[The role of lung volume measurements by plethysmography in the follow-up of asthma in children]

Frequência de alterações espirométricas, aprisionamento aéreo e hiperinsuflação pulmonar em crianças e adolescentes com asma grave resistente à terapia

Objetivos: avaliar a frequência de alterações espirométricas e pletismográficas em crianças e adolescentes com asma grave resistente à terapia (AGRT). Além disso, testaram-se possíveis associações entre esses desfechos.Métodos: trata-se de um estudo retrospectivo, no qual foram incluídas crianças e adolescentes (6-18 anos), com diagnóstico de AGRT, e que se encontravam em acompanhamento ambulatorial regular. Todos deveriam possuir informações antropométricas (peso, altura, índice de massa corporal), demográficas (idade, etnia e sexo), clínicas (teste cutâneo, teste de controle da asma, tabagismo familiar e medicações em uso) e de função pulmonar (espirometria e pletismografia corporal) registradas no banco de dados do serviço. Os testes de função pulmonar seguiram as recomendações das diretrizes nacionais e internacionais. Para fins estatísticos, utilizou-se análise descritiva e o teste de qui-quadrado de Pearson.Resultados: de um total de 15 pacientes com AGRT, 12 deles foram incluídos na amostra. A média de idade foi de 12,2 anos, com predomínio do sexo feminino (66,7%). Destes, 50,0% apresentaram a doença controlada, 83,3% foram considerados atópicos e 50,0% tinham histórico de tabagismo familiar. Em relação aos testes de função pulmonar (% do previsto), as médias dos parâmetros espirométricos e de plestismografia corporal encontraram-se dentro dos limites inferiores da normalidade. Apenas 16,7% da amostra apresentou espirometria alterada (<percentil 5), 25,0% aprisionamento aéreo (volume residual>130,0%) e 16,7% hiperinsuflação pulmonar (capacidade pulmonar total>120,0%). Houve frequência estatisticamente maior (p=0,045) de aprisionamento aéreo nos participantes com espirometria alterada, em comparação à espirometria normal. Contudo, não se observou diferença (p=0,341) em relação à hiperinsuflação pulmonar.Conclusões: os achados demonstraram pouco comprometimento espirométrico e dos volumes e das capacidades pulmonares em crianças e adolescentes com AGRT. Além disso, aqueles participantes com espirometria alterada obtiveram frequência maior de aprisionamento aéreo no exame de pletismografia corporal.

Tricuspid regurgitation velocity and other biomarkers of mortality in children, adolescents and young adults with sickle cell disease in the United States: The PUSH study

In the US, mortality in sickle cell disease (SCD) increases after age 18-20 years. Biomarkers of mortality risk can identify patients who need intensive follow-up and early or novel interventions. We prospectively enrolled 510 SCD patients aged 3-20 years into an observational study in 2006-2010 and followed 497 patients for a median of 88 months (range 1-105). We hypothesized that elevated pulmonary artery systolic pressure as reflected in tricuspid regurgitation velocity (TRV) would be associated with mortality. Estimated survival to 18 years was 99% and to 25 years, 94%. Causes of death were known in seven of 10 patients: stroke in four (hemorrhagic two, infarctive one, unspecified one), multiorgan failure one, parvovirus B19 infection one, sudden death one. Baseline TRV ≥2.7 m/second (>2 SD above the mean in age-matched and gender-matched non-SCD controls) was observed in 20.0% of patients who died vs 4.6% of those who survived (P = .012 by the log rank test for equality of survival). The baseline variable most strongly associated with an elevated TRV was a high hemolytic rate. Additional biomarkers associated with mortality were ferritin ≥2000 μg/L (observed in 60% of patients who died vs 7.8% of survivors, P < .001), forced expiratory volume in 1 minute to forced vital capacity ratio (FEV1/FVC) <0.80 (71.4% of patients who died vs 18.8% of survivors, P < .001), and neutrophil count ≥10x10⁹ /L (30.0% of patients who died vs 7.9% of survivors, P = .018). In SCD children, adolescents and young adults, steady-state elevations of TRV, ferritin and neutrophils and a low FEV1/FVC ratio may be biomarkers associated with increased risk of death.

Investigating the relationships among lung function variables in chronic obstructive pulmonary disease in men

Background

In patients with chronic obstructive pulmonary disease (COPD), the independent contributions of individual lung function variables to outcomes may be lower when they are modelled together if they are collinear. In addition, lung volume measurements may not be necessary after spirometry data have been obtained. However, these hypotheses depend on whether forced vital capacity (FVC) can predict total lung capacity (TLC). Moreover, the definitions of hyperinflation and air trapping according to lung function variables overlap and need be clarified. Therefore, the aim of this study was to evaluate the relationships among various lung function parameters to elucidate these issues.

Methods

Demographic data and 26 parameters of full lung function were measured in 94 men with COPD and analyzed using factor and correlation analyses.

