Spirometry reference equations for central European populations from school age to old age

Development and validation of predictive equations for spirometry in Portuguese children

Background

There are no data on lung function reference values for Portuguese children, and the contribution from the Portuguese data set in the Global Lung Function Initiative (GLI) is scant.

Objectives

We aimed to estimate new up-to-date reference values for Portuguese children by fitting a multivariable regression model to a general population sample. Further, we intended to assess the external validity of the obtained reference values and to compare them to the GLI reference values.

Methods

A random sample of 858 children from 20 primary schools were screened by health questionnaire, physical examination, and spirometry. Spirometric parameters recorded were FVC, FEV1, and FEF25-75. Multiple regression models were used to derive reference equations.

Results

Overall, 481 children, aged between 7 and 12 years, 267 boys (55.5%), were included. Boys had higher values for FVC and FEV1 than girls (P < .05). The strongest correlation was found for FVC with height (r = 0.71 for boys and 0.70 for girls), while the lowest correlation was observed in both sexes for FEF25-75 with age (r = 0.23). Height was the most significant predictor of FVC, FEV1, and FEF25-75 in our models. Weight and body mass index were not significant predictors for boys but had a significant effect on girls' equations for all spirometry parameters. Compared to obtained reference equations with GLI, they performed better for FVC in boys, FEV1 in girls, and FEF25-75 in both boys and girls.

Conclusion

We offer up-to-date reference values of spirometry for Portuguese children that can be used in clinical practice and research.

Survival-Adjusted FEV1 and BMI Percentiles for Patients with Cystic Fibrosis before the Era of Triple CFTR Modulator Therapy in Germany

BACKGROUND

Pulmonary disease is the major cause for morbidity and mortality in cystic fibrosis (CF). In CF, forced expiratory volume in 1 s (FEV1) referenced against a healthy population (FEV1%predicted) and body mass index (BMI) do not allow for the comparison of disease severity across age and gender.

OBJECTIVES

We aimed to determine updated FEV1 and BMI percentiles for patients with CF and to study their dependence on mortality attrition.

METHODS

Age- and height-adjusted FEV1 and BMI percentiles for CF patients aged 6-50 years were calculated from 4,947 patients of the German CF Registry for the period 2016-2019 utilizing quantile regression and a Generalized Additive Model for Location, Scale and Shape (GAMLSS). Further, survival-adjusted percentiles were estimated.

RESULTS

In patients with CF, FEV1 increased throughout childhood until maximal median values at 16 years in females (2.46 L) and 18 years in males (3.27 L). During adulthood, FEV1 decreased substantially. At 17 years of age, the 25th BMI percentile of patients with CF (females 18.50 and males 18.15 kg/m2) was below the 10th BMI percentile of the German reference cohort. From the age of 20 years, survival (96.3%) decreased tremendously. At 50 years of age (survival 15.0%), the 50th CF-specific FEV1 or BMI percentile among the survivors corresponded to the 92.5th percentile among the total CF birth cohort.

CONCLUSIONS

Continuously updated disease-specific FEV1 and BMI percentiles with correction for survival may serve as age-independent measure of disease severity in CF (accessible via https://cfpercentiles.statup.solutions).

Childhood to adulthood: Accounting for age dependence in healthy-reference distributions in 129 Xe gas-exchange MRI

PURPOSE

Xenon-129 (¹²⁹ Xe) gas-exchange MRI is a pulmonary-imaging technique that provides quantitative metrics for lung structure and function and is often compared to pulmonary-function tests. Unlike such tests, it does not normalize to predictive values based on demographic variables such as age. Many sites have alluded to an age dependence in gas-exchange metrics; however, a procedure for normalizing metrics has not yet been introduced.

THEORY

We model healthy reference values for ¹²⁹ Xe gas-exchange MRI against age using generalized additive models for location, scale, and shape (GAMLSS). GAMLSS takes signal data from an aggregated heathy-reference cohort and fits a distribution with flexible median, variation, skewness, and kurtosis to predict age-dependent centiles. This approach mirrors methods by the Global Lung Function Initiative for modeling pulmonary-function test data and applies it to binning methods widely used by the ¹²⁹ Xe MRI community to interpret and quantify gas-exchange data.

METHODS

Ventilation, membrane-uptake, red blood cell transfer, and red blood cell:membrane gas-exchange metrics were collected on 30 healthy subjects over an age range of 5 to 68 years. A GAMLSS model was fit against age and compared against widely used linear and generalized-linear binning ¹²⁹ Xe MRI analysis schemes.

