Spirometric reference values in Tunisian children

BACKGROUND: In Tunisia, there are no normal values of pulmonary function for healthy Tunisian children. OBJECTIVES: The purpose of this study was to set reference values for spirometric lung function in Tunisian children and to compare these results with other data sets. METHODS: Spirometric values were measured with a Minato portable spirometer in 1,114 asymptomatic, nonsmoking Tunisian children (581 boys and 533 girls) 6-16 years of age. Natural logarithmic values of lung function and standing height were used in the final regression model. RESULTS: Prediction equations for forced vital capacity (FVC), forced expiratory volume in 1 s (FEV(1)), FEV(1)/FVC x 100, maximum mid expiratory flow (MMEF 25-75%) and peak expiratory flow (PEF) for both sexes are presented with standing height as the dependent variable. Our data show a significant increase in lung function with standing height in both sexes. Comparing our results with recent data, values of FVC and FEV(1) in both sexes in the present study are close to those in European, white US and Asian children, whereas our values are higher than the Libyan ones. CONCLUSIONS: Healthy Tunisian children showed similar spirometric reference values compared to European, white US and Asian children. Thus, these standards of lung function could also be used in Tunisia.     

Arm span as an independent predictor of pulmonary function parameters: validation and reference values

BACKGROUND AND OBJECTIVES: To determine if arm span can be used as a measure of body length in developing prediction equations for lung function and to compare these equations with height-derived equations. METHODS: Standing height and arm span were measured for all study subjects. Spirometry measurements included FVC, FEV(1), FEV(1)/FVC ratio, PEFR, FEF(25), FEF(50), FEF(75) and FEF(25-75). These data were used to develop prediction equations using multiple regression analysis based on age, gender and arm span. An independent group (225 subjects) was used to evaluate the accuracy of the equations. Predicted values for each parameter were calculated separately for arm span and height and compared with the measured values. RESULTS: Study subjects comprised 1865 healthy non-smoking Persian volunteers. Arm span-based equations accurately predicted all of the spirometric parameters. The standard errors of the estimate for prediction equations based on arm span were slightly smaller than those based on standing height. Average predicted values based on height predicted from arm span did not consistently agree with the measured values. CONCLUSIONS: Predicting pulmonary parameters using equations based on arm span is as reliable as using equations based on standing height and are more accurate for patients in whom height cannot be measured reliably.     

Do NHLBI lung function criteria apply to children? A cross‐sectional evaluation of childhood asthma at National Jewish Medical and Research Center, 1999–2002

Although National Heart Lung Institute (NHLBI) guidelines categorize asthma severity based on spirometry, few studies have evaluated the utility of these spirometric values in grading asthma severity in children. Asthma is thought to be progressive, but little is known about the loss of lung function in childhood. This study sought to determine the spirometric indices in children from 4-18 years of age. Retrospective cross-sectional analysis was performed on all spirometries done in children at the National Jewish Medical and Research Center from 1999-2002. In total, 2,728 children performed 24,388 measures. The mean +/- SD values for forced vital capacity (FVC), forced expired volume in 1 sec (FEV(1)), FEV(1)/FVC ratio, and forced expiratory flow (FEF)(25-75) were 92.7 +/- 16.2, 92.2 +/- 18.0, 85.3 +/- 9.3, and 78.0 +/- 36.5 percent predicted, respectively. Seventy-seven percent of FEV(1) values were >/= 80%, 18.6% were between 60-80%, and 3.1% were <60% of predicted. FEV(1) was highest in 5-year-old children; it declined thereafter, reaching a nadir at 11 years, followed by a partial recovery from 12-18 years. Expressed in liters, FEV(1) values were lower than expected at every age, with the greatest difference at 18 years. FEV(1)/FVC ratios declined through childhood, suggesting impaired airway but not lung growth in children with asthma. In conclusion, the majority of asthmatic children attending a tertiary care facility had FEV(1) values within normal range. With increasing age, the increase in FEV(1) lags behind that of nonasthmatics, so that by 18 years, maximum FEV(1) is impaired. The NHLBI FEV(1) cutoff values do not appear to accurately stratify pediatric asthma, and no useful FEV(1) cutoff could be generated.     

