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.     

Prediction of fat-free body mass from bioelectrical impedance among 9- to 11-year-old Swedish children

AIM: Predictive equations for estimating body composition from bioelectrical impedance analysis (BIA) among Scandinavian children are lacking. In the present study, equations for estimation of fat-free body mass (FFM) and lean tissue mass (LTM) were developed and cross-validated from BIA using dual-energy X-ray absorptiometry (DXA) as the reference measurement of body composition. METHODS: The study population consisted of 49 girls and 52 boys aged 9-11 years from Malm?, Sweden. Bioelectrical impedance was measured between hand and foot at 50 kHz. Predictive equations were developed by multiple linear regression and cross-validated against DXA measurements of body composition. RESULTS: FFM was predicted from BIA and anthropometric variables with an adjusted R(2)= 0.95 and root mean square error (RMSE) = 0.84 kg, and LTM was predicted with an adjusted R(2)= 0.95 and RMSE = 0.87 kg. Cross-validation revealed a mean RMSE = 0.95 kg FFM and a mean RMSE = 0.96 kg LTM. Prediction of body composition from equations developed in previous literature was mixed when applied to the present cohort of children. CONCLUSIONS: FFM and LTM are predicted with sufficient accuracy at the population level. We recommend that the predictive equations developed in the present study are used in prepubescent European children aged 9-11 years only in order to minimize confounding of results because of possible differences in population samples.     

Reference equations for spirometry from a general population sample in central Italy

Aim of this study was to derive new lung function reference equations and compare the predicted values with those from three sets of existing reference equations: one derived from a Northern Italy population and the two others widely used in European (ECCS) and American (NHANES III) clinical practice. Reference equations for flow-volume curve indexes and VC were derived on 497 normal subjects, aged 8-74, from the epidemiological survey in Pisa, Central Italy (1991-1993). By applying natural cubic splines, one single smooth and continuous equation for the entire age range was provided for each index, separately by gender. Along with age and height, reference values also depended on BMI. Differences among the four reference equations for FEV(1), FVC, VC were quantified for average subjects. The magnitude largely varied over the age range in both genders, reaching up to half litre of air volume at specific ages. Age-gender-specific prevalence rates of airway obstruction, as defined by the ERS criterion, largely varied by applying the considered equations, the differences ranging from -3% to 28%. The observed discrepancies confirm that reference equations should be derived from a population most similar to that for which the equations are to be used and based on measurements obtained by the same instrument and testing procedures, in order to minimize technical variability in lung function both for clinical and epidemiological purposes.     

Sources of variation in forced expiratory volume in one second and forced vital capacity.

Published prediction equations for lung function differ considerably, but the components of population variation responsible for the differences are unknown. Data were analysed for 6,323 never-smoking adults who did not report wheeze or asthma, from 42 centres participating in the European Community Respiratory Health Survey. Means and components of variance were estimated for males and females aged 20-24 yrs, and the relationships with age and height were examined in those aged 25-44 yrs. Mean lung function for those aged 20-24 yrs differed between centres, but variation could not be wholly attributed to differences in population or equipment. The maximum difference in means by equipment type was 101 mL for FVC in males. Equipment differences were not statistically significant adjusted for country, but differences in mean forced expiratory volume in one second and forced vital capacity by country, adjusted for instrument, were statistically significant in males. Differences between centres in relation to age and height had less influence on predicted values. In conclusion, there are unexplained differences in lung function between ethnically similar nonsmoking symptom-free populations. Neither national reference curves nor those based on the same ethnic group can be guaranteed to give accurate norms of lung health.     

