Reference values of diffusing capacity of non-smoking Chinese in Hong Kong

BACKGROUND AND OBJECTIVE: This study was conducted to define normal reference values and lower limits of normal (LLN) for single-breath carbon monoxide diffusing capacity (DLco) and DLco per unit of alveolar volume (Kco) for Chinese adults in Hong Kong. METHODS: Healthy non-smoking men and women aged 18-80 years were recruited by random digit dialing. DLco and Kco were measured according to American Thoracic Society standards. Reference equations were obtained by multiple linear regression; LLN were derived by distribution-free method for estimation of age-related centiles. RESULTS: Tests from 568 subjects (259 men, 309 women) were analysed. DLco declined with age in both genders, and increased with height and the interaction term of height and age in men and women, respectively. Considering Hb values did not improve the reference equations. Kco declined with age and increased with weight in both genders, while height and its interaction term with age were additional determinants in women. The reference DLco was lower than some Caucasian values, and was only explained partially by a smaller body size and alveolar volume in Chinese. The distribution-free method yielded better overall approximation to the fifth percentile compared with the traditional method of determining LLN. CONCLUSIONS: The equations for reference values and LLN of diffusing capacity derived in this study are of clinical relevance to Chinese subjects.     

The Global Lung Initiative 2012 reference values reflect contemporary Australasian spirometry

We aimed to ascertain the fit of the European Respiratory Society Global Lung Initiative 2012 reference ranges to contemporary Australasian spirometric data. Z‐scores for spirometry from Caucasian subjects aged 4–80 years were calculated. The mean (SD) Z‐scores were 0.23 (1.00) for forced expirtory volume in 1 s (FEV₁), 0.23 (1.00) for forced vital capacity (FVC), ?0.03 (0.87) for FEV₁/FVC and 0.07 (0.95) for forced expiratory flows between 25% and 75% of FVC. These results support the use of the Global Lung Initiative 2012 reference ranges to interpret spirometry in Caucasian Australasians.     

Recent consumption of a large meal does not affect measurements of lung function

Background and objective: It is currently recommended that patients avoid large meals prior to their lung function tests. The aim of this study is to determine whether this recommendation is necessary in clinical practice. Methods: A randomized controlled cross‐over trial was conducted. Subjects performed lung function tests (spirometry, measurement of lung volumes and gas transfer) prior to, directly following and 2 h after consuming a large breakfast. On the control arm, subjects performed the same lung function tests while fasting for the duration of the morning. The study subjects comprised 12 healthy subjects, 10 COPD patients and 10 patients with interstitial lung disease. Results: There were no significant differences between measurements on the meal and control days for FEV₁, FVC, TLC or DL_CO. There were no significant changes with time in any of these parameters over the course of either the meal or control morning. Conclusions: Common measures of lung function are not affected by the prior consumption of a large meal and it is unnecessary to advise patients to avoid a large meal prior to lung function assessment.     

New Danish reference values for spirometry

Introduction: International recommendations state that reference values for lung function should derive from cross‐sectional studies of healthy nonsmokers and be renewed from time to time because of cohort effect and newer, more accurate, technical equipment. In 1986, the Danish Lung Society published reference values for spirometry based on 570 individuals aged 30–70 years. Objectives: To produce new reference values for lung function and to extend the existing values by including individuals between 20 and 30 years of age and older than 70 years of age. Methods: Two similar but independent studies was used: The 2001–2003 examination of the Copenhagen City Heart Study and the 2003–2010 examination of the Copenhagen General Population Study. Of a total of 69 822 individuals, we included 11 288 healthy never‐smoking white individuals to produce the reference values: 6307 women and 4981 men, 20 years of age or older with adequate lung function. Results: We used sex‐stratified multiple linear regression analysis to find prediction formulas for forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC) and FEV₁/FVC adjusted for age and height. The cutoff value of normal lung function was defined as the fifth percentile (also named the 5% quantile) according to gender, age and height. The robustness of the data was tested and validated in several ways. Conclusion: Compared with the 1986 data, our 2001–2010 material contributes with a substantial number of individuals in the more extreme groups of age and height, and in general, our dataset shows that in most subgroups, the lung function level has improved during the last two decades. Please cite this paper as: Løkke A, Marott JL, Mortensen J, Nordestgaard BG, Dahl M and Lange P. New Danish reference values for spirometry. Clin Respir J 2013; 7: 153–167.     

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.     

