[Body plethysmography (I): Standardisation and quality criteria]

Whole body plethysmography is used to measure lung volumes, capacities and resistances. It is a well standardised technique, and although it is widely used in paediatric chest diseases units, it requires specific equipment, specialist staff, and some cooperation by the patient. Plethysmography uses Boyle's law in order to measure the intrathoracic gas volume or functional residual capacity, and once this is determined, the residual volume and total lung capacity is extrapolated. The measurement of total lung capacity is necessary for the diagnosis of restrictive diseases. Airway resistance is a measurement of obstruction, with the total resistance being able to be measured, which includes chest wall, lung tissue and airway resistance, as well as the specific airway resistance, which is a more stable parameter that is determined by multiplying the measured values of airway resistance and functional residual capacity. The complexity of this technique, the reference equations, the differences in the equipment and their variability, and the conditions in which it is performed, has led to the need for its standardisation. Throughout this article, the practical aspects of plethysmography are analysed, specifying recommendations for performing it, its systematic calibration and the calculations that must be made, as well as the interpretation of the results obtained. The aim of this article is to provide a better understanding of the principles of whole body plethysmography with the aim of optimising the interpretation of the results, leading to improved management of the patient, as well as a consensus among the speciality.

[Validation of a Spanish version of the Childhood Asthma Control Test (Sc-ACT) for use in Spain]

OBJECTIVE

The Childhood Asthma Control Test (c-ACT) is a validated tool for determining pediatric asthma control. However, it is not validated in the Spanish language in Spain. We evaluated the psychometric properties of the Spanish version of the Childhood Asthma Control Test (Sc-ACT) for assessing asthma control in children ages 4 to11.

METHODS

This national, multicentre, prospective study was conducted in Spain with asthmatic children and their caregivers. Patients were assessed at 3 visits (Baseline, 2 Weeks, and 4 Months). Clinical variables included: symptoms, exacerbations, FEV1, asthma classification, PAQLQ and PACQLQ questionnaire scores, and asthma control as perceived by physicians, patients and caregivers. The Sc-ACT feasibility, validity, reliability, and sensitivity to change were assessed.

RESULTS

A total of 394 children were included; mean (SD) time to complete the Sc-ACT was 5.3 (4.4) minutes. Sc-ACT score was correlated with asthma control as perceived by physician (-0.52), patient (-0.53), and caregiver (-0.51) and with the PAQLQ (0.56) and PACQLQ (0.55) scores. Sc-ACT was found to be significantly related to intensity and frequency of asthma symptoms. Cronbach alpha coefficient α was 0.81 and intraclass correlation coefficient was ≥0.85 for all of the items. The global effect size of Sc-ACT was 0.55. The cutoff point scores of 21 or higher indicated a good asthma control and their MCID was 4 points.

CONCLUSION

The Spanish version of the c-ACT was found to be a reliable and valid questionnaire for evaluating asthma control in Spanish-speaking children ages 4 to 11 in Spain.

[Measurement of CO diffusion capacity (II): Standardization and quality criteria]

The diffusion capacity is the technique that measures the ability of the respiratory system for gas exchange, thus allowing a diagnosis of the malfunction of the alveolar-capillary unit. The most important parameter to assess is the CO diffusion capacity (DLCO). New methods are currently being used to measure the diffusion using nitric oxide (NO). There are other methods for measuring diffusion, although in this article the single breath technique is mainly referred to, as it is the most widely used and best standardized. Its complexity, its reference equations, differences in equipment, inter-patient variability and conditions in which the DLCO is performed, lead to a wide inter-laboratory variability, although its standardization makes this a more reliable and reproductive method. The practical aspects of the technique are analyzed, by specifying the recommendations to carry out a suitable procedure, the calibration routine, calculations and adjustments. Clinical applications are also discussed. An increase in the transfer of CO occurs in diseases in which there is an increased volume of blood in the pulmonary capillaries, such as in the polycythemia and pulmonary hemorrhage. There is a decrease in DLCO in patients with alveolar volume reduction or diffusion defects, either by altered alveolar-capillary membrane (interstitial diseases) or decreased volume of blood in the pulmonary capillaries (pulmonary embolism or primary pulmonary hypertension). Other causes of decreased or increased DLCO are also highlighted.

[Neuromuscular disease: respiratory clinical assessment and follow-up]

Patients with neuromuscular disease are an important group at risk of frequently suffering acute or chronic respiratory failure, which is their main cause of death. They require follow-up by a pediatric respiratory medicine specialist from birth or diagnosis in order to confirm the diagnosis and treat any respiratory complications within a multidisciplinary context. The ventilatory support and the cough assistance have improved the quality of life and long-term survival for many of these patients. In this paper, the authors review the pathophysiology, respiratory function evaluation, sleep disorders, and the most frequent respiratory complications in neuromuscular diseases. The various treatments used, from a respiratory medicine point of view, will be analyzed in a next paper.