Spirometry in 3- to 6-year-old children with cystic fibrosis

Spirometry is routinely used to assess pulmonary function of older children and adults with cystic fibrosis (CF); however, few data exist concerning the preschool age group. We have reported normative spirometric data for 3- to 6-year-old children. The current study was designed to assess a similarly aged group of clinically stable patients with CF. Thirty-three of 38 children with CF were able to perform 2 or 3 technically acceptable maneuvers. These patients had significantly decreased FVC, FEV(1), FEV(1)/FVC, and FEF(25-75) when expressed as z scores (number of SD from predicted): -0.75 +/- 1.63, -1.23 +/- 1.97, -0.87 +/- 1.33, and -0.74 +/- 1.63, respectively. There were significant positive correlations of the Brasfield radiological score with FVC and FEV(1) z scores (r(2) = 0.26, p < 0.01 and r(2) = 0.24, p < 0.01). In addition, homozygous patients for the DeltaF508 mutation had lower z scores for FVC (-1.21 versus 0.47, p < 0.01) and FEV(1) (-1.38 versus 0.21, p < 0.05) than heterozygous patients. Of the 14 patients who had full flow-volume spirometric measurements during infancy, 10 had FEF(25-75) z scores greater than -2 at both evaluations. Our findings suggest that spirometry can successfully be used to assess lung function in preschool children with CF and has the potential for longitudinal assessment from infancy through adulthood.     

Pulmonary function in normal south Indian children aged 7 to 19 years

There are only a few studies that have established reference standards for pulmonary function of Indian children. Reference standards for pulmonary function that are reported for Indian children are mainly from northern and western parts of the country and there is a paucity of data on pulmonary function in normal South Indian children. Therefore, pulmonary function tests (spirometry and maximal expiratory flow rates) were carried out in 469 South Indian healthy children (246 boys and 223 girls) between 7-19 years of age to derive regression equations to predict pulmonary function. The correlations of forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were, in general highest with height followed by weight and age. Peak expiratory flow rate (PEFR), forced mid-expiratory flow (FMF) and forced expiratory flow rates at 25%, 50% and 75% of FVC (FEF25% FVC, FEF50%FVC and FEF75%FVC) were also significantly correlated with physical characteristics (age, height and weight). With a view to find out regression equations to predict spirometric functions based on physical characteristics (age, height and/or weight), the functions were regressed over all possible combinations of regressor variables, i.e. age, height and weight separately for boys and girls. The height influences the prediction equation in males to a great extent, whereas age and weight had greater influence in girls. Regression equations were derived for boys and girls for predicting normal pulmonary functions for children in South India. The pulmonary function measurements in South Indian children were similar to those reported for subjects from Western India and lower than those reported for Caucasians.     

Static lung volumes in patients with Cushing's disease.

OBJECTIVE: Numerous clinical manifestations have been described in association with Cushing's syndrome. There are no eligible data on pulmonary function tests in Cushing's disease (CD). We aimed to asses pulmonary function tests including spirometry in a series of patients with active CD. MATERIALS AND METHODS: This cross-sectional study comprised 10 patients with Cushing's disease (F/M, 9/1). The forced expiratory volume in 1st second (FEV1), the forced vital capacity (FVC), the FEV1/FVC ratio and the forced expiratory flow over the middle half of the FVC (FEF 25-75%) values and predicted values were determined by spirometry. RESULTS: Mean age, height, weight, body mass index were 36.7+/-12.6 yrs (range 22-63 years), 156.9+/-8.4 cm, 74.1+/-10.7 kg, 29.6+/-3.8 kg/m(2), respectively. Spirometric abnormalities (impairment of FEV1, FVC, FEV1/FVC and FEF 25-75 values) were not detected, and there were no significant differences compared to reference values. Disease duration and cortisol concentrations by HDDSTs were negatively correlated with predicted FEV1/FVC values and the percentage of predicted FEV1 ratios, respectively. DISCUSSION: The lung volume and ventilatory performance by spirometry were not disturbed in patients with endogenous hypercostisolism due to Cushing's disease.     