Reference values for airway resistance in newborns, infants and preschoolers from a Latin American population

Background and objective: Several studies have determined reference values for airway resistance measured by the interrupter technique (Rint) in paediatric populations, but only one has been done on Latin American children, and no studies have been performed on Mexican children. Moreover, these previous studies mostly included children aged 3 years and older; therefore, information regarding Rint reference values for newborns and infants is scarce. Methods: Rint measurements were performed on preschool children attending eight kindergartens (Group 1) and also on sedated newborns, infants and preschool children admitted to a tertiary‐level paediatric hospital due to non‐cardiopulmonary disorders (Group 2). Results: In both groups, Rint values were inversely associated with age, weight and height, but the strongest association was with height. The linear regression equation for Group 1 (n = 209, height 86–129 cm) was Rint = 2.153 ? 0.012 × height (cm) (standard deviation of residuals 0.181 kPa/L/s). The linear regression equation for Group 2 (n = 55, height 52–113 cm) was Rint = 4.575 ? 0.035 × height (cm) (standard deviation of residuals 0.567 kPa/L/s). Girls tended to have slightly higher Rint values than boys, a difference that diminished with increasing height. Conclusions: In this study, Rint reference values applicable to Mexican children were determined, and these values are probably also applicable to other paediatric populations with similar Spanish‐Amerindian ancestries. There was an inverse relationship between Rint and height, with relatively large between‐subject variability.     

Diffusing capacity of the lung in school-aged children born very preterm,with and without bronchopulmonary dysplasia

The aim of this study was to determine the extent to which bronchopulmonary dysplasia (BPD) affects the diffusing properties of lung tissue in childhood. Pulmonary function in 31 prematurely born children (BW. < 1250 g) was examined at ages 7–11 years. Twenty out of 31 prematurely born children met the criteria for BPD. The remaining 11 children had milder forms of neonatal lung disease. Twenty healthy children of the same age and born at term served as a control group. The diffusing capacity of the lung for carbon monoxide (D_LCO) was measured by the single breath method. Lung volumes were determined in a body plethysmograph and expiratory flow rates with a flow/volume spirometer. D_LCO values of children with histories of BPD did not differ significantly from those of the prematurely born children without BPD. However, D_LCO values in both prematurely born study groups were significantly lower than those in controls born at term. Thoracic gas volumes measured with a body plethysmograph were similar in all groups. Spirometry demonstrated reduced flow rates in both BPD and non-BPD prematurely born children. The results suggest that some structural changes in lung tissues and airways persist for years in children who are born very preterm regardless of whether they develop BPD or not. Pediatr Pulmonol. 1996; 21:353–360. © 1996 Wiley-Liss, Inc.     

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.     

Comparison of spirometric reference values

Lung-function reference values play a vital role in the management of respiratory disorders. There are many proposed reference equations for pediatric spirometry. Recently, spirometric reference equations were proposed, using data from people aged 8-80 years living in the US compiled by the third National Health and Nutrition Examination Survey. Our objective was to compare the predictive value of wider age-range reference equations to established pediatric reference equations for the pediatric population. Spirometry, height, and weight were obtained from 70 normal children aged 6-18 years. The difference between measured and predicted values as suggested by different reference equations was compared. Predicted values from general equations significantly differed from those generated from pediatric equations and from measured values in this population. The difference between measured and predicted values from the wider age-range equations varied between 7-16% for forced expired volume in 1 sec (FEV1) and forced vital capacity (FVC). The difference between measured and predicted values for the pediatric equations varied between 1-4%. Although wider age-range equations provide continuity through age ranges, their predictive accuracy may be low in the pediatric age group, especially for the youngest, smallest children. Extrapolating reference equations beyond the age range of subjects used to generate then is not recommended.     

New reference equations to improve interpretation of infant lung function

Rationale

With increasing use of infant pulmonary function tests (IPFTs) in both clinical and research studies, appropriate interpretation of results is essential.

Objectives

To investigate the potential bias associated with “normalising” IPF by expressing results as a ratio of body size and to develop reference ranges for tidal breathing parameters, passive respiratory mechanics (compliance [C_rs] and resistance [R_rs]) and plethysmographic functional residual capacity (FRC_p) for white infants during the first 2 years of life.

Methods

IPFTs were measured using the Jaeger BabyBody system and standardized protocols. Reference equations, adjusted for body size, age, and sex where appropriate, were created using multilevel modeling.

Results

The ratio of lung function to body length changes markedly with growth, thereby precluding its use for any outcome. While the ratio of tidal volume and C_rs to body weight remained relatively constant with growth, this was not the case for FRC_p. Even in healthy infants, a strong inverse relationship was observed between lung function/body weight and weight z‐score which could distort interpretation of results in growth‐restricted infants with lung disease, such as cystic fibrosis. Reference equations were derived from 153 healthy white infants on 232 test occasions (median age 35.5 weeks [range: 2.6–104.7]). Crown‐heel length was the strongest predictor of IPF.

Conclusions

When reporting IPF, use of size‐corrected ratios should be discouraged, with interpretation instead based on appropriate reference equations. The current equations are applicable to white infants and young children up to 2 years of age, studied using the same commercially available equipment. The extent to which these equations are applicable to infants and young children of other ethnic backgrounds or who are tested with different equipment needs to be established. Pediatr Pulmonol. 2013; 48:370–380. © 2012 Wiley Periodicals, Inc.     