[Spirometry patterns in vocal cord dysfunction]

INTRODUCTION

Vocal cord dysfunction (VCD) is a rare disease characterized by a paradoxical closure of the vocal cords, usually in inspiration, that causes dyspnea and stridor. The spirometry pattern that is more often described is a plateau in the inspiratory curve, but it can be also found in the expiratory loop The aim of this study was to evaluate the most common spirometry characteristics of patients with VCD and, secondarily, to describe the clinical and demographic characteristics and the treatment of patients with a definitive diagnosis of this disease.

MATERIAL AND METHODS

A retrospective study was made of cases of VCD between 2000 and 2010. Diagnosis was considered definitive when a paradoxical closure of the vocal cords became clear on laryngoscopy. Exercise challenge on a treadmill was performed to produce symptoms. Demographic and clinical data were collected, and flow-volume curves were studied.

RESULTS

Of 36 suspected cases, VCD was confirmed in 11 (30.5%). The mean age was 13.5 years, 10 were female. Possible triggers were found in 5 patients. Six patients had a previous history of asthma. All patients had a plateau in the inspiratory curve, and 9 (81%) of them also in the expiratory loop. Only 4 patients had a ratio between maximum inspiratory and expiratory flows at 50% of forced vital capacity (MEF50%/MIF50%) > 2.2.

CONCLUSIONS

Although the most frequent spirometry pattern in VCD is a plateau in the inspiratory curve, a significant percentage of patients also have a plateau in the expiratory curve. This could invalidate the MEF50%/MIF50% ratio for the diagnosis of VCD.

[Diagnosis and treatment guidelines for difficult-to-control asthma in children]

Children suffering from difficult-to-control asthma (DCA) require frequent appointments with their physician, complex treatment regimes and often admissions to hospital. Less than 5% of the asthmatic population suffer this condition. DCA must be correctly characterised to rule out false causes of DCA and requires making a differential diagnosis from pathologies that mimic asthma, comorbidity, environmental and psychological factors, and analysing the factors to determine poor treatment compliance. In true DCA cases, inflammation studies (exhaled nitric oxide, induced sputum, broncho-alveolar lavage and bronchial biopsy), pulmonary function and other clinical aspects can classify DCA into different phenotypes which could make therapeutic decision-making easier.

[Bronchodilator test: is 9% of the predicted value the same as 12% of the initial value]

INTRODUCTION

The bronchodilator test (BDT) is an important tool used in pulmonary function. Changes in forced expiratory volume in one second (FEV1) can be expressed as absolute change, or per cent of initial or predicted value. When the initial value is used, there may be a bias, as the smaller this value is, the greater the response will be. The main objective of this study is to establish whether there is any difference in using per cent of the initial spirometry value or per cent of the predicted value in order to consider a bronchodilator test positive, and if the initial obstruction of the patient influences such differences.

MATERIAL AND METHODS

A retrospective analysis of the BDT made between October 1997 and February 2008. The results using an increase of 9% from the predicted FEV1 were compared with using 12% from the initial FEV1. The patients were divided into three groups depending on initial obstruction: no obstruction (FEV1>80% of predicted), mild (FEV1=60-80% of predicted) and moderate-severe (FEV1<60% of predicted). The kappa index of agreement between both methods was calculated.

RESULTS

A total of 4352 BDT were analysed. The agreement between both methods was high (k=0.832). In the group without initial obstruction (N=3007) the kappa index was 0.781, in the mild obstruction group (N=1067) the kappa index was 0.966 and in the moderate-severe group (N=278) it was 0.788.

CONCLUSION

This study demonstrates that, although there is a good agreement between both methods, in patients with initial moderate-severe obstruction and in patients without initial obstruction this agreement tends to be lower.

[Lung function changes after haematopoietic stem cell transplantation]

OBJECTIVE

To evaluate lung function abnormalities in children who underwent haematopoietic stem cell transplantation (HSCT) and to compare these abnormalities between autologous and allogenic transplantation.

PATIENTS AND METHODS

Prospective observational study from 1996 to 2005. Ninety-three children receiving HSCT, 47 autologous and 46 allogenic, were included. Lung function tests were performed before transplantation and at 2, 6, 12 and 24 months afterwards. The following indices were determined: forced expiratory volume in 1 s (FEV1), FEV1/forced vital capacity (FVC), total lung capacity (TLC), and carbon monoxide diffusing capacity (DLCO). Paired Student's t-test was used for statistical analysis of data.

RESULTS

Before HSCT, 6.8% of the children had FEV1<80%, 1% FEV1/FVC<80%, 7.8% TLC<80% and 13.5% DLCO<70%. At 2 months, FEV1/FVC, TLC and DLCO were significantly reduced, when compared to pre-transplantation values (p=0.05, 0.011 and p<0.001, respectively). Lung function gradually improved from 6 months post-transplantation, but did not reach pre-transplantation values at 24 months. No significant differences were found when comparing allogenic and autologous transplantation, apart from a lower FEV1/FVC value at 6 months (p=0.02) in the first group.

CONCLUSIONS

An important proportion of children who undergo HSCT have early pulmonary abnormalities (at 2 and 6 months after transplantation) with partial recovery at 24 months.