Spirometry in an unselected group of 6-year-old children: the DARC birth cohort study

This study presents reference equations for spirometric parameters in 6-year-old children and evaluates the ability of spirometry to discriminate healthy children from children with asthma. Baseline spirometry and respiratory symptoms were assessed in 404 children participating in a longitudinal birth cohort study. Children with known asthma, possible asthma and a control group also performed bronchodilator measurements. At least two acceptable flow-volume curves at baseline were obtained by 368/404 children (91%). The two best values for FEV1 and FVC were within 5% of each other in 88% and 83% of children, respectively. Linear regression analyses for 242 children included in the reference population demonstrated height to be the main predictor of all spirometric indices except FEV1/FVC. FEV1, FEV75, and FVC correlated reasonably to anthropometric data in contrast to flow parameters. Gender differences were found for FEV1, FVC, and FEV75, but not for flow parameters. Asthma was diagnosed in 25/404 children. Baseline lung function in healthy children and children with asthma overlapped, although asthmatic children could be discriminated to some extent. Bronchodilator tests showed a difference in Delta FEV1(mean) between healthy children and children with asthma (3.1% vs. 6.1%, P < 0.05). At a cut-off point of Delta FEV1 = 7.8%, bronchodilator tests had a sensitivity of 46% and a specificity of 92% for current asthma. Spirometry including bronchodilator measurements was demonstrated to be feasible in 6-year-old children and reference values were determined. Spirometry aids the diagnosis of asthma in young children, but knowledge on sensitivity and specificity of these measurements is a prerequisite.     

Spirometric pulmonary function in 3- to 5-year-old children

Forced expiratory maneuvers are routinely used in children, 6 years of age and older for the diagnosis and follow-up of respiratory diseases. Our objective was to establish normative data for an extensive number of parameters measured during forced spirometry in healthy 3- to 5-year-old children. Children aged between 3 and 5 years were tested in 11 daycare centers. Usual parameters, including FEV1, FVC, PEF, FEF(25-75), FEF25, FEF50, FEF75, and Aex were measured and analyzed in relation to sex, age, height, and weight. In addition, the same analysis was performed for FEV0.5 and FEV0.75. One hundred sixty-four children were recruited for testing including 87 girls and 77 boys. Thirty-five were 3 years old, 63 were 4 years old, and 66 were 5 years old. Overall, 143 children (87%) accepted to perform the test and 128 children (78%) were able to perform at least two technically acceptable expiratory maneuvers. Analyses using different regression models showed that height was the best predictor for every parameter. In conclusion, the present study confirms that most healthy 3-5 years old children can perform valid forced expiratory maneuvers. In agreement with other studies, we found that height is the most important single predictor of various parameters measured on forced spirometry. The present study is the first to establish normative values for FEV0.75, as well as to demonstrate that Aex can be easily performed in the majority of children aged 3-5 years. These are likely important parameters of lung function in this age range.     

Airway hyperreactivity in subjects with tetraplegia is associated with reduced baseline airway caliber

