Normative reference values for lung transfer factor in Isfahan, Iran

OBJECTIVES AND BACKGROUND: Transfer factor or carbon monoxide diffusing capacity (DL(CO)) is a particularly valuable test of the appropriateness of gas exchange across the alveolocapillary membrane. The purpose of this study is to derive predictive equations for DL(CO) and its derivative volume-corrected DL(CO) (DL(CO)/VA) measured by single-breath method in a large non-smoking population sample in Isfahan. METHODOLOGY: We evaluated 1429 randomly selected subjects (732 men, aged 5-85 years). Gender-specific linear prediction equations were developed by multiple regression analysis; with measured DL(CO), and DL(CO)/VA values (mmol/min/kPa), as dependent variables regressed against age (A), height (H) and body surface area (BSA). RESULTS: For both genders, age had negative effects on DL(CO), while height had a positive effect on DL(CO) and DL(CO)/VA (P < 0.01). The prediction equations for DL(CO) and DL(CO)/VA are: '0.152 x height - 0.056 x age - 11.595' and '-0.12 x age + 2.467', for men and: '-0.035 x age - 0.133 x height - 10.707' and '-0.012 x age - 0.02 x height + 2.755', for women, respectively. CONCLUSIONS: Our results therefore provide an original frame of reference for either DL(CO) or DL(CO)/VA in Iranian population, obtained from a standardized single-breath technique.     

Pulmonary function testing in New Zealand: the use and importance of reference ranges

BACKGROUND AND OBJECTIVES: The diagnosis, assessment and management of a wide range of respiratory diseases rely on accurate interpretation of lung function tests through the use of reference equations to generate predicted values. This paper ascertains the suitability of reference equations currently used in New Zealand through comparison with newly derived equations from the Wellington Respiratory Survey, and discusses the relevance of the findings to the Asia Pacific region. METHODS: A survey of lung function testing facilities determined the reference equations in common usage. Pulmonary function test results from healthy, lifelong non-smoking subjects (n = 180) were expressed as percentage predicted values, with comparisons made between the currently used and Wellington Respiratory Survey reference equations. Differences in disease severity classification in subjects with COPD (n = 46) and asthma (n = 61) were determined, using the different reference equations. RESULTS: Currently used equations significantly underpredict measured values for FEV(1), PEF, TLC and RV by up to 20%. Severity classification of COPD and asthma based on per cent predicted FEV(1) was substantially altered by the choice of reference equation. CONCLUSION: Many reference equations in current usage in New Zealand are no longer suitable for use. The applicability of reference equations used in other populations and countries within the Asia Pacific region requires further investigation. We recommend that up-to-date reference equations are derived and implemented if those currently used are shown to be unsatisfactory.     

Static lung volumes and airway resistance reference values in healthy adults

Background and objective: The assessment of static lung volumes and airway resistance is a frequently performed diagnostic procedure and considered as an important tool in medical surveillance to detect pulmonary diseases. The objectives of the study are to establish reference equations for body plethysmographic parameters in a representative adult population across a wide age range and to compare the normative values from this sample with previous ones. Methods: Body plethysmography was applied in 1809 participants (885 males) of a cross‐sectional, population‐based survey (Study of Health in Pomerania). Individuals with cardiopulmonary disorders and/or a pack‐year smoking history >10 years and participants with a body mass index >30 kg/m² were excluded. In total, 686 healthy individuals (275 males) aged 25–85 years were assessed. Results: Prediction equations for both genders were established by quantile regression analysis taking into account the influence of age, height and weight. Conclusions: The study provides a novel set of prediction equations for static lung volumes and airway resistance obtained using body plethysmography. Compared with our findings, existing equations underestimated some normal values. The results emphasize the need for up‐to‐date reference equations.     

Effect of salbutamol on specific airway resistance in infants with a history of wheezing.

