Reference ranges for spirometry across all ages: a new approach

Ethnic differences in the effect of asthma on pulmonary function in children

RATIONALE

The impact of asthma on chronic lung function deficits is well known. However, there has been little study of ethnic differences in these asthma-associated deficits.

OBJECTIVES

To examine whether there are ethnic differences in the effects of asthma on children's lung function.

METHODS

We evaluated the impact of asthma on lung function in 3,245 Hispanic and non-Hispanic white school children (age 10-18 yr) in a longitudinal analysis of the Southern California Children's Health Study. Sex-specific mixed-effects regression spline models were fitted separately for each ethnic group.

MEASUREMENTS AND MAIN RESULTS

Large deficits in flows were observed among children with asthma diagnosed before age 4 years regardless of ethnicity. Hispanic girls with asthma had greater deficits in flows than non-Hispanic girls and were largest for maximal midexpiratory flow (-5.13% compared with -0.58%, respectively). A bigger impact of asthma in Hispanic girls was also found for FEV(1), FEF(75), and PEF (P value 0.04, 0.07, and 0.005, respectively). These ethnic differences were limited to girls diagnosed after age 4 years. In boys, asthma was also associated with greater deficits in flows among Hispanic than in non-Hispanic white children (differences that were not statistically significant). Ethnic differences in prevalence of pets and pests in the home, health insurance coverage, parental education, and smoking did not explain the pattern of lung function differences.

CONCLUSIONS

Larger asthma-associated lung function deficits in Hispanics, especially among girls, merit further investigation to determine public health implications and to identify causes amenable to intervention.

Effects of agriculture crop residue burning on children and young on PFTs in North West India

Variations in pulmonary function tests (PFTs) due to agriculture crop residue burning (ACRB) on children between the age group of 10 to 13 years and the young between 20 to 35 years are studied. The effects of exposure to smoke due to rice-wheat crop residue burning on pulmonary functions like Force Vital Capacity (FVC), Force Expiratory Volume in one second (FEV(1)), Peak Expiratory Flow (PEF) and Force Expiratory Flow in 25 to 75% of FVC (FEF(25-75%)) on 40 healthy subjects of rural/agricultural area of Sidhuwal village of Patiala City were investigated for a period from August 2008 to July 2009. Measurements were taken by spirometry according to the American Thoracic Society standards. High volume sampler (HVS) and Anderson Impactor were used to measure the concentration levels of SPM, PM(10) and PM(2.5) in ambient air of the Sidhuwal village. A significant increase in the concentration levels of SPM, PM(10) and PM(2.5) was observed due to which PFTs of the subjects showed a significant decrease in their values, more prominently in the case of children. PFTs of young subjects recovered up to some extent after the completion of burning period but the PFT values of children remained significantly lower (p<0.001) even after the completion of burning episodes. Small size particulate matter (PM(2.5) and PM(10)) affected the PFTs to a large extent in comparison to the large size particulate matter (SPM). The study indicates that ACRB is a serious environmental health hazard and children are more sensitive to air pollution, as ACRB poses some unrecoverable influence on their PFTs.

Lung function measurement in the assessment of childhood asthma: recent important developments

PURPOSE OF REVIEW

To present three clinically important developments related to the utilization of pulmonary function to objectively assess the asthmatic child.

RECENT FINDINGS

The new asthma guidelines (2007) have added the forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC) ratio to the FEV1 as spirometric criteria for classifying asthma. Although a better indicator of airway obstruction, it has not clearly been shown to correlate with clinical criteria. The normal cut point for the ratio used in the guidelines of 85% for children may be too high, and compared to the lower limits of normal of 80%, could result in unnecessary treatment in some children. The bronchodilator response (BDR) phenotype reflects airway lability and has been associated with biomarkers of inflammation and responsiveness to inhaled corticosteroids as well as predicting long-term outcomes. Several studies have shown improved spirometric techniques in preschoolers as well as defining normal values in this age group. Impulse oscillometry (IOS), which is less demanding than spirometry, has been shown to identify asthmatic preschoolers in some cases better than spirometry and possibly identifying obstruction in the peripheral airways. It may also be a more useful test than spirometry in evaluating long-term drug studies.

SUMMARY

In addition to the FEV1/FVC ratio to detect airway obstruction, the BDR phenotype would appear to give important additional information regarding airway lability and inflammation, and should be included as routine spirometry. IOS is a promising test to identify asthmatic preschoolers, but more studies are needed to determine exactly what it measures and what constitutes normal values.

