Mixed infiltrative and obstructive disease on high-resolution CT: differential diagnosis and functional correlates in a consecutive series

Fourteen of 400 consecutive patients having high-resolution computed tomography (HRCT) with expiratory images showed findings of infiltrative lung disease on inspiratory HRCT and air trapping on expiratory CT. Diagnoses included hypersensitivity pneumonitis, sarcoidosis, atypical infection, and pulmonary edema. The extent of infiltrative abnormalities and air trapping were correlated with pulmonary function tests (PFT) in 11 patients. PFT indicated a mixed pattern in five, an obstructive pattern in three, and a restrictive pattern in three. Forced expiratory volume (FEV) in 1 second/forced vital capacity (FVC) correlated significantly with the extent of air-trapping (r = 0.60; p = 0.05). The extent of infiltrative abnormalities correlated significantly and negatively with forced vital capacity (r = -0.82, p = 0.002), FEV1 (r = -0.59, p = 0.05), total lung capacity (TLC) (r = -0.67, p = 0.05), and DLCO (r = -0.75, p = 0.02). Findings of lung infiltration on inspiratory HRCT scans and air trapping on expiratory CT correlated respectively with PFT measures of restrictive and obstructive lung disease.     

Kurtosis and skewness of density histograms on inspiratory and expiratory CT scans in smokers

The aim of this study is to evaluate the relationship between lung function and kurtosis or skewness of lung density histograms on computed tomography (CT) in smokers. Forty-six smokers (age range 46?81 years), enrolled in the Lung Tissue Research Consortium, underwent pulmonary function tests (PFT) and chest CT at full inspiration and full expiration. On both inspiratory and expiratory scans, kurtosis and skewness of the density histograms were automatically measured by open-source software. Correlations between CT measurements and lung function were evaluated by the linear regression analysis. Although no significant correlations were found between inspiratory kurtosis or skewness and PFT results, expiratory kurtosis significantly correlated with the following: the percentage of predicted value of forced expiratory volume in the first second (FEV(1)), the ratio of FEV(1) to forced vital capacity (FVC), and the ratio of residual volume (RV) to total lung capacity (TLC) (FEV(1)%predicted, R = -0.581, p < 0.001; FEV(1)/FVC, R = -0.612, p < 0.001; RV/TLC, R = 0.613, p < 0.001, respectively). Similarly, expiratory skewness showed significant correlations with PFT results (FEV(1)%predicted, R = -0.584, p < 0.001; FEV(1)/FVC, R = -0.619, p < 0.001; RV/TLC, R = 0.585, p < 0.001, respectively). Also, the expiratory/inspiratory (E/I) ratios of kurtosis and skewness significantly correlated with FEV(1)%predicted (p < 0.001), FEV(1)/FVC (p < 0.001), RV/TLC (p < 0.001), and the percentage of predicted value of diffusing capacity for carbon monoxide (kurtosis E/I ratio, p = 0.001; skewness E/I ratio, p = 0.03, respectively). We conclude therefore that expiratory values and the E/I ratios of kurtosis and skewness of CT densitometry reflect airflow limitation and air-trapping. Higher kurtosis or skewness on expiratory CT scan indicates more severe conditions in smokers.     

Assessment of emphysema in COPD: a functional and radiologic study

OBJECTIVES: A combination of functional measurements reflecting a decrease in maximum flow, a degree of lung hyperinflation, the relationship between maximum inspiratory and expiratory flows, bronchodilator response, and diffusing capacity of the lung for carbon monoxide (DLCO) was used to quantify the extent of emphysema, as assessed by high-resolution CT (HRCT) scanning. DESIGN: Forced inspiratory and expiratory spirometry, lung volumes, reversibility test, and single-breath diffusing capacity were assessed before and after inhaling albuterol, 200 microg. Relationships between lung function variables and emphysema extent, as determined by HRCT scanning, were tested by univariate and multivariate analyses. SUBJECTS: Thirty-nine COPD outpatients with moderate-to-severe obstruction. MEASUREMENTS AND RESULTS: Emphysema extent, as assessed by HRCT scanning, ranged from 18 to 70%. All of the lung function parameters that were studied, except for the change in FEV1 percent predicted after salbutamol inhalation, correlated significantly with the extent of emphysema (r2 range, 0.19 to 0.44). Functional residual capacity, forced expiratory flow at 50% of FVC/forced inspiratory flow at 50% of FVC, DLCO/alveolar volume ratio, and bronchodilator-induced change in FEV1/FVC ratio were the only variables retained by stepwise multiple regression analysis. The multiple regression model explained 71% of the variability of emphysema extent measured by HRCT scanning. CONCLUSIONS: The combination of lung function measurements reflecting lung hyperinflation, bronchial collapsibility, lung diffusing capacity, and bronchodilator response provides a good estimate of the extent of emphysema, as evaluated by HRCT scanning. These data suggest that pulmonary function tests are useful in assessing and monitoring parenchymal damage in COPD patients.     