Nutritional status and energy expenditure in children pre-bone-marrow-transplant

The aims of this study were to establish the nutritional status of children pre-BMT and to determine whether predictive methods of assessing nutritional status and resting energy expenditure (REE) are accurate in this population. We analysed the body cell mass (BCM) (n=26) and REE (n=24) in children undergoing BMT. BCM was adjusted for height (BCM/HT(p)) and expressed as a Z score to represent nutritional status. To determine whether body mass index (BMI) was indicative of nutritional status in children undergoing BMT, BMI Z scores were compared to the reference method of BCM/HT(p) Z scores. Schofield predictive equations of basal metabolic rate (BMR) were compared to measured REE to evaluate the accuracy of the predictive equations. The mean BCM/HT(p) Z score for the subject population was -1.09+/-1.28. There was no significant relationship between BCM/HT(p) Z score and BMI Z score (r=0.34; P>0.05); however there was minimal difference between measured REE and predicted BMR (bias=-11+/-149 kcal/day). The results of this study demonstrate that children undergoing BMT may have suboptimal nutritional status and that BMI is not an accurate indication of nutritional status in this population. However, Schofield equations were found to be suitable for representing REE in children pre-BMT.     

Normal Spirometric Reference Values for Omani Adults

International guidelines recommend the use of population-specific reference values to eliminate the well-recognized influence of ethnic variation on lung function. This study was designed to derive spirometric prediction equations for healthy Omani adults. Forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), peak expiratory flow rate (PEFR), and forced expiratory flow at 25% to 75% of FVC (FEF_25–75%) were measured in 419 “healthy” nonsmoking Omani adults (256 men, 163 women), aged 18–65 years. Multiple linear regression analysis was performed for each spirometric parameter against age, height, and weight for men and women separately, and prediction equations for all the above parameters were derived and compared with values derived using equations published from other populations. All measured spirometric parameters increased with height and decreased with age, and they were all significantly higher in men. In contrast, FEV₁/FVC% values decreased with height and increased with age and were higher in women. The predicted normal values of FVC and FEV₁ for our subjects using the derived equations were lower by 7–17% compared with respective Caucasian values, with smaller difference in the predicted values of PEFR, FEV₁/FVC%, and FEF_25–75%. This report presents previously unavailable spirometric reference equations for the Omani adults. Our findings highlight the need to use reference values based on updated data derived from relevant populations.     

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.     

Spirometric lung volumes in the adult Pacific Islander population: comparison with predicted values in a European population

OBJECTIVE: Prediction equations for spirometric lung volumes have been developed mainly in Europe and North America and may not be relevant to Pacific Islanders. This study was undertaken to determine whether currently available prediction equations adequately describe spirometric lung volumes in the asymptomatic adult Pacific Islander population. METHODOLOGY: Healthy asymptomatic Pacific Island adults aged 15-70 years were recruited. Pulmonary function was measured in the laboratory at Green Lane Hospital, Auckland, New Zealand, in accordance with American Thoracic Society standards. Measured results were compared with predicted values derived from four sets of prediction equations relevant to, or currently used in, New Zealand. RESULTS: A total of 101 volunteers took part in the study; mean age 28 years (range 18-66 years), 39% male, body mass index = 32 (range 22-54). For forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC), when measured values were compared with reference values, the slopes of the regression lines were not significantly different from 1 and the intercepts were not significantly different from zero. Prediction equations derived for African-Americans did not provide a better fit than the prediction equations for Caucasians. Predictions were improved when ideal rather than actual bodyweight was used. CONCLUSION: Respiratory parameters (FEV1 and FVC) in healthy asymptomatic adult Pacific Islanders in New Zealand are adequately described by currently available prediction equations and no adjustment for ethnicity is required.     

Spirometry values in a Greek population: Is there an appropriate reference equation?