Management of severe asthma in children

Children who are referred to specialist care with asthma that does not respond to treatment (problematic severe asthma) are a heterogeneous group, with substantial morbidity. The evidence base for management is sparse, and is mostly based on data from studies in children with mild and moderate asthma and on extrapolation of data from studies in adults with severe asthma. In many children with severe asthma, the diagnosis is wrong or adherence to treatment is poor. The first step is a detailed diagnostic assessment to exclude an alternative diagnosis ("not asthma at all"), followed by a multidisciplinary approach to exclude comorbidities ("asthma plus") and to assess whether the child has difficult asthma (improves when the basic management needs, such as adherence and inhaler technique, are corrected) or true, therapy-resistant asthma (still symptomatic even when the basic management needs are resolved). In particular, environmental causes of secondary steroid resistance should be identified. An individualised treatment plan should be devised depending on the clinical and pathophysiological characterisation. Licensed therapeutic approaches include high-dose inhaled steroids, the Symbicort maintenance and reliever (SMART) regimen (with budesonide and formoterol fumarate), and anti-IgE therapy. Unlicensed treatments include methotrexate, azathioprine, ciclosporin, and subcutaneous terbutaline infusions. Paediatric data are needed on cytokine-specific monoclonal antibody therapies and bronchial thermoplasty. However, despite the interest in innovative approaches, getting the basics right in children with apparently severe asthma will remain the foundation of management for the foreseeable future.

Asthma severity in childhood, untangling clinical phenotypes

Assessment of childhood asthma severity and asthma control encompasses heterogeneous clinical presentations. The relationship between patterns of asthma symptoms and objective measurements is poorly defined in paediatric asthma. This study includes 115 asthmatic schoolchildren, of which 31 were at inclusion defined as Problematic severe asthma because of inadequate asthma control in the presence of high-dose inhaled corticosteroid (HD-ICS) treatment and at least one other asthma controller drug. Two partially overlapping clinical outcomes were defined irrespective of severity classification (Exacerbations and Chronic persistent asthma) in patients with uncontrolled asthma. The same symptom criteria were used as for Problematic severe asthma, but disregarding current medication. Lung function, exhaled nitric oxide (FE(NO)), bronchial hyperresponsiveness, allergic sensitization and Quality of life (QoL) in the symptom subgroups were compared to children with well-controlled asthma. Multifactor analysis was performed to assess the relative explanatory power of clinical asthma presentations and of HD-ICS treatment on objective measurements. Whereas children included in the Exacerbations subgroup had objective features similar to patients with well-controlled asthma, the Chronic persistent asthma subgroup demonstrated significantly reduced lung function, increased immunoglobin E, allergic poly-sensitization and impaired QoL, similar to that in patients pre-defined as Problematic severe asthma. The presence of chronic asthma symptoms was a significant explanatory factor for reduced lung function, QoL and increased FE(NO) in multifactor analysis. Differences in objective measurements suggest that children with Chronic persistent asthma and those who are symptomatic predominantly during exacerbations may represent distinct phenotypes of childhood asthma with different clinical prognoses.

Lung function and respiratory symptoms at 11 years in children born extremely preterm: the EPICure study

RATIONALE

The long-term respiratory sequelae of infants born extremely preterm (EP) and now graduating from neonatal intensive care remains uncertain.

OBJECTIVES

To assess the degree of respiratory morbidity and functional impairment at 11 years in children born EP (i.e., at or less than 25 completed weeks of gestation) in relation to neonatal determinants and current clinical status.

METHODS

Pre- and postbronchodilator spirometry were undertaken at school in children born EP and classroom control subjects. Physical examination and respiratory health questionnaires were completed. Multivariable regression was used to estimate the predictive power of potential determinants of lung function.

MEASUREMENTS AND MAIN RESULTS

Spirometry was obtained in 182 of 219 children born EP (129 with prior bronchopulmonary dysplasia [BPD]) and 161 of 169 classmates, matched for age, sex, and ethnic group. Children born EP had significantly more chest deformities and respiratory symptoms than classmates, with twice as many (25 vs. 13%; P < 0.01) having a current diagnosis of asthma. Baseline spirometry was significantly reduced (P < 0.001) and bronchodilator responsiveness was increased in those born EP, the changes being most marked in those with prior BPD. EP birth, BPD, current symptoms, and treatment with beta-agonists are each associated independently with lung function z-scores (adjusted for age, sex, and height) at 11 years. Fifty-six percent of children born EP had abnormal baseline spirometry and 27% had a positive bronchodilator response, but less than half of those with impaired lung function were receiving any medication.

CONCLUSIONS

After extremely preterm birth, impaired lung function and increased respiratory morbidity persist into middle childhood, especially among those with BPD. Many of these children may not be receiving appropriate treatment.

Predictors of mortality in elderly subjects with obstructive airway disease: the PILE score

PURPOSE

To identify significant covariates in addition to spirometry that predict mortality in elderly subjects with obstructive airway disease (OAD).

METHODS

Two hundred sixty-eight (268) participants with OAD from the Health, Aging and Body Composition study, a community-based observational cohort of well-functioning elderly aged 70-79 years, were followed on average for 6.1 years. Covariates related to pulmonary and physical function, comorbidity, demographics, and three inflammatory markers (interleukin-6, tumor necrosis factor-alpha, C-reactive protein) were evaluated for their association with all-cause mortality (31%) by means of Kaplan Meier analysis and Cox proportional hazards modeling.

RESULTS

Percent predicted forced expiratory volume in one second (PPFEV1; hazard ratio [HR] = 2.03, p < 0.0001), knee extensor strength (HR = 1.36, p = 0.0002), interleukin-6 (HR = 1.37, p = 0.0002) and 400 m corridor walk time (HR = 1.24, p = 0.008) significantly predicted mortality. A multidimensional index, the PILE score, was constructed from PPFEV(1), interleukin-6, and knee extensor strength. Each one-point increase in PILE score (range: 1-10) was associated with a 30% increase in mortality (95% confidence interval: 0.16-0.47) after adjusting for age, race, gender, smoking, and comorbidity, resulting in a 10.4-fold higher risk of death between the highest and lowest risk category.