Maternal and personal cigarette smoking synergize to increase airflow limitation in adults

Susceptibility of the lungs to cigarette smoke is poorly understood. It is not known whether maternal smoking increases chronic obstructive pulmonary disease (COPD) risk. In 1998 we reported an inverse association between maternal smoking (prerecorded) and FEV(1) in adults. Because FEV(1) and FVC are strongly correlated, it is unclear whether the association in question reflects a link with lung volume, airflow limitation, or both. We extended our original analysis to investigate whether maternal and personal smoking synergize to increase airflow limitation. We estimated residual FEV(1) to express FEV(1) variation that was not associated with FVC. Maternal smoking was inversely associated with FVC and FEV(1) irrespective of personal smoking. It was inversely associated with FEV(1)/FVC, forced midexpiratory flow rates (FEF(25-75) [mean forced expiratory flow during the middle half of the FVC], FEF(25-75)/FVC), and residual FEV(1) in current smokers but not in never or former smokers (heterogeneity p = 0.016, 0.024, 0.021, and 0.016, respectively). We tested the clinical relevance of findings in ever smokers without asthma: 10 cigarettes/day maternal smoking increased prevalent COPD by 1.7 (95% confidence interval: 1.2-2.5) after adjustment for covariates. Maternal smoking impairs lung volume irrespective of personal smoking and appears to synergize with personal smoking to increase airflow limitation and COPD.     

COPD和哮喘患者支气管舒张实验用力肺活量和呼气容积的变化

目的 探讨COPD和哮喘患者支气管舒张实验用力肺活量和呼气容积变化.方法 随机选取COPD急性加重期78例和哮喘急性发作期64例,采用支气管舒张实验比较COPD和哮喘患者实验前后用力肺活量(FVC)、一秒用力呼气容积(FEV1)的增加量和增加率.结果 支气管舒张实验后,COPD患者的用力肺活量(FVC)的增加量191 ml,较舒张前增加12.93%,而一秒用力呼气容积(FEV1)的增加量63 ml,较舒张前增加10.01%;哮喘患者的用力肺活量(FVC)的增加量363 ml,较舒张前增加15.34%,而一秒用力呼气容积(FEV1)的增加量289 ml,较舒张前增加23.57%.结论 COPD患者支气管舒张试验后用力肺活量的增加幅度大于呼气容积的增加幅度,而哮喘患者正好相反,因此用力肺活量可鉴别COPD和哮喘患者病情的客观指标.     

The characteristics of different diagnostic tests in adult mild asthmatic patients: comparison with patients with asthma-like symptoms by gastro-oesophageal reflux

BACKGROUND: Diagnosing asthma cannot be always easy. It is important to consider the validity of the diagnostic tests, and/or how much more commonly they are positive in patients with asthma compared to healthy subjects and, particularly, to patients with asthma-like symptoms. OBJECTIVE: To evaluate the validity of diagnostic tests for asthma, in terms of sensitivity, specificity, positive and negative predictive values, in patients with bronchial asthma compared to patients affected by gastro-oesophageal reflux disease (GERD) with asthma-like symptoms, and healthy control subjects without asthma and gastro-oesophageal reflux (GER). DESIGN: Single-center, cross-sectional, observational study. PATIENTS: We studied 60 patients with mild asthma, 30 patients with GERD and asthma-like symptoms and 25 healthy control subjects. MEASUREMENTS: We measured provocative concentration of methacholine causing a 20% fall in the forced expiratory volume in 1s (MCh PC(20)/FEV(1)), the amplitude percent mean of peak expiratory flow (A%M of PEF), derived from twice-daily readings for >2 weeks, the FEV(1)/forced vital capacity (FEV(1)/FVC) ratio, the eosinophil count in blood and in induced sputum and the serum eosinophil cationic protein (ECP) levels. RESULTS: FEV(1)/FVC ratio, A%M of PEF, blood eosinophils counts and serum ECP levels were less sensitive and specific when the reference population was composed of patients with asthma-like symptoms by GER. While, MCh PC(20)/FEV(1) and induced sputum eosinophils count were the most sensitive (both 90%) and specific (89% and 92%, respectively) tests. CONCLUSION: Our findings demonstrate that MCh PC(20)/FEV(1) and the induced sputum eosinophil count are the most useful objective tests in patients with mild asthma. All patients with asthma presented both an MCh PC(20)/FEV(1) <1500 microg and eosinophils count in the induced sputum >1%.     