RESULTS

All 4 gas-exchange metrics had significant skewness, and membrane-uptake had significant kurtosis compared to a normal distribution. Age has significant impact on distribution parameters. GAMLSS-binning produced narrower bins compared to the linear and generalized-linear binning schemes and distributed signal data closer to a normal distribution.

CONCLUSION

The proposed "proof-of-concept" GAMLSS-binning approach can improve diagnostic accuracy of ¹²⁹ Xe gas-exchange MRI by providing a means of modeling voxel distribution data against age.

Increase in Airway Obstruction between 1993 and 2012 in Switzerland. An Observational Study

Rationale: Most studies determining the prevalence of airway obstruction are limited to short time periods.Objectives: Because temporal trends of obstruction in populations are largely unknown, we determined the prevalence of airway obstruction over 20 years in yearly general population samples in Switzerland between 1993 and 2012.Methods: We analyzed data of 85,789 participants aged 35 years and older who provided spirometric measurements as part of the LuftiBus lung function campaign. We linked data from the 2003-2012 period to the Swiss National Cohort to adjust for annual population differences. Spirometry was performed without bronchodilation, according to American Thoracic Society guidelines. We used Global Lung Initiative (GLI) and Hankinson reference equations to identify obstruction.Results: Obstruction prevalence increased between 1993 and 2012 from 6.1% (95% confidence interval [CI], 5.5 to 6.7) to 15.6% (95% CI, 13.8 to 17.3) based on GLI estimates and from 5.3% (95% CI, 4.7 to 5.9) to 15.4% (95% CI, 13.6 to 17.1) based on Hankinson estimates. When adjusted for participant demographics, air pollutant and occupational exposures, altitude, and season, the prevalence ratios of obstruction were 1.54 (95% CI, 1.22 to 1.93) and 1.65 (95% CI, 1.33 to 2.04) for GLI- and Hankinson-defined airway obstruction, respectively, for 2012 compared with 2003.Conclusions: Though prebronchodilator measurements likely overestimate the prevalence of airway obstruction in absolute terms compared with post-bronchodilator measurements, we found an increase in airway obstruction prevalence. Even with adjustment for several well-known risk factors for obstruction to make the populations across the years more comparable, we still saw a statistically significant increase in prevalence over this time period.

Development and validation of models to predict respiratory function in persons with long-term spinal cord injury

STUDY DESIGN

Multicenter, cross-sectional study.

OBJECTIVES

To validate previously developed respiratory function prediction models for persons with long-term spinal cord injury (SCI) and if necessary develop and validate new models.

SETTING

Ten SCI rehabilitation centers.

METHODS

Five respiratory function parameters were measured in adults with chronic, traumatic, motor complete SCI (C4-T12). First, the models published in 2012 were validated using Bland-Altman plots. Then, new models were calculated using 80% of the dataset by multiple regression analysis with the candidate predictors gender, age, height, weight, time post injury (TPI), lesion level, and smoking. In a third step, the new models were validated using the other 20% of the dataset by Bland-Altman plots.

RESULTS

In total 613 participants were included. For persons with long-term SCI, the 2012 models were poorly predictive, especially for respiratory muscle strength (R2 = 0.4). Significant predictors for all respiratory function parameters in the new models (R2 = 0.7-0.8) were lesion level, gender and weight. Small effects on single outcome parameters were observed for TPI and age whereas smoking had no effect. For the new models the mean differences between measured and predicted values for respiratory muscle strength were 4.0 ± 36.0 cm H₂O and for lung function parameters -0.5 ± 1.2 L (FVC), -0.3 ± 0.9 L (FEV1) and -0.5 ± 2.0 L/s (PEF).

CONCLUSION

We did not find better models for lung function in long-term SCI but those for respiratory muscle strength showed better accuracy.

SPONSORSHIP

The content of this publication was developed under grant from Wings for Life, grant number WFL-CH-017/14.

Noninvasive ventilation failure in pneumonia patients ≥65years old: The role of cough strength

PURPOSE

To explore the association between cough strength and outcomes in elderly patients who received noninvasive ventilation (NIV) due to acute respiratory failure caused by pneumonia.

MATERIALS AND METHODS

We enrolled patients ≥65years old with acute respiratory failure caused by pneumonia. Just before NIV treatment, cough strength was assessed on a cough-strength scale graded from 0 to 5. Patients graded 0-2 were defined as having no/weak coughs and those graded 3-5 were defined as having moderate/strong coughs.