CONCLUSIONS

Subjects with OAD have a wide gradient of risk for mortality that can potentially be incorporated in clinical decision making.

Airway obstruction at time of symptoms prompting use of reliever therapy in children with asthma

BACKGROUND

In asthma treatment, doses of inhaled corticosteroids are often adapted to symptoms and need for bronchodilators. However, in cross-sectional studies in emergency room settings, lung function and respiratory symptoms are not always concordant. Available longitudinal data are based on written peak flow diaries, which are unreliable. Using home spirometry, we studied prospectively whether mild respiratory symptoms, prompting reliever therapy are accompanied by a clinically relevant drop in lung function in children with asthma.

METHODS

For 8 weeks, children with asthma scored symptoms and measured peak expiratory flow (PEF) and forced expiratory volume in 1 sec (FEV(1)) on a home spirometer twice daily. Additional measurements were recorded when respiratory symptoms prompted them to use bronchodilators.

RESULTS

The mean difference between symptom free days and at times of symptoms was 6.6% of personal best for PEF (95% CI: 3.2-10.0; p = 0.0004) and 6.0% of predicted for FEV(1) (95% CI: 3.0-9.0; p = 0.0004). There was complete overlap in PEF and FEV(1) distributions between symptom free days and at times of symptoms.

CONCLUSIONS

Although statistically significant, the degree of airway narrowing at times of respiratory symptoms, prompting the use of reliever therapy, is highly variable between patients, limiting the usefulness of home spirometry to monitor childhood asthma.

Year-to-year changes in lung function in individuals with cystic fibrosis

BACKGROUND

We examined the year-to-year change in FEV(1) for individuals and the overall cystic fibrosis population to better understand how individual trends may differ from population trends.

METHODS

We calculated individual yearly changes using the largest annual FEV(1) percent predicted (FEV(1)%) measurement in 20,644 patients (6-45years old) included in the Epidemiologic Study of Cystic Fibrosis. We calculated yearly population changes using age-specific medians.

RESULTS

FEV(1)% predicted decreased 1-3 points per year for individuals, with maximal decreases in 14-15year olds. Population changes agreed with individual changes up to age 15; however after age 30, yearly population change approximated zero while individual FEV(1)% predicted decreases were 1-2 points per year.

CONCLUSIONS

Adolescents have the greatest FEV(1)% predicted decreases; however, loss of FEV(1) is a persistent risk in 6-45year old CF patients. Recognizing individual year-to-year changes may improve patient-specific care and may suggest new methods for measuring program quality.

Regional differences in prediction models of lung function in Germany

Background

Little is known about the influencing potential of specific characteristics on lung function in different populations. The aim of this analysis was to determine whether lung function determinants differ between subpopulations within Germany and whether prediction equations developed for one subpopulation are also adequate for another subpopulation.

Methods

Within three studies (KORA C, SHIP-I, ECRHS-I) in different areas of Germany 4059 adults performed lung function tests. The available data consisted of forced expiratory volume in one second, forced vital capacity and peak expiratory flow rate. For each study multivariate regression models were developed to predict lung function and Bland-Altman plots were established to evaluate the agreement between predicted and measured values.

Results

The final regression equations for FEV₁ and FVC showed adjusted r-square values between 0.65 and 0.75, and for PEF they were between 0.46 and 0.61. In all studies gender, age, height and pack-years were significant determinants, each with a similar effect size. Regarding other predictors there were some, although not statistically significant, differences between the studies. Bland-Altman plots indicated that the regression models for each individual study adequately predict medium (i.e. normal) but not extremely high or low lung function values in the whole study population.

Conclusions

Simple models with gender, age and height explain a substantial part of lung function variance whereas further determinants add less than 5% to the total explained r-squared, at least for FEV1 and FVC. Thus, for different adult subpopulations of Germany one simple model for each lung function measures is still sufficient.

Chronic obstructive pulmonary disease in older persons: A comparison of two spirometric definitions

BACKGROUND

Among older persons, we previously endorsed a two-step spirometric definition of chronic obstructive pulmonary disease (COPD) that requires a ratio of forced expiratory volume in 1sec to forced vital capacity (FEV(1)/FVC) below .70, and an FEV(1) below the 5th or 10th standardized residual percentile ("SR-tile strategy").

OBJECTIVE

To evaluate the clinical validity of an SR-tile strategy, compared to a current definition of COPD, as published by the Global Initiative for Obstructive Lung Disease (GOLD-COPD), in older persons.

METHODS

We assessed national data from 2480 persons aged 65-80 years. In separate analyses, we evaluated the association of an SR-tile strategy with mortality and respiratory symptoms, relative to GOLD-COPD. As per convention, GOLD-COPD was defined solely by an FEV(1)/FVC<.70, with severity staged according to FEV(1) cut-points at 80 and 50 percent predicted (%Pred).