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.     

Spirometry reference values for Navajo children ages 6–14 years

Spirometry is the most important tool in diagnosing pulmonary disease and is the most frequently performed pulmonary function test. Since respiratory disease is the single greatest cause for morbidity and mortality on the Navajo Nation, the purpose of this study was to create new age and race‐specific pulmonary nomograms for Navajo children. Five hundred fifty‐eight healthy children, ages 6–14 years, attending Navajo Nation elementary schools in Arizona, were asked to perform spirometry to develop population‐specific and tribe‐specific nomograms for forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), and FEV1 Ratio (FEV1/FVC). Spirometry tests from 284 girls and 274 boys met American Thoracic Society quality control standards. Lung function values, except for FEV1/FVC, all increased with height. The lower limit of the normal range for FEV1/FVC was 80%. The spirometry reference equations from the healthy boys and girls were developed. Height and the natural log of height were significant predictors of FEV1, FVC, and FEF_25–75% in the gender‐specific models. The resulting population‐specific spirometry reference equations should be used when testing Navajo children ages 6–14 years. However, the use of the NHANES III spirometry reference equations for Caucasian children may not result in significant misclassification in clinical settings providing that a maximal effort is given by the Navajo child being tested. Pediatr Pulmonol. 2009; 44:489–496. © 2009 Wiley‐Liss, Inc.     

Choice of spirometric reference values for compensation assessment

Background and objective:   Two sets of local reference values are available for spirometry in Hong Kong, but it is uncertain how well they work in the assessment of occupational lung diseases. This study examined their relative performance in the compensational assessment of silicosis.
Methods:   Local reference values published in 1982 and 2006 were compared in two different populations comprising normal construction/quarry workers and silicosis patients. Only men aged 20–74 years were included.
Results:   The FVC results of 93 normal workers were significantly higher than those predicted by either the 1982 or the 2006 reference values. Compared with the 1982 reference values, the mean FEV₁% or FVC% was age-dependent and 5.2% higher in the normal workers. Smoking decreased the forced expiratory ratio, but did not show a major effect on FEV₁ or FVC among asymptomatic subjects. Despite their derivation largely from never-smokers, the 2006 reference values better predicted FEV₁ and FVC among all smoking categories. Among the 357 silicosis patients, the 1982 reference values also gave 8.8% higher FEV₁% and 7.4% higher FVC%. These spirometric values differed by more than 10% in patients aged 60 years or more. Despite the presence of disease, the mean FVC% was still significantly above 100%.
Conclusions:   Both the 1982 and 2006 local reference values underestimated the FVC of normal construction and quarry workers, reflecting possible occupational selection factors. The 2006 reference values outperformed the 1982 ones, especially among older subjects. Careful calibration with similar occupational groups in the same laboratory is highly desirable in the choice of spirometric reference values for compensation assessment. Smoking does not appear to affect this choice.     

Relative contribution of resting haemodynamic profile and lung function to exercise tolerance in male patients with chronic heart failure

OBJECTIVE—To clarify the relative contribution of resting haemodynamic profile and pulmonary function to exercise capacity in patients with heart failure.
SETTING—Cardiology department and cardiac rehabilitation unit in a tertiary centre.
DESIGN—161 male patients (mean (SD) age 59 (9) years) with heart failure (New York Heart Association class II-IV, left ventricular ejection fraction 23 (7)%) underwent spirometry, alveolar capillary diffusing capacity (DLCO), and mouth inspiratory and expiratory pressures (MIP, MEP, respectively, in 100 patients). Right heart catheterisation and a symptom limited cardiopulmonary exercise test were performed in 137 patients within 3-4 days.
RESULTS—Mean peak exercise oxygen consumption (V̇O₂) was 13 (3.9) ml/kg/min. Among resting haemodynamic variables only cardiac index showed a significant correlation with peak V̇O₂. There were no differences in haemodynamic variables between patients with peak V̇O₂ ⩽ or > 14 ml/kg/min. There was a moderate correlation (p < 0.05) between several pulmonary function variables and peak V̇O₂. Forced vital capacity (3.5 (0.9) v 3.2 (0.8) l, p < 0.05) and DLCO (21.6 (6.9) v 17.7 (5.5) ml/mm Hg/min, p < 0.05) were higher in patients with peak V̇O₂ > 14 ml/kg/min than in those with peak V̇O₂ ⩽ 14 ml/kg/min. Using a stepwise regression analysis, the respiratory and haemodynamic variables which correlated significantly with peak V̇O₂ were DLCO, MEP, and cardiac index, with an overall R value of 0.63.
CONCLUSIONS—The data confirm previous studies showing a poor correlation between resting indices of cardiac function and exercise capacity in heart failure. However, several pulmonary function variables were related to peak exercise V̇O₂. In particular, lung diffusing capacity and respiratory muscle function seem to affect exercise tolerance during heart failure.