The purpose of this study was to assess the effectiveness of nebulized salbutamol in infants with a history of wheezing. Eighty-eight children aged 3-24 months with a history of wheezing were studied, in seven groups: I (n = 15) and I/A (n = 17) with elevated specific airway resistance (SRaw); II (n = 17) with normal SRaw; III (n = 23), III/A (n = 17), and IV (n = 18) with normal SRaw exposed to carbachol bronchial challenge (CBC); and V (n = 13) serving as control. Infants for groups I/A and III/A were selected to match by age and by baseline and post-carbachol SRaw values, respectively. Baseline airway resistance and thoracic gas volume (TGV) were measured plethysmographically. Specific airway resistance was selected as an index of bronchial function. Thereafter every child in groups I, I/A and II inhaled 200 micrograms of salbutamol by tidal breathing, and the children in groups III, III/A, and IV were exposed to CBC. Following positive reaction to carbachol, children of groups III and III/A inhaled salbutamol (200 micrograms, tidal breathing), and those of group IV received no drug. Controls from group V with normal SRaw received placebo (phosphate-buffered saline). Plethysmography was repeated in all children at 5 minute intervals. Following salbutamol SRaw was reduced in children with elevated and normal SRaw. In contrast, children not receiving salbutamol had unchanged SRaw value. The response to salbutamol measured by SRaw, Raw, and TGV was not significantly different in the spontaneously obstructed infants compared to those who received carbachol. In conclusion, infants with a history of wheezing do respond to inhaled salbutamol.     

Body plethysmographic study of specific airway resistance in a sample of healthy adults

Background and objective: sRaw (specific airway resistance) is a corrected index (Raw multiplied by thoracic gas volume) that describes airway behaviour regardless of lung volume. Normal values of sRaw in adult subjects have never been formally defined. To establish sRaw interpretation criteria and to define a range of reference values, we evaluated variability, reproducibility and reliability of sRaw measurements in a group of healthy adults. Methods: We analysed 517 subjects of both genders, aged 18–65 (group A), and to assess the reproducibility of the measurements, we investigated intra‐individual variation and potential daily and weekly sRaw rhythms in a subgroup of 18 co‐operative healthy subjects (group B). Results: In group A, there was no pattern of association between any of the considered anthropometric parameters; mean sRaw was higher in men (6.24 vs 5.95 cmH₂O s in females; P = 0.0128), but when the data were stratified by age, gender‐related differences were only found in the group aged 46–60 (males 6.45 cmH₂O s, females 6.01 cmH₂O s; P = 0.0219). In group B, there was no statistically significant, time‐dependent variation during the single tests, nor any circadian or weekly rhythm. Conclusions: sRaw is a reliable parameter; therefore, we propose that the lower and upper 95% confidence limits should be considered as reference values for adults of both genders, regardless of age. The availability of reference values may be useful in clinical practice and research.     

Reference equations for pulmonary function tests in preschool children: a review

Recent developments in pulmonary function tests (PFTs) in preschool children (2-5 years of age) have meant that objective assessments of respiratory function are now possible for this age group. However, the application and interpretation of these tests may be limited by the relative paucity of appropriate reference equations. This review summarizes available preschool reference equations, identifies the current gaps and limitations in the methodologies and statistics used and proposes future directions for improving reference data. A PubMed search which included the MeSH terms (preschool [2-5years]), (respiratory function test), and (reference value) yielded 214 publications which were screened to identify 34 publications presenting 36 reference equations for seven techniques. There were considerable differences with respect to population characteristics, recruitment strategies, equipment and methodologies and reported parameters both within and between each measurement technique. Despite an increasing number of reference equations for PFT for preschool children, the extent to which these can be generalized to other populations may be limited in some cases by inclusion of relatively few children less than 5 years of age, a lack of details regarding the sample populations and measurement techniques and/or inappropriate statistical analysis. A fresh approach based on large sample sizes, clearly documented population characteristics, equipment and protocols, and more rigorous modern statistical methods both for developing reference equations and interpreting results could enhance clinical application of these tests. This in turn would maximize the tremendous opportunities to detect early lung disease offered by the recent surge in developing suitable tests for preschool children.     

Children with smoking parents have a higher airway resistance measured by the interruption technique

Children exposed to environmental tobacco smoke, during or after pregnancy, are known to have decreased lung function. So far this has been measured using spirometry in schoolchildren and invasive techniques in newborns. The interruption technique (Rint) is a noninvasive technique to measure airway resistance in preschool children. Our aim in this study was to investigate the effect of passive smoke exposure on Rint values in preschool and school-aged children. Rint values were obtained from 557 children in two nursery and two primary schools in the north of the Netherlands. Besides information on parental smoking habits, we collected data on characteristics that might affect airway resistance (respiratory symptoms, atopy, and family history for asthma), using a short questionnaire. Multiple linear regression was used to estimate the associations of these characteristics with Rint, for the whole group as well as for the preschool group separately. Atopy or a positive family history for asthma did not affect Rint values in the total group of 4-12-year-olds. However, as may be expected, height, age, weight, and having respiratory symptoms were associated with Rint. Moreover, Rint was significantly increased if parents smoked three or more cigarettes a day in the presence of their child. This result remained after subgroup analysis in the preschool children (4-6 years old). We conclude that passive smoke exposure is associated with a significantly higher airway resistance in preschool and school-aged children measured by Rint.     