RESULTS

Among 831 participants with GOLD-COPD, the risk of death was elevated only in 179 (21.5%) of those who also had an FEV(1)<5th SR-tile; and the odds of having respiratory symptoms were elevated only in 310 (37.4%) of those who also had an FEV(1)<10th SR-tile. In contrast, GOLD-COPD staged at an FEV(1) 50-79%Pred led to misclassification (overestimation) in terms of 209 (66.4%) and 77 (24.6%) participants, respectively, not having an increased risk of death or likelihood of respiratory symptoms.

CONCLUSION

Relative to an SR-tile strategy, the majority of older persons with GOLD-COPD had neither an increased risk of death nor an increased likelihood of respiratory symptoms. These results raise concerns about the clinical validity of GOLD guidelines in older persons.

Identifying problematic severe asthma in the individual child--does lung function matter?

AIM

Measures of lung function (usually FEV(1) <80% predicted) are used to classify asthma severity in both adults and children, despite evidence that lung function impairment is less pronounced in the paediatric asthma population. The present study assesses the relevance of lung function measurements as discriminators of severe childhood asthma.

METHODS

Fifty-one school-aged children with problematic severe asthma, 37 mild-to-moderate asthmatics and 29 healthy controls underwent a comprehensive clinical work-up. Problematic severe asthma was defined in patients exhibiting poor asthma control despite high-dose inhaled corticosteroid treatment and at least one other asthma controller drug. Mild-to-moderate asthmatic children used low-dose inhaled steroids and reported minimal asthma symptoms.

RESULTS

Baseline FEV(1) values were significantly reduced in children with problematic severe asthma, yet FEV(1) <80% predicted showed a low sensitivity (41%) for discriminating severe vs. mild-to-moderate asthma. Receiver-operated characteristic analysis estimated the optimal cut-off of FEV(1) to be 90% predicted in this population (sensitivity 61%, specificity 83%). Baseline FEV(1)/FVC and FEF(25-75) values were not superior to FEV(1) in discriminating problematic severe asthma, and neither exhaled nitric oxide levels nor bronchial hyperresponsiveness differentiated between the two asthmatic study populations.

CONCLUSION

Spirometric measurements are insensitive discriminators of problematic severe asthma in childhood.

Comparison of pulmonary function in immigrant vs US-born Asian Indians

OBJECTIVE

This study investigated whether there is a difference in pulmonary function between healthy adult US-born Asian Indians and immigrant Asian Indians attributable to country of birth, environmental, and socioeconomic factors.

DESIGN

FEV(1), FVC, and forced mid-expiratory flow between 25% and 75% of vital capacity (FEF(25-75)) were measured in India-born and US-born subjects residing in the Chicago metropolitan area. Hollingshead Index of Social Position was used to evaluate socioeconomic factors.

RESULTS

There were 262 India-born (61.8% male), and 200 US-born (50% male) subjects who were healthy lifelong nonsmokers; their age range was 16 to 36 years. US-born Asian Indian men and women were taller and had higher pulmonary function values for height and age compared with immigrant Asian Indian men and women. The differences were most pronounced in women: about 7% for FVC, 9% for FEV(1), and 17% for FEF(25-75). Immigrant and US-born subjects did not differ in socioeconomic position.

CONCLUSION

We conclude that US-born Asian Indian men and women have higher pulmonary function values for age and height compared with immigrant Asian Indian men and women. This probably reflects the effect of differing environmental conditions, which cause year-of-birth trends in lung volumes.

Spirometric reference equations for healthy children aged 6 to 11 years in Taiwan

BACKGROUND

Spirometry is a valuable technique for evaluating pulmonary function, but there were few normative reference values for young children in Taiwan, and none for the last 10 years. The objective of our study was to establish updated reference values and equations for children aged 6-11 years in northern Taiwan.

METHODS

A total of 309 healthy children (153 boys and 156 girls) were enrolled in the present study. The data of at least 3 trials for each child were collected, and the highest values analyzed. The analyzed pulmonary function parameters were focused on forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), peak expiratory flow rate (PEF), forced expiratory flow between 25% and 75% expired volume (FEF25-75), and the ratio of FEV1/FVC.

RESULTS

The results revealed that there were mostly no significant differences between boys and girls, and the standing height (H, cm) was the factor with the highest correlation with the pulmonary function parameters. Regression equations of the major pulmonary function parameters for both boys and girls were obtained: FVC = -2.690 + 0.0330H; FEV1 = -2.559 + 0.0311H; PEF = -300.231 + 3.938H; FEF25-75 = -3.218 + 0.0425H (p < 0.001).

CONCLUSION

Our study determined the updated normative values and reference equations for Chinese children aged 6-11 years living in northern Taiwan. These values can be used as normative reference values to evaluate pulmonary function in diseased children with the same ethnicity and lifestyle.

The ratio of FEV1 to FVC as a basis for establishing chronic obstructive pulmonary disease

RATIONALE

The lambda-mu-sigma (LMS) method is a novel approach that defines the lower limit of normal (LLN) for the ratio of FEV1/FVC as the fifth percentile of the distribution of Z scores. The clinical validity of this threshold as a basis for establishing chronic obstructive pulmonary disease is unknown.