肺泡蛋白沉着症患者的肺功能与胸部分辨率CT的相关性

目的 探讨PAP患者的肺功能与高分辨率CT定量测量指标之间的相关性.方法 对2004至2007年在广州医学院第一附属医院呼吸疾病研究所住院的17例PAP患者(男10例,女7例,年龄15～51岁)进行肺通气及弥散功能检查和高分辨率CT检查,分析肺功能指标与高分辨率CT定量指标之间的相关性.比较其中6例行全肺肺泡灌洗治疗前、后的肺功能和高分辨率CT定量指标的变化.采用SPSS 13.0软件进行数据处理,结果 以x±s表示.结果 PAP患者的肺功能检查结果 以限制性通气功能障碍和弥散功能下降为主,弥散功能下降更为显著,DLCO占预计值%为(46±22)%,异常率为94.1%.肺功能检查结果 与高分辨率CT定量检查结果 之间存在一定的相关性,其中平均肺密度与FVC、肺重量与FEV1、肺含气容积比与呼气峰流量、DL.CO、DLCO与肺泡通气量比值(DLCO/VA)等指标的改变差异有统计学意义,(r值分别为-0.469、-0.482、0.511、0.659、0.692,均P<0.05),在所有指标中以肺含气容积比与DLCO/VA关系最为密切.6例肺泡灌洗术治疗的患者术后肺功能和高分辨率CT定量测量指标有所改善.结论 PAP的肺功能和胸部高分辨率CT改变之间存在相关性.2项检查同时进行可作为PAP患者随访的重要参考指标.     

Quantitative assessment of pulmonary function in lymphangioleiomyomatosis patients using high-resolution computed tomography and pulmonary function tests

BackgroundTo explore the feasibility of using quantitative high-resolution computed tomography (HRCT) to evaluate pulmonary function in patients with pulmonary lymphangioleiomyomatosis (PLAM).MethodsPulmonary function tests (PFTs) were performed in 30 patients with pathologically confirmed PLAM with the use of HRCT. These results were correlated with quantitative HRCT in 21 patients.ResultsThere were significant correlations between the HRCT parameters for lung function and PFT parameters. Among these parameters, emphysema volume (EV), pulmonary volume with a pixel index less than the trigger threshold (−950 HU) to account for a proportion of total lung volume [PI-950 (%)] and forced expiratory volume in 1 second/forced vital capacity [FEV1/FVC (%)] had the strongest correlations, reaching values between −0.71 and −0.68. HRCT lung function might therefore also be helpful for predicting changes in lung function before and after treatment.ConclusionsHRCT is helpful for the assessment of pulmonary function in PLAM patients and can assist in the clinical evaluation of lung function and treatment response in patients with this disease.     

Evaluation of airway wall thickness and air trapping by HRCT in asymptomatic asthma.

The aim of this study was to examine the relationship between the structural changes in large and small airways in asymptomatic asthmatics quantified by high-resolution computed tomography (HRCT) and airflow obstruction. The bronchial wall thickness at the trunk of the apical bronchus (B1) of the right upper lobe was used for assessment of the large airways. Air trapping, evaluated by the ratio of the average CT-determined values for the bilateral upper and lower lung segments at full expiration to that at full inspiration (E/I ratio), was used for assessment of the small airways. Measurements were obtained with a helical HRCT in 24 asymptomatic asthmatics followed by optimal treatment with inhaled and/or oral corticosteroids for >6 months. Prior (20-30 min) to the HRCT examination, all patients were given an inhaled bronchodilator. The ratio of airway wall thickness to outer diameter (T/D) and the percentage wall area (WA%) at the B1 bronchus and the E/I ratio were significantly greater for the 14 asthmatics with deficient reversible airflow obstruction (forced expiratory volume in one second (FEV1) <80% prediced or FEV1/forced vital capacity <70% after bronchodilator inhalation) than for the 10 asthmatics with normal spirometry and seven normal subjects. T/D, WA%, and E/I ratio showed significant negative correlations with FEV1 % pred after bronchodilator inhalation. The E/I ratio also showed significant positive correlations with T/D, WA%, and residual volume/total lung capacity. These findings suggest that, in spite of optimal treatment, structural changes in both large and small airways may simultaneously occur in asthmatics with deficient reversible airflow obstruction.     