Reference values for resistance and compliance based on the single occlusion technique in healthy infants from Southeast China

Background

Respiratory disease is a major cause of morbidity and mortality in infants and has a large impact on health care. The aim of this study was to present the reference values of resistance and compliance by using a single occlusion technique (SOT) in healthy infants in Southeast China.

Methods

Respiratory compliance (Crs) and respiratory resistance (Rrs) were measured in healthy infants, aged 1–96 weeks, by using SOT in the Children’s Hospital of FuDan University (Shanghai, China). For comparison, the infants were grouped by age as follows: 1–24, 25–48, 49–72 and 73–96 weeks. Multiple regression analysis was performed using age, length, weight, and body mass index (BMI) as the independent variables to obtain predictive equations, separated according to sex.

Results

We measured 205 healthy infants from birth up to 96 weeks of age (112 boys, 93 girls). Height and weight increased significantly with age. The Rrs declined with length, whereas the Crs increased. The median Rrs was 5.04 kPa/L/sec (range, 3.73–6.82 kPa/L/sec), and the mean Crs was 119.52±60.47 mL/kPa. Regression equations for Rrs and Crs were obtained.

Conclusions

We obtained reference values for passive respiratory mechanics by using SOT in healthy infants from Southeast China. These data provide references for assessing the normality of SOT measurements in infants.     

Effect of airway inflation pressure on forced expiratory maneuvers from raised lung volume in infants.

The raised lung volume technique is increasingly used to measure forced expiratory maneuvers in infants. However, there is no consensus regarding the optimal airway inflation pressure (P(inf)) required for such maneuvers, or the influence of small changes in P(inf) within and between infants. The aim of this study was to assess the effect of small differences (0.2-0.3 kPa) in P(inf) on forced vital capacity (FVC), forced expired volume in 0.5 sec (FEV(0.5)), and forced expired flow at 75% of vital capacity (FEF(75)), all derived from the raised volume rapid thoraco-abdominal compression (RVRTC) technique. Randomized paired forced expiratory maneuvers were obtained in 32 healthy infants ( 3.9-39.3 weeks old, 3.8-9.9 kg) with the safety pressure relief valve for P(inf) set to 2.7 kPa or 3.0 kPa (27 or 30 cm H(2)0). When mean (SD) P(inf) was increased by 8.4 (2.8)%, there was a significant (P < 0.01) increase in mean (SD) FVC, FEV(0.5), and FEF(75) by 5.8 (5.7)%, 6.1 (6)%, and 8.3 (16.2)%, respectively. In conclusion, relatively small differences in P(inf) will result in significant differences in FVC, FEV(0.5), and FEF(75) by RVRTC technique. Precision in setting and reporting the applied P(inf) is therefore essential, particularly if data are to be compared between centers.     

Limitations of electronic compensation for measuring plethysmographic airway resistance in infants

Electronic compensation to overcome thermal artifacts during plethysmographic estimations of airway resistance is now used routinely in adults and school-age children, and was shown to be a valuable means of discriminating airway function between preschool children with and without lung disease. A similar system is now commercially available for infants, which could increase the applicability of this technique. However, we noted marked discrepancies in electronically calculated values of airway resistance in this age group, both with respect to absolute values displayed and marked within-subject variability on a single test occasion. The aim of this technical report is to summarize our recent findings in order to alert other users to potential problems. Airway resistance (R(aw)) was measured in 62 infants (28 with cystic fibrosis (CF); 34 healthy). Three to five epochs of quiet regular tidal breathing were collected in each infant. Marked within-subject, within-test variability was observed, with the median coefficient of variation (CV) being 9.1% (range, 1.2-52.6%) within and 8.5% (0.1-112%) between epochs. Among healthy infants, R(aw) varied from 0.1-6.4 (kPa x liter(-1) x sec), with no relationship to either body or lung size and complete overlap of results with those from infants with CF, despite abnormal lung function in the latter when assessed by other means. The marked within- and between-subject variability in healthy infants, and lack of discriminative power of R(aw) when derived from electronically compensated values, currently preclude application in either clinical or research studies.     