OBJECTIVES: We administered aerosolized histamine to 32 subjects with tetraplegia to determine whether there were differences in spirometric and/or lung volume parameters between responders and nonresponders. RESULTS: Baseline pulmonary function parameters revealed mild to moderate restrictive dysfunction. We found that 25 subjects (78%) were hyperreactive to histamine (mean provocative concentration of a substance causing a 20% fall in FEV(1) [PC(20)], 1.77 mg/mL). Responders (PC(20), < 8 mg/mL) had significantly lower values for forced expiratory flow between 25% and 75% of the outflow curve (FEF(25-75)), FEF(25-75) percent predicted, and FEF(25-75)/FVC ratio. Among all 32 subjects, the natural logarithmic transformation performed on PC(20) values (lnPC(20)) correlated with FEF(25-75) percent predicted, FEV(1) percent predicted, and FEF(25-75)/FVC ratio but not with FVC percent predicted. Responders with PC(20) values < 2 mg/mL (n = 13) had significantly reduced values for FVC, FVC percent predicted, FEV(1), and FEV(1) percent predicted compared to those with PC(20) values between 2 mg/mL and 8 mg/mL. In addition, among responders, there was a significant correlation between lnPC(20) and FVC percent predicted. A significant relationship was found between maximal inspiratory pressure (PImax) and both FEV(1) percent predicted and FEF(25-75) percent predicted, but not between lnPC(20) and either PImax or maximal expiratory pressure (PEmax). CONCLUSIONS: These findings demonstrate that subjects with tetraplegia who exhibit airway hyperreactivity (AHR) have reduced baseline airway caliber and that lower values for lnPC(20) are associated with parallel reductions in surrogate spirometric indexes of airway size (FEV(1) percent predicted and FEF(25-75) percent predicted) and airway size relative to lung size (FEF(25-75)/FVC ratio). The absence of an association between lnPC(20) and FVC percent predicted for the entire group or between lnPC(20) and either PImax or PEmax indicates that reduced lung volumes secondary to respiratory muscle weakness cannot explain the mechanism(s) underlying AHR. Among responders, however, a possible role for reduction in lung volume, as it pertains to increasing AHR, cannot be excluded. Proposed mechanisms for reduced baseline airway caliber relative to lung size in subjects with tetraplegia include unopposed parasympathetic activity secondary to the loss of sympathetic innervation to the lungs and/or the inability to stretch airway smooth muscle with deep inhalation.     

How accurate is spirometry at predicting restrictive pulmonary impairment?

OBJECTIVE: To determine the accuracy with which spirometric measurements of FVC and expiratory flow rates can diagnose the presence of a restrictive impairment. DESIGN: The pulmonary function tests of 1,831 consecutive white adult patients who had undergone both spirometry and lung volume measurements on the same visit over a 2-year period were analyzed. The probability of restrictive pulmonary impairment, defined as a reduced total lung capacity (TLC) below the lower limit of the 95% confidence interval, was determined for each of several categoric classifications of the spirometric data, and additionally for each of several interval levels of the FVC and the FEV1/FVC ratio. SETTING: A large clinical laboratory in a university teaching hospital using quality-assured and standardized spirometry and lung volume measurement techniques according to American Thoracic Society standards. RESULTS: Two hundred twenty-five of 1,831 patients (12.3%) had a restrictive defect. The positive predictive value of spirometry for predicting restriction was relatively low; of 470 patients with a low FVC on spirometry, only 41% had restriction confirmed on lung volume measurements. When the analysis was confined to the 264 patients with a restrictive pattern on spirometry (ie, low FVC and normal or above normal FEV1/FVC ratio), the positive predictive value was 58%. Conversely, spirometry had a very favorable negative predictive value; only 2.4% of patients (32 of 1,361) with a normal vital capacity (VC) on spirometry had a restrictive defect by TLC measurement. The probability of a restrictive defect was directly and linearly related to the degree of reduction of FVC when the FVC was < 80% of predicted (p = 6.002). Combining the FVC and the FEV1/FVC ratio improved the predictive ability of spirometry; for all values of FVC < 80% of the predicted amount, the likelihood of restrictive disease increased as the FEV1/FVC ratio increased. CONCLUSIONS: Spirometry is very useful at excluding a restrictive defect. When the VC is within the normal range, the probability of a restrictive defect is < 3%, and unless restrictive lung disease is suspected a priori, measurement of lung volumes can be avoided. However, spirometry is not able to accurately predict lung restriction; < 60% of patients with a classical spirometric restrictive pattern had pulmonary restriction confirmed on lung volume measurements. For these patients, measurement of the TLC is needed to confirm a true restrictive defect.     