Reduction in bronchodilation following a deep inhalation is poorly related to airway inflammation in asthma.

In patients with bronchial asthma, forced expiratory flows are differently sensitive to a previous volume history. A reduced ability of a deep inhalation (DI) to dilate obstructed airways has been hypothesized to be a physiological marker for the degree of airway responsiveness and to relate to the presence and magnitude of inflammation in the lung, even in mild stable asthma. However, there are at present doubts as to whether functional changes could be used as a substitute for airway inflammation studies. In order to investigate the interrelations among airway inflammation, bronchial hyperresponsiveness and effects of volume history, 58 consecutive asthmatics with mild to moderate asthma were studied. The effects of DI were assessed as the isovolumic ratio of flows from forced expiratory manoeuvres started from maximal (M) or partial (P) lung inflation. Airway inflammation was assessed by using induced sputum. Sputum was analysed for total and differential cell counts, and levels of eosinophil cationic protein (ECP) which reflects eosinophil activation. Airway responsiveness was assessed as the provocative concentration of histamine which caused a 20% fall in forced expiratory volume in one second (FEV1) from control (PC20). The M/P ratio was significantly related to ECP (r=-0.31, p<0.03) and eosinophils (r=-0.29, p<0.03), FEV1/vital capacity (VC) (r=0.32; p<0.01), clinical score (r=-0.33; p<0.03) and age (r=-0.41; p<0.0001). In a stepwise multiple regression analysis including age, score, baseline lung function, ECP, number of eosinophils and the response to beta2-agonist, age (p<0.037) predicted a small amount of the variance in M/P ratio (r2=0.12). It is concluded that volume history response is substantially independent of both sputum outcomes (inflammatory cell number and eosinophil cationic protein) and bronchial hyperresponsiveness; rather it seems to be associated with anthropometric characteristics. Functional aspects do not provide information on eosinophilic, probably central, airway inflammation.     

Lung function in patients with chronic airflow obstruction due to tuberculous destroyed lung

Lung function in cases of chronic airflow obstruction (CAO) due to tuberculous destroyed lung, which is still common in Korea, has not been objectively investigated. We evaluated lung functions and postbronchodilator responses in 21 CAO patients with a forced expiratory volume in 1 s (FEV1) of 30-65% of the predicted value, and compared some of these results with those of age-, sex- and FEV1% predicted-matched patients with chronic obstructive pulmonary disease (COPD). In addition, we analyzed the lung functions of CAO patients with respect to wheezing. The forced vital capacity (FVC) (P < 0.05) and postbronchodilator FEV1 of CAO patients were lower than those of COPD patients (P < 0.05). When a positive bronchodilator response was defined as an absolute change of FEV1 (FEV1 delta(abs)) of more than 0.2 l (P < 0.05) and a percentage of initial FEV1 (FEV1 delta%init) of more than 12%, the positive rates in CAO patients were lower than in COPD patients (P < 0.05). Among the CAO patients, patients with wheezing showed lower forced expiratory flow 25%-75% (FEF(25-75%)) (P < 0.05) and higher airway resistance than those without wheezing (P < 0.05). CAO patients with wheezing were more responsive to bronchodilator than those without wheezing. Although the pathophysiology of CAO differs from that of COPD, bronchodilator therapy could be useful for treating CAO, especially in cases presenting with wheezing.     

