmatics, using both sniff and partially occluded airway technique. All 18 asthmatics had markedly abnormal maximal expiratory flow-volume curves at both high and low lung volumes. Hyperinflation was present at residual volume (RV), FRC, and TLC in all subjects. Diffusing capacity was normal or elevated and lung computed tomography (CT) was normal in all 18 asthmatic subjects. There was a significant loss of lung elastic recoil in three of four asthmatics age 30 to 49, all five age 51 to 60 yr, and seven of nine age 61 to 82 yr. Maximal expiratory airflow limitation in only four elderly asthmatics and only at low lung volumes was due completely to loss of lung elastic recoil. In the others, we estimate the reduction in lung elastic recoil was responsible for 35% reduction in maximal expiratory airflow at 80% of TLC, and 55% at 70% of TLC. Despite hyperinflation, transdiaphragmatic pressures and strength were normal. The mechanisms responsible for loss of lung elastic recoil remain elusive. The high incidence of loss of lung elastic recoil in chronic persistent asthma was unexpected, and its contribution to abnormal lung function needs to be emphasized.

Expiratory time constants in mechanically ventilated patients with and without COPD.

In mechanically ventilated patients, the expiratory time constant provides information about the respiratory mechanics and the actual time needed for complete expiration. As an easy method to determine the time constant, the ratio of exhaled tidal volume to peak expiratory flow has been proposed. This assumes a single compartment model for the whole expiration. Since the latter has to be questioned in patients with chronic obstructive pulmonary disease (COPD), we compared time constants calculated from various parts of expiration and related these to time constants assessed with the interrupter method. Prospective study. A medical intensive care unit in a university hospital. Thirty-eight patients (18 severe COPD, eight mild COPD, 12 other pathologies) were studied during mechanical ventilation under sedation and paralysis. Time constants determined from flow-volume curves at 100%, the last 75, 50, and 25% of expired tidal volume, were compared to time constants obtained from interrupter measurements. Furthermore, the time constants were related to the actual time needed for complete expiration and to the patient's pulmonary condition. The time constant determined from the last 75% of the expiratory flow-volume curve (RCfv75) was in closest agreement with the time constant obtained from the interrupter measurement, gave an accurate estimation of the actual time needed for complete expiration, and was discriminative for the severity of COPD. In mechanically ventilated patients with and without COPD, a time constant can well be calculated from the expiratory flow-volume curve for the last 75% of tidal volume, gives a good estimation of respiratory mechanics, and is easy to obtain at the bedside.

Pet Ownership is Not Associated with Future Health: a Nine Year Prospective Study in Older Australians

Objective: To examine the relationship between pet ownership and future health in older Australians. Method: A longitudinal study was conducted over 110 months in Dubbo, New South Wales, in a community-based sample of subjects 60 years and over (1,235 men and 1,570 women). There was a baseline survey of demographic, psychosocial and cardiovascular risk factors in 1988–89, with follow-up of all-causes mortality and hospitalisation. Results were modeled using multiple logistic regression. Results: At baseline, 52% of men and 42% of women owned a pet. In comparison with non-owners, older people who owned pets were younger and more likely to be married, yet they were less likely to live alone or use blood pressure medication. Among women only, pet owners had a greater peak expiratory flow volume than non-owners and were less likely to have physical disability. After controlling for the confounding effects of age and other factors likely to influence mortality, there was no significant relationship between pet ownership and all-causes mortality in either sex (odds ratio [95% confidence interval] in men 1.02 [0.75–137], in women 1.27 [0.93–1.75]). Pet ownership was associated with reduced risk of a hospitalisation in women (odds ratio 0.72 [0.54–0.96]). Conclusions: Pet ownership in older subjects is not associated with all-causes mortality. Female owners have a slightly reduced risk of hospitalisation.

Maximal and partial expiratory flow rates in a population sample of 10- to 11-yr-old schoolchildren. Effect of volume history and relation to asthma and maternal smoking.

The effect of volume history on forced expiratory flow rates has been reported to differ between patients with asthma and healthy persons, and it has been hypothesized that the peripheral airway inflammation of patients with asthma may underlie this difference. There are no published data, however, on the distribution of such volume history effects or the relation of these effects to airways disease in children. We obtained combined partial and maximal forced expiratory flow-volume curves on 1,834 children, age 10-11 yr, in eight communities in the United States and Canada. The effect of a deep inhalation on forced expiratory flow rates at low lung volumes was quantitated by the ratio of V (30) during a maximal expiratory maneuver (V (30M)) to V (30) during a partial expiratory maneuver (V (30P)). The V (30M)/V (30P) ratio was slightly higher among girls than boys (1.26 versus 1.18, p = 0.0001) indicating that a deep inhalation increased V (30) slightly more among girls than among boys. The V (30M)/V (30P) ratio was related to neither history of asthma nor to maternal smoking. In contrast, most spirometric indices from either the maximal or the partial expiratory flow-volume curve were lower in association with a history of asthma or a report of maternal smoking. The ratio of FEF(25-75)/FVC was particularly consistent as a measurement that discriminated both of these effects in boys and girls. These results suggest that the measurement of volume history effects offers no benefits for epidemiological studies of childhood respiratory disease whereas spirometric indices such as the FEF(25-75)/FVC ratio are quite sensitive to the effects of asthma and environmental tobacco smoke exposure on the airways.