OBJECTIVE

To evaluate the association between the LMS method of determining the LLN for the FEV1/FVC, set at successively higher thresholds, and clinically meaningful outcomes.

METHODS

Using data from a nationally representative sample of 3,502 white Americans aged 40-80 years, we stratified the FEV1/FVC according to the LMS-LLN, with thresholds set at the 5th, 10th, 15th, 20th, and 25th percentiles (i.e., LMS-LLN5, LMS-LLN10, etc.). We then evaluated whether these thresholds were associated with an increased risk of death or prevalence of respiratory symptoms. Spirometry was not specifically completed after a bronchodilator.

MEASUREMENTS AND MAIN RESULTS

Relative to an FEV1/FVC greater than or equal to LMS-LLN25 (reference group), the risk of death and the odds of having respiratory symptoms were elevated only in participants who had an FEV1/FVC less than LMS-LLN(5), with an adjusted hazard ratio of 1.68 (95% confidence interval, 1.34-2.12) and an adjusted odds ratio of 2.46 (95% confidence interval, 2.01-3.02), respectively, representing 13.8% of the cohort. Results were similar for persons aged 40-64 years and those aged 65-80 years.

CONCLUSIONS

In white persons aged 40-80 years, an FEV1/FVC less than LMS-LLN5 identifies persons with an increased risk of death and prevalence of respiratory symptoms. These results support the use of the LMS-LLN5 threshold for establishing chronic obstructive pulmonary disease.

Time for new reference values for ventilatory lung function

OBJECTIVE

The anthropometrical data of our aging population has significantly changed within the last five decades. Therefore the question arises whether or not the commonly used reference values of the European Community (ECCS) for lung function, may still be accepted today. Measured values for elderly are classified by extrapolation beyond the range of reference equations.

MATERIAL AND METHODS

Lung function was examined by pneumotachography for recording static lung volumes and flow-volume-curves in 257 asymptomatic non smoking males, aged 20-90 years. Results were compared to the reference values of ECCS, SAPALDIA, LuftiBus, and NHANES.

RESULTS

For analysis age and height dependence of investigated respiratory parameters (VC, FVC, FEV(1), FEV(1) %FVC, PEF, MEF(75,50,25)) can for simplicity be described by linear functions (y = a . height(H)-b . age (A)+c). The forced expiratory volume in one second, FEV(1), was calculated by FEV(1) = 0.0432 . H-0.0347 . A -2.114; where H - height, A - age; r = 0.78. Mean FEV(1) for younger subjects was found to be 106.1 +/- 11.2% of the ECCS reference values and 97.8 +/- 11.7% in older subjects. For all parameters investigated linear regressions on age were steeper than described by the ECCS reference values. The regression of lung function to height largely follows the ECCS prescriptions.

SUMMARY

Bochum lung function values of healthy subjects showed a steeper age descent compared to the reference values of the ECCS. The alternatively discussed reference values of the SAPALDIA-, NHANES- or LuftiBus-Study are higher, but do not cover all necessary parameters and/or the age range. A multi centre study for contemporary reference values is recommended.

Performance of American Thoracic Society-recommended spirometry reference values in a multiethnic sample of adults: the multi-ethnic study of atherosclerosis (MESA) lung study

BACKGROUND

The American Thoracic Society recommends race-specific spirometric reference values from the National Health and Nutrition Survey (NHANES) III for clinical evaluation of pulmonary function in whites, African-Americans, and Mexican-Americans in the United States and a correction factor of 0.94 for Asian-Americans. We aimed to validate the NHANES III reference equations and the correction factor for Asian-Americans in an independent, multiethnic sample of US adults.

METHODS

The Multi-Ethnic Study of Atherosclerosis (MESA) recruited self-identified non-Hispanic white, African-American, Hispanic, and Asian-American participants aged 45 to 84 years at six US sites. The MESA-Lung Study assessed prebronchodilator spirometry among 3,893 MESA participants who performed acceptable tests, of whom 1,068 were asymptomatic healthy nonsmokers who performed acceptable spirometry.

RESULTS

The 1,068 participants were mean age 65 +/- 10 years, 60% female, 25% white, 20% African-American, 23% Hispanic, and 32% Asian-American. Observed values of FEV(1), FEV(6), and FVC among whites, African-Americans, and Hispanics of Mexican origin in MESA-Lung were slightly lower than predicted values based on NHANES III. Observed values among Hispanics of non-Mexican origin were consistently lower. Agreement in classification of participants with airflow obstruction based on lower limit of normal criteria was good (overall kappa = 0.88). For Asian-Americans, a correction factor of 0.88 was more accurate than 0.94.

CONCLUSIONS

The NHANES III reference equations are valid for use among older adults who are white, African-American, or Hispanic of Mexican origin. Comparison of white and Asian-American participants suggests that a correction factor of 0.88, applied to the predicted and lower limits of normal values, is more appropriate than the currently recommended value of 0.94.