Lung volumes in healthy Afro-Caribbean children aged 4-17 years

Lung volumes in healthy children differ according to their ethnic origin. We wished to determine if any differences in the lung volumes of Afro-Caribbean (AC) children from those predicted by Caucasian reference values disappeared if the results were related to sitting height or to 90% or 77% of lung volumes predicted for height from Caucasian reference values based on standing height. We took, as our working hypothesis, that it is inappropriate to use Caucasian reference values to interpret data from Afro-Caribbean children, and that ethnic-specific reference values are required. This was a prospective, observational study. Subjects included 80 AC children with a median age of 9 (range, 4.3-17.8) years. Standing and sitting height were measured. Lung volumes were measured by body plethysmography (total lung capacity, TLC(pleth); functional residual capacity, FRC(pleth); and vital capacity, VC(pleth)), helium gas dilution (functional residual capacity, (FRC(He)), spirometry (forced expiratory volume in 1 sec, FEV(1)), and forced vital capacity (FVC). The lung volumes of AC children correlated significantly with standing height, but differed significantly from values predicted from Caucasian reference values based on standing height (P < 0.05). Significant differences remained for TLC(pleth), FRC(pleth), FRC(He), RV(pleth), VC(pleth), FEV(1), and FVC when the results were related to sitting height or 90% or 77% of values predicted from Caucasian reference values based on height (P < 0.05). Lung volumes in Afro-Caribbean children should be compared to ethnic-specific reference values.     

Spirometry and maximal expiratory flow-volume curve reference standards for Polynesian, European, and Chinese teenagers

Lung function was compared and reference standards were determined in 1,007 Polynesian, European, and Chinese teenagers attending school in Tahiti (517 boys, 490 girls; mean age, 14.4 years). Spirometric study results and maximal expiratory flow-volume curves were measured using techniques recommended by the American Thoracic Society. Age, standing height, and weight were chosen as the independent variables for males, and age and standing height for females. Regression equations constructed with logarithmically transformed dependent variables provided accurate predictions. We observed significant racial differences: in the Europeans, forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were higher than the mean values predicted for the whole study population, while forced expiratory flow during the middle half of the FVC (FEF25-75%) and maximal expiratory flows after 25, 50, and 75 percent of FVC had been exhaled (V max 25, 50, and 75, respectively) were about equal to the mean values; in the Polynesians, volumes and flows were mostly lower than the mean; in the Chinese, FVC in boys and girls, and FEV1 in girls only, were lower, while the other flows were higher. The FEV1/FVC, FEF25-75%/FVC, Vmax25/FVC, Vmax50/FVC, and Vmax75/FVC were significantly higher than the mean in the Chinese boys and girls and often lower in the Europeans.     