Impulse oscillometry: a measure for airway obstruction

The impulse oscillometry system (IOS) was introduced as a new technique to assess airflow obstruction in patients who are not able to perform forced breathing maneuvers, e.g., subjects with cerebral palsy or severe mental retardation, and young children. This study evaluates the sensitivity and specificity of IOS parameters to quantify changes in airflow obstruction in comparison with forced expiratory volume in the first second (FEV(1)) and peak expiratory flow (PEF) measurements. Measurements of FEV(1), PEF, and resistance (R) and reactance (X) at frequencies of 5-35 Hz were performed in 19 children with asthma before, during, and after methacholine challenge and subsequent bronchodilatation. All parameters changed significantly during tests. Values of R5 and R10 correlated with FEV(1) (r = -0.71 and -0.73, respectively, P < 0.001), as did values of X5 and X10 (r = 0.52 and 0.57, respectively, P < 0.01). Changes in R preceded changes in PEF and FEV(1) during methacholine challenge. The area under the receiver operating characteristic (ROC) curve to predict a 15% fall in FEV(1) showed better sensitivity and specificity for R5 (area under the curve, 0.85) compared to PEF (0.79) or R10 (0.73). We conclude that IOS parameters can be easily used as an indirect measure of airflow obstruction. This might be helpful in patients who are not able to perform forced breathing maneuvers. In individual subjects, R values measured at 5 Hz showed to be superior to PEF measurements in the detection of a 15% fall in FEV(1).     

不同指标对老年严重慢性阻塞性肺疾病患者吸入支气管舒张剂疗效的评价

目的 对评价严重慢性阻塞性肺疾病(COPD)患者吸入支气管舒张剂疗效的3种指标进行比较. 方法 吸人复方异丙托溴胺溶液前后对18例稳定期严重COPD患者行肺通气功能和肺容量测定,并采用呼气负压技术同步检测呼气流速受限(EFL). 结果 与安慰剂比较,吸入支气管舒张剂后COPD患者第1秒用力呼气容积占预计值(FEV1)百分比、用力肺活量占预计值(FVC)百分比、深吸气量占预计值(IC)百分比显著改善,残气量占预计值(RV)百分比和功能残气量占预计值(FRC)百分比显著降低,肺总量占预计值(TLC)百分比无显著改变;Borg呼吸困难评分显著降低;5分法EFL评分无显著改变,呼吸方式无显著改变.IC、FEV,和5分法EFL评分的平均改善率分别是(20.42±15.02)%、(10.98±7.28)%和(5.15±11.24).△IC与ABorg呈负相关(r=0.732,P<0.05),AFEVl与ABorg相关关系无统计学意义(r=0.343,P>0.05).应用受试者工作特征曲线方法分析3种不同指标诊断呼吸困难的价值,结果表明,IC、FEV1和5分法EFL评分的曲线下面积分别为0.868、0.681和0.557. 结论 与FEV1相比,IC评价严莺COPD患者支气管舒张剂疗效更为灵敏和准确,5分法EFL评分不宜作为评价严重COPD患者吸人支气管舒张剂疗效的指标.     

Inhaled Fluticasone and Salmeterol Suppress Eosinophilic Airway Inflammation in Chronic Obstructive Pulmonary Disease: Relations with Lung Function and Bronchodilator Reversibility

The aim of this study was to determine whether combined inhaled corticosteroids and long-acting β₂ agonists can suppress eosinophilic inflammation in chronic dostructive plumonary disease (COPD) and to investigate the association between the level of eosinophilia and the degree of bronchodilator reversibility. Sixty-two patients with stable COPD (forced expiratory volume in 1 [FEV₁] of 30%–70% predicted before bronchodilation) were enrolled from our outpatient clinic. Patients received inhaled fluticasone (100 μg)/salmeterol (50 μg) twice daily for two months. Lung function measurements, bronchodilator tests, and sputum induction were performed. The number of inflammatory cells and mediators, including interleukin-8 (IL-8), tumor necrosis factor-α (TNF-α), and eosinophilic cationic protein (ECP), were measured. Treatment with inhaled fluticasone and salmeterol significantly suppressed eosinophilic inflammation in COPD patients with sputum eosinophilia (mean 8.9% ± 2.0% vs. 1.6% ± 0.5%, p = 0.003), but insignificant differences in FEV₁ and FVC between patients with and without eosinophilia suggested that suppression of eosinophilic inflammation had no effect on FEV₁ or FVC. Reduction in the percentage of eosinophils was significantly correlated with decreased levels of ECP (r = 0.48, p < 0.001). Levels of neutrophils, IL-8, and TNF-α were not affected. Sputum eosinophilia was not related to the degree of bronchodilator reversibility. The degree of bronchodilator reversibility did not predict the increase in FEV₁ and FVC after treatment with inhaled corticosteroids/long-acting β₂ agonists. Suppression of eosinophilic inflammation and bronchodilator responsiveness indices were not correlated with clinical outcomes in COPD patients treated with inhaled corticosteroids/long-acting β₂ agonists. Diahn-Warng Perng and Cheng-Che Wu contributed equally to this work.     