Background and objective: Most published reference values for lung function test (LFT) parameters introduce systematic bias. The aim of this study was to compare measured values of FEV₁ and FVC with the corresponding normal predicted values in a Greek population, and to produce reference equations for LFT parameters in this population. Methods: In a cross‐sectional study conducted in Macedonia, Greece, 1080 adult healthy, non‐smokers (432 men, 648 women, aged 18–80 years), underwent spirometry. Measured values of FVC and FEV₁ were compared with predicted values determined using three existing sets of reference equations: one recently derived from a European population and two others widely used in Europe (European Coal and Steel Community; ECSC) and the USA (National Health and Nutrition Examination Survey; NHANES III). Height and age were entered into the multivariate regression analysis to produce reference equations for LFT parameters. Results: All three published sets of equations underpredicted FEV₁ in men. FVC was accurately predicted by all equations except NHANES III. The discrepancy was even greater among women; the ECSC equation underpredicted both FEV₁ and FVC, the NHANES III equation overpredicted both FEV₁ and FVC, while the third set of equations accurately predicted FEV₁ but overpredicted FVC. The derived reference equation for FEV₁ in men was ?0.28 × age + 0.057 × height ? 4.91, and in women ?0.021 × age + 0.039 × height ? 2.58. The derived reference equation for FVC in men was ?0.28 × age + 0.071 × height ? 6.763, and in women ?0.019 × age + 0.056 × height ? 5.018. Conclusions: Measured FEV₁ and FVC values in a Greek population differed significantly from those predicted using previously published reference equations. The new locally derived spirometry reference equations may be more suitable for evaluation of lung function in everyday practice.     

Prediction equations for pulmonary function values in healthy young Iranians aged 8-18 years

OBJECTIVE: Pulmonary function test (PFT) variables are dependent on height, age and gender. In addition, there is evidence of PFT variation in different ethnic groups. Prediction equations for PFT from a healthy, non-smoking, urban young population in the city of Mashhad (north-east Iran) have been derived. METHODOLOGY: Prediction equations for normal pulmonary function were derived from 336 healthy, non-smoking subjects, including 187 males (height 103-188.5 cm) and 149 females (height 104-183 cm) aged 8-18 years. The subjects underwent measurement of spirometric flow and volume. The following variables were measured: FVC, FEV1, maximal mid-expiratory flow (MMEF), PEF, maximal expiratory flow at 75, 50 and 25% of the FVC (MEF75, MEF50, and MEF25, respectively), tidal volume (VT), inspiratory reserve volume (IRV), expiratory reserve volume (ERV), inspiratory capacity (IC), and vital capacity (VC). Regression analysis using height and age as independent variables was applied to provide predicted values for both genders. RESULTS: There were positive correlations for each pulmonary function variable with height and age. The largest positive correlations were found for FEV1 with height and age, in both genders. Comparison of PFT variables derived from the equations obtained in the present study showed significant differences to those calculated from several previously published equations (P < 0.001 for most variables). For example, the values of FVC and FEV1 derived from the equations obtained in the present study were 2.83 +/- 0.99 and 2.50 +/- 0.89 for males, and 2.41 +/- 0.54 and 2.19 +/- 0.53 for females, while the values derived from the equations of the European Community for Steel and Coal study were 3.12 +/- 1.06 and 2.62 +/- 0.89 for males and 2.79 +/- 0.67 and 3.35 +/- 0.57 for females, respectively. CONCLUSIONS: A set of PFT reference values and prediction equations for both genders has been derived using a relatively large, healthy, non-smoking Iranian young population, and has generated results that differ from several other prediction equations.     

Reference values and repeatability of inspiratory capacity for men and women aged 65-85

The inspiratory capacity (IC) has recently gained importance because it may signal the occurrence of dynamic hyperinflation at rest or during exercise by reflecting changes in the end expiratory lung volume (EELV). However, reliable predicted values for IC are not currently available. The aim of the study was to generate predictive equations for reference values of IC in adults aged 65-85 living in Italy and to determine its limits of the within test-session repeatability. From the control group (n=429) of the SARA study data base, 241 (161 females) never smoked, non-obese (BMI<30 kg/m2) healthy subjects aged 65-85 who were able to correctly perform at least two manoeuvres of IC were selected. A model that incorporated age, height and body mass index as significant predictors in either sexes produced predicting equations for IC with a coefficient of determination of r2=.36 and .34 for females and males, respectively. Ninety per cent of all the subjects were able to keep the second highest IC within 200 ml (<9%) from the best IC. No significant gender difference was found for IC repeatability. We provided the equations for deriving reliable IC reference values that can be applied in the elderly people living in southern Europe. In this population IC showed limits of the within-session repeatability similar to those accepted for other spirometric indices such as FEV1 and FVC.     