Expiratory Flow Limitation and Intrinsic Positive End-Expiratory Pressure at Zero Positive End-Expiratory Pressure in Patients with Adult Respiratory Distress Syndrome

It has been suggested that in patients with adult respiratory distress syndrome (ARDS), intrinsic positive end-expiratory pressure (PEEPi) is generated by a disproportionate increase in expiratory flow resistance. Using the negative expiratory pressure (NEP) technique, we assessed whether expiratory flow limitation (EFL) and PEEPi were present at zero PEEP in 10 semirecumbent, mechanically ventilated ARDS patients. Because bronchodilators may decrease airway resistance, we also investigated the effect of nebulized salbutamol on EFL, PEEPi, and respiratory mechanics in these patients, and in seven patients we measured the latter variables in the supine position as well. In the semirecumbent position, eight of the 10 ARDS patients exhibited tidal EFL, ranging from 5 to 37% of the control tidal volume (VT), whereas PEEPi was present in all 10 subjects, ranging from 0.4 cm H(2)O to 7.7 cm H(2)O. The onset of EFL was heralded by a distinct inflection point on the expiratory flow-volume curve, which probably reflected small-airway closure. Administration of salbutamol had no statistically significant effect on PEEPi, EFL (as %VT), or respiratory mechanics. EFL (%VT) and PEEPi were significantly higher in the supine position than in the semirecumbent position, whereas the other respiratory variables did not change. Our results suggest that in the absence of externally applied PEEP, most ARDS patients exhibit EFL associated with small-airway closure and a concomitant PEEPi.

Forced expiration: a test for airflow obstruction in horses.

The purpose of this study was to assess whether our method of inducing forced expiration detects small airway obstruction in horses. Parameters derived from forced expiratory flow-volume (FEFV) curves were compared with lung mechanics data obtained during spontaneous breathing in nine healthy horses, in three after histamine challenge, and in two with chronic obstructive pulmonary disease (COPD) pre- and posttherapy with prednisone. Parameters measured in the healthy horses included forced vital capacity (FVC = 41.6 +/- 5.8 liters; means +/- SD) and forced expiratory flow (FEF) at various percentages of FVC (range of 20.4-29.7 l/s). Histamine challenge induced a dose-dependent decrease in FVC and FEF at low lung volume. After therapy, lung function of the two COPD horses improved to a point where one horse had normal lung mechanics during tidal breathing; however, FEF at 95% of FVC (4.9 l/s) was still decreased. We concluded that FEFV curve analysis allowed the detection of induced or naturally occurring airway obstruction.

Respiratory mechanics and maximal expiratory flow in the anesthetized mouse

Mice have been widely used in immunologic and other research to study the influence of different diseases on the lungs. However, the respiratory mechanical properties of the mouse are not clear. This study extended the methodology of measuring respiratory mechanics of anesthetized rats and guinea pigs and applied it to the mouse. First, we performed static pressure-volume and maximal expiratory flow-volume curves in 10 anesthetized paralyzed C57BL/6 mice. Second, in 10 mice, we measured dynamic respiratory compliance, forced expiratory volume in 0.1 s, and maximal expiratory flow before and after methacholine challenge. Averaged total lung capacity and functional residual capacity were 1.05 +/- 0.04 and 0.25 +/- 0.01 ml, respectively, in 20 mice weighing 22.2 +/- 0.4 g. The chest wall was very compliant. In terms of vital capacity (VC) per second, maximal expiratory flow values were 13.5, 8.0, and 2.8 VC/s at 75, 50, and 25% VC, respectively. Maximal flow-static pressure curves were relatively linear up to pressure equal to 9 cm H(2)O. In addition, methacholine challenge caused significant decreases in respiratory compliance, forced expiratory volume in 0.1 s, and maximal expiratory flow, indicating marked airway constriction. We conclude that respiratory mechanical parameters of mice (after normalization with body weight) are similar to those of guinea pigs and rats and that forced expiratory maneuver is a useful technique to detect airway constriction in this species.