Assessment of bronchial obstruction and its reversibility by shape indexes of the flow‐volume loop in asthmatic children

Asthma assessment by spirometry is challenging in children as forced expiratory volume in 1 s (FEV1) is frequently normal at baseline. Bronchodilator (BD) reversibility testing may reinforce asthma diagnosis but FEV1 sensitivity in children is controversial. Ventilation inhomogeneity, an early sign of airway obstruction, is described by the upward concavity of the descending limb of the forced expiratory flow‐volume loop (FVL), not detected by FEV1. The aim was to test the sensitivity and specificity of FVL shape indexes as β‐angle and forced expiratory flow at 50% of the forced vital capacity (FEF50)/peak expiratory flow (PEF) ratio, to identify asthmatics from healthy children in comparison to “usual” spirometric parameters. Seventy‐two school‐aged asthmatic children and 29 controls were prospectively included. Children performed forced spirometry at baseline and after BD inhalation. Parameters were expressed at baseline as z‐scores and BD reversibility as percentage of change reported to baseline value (Δ%). Receiver operating characteristic curves were generated and sensitivity and specificity at respective thresholds reported. Asthmatics presented significantly smaller zβ‐angle, zFEF50/PEF and zFEV1 (p ≤ .04) and higher BD reversibility, significant for Δ%FEF50/PEF (p = .02) with no difference for Δ%FEV1. zβ‐angle and zFEF50/PEF exhibited better sensitivity (0.58, respectively 0.60) than zFEV1 (0.50), and similar specificity (0.72). Δ%β‐angle showed higher sensitivity compared to Δ%FEV1 (0.72 vs. 0.42), but low specificity (0.52 vs. 0.86). Quantitative and qualitative assessment of FVL by adding shape indexes to spirometry interpretation may improve the ability to detect an airway obstruction, FEV1 reflecting more proximal while shape indexes peripheral bronchial obstruction.     

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.     

Determinants of tidal flow volume loop indices in neonates and children with and without asthma

The tidal flow volume (TFV) loop ratios of (1) time to peak flow (tPTEF ) to total expiratory time (tE ) [tPTEF /tE ] and (2) volume to peak flow (VPTEF ) to expired volume (VE ) [VPTEF /VE ] are reported to decrease with age in early life, and to decrease in subjects with obstructive airways disease (OAD). However, the mechanisms behind these changes are not well known. Thus, we reanalyzed data from 24 healthy neonates (mean birthweight: 3.49 kg ± 0.42 kg (SD)), 26 presently asymptomatic asthmatic children (age: 33 ± 21 months), and 26 controls (age: 34 ± 19 months) to elucidate what is responsible for the changes in these ratios in health and disease. Lung function was measured by TFV loops (SensorMedics 2600) at 1 hour of life and on the following day in the neonates, and before and after inhaled nebulized salbutamol (0.05 mg/kg) in the asthmatics and their controls. The observed decreases in mean tPTEF /tE and VPTEF /VE from 1 hour to 1 day of life (neonates) were entirely due to increased tE and VE , respectively secondary to a decrease in respiratory rate (P = 0.03). In asthmatics (young children), the decreased baseline tPTEF /tE and VPTEF /VE were due to lower tPTEF and VPTEF , with no significant differences in tE e and VE in asthmatics and controls. The improved ratios in asthmatic children following inhalation of a bronchodilator were mainly due to increased tPTEF and VPTEF . Our observations point out the importance of evaluating both tPTEF and either tPTEF /tE or VPTEF /VE when attempting to differentiate between changes in ratios that are related to age versus changes that reflect underlying obstructive airways disease. Pediatr. Pulmonol. 1997; 24:391–396. © 1997 Wiley-Liss, Inc.     

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 (FEF₂₅, FEF₅₀, and FEF₇₅) 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. Pediatr Pulmonol. 2009; 44:676–682. © 2009 Wiley‐Liss, Inc.     