Results

Factor analysis revealed five latent factors. Inspiratory capacity (IC)/TLC and residual volume (RV)/TLC were most strongly correlated with all other lung volumes. IC/TLC, RV/TLC, and functional residual capacity (FRC)/TLC were collinear and were potential markers of air trapping, whereas TLC%, FRC%, and RV% were collinear and were potential markers of hyperinflation. RV/TLC >0.4 (or IC/TLC <0.4) was comparable with the ratio of forced expiratory volume in one second (FEV₁) and FVC <0.7. FVC% and FEV₁% were poorly correlated with TLC%. The correlation study showed that TLC%, RV/TLC, and FEV₁% could be used to represent individual latent factors for hyperinflation, air trapping, inspiration, expiration, and obstruction. Combined with diffusion capacity%, these four factors could be used to represent comprehensive lung function.

Conclusions

This study identified collinear relationships among individual lung function variables and thus selecting variables with close relationships for correlation studies should be performed with caution. This study also differentiated variables for air trapping and lung hyperinflation. Lung volume measurements are still required even when spirometry data are available. Four out of 26 lung function variables from individual latent factors could be used to concisely represent lung function.

Measuring Airway Obstruction in Severe Asthma in Children

Lung function is an important tool in the diagnosis and monitoring of patients with asthma at all ages. Airway obstruction is a typical feature of asthma and it can be assessed with several lung function techniques. Spirometry, respiratory resistance and reactance, and lung volumes are available to measure it at different ages and in children. The assessment of a bronchodilator response is always recommended to show the reversibility of the obstruction. Poor lung function is a predictor of poor asthma outcome and a low Forced Expiratory Volume in the first second of expiration percent predicted measured with spirometry, has been shown to be associated with a higher risk of having an exacerbation during the following year independently of the presence of asthma symptoms. In severe asthma lung function assessment is used to distinguish different phenotypes, children with severe asthma have worse airflow limitation prior to administration of a bronchodilator than children with non severe asthma. Airway resistance and reactance are indirect measurements of airway obstruction and they can be measured with the forced oscillation technique, which is feasible also in non-collaborative children. This technique can be more informative in discriminating patients with asthma from healthy controls and is able to indicate a more peripheral involvement of the airways. The role of this technique in severe asthma is still debated. In conclusion lung function is useful in the clinical management of children with severe asthma.

Monitoring asthma in childhood: lung function, bronchial responsiveness and inflammation

This review focuses on the methods available for measuring reversible airways obstruction, bronchial hyperresponsiveness (BHR) and inflammation as hallmarks of asthma, and their role in monitoring children with asthma. Persistent bronchial obstruction may occur in asymptomatic children and is considered a risk factor for severe asthma episodes and is associated with poor asthma outcome. Annual measurement of forced expiratory volume in 1 s using office based spirometry is considered useful. Other lung function measurements including the assessment of BHR may be reserved for children with possible exercise limitations, poor symptom perception and those not responding to their current treatment or with atypical asthma symptoms, and performed on a higher specialty level. To date, for most methods of measuring lung function there are no proper randomised controlled or large longitudinal studies available to establish their role in asthma management in children. Noninvasive biomarkers for monitoring inflammation in children are available, for example the measurement of exhaled nitric oxide fraction, and the assessment of induced sputum cytology or inflammatory mediators in the exhaled breath condensate. However, their role and usefulness in routine clinical practice to monitor and guide therapy remains unclear, and therefore, their use should be reserved for selected cases.

Small airway impairment in moderate to severe asthmatics without significant proximal airway obstruction

Asthma is a disease characterized by inflammation which affects both proximal and distal airways. We evaluated the prevalence of small airway obstruction (SAO) in a group of clinically stable asthmatics with both normal forced expiratory volume in the first second (FEV1) and normal FEV1/forced vital capacity (FVC) and treated with an association of inhaled corticosteroids (ICSs) and long acting β2-agonists (LABAs). Clinical evaluation included the measurement of dyspnea, asthma control test and drug compliance. The prevalence of SAO was estimated by spirometry and plethysmography and defined by the presence of one or more of the following criteria: functional residual capacity (FRC) > 120% predicted (pred), residual volume (RV) > pred + 1.64 residual standard deviation (RSD), RV/total lung capacity (TLC) > pred + 1.64 RSD, forced expiratory flow (FEF)25-75% < pred - 1.64 RSD, FEF50% < pred - 1.64 RSD, slow vital capacity (SVC) - FVC > 10%. Among the 441 patients who were included, 222 had normal FEV1 and FEV1/FVC. At least one criteria of SAO was found in 115 (52%) mainly lung hyperinflation (39% based on high FRC, RV or RV/TLC) and more rarely distal airflow limitation (15% based on FEF25-75% or FEF50%) or expiratory trapping (10% based on increased SVC - FVC). In the patients with only SAO (no PAO), there was no relationship between SAO, asthma history and the scores of dyspnea, asthma control or drug compliance. These results suggest that in asthmatics with normal FEV1 and FEV1/FVC, treated with ICSs and LABAs, SAO is found in more than half of the patients indicating that the routinely used lung function tests can underestimate dysfunctions occurring in the small airways.