Screening for and early detection of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a substantially underdiagnosed disorder, with the diagnosis typically missed or delayed until the condition is advanced. Spirometry is the most frequently used pulmonary function test and enables health professionals to make an objective measurement of airflow obstruction and assess the degree to which it is reversible. As a diagnostic test for COPD, spirometry is a reliable, simple, non-invasive, safe, and non-expensive procedure. Early diagnosis of COPD should provide support for smoking cessation initiatives and lead to reduction of the societal burden of the disease, but definitive confirmation of both proves elusive. Despite substantial effort and investment, implementation of quality spirometry is deficient because of several hurdles and limitations, described in this Review. All in all, spirometry is recognised as the essential test for diagnosis and monitoring of COPD.

Using index of ventilation to assess response to treatment for acute pulmonary exacerbation in children with cystic fibrosis

BACKGROUND

The use of alternative more sensitive measures has become a focus of research in CF. The utility of indexes of ventilation, Lung Clearance Index (LCI) and peak aerobic capacity (peak VO(2)), were studied as assessment tools in gauging response to intravenous (IV) therapy in acute pulmonary exacerbation, in comparison to the more commonly used index of forced expiratory volume in 1 sec (FEV(1)). The utility of a previously published clinical score was further explored.

METHODS

Patients aged 8-18 years admitted for IV antibiotic treatment of a pulmonary exacerbation were recruited. Spirometry, plethysmography, multiple breath nitrogen washout, exercise testing, and Cystic Fibrosis Clinical Score (CFCS) were performed on admission and prior to discharge.

RESULTS

Twenty-eight patients were recruited, with a mean (range) age of 13.7 (8; 17) years, 16 female and 12 male. Mean (range) admission FEV(1) was 61.4 (28; 92)% predicted, or z-score -3.09 (-6.15; -0.52), FVC 83.0 (38; 120)% predicted, or z-score -1.71 (-5.66; -1.17), and Shwachman-Kulczycki 68.9 (50; 90). FEV(1) increased by 7.0% (P < 0.01) from admission to discharge. Mean (range) admission LCI, 10.10 (6.87; 14.83), decreased by 3.8% (P = 0.03). Mean (range) admission peak VO(2) (ml/kg/min), 31.2 (23.4; 45.4), increased on discharge by 6.6% (P < 0.01). Proposed clinical thresholds, based on the available variability data, highlighted the heterogeneity of response in lung function tests. Mean (range) admission CFCS, 26.5 (19; 39), decreased to 19.9 (13; 31) on discharge, a 25.2% improvement (P < 0.01). CFCS demonstrated improvement in 27 of 28 patients. Changes in peak VO(2) (r = -0.50, P = 0.02) and LCI (r = 0.48, P = 0.01) correlated with CFCS change.

CONCLUSIONS

In children with mild-to-moderate CF, whilst statistically significant improvement in both LCI and peak VO(2) were seen, heterogeneity of response was evident. The most consistent improvement was seen in CFCS. Correlation of LCI and peak VO(2) with change in clinical score (CFCS) was seen. The full clinical significance of these changes in LCI and peak VO(2) needs to be evaluated further with additional variability data. The CFCS may be useful in the assessment of response to treatment in CF but requires formal validation.

Spirometric pulmonary function parameters of healthy Chinese children aged 3-6 years in Taiwan

Spirometry is a well-known technique for evaluating pulmonary function, but few studies have focused on preschool children. The aim of this study was to determine reference values of forced spirometric parameters in young Chinese children, aged 3-6 years, in Taiwan. Spirometric measurements were performed at day care centers by experienced pediatricians. Of 248 children without a history of chronic respiratory illness, at least two valid spirometric attempts were obtained from 214 children (109 boys and 105 girls; age: 36-83 [mean = 61] months; height: 90-131 [mean = 111] cm). Values of forced expiratory volume in 1 sec (FEV1) and 0.5 sec (FEV(0.5)), forced vital capacity (FVC), peak expiratory flow rate (PEF), forced expiratory between 25% and 75% FVC (FEF(25-75)), and forced expiratory flow rate at 25%, 50%, and 75% of FVC (FEF(25), FEF(50), and FEF(75)) were derived and analyzed. There were significant positive correlations between study parameters and body height, body weight, and age. Height was the most consistently correlated measurement in both boys and girls. Although boys tended to have higher spirometric values than girls, we found significant differences only in FVC and FEV1 between boys and girls aged 6 years. The regression equations of each parameter were obtained. In conclusion, spirometric pulmonary function tests are feasible in 3- to 6-year-old children. The obtained values and regression equations provide a reference for Chinese preschool children and may be of value in evaluating pulmonary function of children with respiratory problems in this age group.

Defining chronic obstructive pulmonary disease in older persons

OBJECTIVE

To develop a more age-appropriate spirometric definition of chronic obstructive pulmonary disease (COPD) among older persons.

METHODS

Using data from the Third National Health and Nutrition Examination Survey (NHANES III), we developed a two-part spirometric definition of COPD in older persons, aged 65-80 years, that 1) determines a cut-point for the ratio of forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC) based on mortality risk; and 2) among persons below this critical FEV1/FVC threshold, determines cut-points for the FEV1, expressed as a standardized residual percentile (SR-tile) and based on the prevalence of respiratory symptoms and mortality risk. Measurements included spirometry, health questionnaires, and mortality (National Death Index).