Defining ‘healthy’ in preschool‐aged children for forced oscillation technique reference equations

Background and objective

Selecting ‘healthy’ preschool‐aged children for reference ranges may not be straightforward. Relaxing inclusion criteria for normative data does not affect spirometry z‐scores. We therefore investigated the effect of similarly relaxing inclusion criteria in preschoolers on reference ranges for respiratory impedance (Zrs) using a modified forced oscillation technique (FOT).

Methods

The International Study of Asthma and Allergies in Childhood questionnaire classified 585 children into a healthy and five mutually exclusive groups. Zrs was measured between 4 and 26 Hz and resistance (R) and compliance (C) obtained by model fitting. Prediction models were determined using mixed effect models and z‐scores compared between healthy children and the five groups.

Results

Zrs data were obtained for 494 participants (4.30 ± 0.7 years) on 587 occasions. Comparison of the Zrs z‐scores between the healthy children and the health groups found significant differences in children with asthma, current wheeze and respiratory symptoms, but not in children born preterm or with early‐life wheeze. Adding these two groups to the healthy dataset had no significant effect on the distribution of z‐scores and increased the size of the dataset by 22.3%.

Conclusion

Our data suggest that preschool‐aged children born preterm or with early‐life wheeze can be included in FOT reference equations, while those with asthma, current wheeze and respiratory symptoms within 4 weeks of testing should be excluded. This more inclusive approach results in more robust FOT reference ranges.

     

Lung function testing in preschool‐aged children with cystic fibrosis in the clinical setting

In cystic fibrosis (CF) lung function testing is a means of monitoring progression of lung disease. The preschool years have often been referred to as the “silent years” due to the previous lack suitable measures of lung function testing in this age group. This review outlines the various techniques of lung function testing in preschool children with CF in the clinical setting. This includes measures requiring tidal breathing including the forced oscillation technique, the interrupter technique, plethysmography, and multiple breath washout, as well as spirometry that requires respiratory maneuvers. We describe the feasibility and variability of different lung function methods used in preschoolers and report measurements made during tidal breathing have greater feasibility, although greater variability compared to spirometry. We also report associations with lung function and markers of CF lung disease. In the preschool age group measurements made during tidal breathing may be more appropriate in the clinic setting than those that require a higher degree of cooperation and specific respiratory maneuvers.maneuvers. Pediatr Pulmonol. 2010; 45:419–433. © 2010 Wiley‐Liss, Inc.     

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.     

Reference values for the Timed Up and Go test in healthy Japanese elderly people: Determination using the methodology of meta‐analysis

Aim: The purpose of this study was to determine the reference value for the Timed Up and Go test (TUG) in healthy Japanese elderly people using the methodology of meta‐analysis, and to determine the value for different measurement protocols. Methods: Relevant research articles were identified from electronic databases: MEDLINE, Cumulative Index to Nursing and Allied Health Literature (CINAHL) and Igaku‐cyuouzasshi. The search was conducted from January 1991 to June 2010, and the terms “timed up and go” and “elderly” were used in combination in the search. Furthermore, the searches were limited to articles involving Japanese healthy elderly people aged 60 years and older. Weighted means of TUG were calculated by a fixed effect model and a random effect model to estimate reference values. Furthermore, the 95% confidence interval (CI) for the weighted mean of TUG was also estimated. Results: Twelve studies fulfilled the inclusion criteria: eight provided data for maximum effort, and five provided data related to usual pace. When weighted means of TUG were estimated by the fixed effect model, there was significant heterogeneity. Therefore, a random effect model was used for re‐estimation. As a result, the weighted mean of TUG with maximum effort was 6.60 s (95% CI = 6.18–7.02 s), and that at usual pace was 8.86 s (95% CI = 7.99–9.72 s). Conclusion: The reference values of TUG in Japanese healthy elderly people calculated in this study are certainly shorter than in African‐Americans and Caucasians. The reference values of TUG estimated by our study appear to be specific for healthy, elderly, Japanese people. Geriatr Gerontol Int 2011; 11: 445–441.     

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.