Fifteen-year interval spirometric evaluation of the Oregon predictive equations

The 1969 Oregon spirometric predictive equations were evaluated by retesting 199 of the 988 original sample population after 15 years. The 1969 data were used to test for sample bias between the retested and not-retested groups. There was no significant difference in mean values for age, height, or test results except for a five-year age difference in men. Regression analysis of residuals and the differences between calculated and predicted values of annual decrements of FVC, FEV1, and FEF25-75% on age revealed no statistically significant age trend. Although residual means were statistically significant for FVC and FEV1 for men and FVC and FEF25-75% for women, the differences between calculated and predicted annual decrements were significant only for women in FEF25-75%. Although group performance was accurately predicted for most tests, test SDs and SEMs demonstrated considerable individual variation. Lower limits of normality are suggested to assist in evaluating previously-tested patients.     

Post-bronchodilator spirometry reference values in adults and implications for disease management

RATIONALE: International guidelines promote the use of post-bronchodilator spirometry values in the definition and severity classification of chronic obstructive pulmonary disease. However, post-bronchodilator reference values have not yet been developed. OBJECTIVES: To derive reference values for post-bronchodilator forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and FEV1/FVC, and to compare these reference values with locally derived and existing pre-bronchodilator reference values. METHODS: Based on a random sample of a general adult population, 2,235 subjects (70% of invited subjects) performed spirometry with reversibility testing. A reference population of healthy never-smokers constituted 23% of the study population (n=515). Reference values for median and lower-limit-of-normal pre- and post-bronchodilator lung function and bronchodilator response were modeled using quantile regression analyses. MAIN RESULTS: The reference population had equal proportions of men and women in the age range 26-82 yr. Both FEV1 and FVC decreased with age and increased with height. FEV1/FVC decreased with age, although this trend was not statistically significant for men after bronchodilatation. Linear models gave the best overall fit. Lower-limit-of-normal post-bronchodilator FEV1/FVC exceeded 0.7 for both sexes. Post-bronchodilator prediction equations gave higher predicted FEV1 and FEV1/FVC than both locally derived and existing pre-bronchodilator equations. The bronchodilator response decreased with age. CONCLUSIONS: The present study is the first to develop reference values for post-bronchodilator lung function. Post-bronchodilator prediction equations can facilitate better management of patients with chronic obstructive pulmonary disease by avoiding falsely high FEV1% predicted with a subsequent underestimation of disease severity.     

Spirometric reference equations for European females and males aged 65-85 yrs.

The aim of this study was to describe spirometric reference equations for healthy never-smoking European adults aged 65-85 yrs and to compare the predicted values of this sample with those from other studies including middle-aged and/or older adults. Reference equations and normal ranges for forced expiratory volume in one second (FEV1), forced vital capacity (FVC), forced expiratory volume in six seconds (FEV6), FEV1/FVC ratio and FEV1/FEV6 ratio were derived from a healthy subgroup of 458 subjects aged 65-85 yrs. Spirometry examinations followed the 1994 American Thoracic Society recommendations and the quality of the data was continuously monitored and maintained. Reference values and lower limits of normal were derived using a piecewise polynomial model with age and height as predictors. The reference values of FEV1 and FVC from the present study were higher than those given by prediction equations from the European Community for Coal and Steel. By contrast, use of prediction equations from Caucasian-American elderly subjects (Cardiovascular Health Study) consistently overpredicted FVC and FEV1 in females by 8.5 and 2.1%, respectively. In males, equations from the Cardiovascular Health Study overpredicted FVC by 2.8%, whilst underpredicting FEV1 by 2.5%. In conclusion, these results underscore the importance of using prediction equations appropriate to the origin, age and height characteristics of the subjects being studied.     

Spirometric reference values in a large Middle Eastern population.