Exhaled nitric oxide and sputum eosinophil markers of inflammation in asthmatic children.

Exhaled nitric oxide and eosinophil sputum markers are considered noninvasive ways in which to evaluate airway inflammation in asthma. The aim of this study was to evaluate the relationships between these methods of evaluation in asthmatic children. In a cross-sectional study of 25 mild-moderate asthmatic children (aged 6-13 yrs, 10 patients on inhaled steroids) exhaled NO was measured along with induced sputum by inhalation of hypertonic saline solution. The sputum was processed for eosinophil count and eosinophil cationic protein (ECP) determination. Serum ECP and lung function (forced expiratory volume in one second (FEV1)) were also measured. A significant correlation was observed between exhaled NO and sputum eosinophils (r = 0.438, p = 0.032) as well as between sputum eosinophils and sputum ECP (r = 0.532, p<0.01). No correlation was observed among exhaled NO and serum ECP, sputum ECP, FEV1, respectively. Furthermore no correlation was observed between sputum eosinophil (%) and serum ECP and between sputum eosinophils and FEV1. There was no correlation among the investigated parameters in children treated with inhaled steroids. In conclusion, exhaled NO and sputum eosinophil counts are concordant in evaluating the degree of airway inflammation in patients with mild-to-moderate asthma. However, the association between these two noninvasive markers becomes less in steroid treated patients.     

Spirometrically gated high-resolution CT findings in COPD: lung attenuation vs lung function and dyspnea severity

STUDY OBJECTIVES: The aim of this study was to investigate the relationship between high-resolution CT (HRCT) lung attenuation measurements, acquired under spirometric control of inspiratory and expiratory lung volume, and pulmonary dysfunction as well as dyspnea severity in patients with COPD.Patients and design: In 51 patients with COPD, we compared by linear regression, univariate and multivariate logistic regression airflow limitation (FEV(1)/vital capacity [VC]), hyperinflation (percentage of predicted residual volume [RV%]), parenchymal loss (percentage of predicted diffusing capacity of the lung for carbon monoxide [Dlco%]), and Medical Research Council (MRC) dyspnea scale with relative area with attenuation values < - 950 HU at 90% of VC [RAI(950)] and < - 910 HU at 10% of VC, respectively, and with mean lung attenuation measured at the same levels of VC (mean CT lung density at 10% of VC, and mean CT lung density at 90% of VC [MeanCTEXP]). RESULTS: All HRCT attenuation measurements were significantly related with functional abnormalities and dyspnea severity. In multivariate logistic models, with 1 indicating worse changes in dichotomous outcome variables, MeanCTEXP independently predicted FEV(1)/VC (odds ratio [OR], 0.24; 95% confidence interval [CI], 0.11 to 0.56), RV% (OR, 0.57; 95% CI, 0.42 to 0.77), and MRC dyspnea scale (OR, 0.63; 95% CI, 0.48 to 0.82), while RAI(950) independently predicted Dlco% (OR, 1.90; 95% CI, 1.37 to 2.65). CONCLUSIONS: Spirometrically gated measurements of HRCT lung attenuation reflect differently functional changes and dyspnea perception in COPD. Inspiratory measurements assess the extent of emphysematous tissue loss, and expiratory measurements may reflect airflow limitation and lung hyperinflation with attendant dyspnea perception. Pulmonary dysfunction in COPD cannot be assessed by a single modality of lung attenuation measurement.     

Should forced expiratory volume in six seconds replace forced vital capacity to detect airway obstruction?

It has been suggested that forced expiratory volume in six seconds (FEV(6)) should be substituted for forced vital capacity (FVC) to measure fractions of timed expired volume for airflow obstruction detection. The present authors hypothesised that this recommendation might be questionable because flow after 6 s of forced expiration from more diseased lung units with the longest time constants was most meaningful and should not be ignored. Furthermore, previous studies comparing FEV(6) and FVC included few subjects with mild or no disease. The present study used spirometric data from the USA Third National Health and Nutrition Evaluation Survey with prior published ethnicity- and sex-specific equations for FEV(1)/FEV(6), FEV(1)/FVC and FEV(3)/FVC, and new equations for FEV(3)/FEV(6), all derived from approximately 4,000 adult never-smokers aged 20-80 yrs. At 95% confidence intervals, 21.3% of 3,515 smokers and 41.3% of smokers aged >51 yrs had airway obstruction; when comparing FEV(1)/FEV(6) with FEV(1)/FVC, 13.5% were concurrently abnormal, 1.5% were false positives and 4.1% were false negatives; and when comparing FEV(3)/FEV(6) with FEV(3)/FVC, 11.6% were concurrently abnormal, 3.3% were false positives and 5.7% were false negatives. Substituting forced expiratory volume in six seconds for forced vital capacity to determine the fractional rates of exhaled volumes reduces the sensitivity of spirometry to detect airflow obstruction, especially in older individuals and those with lesser obstruction.     