Spirometry in early childhood in cystic fibrosis patients

BACKGROUND: Spirometry data in cystic fibrosis (CF) patients in early childhood is scarce, and the ability of spirometry to detect airways obstruction is debatable. OBJECTIVE: To evaluate the ability of spirometry to detect airflow obstruction in CF patients in early childhood. METHODS: CF children (age range, 2.5 to 6.9 years) in stable clinical condition were recruited from five CF centers. The children performed guided spirometry (SpiroGame; patented by Dr. Vilzone, 2003). Spirometry indices were compared to values of a healthy early childhood population, and were analyzed with relation to age, gender, and clinical parameters (genotype, pancreatic status, and presence of Pseudomonas in sputum or oropharyngeal cultures). RESULTS: Seventy-six of 93 children tested performed acceptable spirometry. FVC, FEV1, forced expiratory flow in 0.5 s (FEV0.5), and forced expiratory flow at 50% of vital capacity (FEF50) were significantly lower than healthy (z scores, mean +/- SD: - 0.36 +/- 0.58, - 0.36 +/- 0.72, - 1.20 +/- 0.87; and - 1.80 +/- 1.47, respectively; p < 0.01); z scores for FEV1 and FVC were similar over the age ranges studied. However, z scores for FEV0.5 and forced expiratory flow at 25 to 75% of vital capacity were significantly lower in older children compared to younger children (p < 0.001), and a higher proportion of 6-year-old than 3-year-old children had z scores that were > 2 SDs below the mean (65% vs 5%, p < 0.03). Girls demonstrated lower FEF50 than boys (z scores: - 2.42 +/- 1.91 vs - 1.56 +/- 1.23; p < 0.001). Clinical parameters evaluated were not found to influence spirometric indices. CONCLUSIONS: Spirometry elicited by CF patients in early childhood can serve as an important noninvasive tool for monitoring pulmonary status. FEV0.5 and flow-related volumes might be more sensitive than the traditional FEV1 in detecting and portraying changes in lung function during early childhood.     

Normal spirometric reference values for Omani children and adolescents

OBJECTIVES: Normal lung function has been shown to be population specific. The aim of this study was to derive normal reference spirometric values for Omani children and adolescents. METHODOLOGY: Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV(1)), peak expiratory flow and forced mid-expiratory flow were measured in 837 healthy Omani school children aged 6-19 years. Multiple linear regression analysis was performed for each spirometric parameter against age, height and weight for boys and girls separately. RESULTS: All measured spirometric parameters increased with age and height and were significantly higher in boys than girls. Height explained the maximum variance for all parameters. After accounting for height in the prediction equations, the contribution of age and weight was minimal. The expiratory ratio (FEV(1)%FVC) was independent of age and height and its mean values (+/- standard deviation) were slightly higher in girls (91.1 +/- 6.1%) than boys (86.5 +/- 7.1%; P < 0.001). The predicted normal values of the subjects using the derived equations were between 5 and 10% lower than the respective values for subjects in Caucasian sample groups. CONCLUSION: The developed prediction equations can be used in clinical practice in Oman and can be considered for use in neighbouring Arab countries.     

Effects of indoor air pollution on lung function of primary school children in Kuala Lumpur

In a cross-sectional study of 7-12 year-old primary school children in Kuala Lumpur city, lung function was assessed by spirometric and peak expiratory flow measurements. Spirometric and peak expiratory flow measurements were successfully performed in 1,214 and 1,414 children, respectively. As expected, the main predictors of forced vital capacity (FVC), forced expiratory volume in one second (FEV1), forced expiratory flow between 25% and 75% of vital capacity (FEF25-75), and peak expiratory flow rate (PEFR) were standing height, weight, age, and sex. In addition, lung function values of Chinese and Malays were generally higher than those of Indians. In multiple regression models which included host and environmental factors, asthma was associated with significant decreases in FEV1, FEF25-75, and PEFR. However, family history of chest illness, history of allergies, low paternal education, and hospitalization during the neonatal period were not independent predictors of lung function. Children sharing rooms with adult smokers had significantly lower levels of FEF25-75. Exposures to wood or kerosene stoves were, but to mosquito repellents were not, associated with decreased lung function.     