Ethnic differences in pulmonary function have been frequently reported. The purposes of this study were to derive equations for the prediction of normative spirometry values for a large population of Persians in Isfahan and compare them to reference values from a White Euro-USA population. Spirometry measurements were obtained from 4,341 randomly selected healthy nonsmoker subjects in Isfahan, Iran, utilising American Thoracic Society guidelines and a vigorous quality assurance program. Measured data from 3,213 subjects were analysed using multiple regression techniques to derive prediction equations for spirometric variables; the remaining 1,128 subjects were used as a control group to test the validity of the derived equations. In addition, predicted values were compared with values derived from recently published equations for the USA. Derived prediction equations showed good performance for most spirometric parameters. Compared with USA Whites, adult Persians have minimally lower forced vital capacities, while the values for children are close to USA Whites. In comparison with reference equations based on European or USA populations, local reference values are more biologically and technically suitable for the interpretation of spirometric data from Iranian populations.     

Comparison of the automated non-invasive oscillometric blood pressure monitor (BpTRU) with the auscultatory mercury sphygmomanometer in a paediatric population

BACKGROUND: To directly compare the accuracy of the BpTRU (an automated oscillometric blood pressure device) with standard auscultatory mercury sphygmomanometry in a pediatric population. DESIGN: The BpTRU was connected in parallel with a standard mercury sphygmomanometer. Two observers measured the blood pressures at the same time as it was being measured by the BpTRU. The observers and the BpTRU were all blinded from each other. METHODS: For each of the demographic data--subject age, sex and arm sizes--the mean, standard deviation (SD) and range was calculated. The difference between the mean BpTRU and the standard reference measurements (observer average) was calculated with SD and ranges. The percentage of measurements within 5, 10 and 15 mmHg agreement was expressed. RESULTS: From the 36 subjects recruited aged 3-18 years, 162 pairs of sitting blood pressures were included. The difference between the mean BpTRU readings and the reference standard measurements (as determined by the observers) was 1.45+/-5.67 mmHg for systolic blood pressures, and -3.24+/-7.39 mmHg for diastolic pressure and 0.20+/-2.47 bpm for heart rate. CONCLUSION: The BpTRU is of similar accuracy in measuring blood pressure in children as it was in an adult population.     

Forced expiratory flow between 25 and 75% of vital capacity might be a predictive factor for bronchial hyperreactivity in children with allergic rhinitis, asthma, or both

Allergic rhinitis and asthma are closely associated. Bronchial hyperreactivity (BHR) is a pathophysiological characteristic of asthma. Forced expiratory flow between 25 and 75% of vital capacity (FEF(25-75)) has been previously shown to be able to predict BHR in adult patients with allergic rhinitis. Therefore, the aim of this study was (i) to evaluate the presence of BHR in a large group of children with allergic rhinitis, asthma or both and (ii) to confirm whether FEF(25-75) might be related to BHR and may predict BHR also in a pediatric population. Nine hundred fifty children with allergic rhinitis (350), asthma (300), or both (300) were enrolled. Clinical examination, skin-prick test, spirometry, and methacholine challenge were performed in all patients. Severe BHR was quite frequent in allergic children, mainly in asthmatic patients. FEF(25-75) values were significantly related to BHR grade, mainly in children with rhinitis (r = 0.69). Impaired FEF(25-75) values (such as ≤65% of predicted) constituted a relevant predictive factor for severe BHR, mainly in children with rhinitis (odds ratio, 8.9). In conclusion, this pediatric study confirmed that impaired FEF(25-75) values might predict severe BHR in children, mainly in those with allergic rhinitis. Therefore, low FEF(25-75) values could suggest BHR in children.     

Normal values for respiratory resistance using forced oscillation in subjects>65 years old.