Reference values for spirometry and their use in test interpretation: A Position Statement from the Australian and New Zealand Society of Respiratory Science

Traditionally, spirometry testing tended to be confined to the realm of hospital‐based laboratories but is now performed in a variety of health care settings. Regardless of the setting in which the test is conducted, the fundamental basis of spirometry is that the test is both performed and interpreted according to the international standards. The purpose of this Australian and New Zealand Society of Respiratory Science (ANZSRS) statement is to provide the background and recommendations for the interpretation of spirometry results in clinical practice. This includes the benchmarking of an individual's results to population reference data, as well as providing the platform for a statistically and conceptually based approach to the interpretation of spirometry results. Given the many limitations of older reference equations, it is imperative that the most up‐to‐date and relevant reference equations are used for test interpretation. Given this, the ANZSRS recommends the adoption of the Global Lung Function Initiative (GLI) 2012 spirometry reference values throughout Australia and New Zealand. The ANZSRS also recommends that interpretation of spirometry results is based on the lower limit of normal from the reference values and the use of Z‐scores where available.     

Prevalence and predictors of undiagnosed chronic obstructive pulmonary disease in a Norwegian adult general population

Objectives: To determine the prevalence and predictors of undiagnosed chronic obstructive pulmonary disease (COPD) in Norway. Methods: An age and gender stratified random sample of all adults aged 47–48 and 71–73 years in Bergen, Norway, were invited. The 3506 participants filled in questionnaires including symptoms of COPD, smoking, socio‐economic status, self‐rated health and cardiac co‐morbidity. Spirometry was performed before and after inhalation of 400 µg of salbutamol. COPD was defined as post‐bronchodilator forced expiratory volume in 1 s (FEV1) / forced vital capacity (FVC) < 0.7 whereas diagnosed COPD was defined as having received treatment for obstructive lung disease the last year. Results: Three hundred‐three persons (9%) were classified as having COPD, and the undiagnosed fraction was 66%. In multiple logistic regression analysis, including multiple imputation, predictors of undiagnosed COPD were absence of COPD symptoms [odds ratio (OR) 6.92, P = 0.001], and self‐report of being in good/excellent health (OR 2.39, P = 0.005). When post‐bronchodilator FEV1 was added to the analysis, undiagnosed disease was predicted by pack years [OR 1.21 (1.01–1.47) per 10 pack‐year increase, P = 0.043], and close to normal lung function [OR 1.48 (1.22–1.80) per 10% increase in post‐bronchodilator FEV1 % predicted, P < 0.001]. Anthropometrical variables, socio‐economic status and cardiac co‐morbidity were not associated with having undiagnosed COPD. Conclusion: Two out of three COPD patients in Norway are undiagnosed. Risk factors for being undiagnosed are moderate reduction in lung function, absence of COPD symptoms and self‐report of being in good health. Please cite this paper as: Hvidsten SC, Storesund L, Wentzel‐Larsen T, Gulsvik A and Lehmann S. Prevalence and predictors of undiagnosed chronic obstructive pulmonary disease in a Norwegian adult general population. The Clinical Respiratory Journal 2009; DOI:10.1111/j.1752‐699X.2009.00137.x.     

Reference values of leukocyte and lymphocytes populations in umbilical cord and capillary blood in healthy Mexican newborns

IntroductionIn newborns, dramatic changes occur in the blood and bone marrow during the first hours; there are rapid fluctuations in the quantities of leukocytes populations. In this work, we investigated leukocytes subsets counts in two types of blood samples (cord blood and capillary blood) extracted from healthy newborns.MethodsBlood samples from Mexican neonates were collected by Instituto Nacional de Pediatría with written informed consent. For all samples we determined leukocytes populations; neutrophils, monocytes, total lymphocytes, and populations: T CD3+ cells, TCD4+ cells, T CD8+ cells, B CD19+ cells and NK CD16+56 cells by flow cytometry. We used the Mann–Whitney U test to compare leukocytes of cord and capillary blood; also to analyze the differences between gender and we obtained reference values of the cord and capillary blood in neonates.ResultsWe observed higher absolute counts and frequencies of total lymphocyte in capillary blood compared with cord blood. In absolute numbers, the capillary blood showed significant differences in neutrophils, monocytes, lymphocytes, T CD3+ cells, T CD4+ cells, T CD8+ cells, B CD19+ cells, and NK cells; no significant differences were observed between genders.DiscussionOur data contribute to newborn Mexican reference values for all these populations of leukocytes. We found that the dispersal range differs between the two types of blood, suggesting a different fate in the immune response. Immunophenotyping of the blood cell population to identify these cells is an essential tool in the diagnosis and follow-up of neonates with immunodeficiencies and other immune disorders.