Lung function in diastrophic dysplasia

Diastrophic dysplasia (DD) is a rare skeletal dysplasia characterized by short-limbed short stature, contractures and early degeneration of joints, and spinal deformities such as scoliosis. Mortality is increased in the neonatal period, in part due to tracheo- and bronchomalacia. Additionally, spinal deformities are very rigid, decreasing mobility of the chest cage. The aim of our study was to evaluate lung volumes and airway flow dynamics in patients with DD. A total of 31 patients (12 males, 19 females) underwent a detailed clinical examination measurements of standing height PA-radiography of the spine, flow-volume spirometry, and body plethysmography. The patients were assigned to two groups: children and adolescents (0-18 years, n = 18) and adults (over 18 years, n = 13). The mean spirometric parameters were mostly within the predicted value range, although the variation was wide. At least one abnormally low spirometry parameter was found in 6 (33%) of the children and adolescents and in 7 (54%) of the adults. Mean forced vital capacity (FVC) was 104% (range 48-163%) of predicted values in the children and adolescents and 95% (58-140%) of the adults. Peak expiratory flow (PEF) values were abnormal in 4 (22%) of the children and adolescents and in 5 (39%) adults. The mean plethysmographic parameters were all within the predicted value range. At least one abnormal plethysmographic value was found in 6 (33%) of the children and adolescents and in 4 (31%) of the adults. Airway resistance (Raw) was significantly higher in the adults than in the children and adolescents (P = 0.016), and was abnormally high in 3 (23%) of the adults. The angle of thoracic or thoracolumbar scoliosis correlated with the percentages of the predicted values of FVC (r(s) = - 0.66), forced expired volume in 1 sec (FEV(1)) (r(s) = - 0.56), and total lung capacity (TLC) (r(s) = - 0.67). Age correlated with the FEV(1)/FVC ratio (r(s) = - 0.41), with the maximal expired flow at 50% FEV (MEF(50)) values (r(s) = - 0.55), with the residual volume (RV) values (r(s) = - 0.47), and with the RV/TLC ratio (r(s) = - 0.43). Variable bronchial obstruction was found in 1 (6%) child and in 2 (17%) adults. Although the patients with DD had, on average, normal lung volumes, large individual variation occurred. Airway resistance was increased in adults. The angle of scoliosis correlated inversely with lung volume parameters.     

Comparison between specified percentage and fifth percentile criteria for spirometry interpretation in Thai patients

OBJECTIVES: The present study was conducted to determine the degree of agreement between the interpretation of spirometry using a specified percentage of predicted value (SPC) and the fifth percentile (FPC) as the cut off between normal and abnormal. METHODOLOGY: Spirometric values were collected for 1754 subjects attending the respiratory service at Siriraj Hospital between February 2000 and April 2001. These values included forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC, maximal mid-expiratory flow (FEF25-75%) and peak expiratory flow (PEF). A comparison of results between SPC and FPC was performed. The SPC cut-off values for FVC, FEV1, FEV1/FVC, FEF25-75% and PEF were 80% predicted, 80% predicted, 70%, 65% predicted and 80% predicted, respectively. The FPC cut-off values were calculated from reference equations for the Thai population. Inter-rater agreement was calculated as the kappa score. RESULTS: High kappa scores were obtained for FVC (0.84), FEV1 (0.88) and FEF25-75% (0.80). However, poor agreement was found for FEV1/FVC (0.72) and PEF (0.61). When the cut-off values for SPC were modified to 90% of predicted values for FEV1/FVC and to 65% of predicted values for PEF, agreement was substantially improved to 0.92 and 0.89, respectively. CONCLUSIONS: Interpretation by SPC using cut-off values of 80% predicted for FVC and FEV1 and 65% predicted for FEF25-75% resulted in good agreement with FPC. However, the SPC cut-off values for FEV1/FVC and PEF should be modified to 90% predicted and 65% predicted, respectively.     

Sex and race differences in the development of lung function

The second National Health and Nutrition Examination Survey (1976 to 1980) provided spirometric examinations for a nationwide sample of individuals 6 to 24 yr of age. We analyzed spirometric data on 1,963 healthy, nonsmoking blacks and whites to examine sex and race differences in FVC, FEV1, FEV3, PEF, Vmax50, Vmax75, and mid-maximal expiratory flow (MMEF). The population was divided into three age groups: children (6 to 11), teens (males 12 to 20, females 12 to 17), and young adults (males 21 to 24, females 18 to 24). Controlling for sex, age, standing height, and body mass index, blacks had consistently lower levels of lung function for most measures. The inclusion of sitting height explained part of this reduction. Controlling for lung size using FVC as a surrogate, the performance of blacks on other spirometry measures was equal to whites in all age groups. Males tended to outperform females with the same anthropometric characteristics before the inclusion of FVC as a predictor variable. However, after controlling for lung size (FVC), female performance exceeded that of males. The higher female performance is particularly noticeable in the later flow measures. Both anatomic and physiologic factors may account for these findings.     