The aim of the present study was to determine reference values and predictive variables for respiratory impedance (Zrs) by the forced oscillation technique (FOT) in subjects aged>65 yrs. The investigation involved a prospective study of nonsmoking subjects, with normal forced expiratory volumes. The Zrs parameters, which included average resistance between 4-16 Hz (R4-16), average resistance between 4-30 Hz (RM), resonant frequency (FN), capacitance (C) and inertance (I), were measured along with forced expiratory manoeuvres. Every subject had each parameter measured in the same sequence using FOT and spirometry. A total of 223 subjects aged 83+/-8 yrs were included in the study. The mean values for forced expiratory volume in one second (FEV1) % predicted were 110+/-23. The forced vital capacity (FVC) % pred was 114+/-21 and the FEV1/FVC % pred was 112+/-11. The mean values for the Zrs parameters were: R4-16: 0.25+/-0.07 kPa.s-1.L-1; RM: 0.25+/-0.06 kPa.s-1.L-1; FN: 11.0+/-2.8 Hz; I: 1.17+/-0.26 Pa.L-1.s-2; and C: 20.5+/-9.0 mL.hPa-1. In multiple regression models adjusted for age, sex, height and weight, height was the most influential predictor for Zrs parameters based on the magnitude of the regression coefficient. In conclusion, it was found that height was the best predictor for respiratory impedance parameters. Contribution of age and weight was negligible. However, the level of predictability for respiratory impedance parameters by regression equations was low.     

Recent trends and prognosis of pulmonary diseases in Japan

To determine trends of death rates for patients with chronic pulmonary diseases the author compiled the numbers of deaths per 100,000 Japanese population per annum based on the annual reports of the Japan Vital Statistics for the past 43 years. Death rates for the newborn population as well as for the younger population decreased while those for the aged population remained unchanged. Increasing numbers of deaths from lung cancer and decreasing numbers of death from pulmonary tuberculosis were noted. The death rate from the chronic obstructive lung diseases was maintained while the death rate for diffuse fibrotic lung diseases tended to be elevated. Baseline reference values for respiratory physiology parameters, established by the Special Commission for Respiration Physiology of the Japan Society of Chest Diseases, were presented by single linear regression equations represented in terms of age covering the subject's whole age span, including the aged population. The author carried out further analyses based on the data collected in a multi-center cross-sectional survey and concerning, some parameters found consistent differences the linear regression equation calculated for the aged population from those for the younger population. A longitudinal survey conducted by follow-up observations at Keio University Hospital to determine the annual decline of parameters on respiration physiology was designed to cover healthy subjects as well as subjects with chronic pulmonary diseases. Annual declines in vital capacity, forced vital capacity, forced expiratory volume in one second, arterial oxygen tension and arterial carbon dioxide tension showed linear changes throughout the entire age span. Some parameters, such as flow max at 25% vital capacity or alveolar-arterial oxygen tension difference (AaDO2), demonstrated statistically consistent differences in annual decline between younger and older age populations. The annual decline of parameters in patients with chronic pulmonary diseases demonstrated consistently larger values compared with those for healthy subjects. In a study on the pathophysiology and prognosis of patients with respiratory failure with/or without cor pulmonale extension of the survival period for the patients with cor pulmonale was demonstrated.     

Lung function values in healthy non-smoking urban adults in iran

BACKGROUND: The values of lung function tests (LFTs) are dependent on height, age, and sex. In addition, there is evidence of LFT variation in different ethnic groups. OBJECTIVE: We have therefore derived prediction equations for LFTs from a healthy, non-smoking, urban adult population in the city of Mashhad (northeast Iran). METHODS: Predicted equations for normal lung function have been derived from 572 healthy, non-smoking subjects including 326 men (height 154-195 cm) and 246 women (height 144-174 cm) aged 18-65 years. The subjects underwent measurement of spirometric flow and volume. The following variables were measured: forced vital capacity (FVC), forced expiratory volume in 1 s (FEV(1)), maximal mid-expiratory flow (MMEF), peak expiratory flow (PEF) and maximal expiratory flow at 75, 50 and 25% of the FVC (MEF(75), MEF(50), and MEF(25), respectively). Regression analysis using height and age as independent variables was applied to provide predicted values for both sexes. RESULTS: There was a negative correlation between each lung function and age. The largest negative correlations were found for FEV(1) and FVC in men and women, respectively. All parameters correlated positively with height; the largest positive correlation was observed for FVC in both sexes. Comparison of LFTs derived from the equations of the present study showed significant differences with those of several previous studies. CONCLUSION: In this study, a set of LFT reference values and prediction equations for both sexes have been derived using a relatively large, healthy, non-smoking Iranian, adult population which was different from several other prediction equations.