RESULTS

There were 2480 older participants with a mean age of 71.7 years; 1372 (55.4%) had a smoking history, 1097 (44.2%) had respiratory symptoms and, over the course of 12-years, 868 (35.0%) had died. Among participants with an FEV1/FVC<.70 and FEV1<5th SR-tile, representing 7.7% of the cohort, the risk of death was doubled (adjusted hazard ratio, 2.01; 95% confidence interval [CI], 1.60-2.54). Among participants with an FEV1/FVC<.70 and FEV1<10th SR-tile, representing 13.4% of the cohort, the prevalence of respiratory symptoms was elevated (adjusted odds ratio, 2.44; CI, 1.79-3.33).

CONCLUSION

In a large, nationally representative sample of community-living older persons, defining COPD based on an FEV1/FVC<.70, with FEV1 cut-points at the 10th and 5th SR-tiles, identifies individuals with an increased prevalence of respiratory symptoms and an increased risk of death, respectively.

Comparison of spirometry criteria for the diagnosis of COPD: results from the BOLD study

Published guidelines recommend spirometry to accurately diagnose chronic obstructive pulmonary disease (COPD). However, even spirometry-based COPD prevalence estimates can vary widely. We compared properties of several spirometry-based COPD definitions using data from the international Burden of Obstructive Lung Disease (BOLD)study. 14 sites recruited population-based samples of adults aged > or =40 yrs. Procedures included standardised questionnaires and post-bronchodilator spirometry. 10,001 individuals provided usable data. Use of the lower limit of normal (LLN) forced expiratory volume in 1 s (FEV(1)) to forced vital capacity (FVC) ratio reduced the age-related increases in COPD prevalence that are seen among healthy never-smokers when using the fixed ratio criterion (FEV(1)/FVC <0.7) recommended by the Global Initiative for Chronic Obstructive Lung Disease. The added requirement of an FEV(1) either <80% predicted or below the LLN further reduced age-related increases and also led to the least site-to-site variability in prevalence estimates after adjusting for potential confounders. Use of the FEV(1)/FEV(6) ratio in place of the FEV(1)/FVC yielded similar prevalence estimates. Use of the FEV(1)/FVC<LLN criterion instead of the FEV(1)/FVC <0.7 should minimise known age biases and better reflect clinically significant irreversible airflow limitation. Our study also supports the use of the FEV(1)/FEV(6) as a practical substitute for the FEV(1)/FVC.

The natural history of chronic airflow obstruction revisited: an analysis of the Framingham offspring cohort

RATIONALE

Understanding normal lung development and aging in health and disease, both in men and in women, is essential to interpreting any therapeutic intervention.

OBJECTIVES

We aimed to describe lung function changes in healthy never-smoking males and females, from adolescence to old age, and to determine the effects of smoking and those derived from quitting.

METHODS

Prospective cohort study within all participants of the Framingham Offspring cohort who had two or more valid spirometry measurements during follow-up (n = 4,391; age range at baseline 13 to 71 yr), with a median follow-up time of 23 years.

MEASUREMENTS AND MAIN RESULTS

To best fit the curves describing FEV(1) changes with age to raw data, we used a generalized additive model with smooth terms and incorporating the subject-specific (longitudinal) random effects. We found that: (1) healthy never-smoker females achieve full lung growth earlier than males, and their rate of decline with age was slightly, but not significantly, lower; (2) smoking increases the rate of lung function decline, both in males and in females; (3) there is a range of susceptibility to the effects of smoking. The presence of respiratory symptoms at baseline and/or a respiratory diagnosis during follow-up appears to identify a group of susceptible smokers; and (4) quitting smoking has a beneficial effect at any age, but it is more pronounced in earlier quitters.

CONCLUSIONS

Lung function changes from adolescence to old age differ in males and females, smoking has similar deleterious effects in both sexes, and quitting earlier is better.

Age- and size-related reference ranges: a case study of spirometry through childhood and adulthood

Age-related reference ranges are useful for assessing growth in children. The LMS method is a popular technique for constructing growth charts that model the age-changing distribution of the measurement in terms of the median, coefficient of variation and skewness. Here the methodology is extended to references that depend on body size as well as age, by exploiting the flexibility of the generalised additive models for location, scale and shape (GAMLSS) technique. GAMLSS offers general linear predictors for each moment parameter and a choice of error distributions, which can handle kurtosis as well as skewness. A key question with such references is the nature of the age-size adjustment, additive or multiplicative, which is explored by comparing the identity link and log link for the median predictor.There are several measurements whose reference ranges depend on both body size and age. As an example, models are developed here for the first four moments of the lung function variables forced expiratory volume in 1 s (FEV(1)), forced vital capacity (FVC) and FEV(1)/FVC in terms of height and age, in a data set of 3598 children and adults aged 4 to 80 years. The results show a strong multiplicative association between spirometry, height and age, with a large and nonlinear age effect across the age range. Variability also depends nonlinearly on age and to a lesser extent on height. FEV(1) and FVC are close to normally distributed, while FEV(1)/FVC is appreciably skew to the left. GAMLSS is a powerful technique for the construction of such references, which should be useful in clinical medicine.