RESULTS

We enrolled 349 patients in this study. The prevalence of no/weak cough was 24% (84/349). Moderate/strong cough patients had lower NIV failure (92/265 [34.7%] vs. 67/84 [79.8%], p<0.01) and lower hospital mortality (85/265 [32.1%] vs. 60/84 [71.4%], p<0.01) than no/weak cough patients. In multivariate logistic regression analysis, we also found that no/weak cough was an independent risk factor for NIV failure (odds ratio=13.83, 95% confidence interval: 6.01-31.81) and death in hospital (odds ratio=4.41, 95% confidence interval: 2.49-7.81).

CONCLUSIONS

In pneumonia patients ≥65years old, no/weak cough is associated with NIV failure and death in hospital. NIV must be used only with caution in no/weak cough patients.

Global Lung Function Initiative 2012 reference values for spirometry in South Italian children

RATIONALE

Despite the widespread use of the Global Lung Function Initiative (GLI) 2012 reference values, there is still the need of testing their applicability in local areas.

OBJECTIVES

The aims of this study are to evaluate applicability of GLI reference equations in a large population-based sample of normal schoolchildren from Sicily, and to compare GLI and previous prediction equations in terms of spirometry test interpretation.

METHODS

GLI equations were evaluated in 1243 normal schoolchildren, 49% males, aged 7-16 years, height 116-187 cm. Normality assumptions for the GLI z-scores (FEV₁, FVC, FEV₁/FVC) were tested, and bootstrap confidence intervals for the mean (0 expected) and the variance (1 expected) were derived. GLI and other reference equations were compared in terms of probabilities to fall below the lower limit of normal (LLN).

RESULTS

The GLI z-score normality assumption held for males but not for females (p < 0.001). According to the mean z-score, predicted values were: slightly underestimated for FEV₁ (0.15 in males, 0.07 in females); overestimated for FVC (-0.27 in males, -0.32 in females); highly underestimated for FEV₁/FVC (0.75 in males, 0.81 in females). Variability was correctly estimated. The probability of FEV₁<LLN correctly approached 0.05 when using GLI, Hankinson and Quanjer equations. Wang equations yielded correct probabilities of abnormal FVC; Pistelli equations yielded correct probabilities of abnormal FEV₁/FVC for females.

CONCLUSIONS

GLI 2012 references underestimate FEV₁/FVC predicted values in a sample of normal South Italian children. Physicians interpreting spirometry should be aware to test reference values prior to their use in a local area.

Asthma in the elderly: a different disease?

KEY POINTS

Asthma in the elderly can be difficult to identify due to modifications of its clinical features and functional characteristics.Several comorbidities are associated with asthma in the elderly, and this association differs from that observed in younger patients.In clinical practice, physicians should treat comorbidities that are correlated with asthma (i.e. rhinitis or gastro-oesophageal reflux), assess comorbidities that may influence asthma outcomes (i.e. depression or cognitive impairment) and try to prevent comorbidities related to -'drug-associated side-effects (i.e. cataracts, arrhythmias or osteoporosis)."Geriatric asthma" should be the preferred term because it implies the comprehensive and multidimensional approach to the disease in the older populations, whereas "asthma in the elderly" is only descriptive of the occurrence of the disease in this age range.

EDUCATIONAL AIMS

To present critical issues in performing differential diagnosis of asthma in the elderly.To offer the instrument to implement the management of asthma in the most advanced ages. Asthma is a chronic airway disease that affects all ages, but does this definition also include the elderly? Traditionally, asthma has been considered a disease of younger age, but epidemiological studies and clinical experience support the concept that asthma is as prevalent in older age as it is in the young. With the ever-increasing elderly population worldwide, the detection and proper management of the disease in old age may have a great impact from the public health perspective. Whether asthma in the elderly maintains the same characteristics as in young populations is an interesting matter. The diagnostic process in older individuals with suspected asthma follows the same steps, namely a detailed history supported by clinical examination and laboratory investigations; however, it should be recognised that elderly patients may partially lose reversibility of airway obstruction. The correct interpretation of spirometric curves in the elderly should take into account the physiological changes in the respiratory system. Several factors contribute to delaying the diagnosis of asthma in the elderly, including the age-related impairment in perception of breathlessness. The management of asthma in advanced age is complicated by the comorbidities and polypharmacotherapy, which advocate for a comprehensive approach with a multidimensional assessment. It should be emphasised that older age frequently represents an exclusion criterion for eligibility in clinical trials, and current asthma medications have rarely been tested in elderly asthmatics. Ageing is associated with pharmacokinetic changes of the medications. As a consequence, absorption, distribution, metabolism and excretion of antiasthmatic medications can be variably affected. Similarly, drug-to-drug interactions may reduce the effectiveness of inhaled medications and increase the risk of side-effects. For this reason, we propose the term "geriatric asthma" be preferred to the more generic "asthma in the elderly".