Duration of asthma and lung function in life-long nonsmoking adults.

BACKGROUND: The airways of adult or elderly asthmatics are likely candidates for airway remodeling, resulting in persistent airflow obstruction. This population can provide a good model for cross-sectional evaluation of the effect of asthma duration on airflow. METHODS: We evaluated postbronchodilator airflow and lung volumes at baseline and after a short course of oral prednisone in a group of 42 never-smokers with persistent mild or moderate asthma aged 55 years or older. Patients were grouped as having short duration asthma (SDA, <14 years) or long duration asthma (LDA, > or =14 years) according to the median duration of the disease (14 years) of the sample. RESULTS: There were no significant differences in patient characteristics or asthma severity indices between the groups. After a short course of prednisone, forced expiratory volume in 1 second (FEV1) and the ratio of FEV to forced vital capacity (FVC) were significantly higher for the SDA group. Only 3 patients presented persistent airflow limitation (FEV1/FVC% < 75%). An inverse correlation was demonstrated between duration of asthma and postbronchodilator FEV1 (% predicted) (r = -0.43, P = .01) and FEV1/FVC% (r = -0.50, P = .003). CONCLUSION: Our data show a close relationship between duration of disease and loss of lung function, supporting the concept of asthma as a slow, progressive disease at least among those patients with a mild-to-moderate severity. Permanent airflow obstruction in mild or moderate asthma is unusual, but can occur in a small number suffering from the disease for years.     

Determinants of bronchodilator responsiveness in patients with controlled asthma.

Short-term bronchodilator responsiveness to an inhaled ss 2 adrenergic agonist was assessed by changes in forced expiratory volume in 1 second (FEV(1)) in nonsmoking adults with controlled asthma (mild disease, 20 patients; moderate disease, 20 patients; severe disease, 18 patients). Responsiveness correlated significantly with age and with percent of predicted FEV(1) (%FEV(1)) except in patients with severe asthma, who showed significantly less responsiveness than others. Thus, responsiveness is closely associated with degree of airflow limitation in patients with controlled asthma and is significantly influenced by severity of disease and by aging.     

Sources of error in flow-volume curves. Effect of expired volume measured at the mouth vs that measured in a body plethysmograph

The popularity of the maximum expiratory flow-volume curve (FVC) is in part due to the effort independence of expiratory flow. Of interest are expiratory flow rates at specific lung volumes, usually 50 and 25 percent of vital capacity (VC); Vmax50 and Vmax25, which make accurate assessment of lung volumes essential. Changes in lung volume during the test are due to both the volume of gas expired and the volume change due to gas compression (Vcomp). In normal subjects, Vcomp is small but may be considerable in those with airflow obstruction. When the FVC is measured in a plethysmograph (FVCp), both expired volume and Vcomp are measured. When the volume of the FVC is derived from gas expired at the mouth (FVCm), Vcomp is not considered and differences in Vmax25 or Vmax50 may occur. The magnitude of these errors was assessed in 30 children and young adults: nine normal subjects, ten with cystic fibrosis (CF) and 11 with asthma. For Vmax50, use of FVCm instead of FVCp resulted in an error of 8 +/- 7 percent (mean +/- 1 SD) in the normal subjects compared to 32 +/- 23 in those with CF (p less than 0.01) and 24 +/- 18 for those with asthma (p less than 0.05). For Vmax25, the errors were similar. These errors were not predictable from FEV1 or RV/TLC but were related to a combination of expiratory effort, the shape of the FVCp, and the absolute volume of gas that was being compressed (p less than 0.0001). These findings suggest that expiratory flows in the FVCm are not effort-independent in the face of significant airflow obstruction and that comparisons of values derived from an FVCp with those from an FVCm may not be valid.