Discriminating measures and normal values for expiratory obstruction

OBJECTIVES: To develop mean and 95% confidence limits for the lower limit of normal (LLN) values for forced expiratory volume in 3 s (FEV3)/FVC ratio for Latin, black, and white adults; to ascertain comparative variability of the FEV1/FVC ratio, the FEV3/FVC ratio, and forced expiratory flow, midexpiratory phase (FEF(25-75)) in never-smoking adults; to evaluate their utility in measuring the effect of smoking on airflow limitation; and to develop and use the fraction of the FVC that had not been expired during the first 3 s of the FVC (1 - FEV3/FVC) to identify the growing fraction of long-time-constant lung units. DESIGN: Analysis of the Third National Health and Nutrition Examination Survey (NHANES III) database of never-smokers and current smokers. PARTICIPANTS: A total of 5,938 adult never-smokers and 3,570 current smokers from NHANES III with spirometric data meeting American Thoracic Society standards. MEASUREMENTS AND RESULTS: After establishing new databases for never-smokers and current smokers, we quantified the mean and LLN values of FEV3/FVC in never-smokers, and identified spirometric abnormalities in current smokers. When associated with older age, FEV3/FVC decreases and 1 - FEV3/FVC increases as FEV1/FVC decreases. On average, using these measurements, the condition of current smokers worsened about 20 years faster than that of never-smokers by middle age. If < 80% of the mean predicted FEF(25-75) was used to identify abnormality, over one quarter of all never-smokers would have been falsely identified as being abnormal. Using 95% confidence limits, 42% of 683 smokers with reduced FEV1/FVC and/or FEV3/FVC would have been judged as normal by FEF(25-75). CONCLUSIONS: FEV1/FVC, FEV3/FVC, and 1 - FEV3/FVC characterize expiratory obstruction well. In contrast, FEF(25-75) measurements can be misleading and can cause an unacceptably large number of probable false-negative results and probable false-positive results.     

Spirometry in 5-year-olds--validation of current guidelines and the relation with asthma

INTRODUCTION: Spirometry is more frequently measured in younger children. Our primary aim was to validate 2005 ATS-ERS Task Force standards for spirometry in adults and older children among a population of 5-year-old children. Our secondary aim was to relate spirometry to asthma symptoms. METHODS: Children were participants in a longitudinal cohort study where asthma symptoms and spirometry were assessed. RESULTS: Of the 827 children assessed, spirometry was obtained in 638 (85 with wheeze). A back-extrapolated volume/FVC ratio of <5% was achieved in 99% of children, the best two FVC were < or =150 ml of each other in 89% and three efforts were obtained within six attempts in 88%. The best two FVC were within 10% of each other in 82% of children. Only 13% achieved a forced expiratory time (FET) of > or =3 sec, whereas 80% had an FET of > or =1 sec. All criteria (including FET > or =1 s and FVC < or =10%) were met in 400 (65%) of the 638 children. Most spirometric indices were reduced in association with current wheeze and a history of asthma; children with current wheeze had a mean reduction of 0.65 FEV(1) z score compared to healthy children, P < 0.001. An FEV(1) z score of -1.0 had 82% sensitivity but only 50% specificity for current wheeze, the corresponding numbers for an FEF(50) z score of -1.0 being 79% and 71%. CONCLUSIONS: The standards for spirometry are mostly achieved in this age group but are not necessarily valid and require revision. Reliable spirometry is feasible in 5-year-old children where reduced measurements are associated with asthma symptoms and in whom FEF(50) appears to be the most discriminatory variable.