Transient reference values for impulse oscillometry for children aged 3-18 years

Impulse oscillometry (IOS) is a technique of assessing mechanical properties of respiratory system by means of measuring resistances and reactances in a number of frequencies during tidal breathing. It is especially useful in preschool children, however has also been validated in older children and adults. The aim of the present study was to construct equations describing normal values of oscillatory parameters in pediatric population of healthy polish children. Six hundred twenty-six healthy children aged 3.1-18.9 years (278 boys and 348 girls) completed the study. Analysis revealed that body height was the best predictor and resistances are best described with exponential model while reactances with linear one, with correlation coefficient r reaching the value of 0.9. Oscillometric resistances decrease with height, while reactances increase. Reference values for children and adolescents will allow not only the interpretation of the measurement, but also will make possible to study changes of oscillometric indices during growth.

The EPICure study: comparison of pediatric spirometry in community and laboratory settings

RATIONALE

Accuracy of spirometry testing is a prerequisite for its use as an objective outcome measure in large epidemiological studies. We compared spirometry measurements obtained by trained pediatricians in a variety of school settings with those obtained in the laboratory by respiratory physiologists.

METHODS

Following a 3-day training course, three pediatricians carried out spirometry in children born extremely preterm (EP) and age matched controls in schools across the UK and Ireland (The EPICure study). A subgroup had repeated measurements in the laboratory. Spirometric flows and volumes were expressed as Z-scores. Bland-Altman analysis was used to calculate within-subject differences.

RESULTS

Fifty children (40% boys), 37 (74%) of whom were born EP, with a mean age 10.8 years had paired spirometry results (average interval between tests: 20.3 weeks). There was no statistically significant difference between any of the outcome variables: mean (95% CI of difference) in Z-scores [school-laboratory]) being 0.0 (-0.1; 0.1) for FEV(1), 0.1 (-0.1; 0.3) for FVC, -0.1 (-0.3; 0.1) for FEF(25-75), and 0.0 (-0.3; 0.1) for FEV(1)/FVC. Within individuals, the 95% limits of agreement for repeated measures were within +/- 1 Z-score for FEV(1) and FVC, and within +/- 1.5 Z-score for FEF(25-75) and FEV(1)/FVC.

CONCLUSION

With appropriate training, quality control, and support, pediatric spirometry can reliably be performed outside the lung function laboratory.

Cross-sectional and longitudinal spirometry in children and adolescents: interpretative strategies

RATIONALE

Single and serial spirometric data are commonly compared with predicted values to assess pulmonary function and normal lung growth.

OBJECTIVES

Do reference equations adequately describe pulmonary function in a population and in growing individuals?

METHODS

We applied five sets of reference equations with appropriate age ranges to cross-sectional data of FEV(1), FVC, and FEV(1)/FVC from the United States, Estonia, and The Netherlands (1,487 boys and 1,340 girls, 6 to 18 years of age), and to serial measurements in Dutch (430 girls and 769 boys, 6 to 19 years of age) and in German and Austrian children (1,305 girls and 1,303 boys, 6 to 13 years of age).

MEASUREMENTS AND MAIN RESULTS

Compared with reference equations from Polgar and Zapletal, cross-sectional FEV(1) and FVC declined between the ages of 6 and 12 and then increased, leading to a spurious change of up to 25% predicted; this pattern was most pronounced in boys. In cross-sectional data this trend was much weaker when using reference equations from Hankinson, Quanjer, and Stanojevic, and these equations provided a good fit from the age of 12 upward. In longitudinal data (i.e., within individuals), the trend was more pronounced for FEV(1) in boys than in girls. No set of equations provided a satisfactory fit in the lower limits of normal, but Hankinson and Stanojevic equations performed best.

CONCLUSIONS

Spirometric reference equations that use only height for predicting pulmonary function are unsuitable for describing the progression of pulmonary function. Those that incorporate height and age demonstrate some discrepancy with longitudinal data. Failure to take these spurious trends into account leads to significant errors in estimating the natural course of respiratory disease, in allocating patients to treatment groups, or in assessing long-term effects of drug intervention in school children and adolescents.

Effects of cystic fibrosis lung disease on gas mixing indices derived from alveolar slope analysis

S(cond) and S(acin) are derived from analysis of concentration-normalized phase III slopes (Sn(III)) of a multiple breath inert gas washout. Studies in healthy and COPD subjects suggest these reflect ventilation heterogeneity in conducting and acinar airway zones respectively, but similar studies in cystic fibrosis (CF) are lacking. S(cond), S(acin) and lung clearance index (LCI, a measure of overall gas mixing efficiency) were measured in 22 adults and 18 children with CF and 17 adult and 29 child controls. Plethysmography and gas transfer measurements were performed in adults, and spirometry in all subjects. S(cond) was elevated in almost all CF patients, including children with mild disease and normal LCI. However, S(cond) did not correlate with other measurements and appeared to reach a maximum; further increase in ventilation heterogeneity being restricted to S(acin). The nature and/or severity of CF lung disease may invalidate assumptions underlying the ability to separate phase III slope analysis of ventilation heterogeneity into proximal and peripheral components, and LCI may be a better indicator of gas mixing in this population.