[Respiratory function assessment in cooperative patients. Part II]

Analysis of bronchial hyperresponsiveness using bronchial provocation tests are a key feature in the diagnosis of asthma, as well as a valid tool for monitoring disease severity, clinical course, and treatment response. We review non-specific bronchial challenge tests, including pharmacological stimuli (methacholine, adenosine) and physical stimuli (exercise, hypertonic saline, cold air hyperventilation). Although there is some correlation among responses to the distinct tests, individual responses are also observed. The indication for a single test will depend on whether the procedure will be used for diagnostic or epidemiologic purposes, and on experience of its use. Frequently, complementary information will be obtained. Indirect airway challenges tests such as physical stimuli and adenosine are more specific for asthma diagnosis.

[Resistance by oscillometry. Comparison of its behavior in patients with asthma and cystic fibrosis]

This study aims to assess the behavior of the oscillometric parameters in 60 patients with bronchial asthma and in 39 with cystic fibrosis. All of them underwent an impulse oscillometry (IOS) and forced spirometry. The correlations existing between FEV1 and different oscillometric endpoints were assessed. In asthmatic subjects, the oscillometry parameters that correlated best with FEV1 were impedance (Zsr) and resistance to 5 hertz (Rsr5), while it was the Zsr and reactance to 5 hertz (Xsr5) in the individuals with cystic fibrosis. In the last group of patients, no correlation was found between FEV1 and Rsr in most of the frequencies evaluated. We conclude that there are differences in the behavior of the oscillometric parameters in patients with bronchial asthma and cystic fibrosis. The oscillometric parameters having the greatest use in the detection of the obstruction to airflow vary according to the disease studied.

Enfermedad pulmonar obstructiva tras trasplante alogénico de progenitores hematopoyéticos en niños

INTRODUCTION

Bronchiolitis obliterans is recognized as a life-threatening pulmonary complication that can develop 3 months after bone marrow transplantation.

OBJECTIVE

To determine the incidence and clinical progression of obstructive lung disease (OLD) in a population of children who had undergone allogenic hematopoietic stem cell transplantation (HSCT).

PATIENTS AND METHODS

We examined a sequential sample of 110 patients who received allogeneic HSCT between January 1992 and June 2002. The incidence of OLD in the 77 children who survived for more than 100 days after transplantation was analyzed. The diagnosis of OLD was based on clinical findings with no evidence of infection, pulmonary function test (FEV1/FVC less than 80 % and FEV1 less than 80 % of predicted value) and computed tomography scan.

RESULTS

Eight patients (10.4 %) developed OLD at a median time of onset of 184 days after allogenic HSCT (range: 100-1735 days). All patients with OLD had respiratory symptoms. In six out of eight patients airflow obstruction was diagnosed within 1 year of transplantation. All patients showed chronic graft-versus-host disease (GVHD) (p < 0.01). The incidence of OLD in the 23 patients with chronic GVHD was 34.8 %. Two patients (25 %) had a complete response to intensified treatment of chronic GVHD with immunosuppressant therapy. FEV1 declined rapidly in three patients (37.5 %) who died of respiratory failure. Two patients (25 %) had partial reversal but pulmonary function continued below normal values. In one patient (12.5 %) severe obstructive disease was stable.

CONCLUSIONS

The time of onset and form of progression of OLD after HSCT may vary. OLD is strongly associated with chronic GVHD and its incidence depends on the number of patients with chronic GVHD.

[Obstructive sleep apnea syndrome in childhood]

Obstructive sleep apnea syndrome (OSAS) is a well-known clinical entity in adults but until now it has been less well studied in children. Several studies have shown that the prevalence of pediatric OSAS is high (between 1% and 3%) and its consequences can be serious. Major risk factors for OSAS in children include adeno-tonsillar hypertrophy, neuromuscular disease and syndromes such as Down's or Pierre-Robin's syndrome. Definitive diagnosis is by nocturnal polysomnography while other methods such as cardiorespiratory records and nocturnal pulse oximetry are undoubtedly useful. Adenotonsillectomy plays a major role in the treatment of OSAS. Nasal continuous positive airway pressure is an alternative in children who show poor response to surgical treatment or in those with craniofacial alterations. In a few cases, nocturnal oxygen administration can be useful.

[Reproducibility of the walking test in patients with cystic fibrosis]

OBJECTIVE

The walking test is a useful and objective method for evaluating the tolerance for exercise in patients with chronic bronchopulmonary diseases. Our objective was to check the reproducibility of this test and evaluate whether there are differences between tests of varying duration (2 and 6 minutes) in a group of patients with cystic fibrosis.

PATIENTS AND METHODS

We utilized the walking test on 29 patients who were in a stable phase and under care in the Cystic Fibrosis Unit of our hospital. Two tests were carried out, one of 2 minutes and the other of 6 minutes duration, both of which were repeated after a 15-minute interval.

RESULTS

The reproducibility of the walking test in this type of patient was very good and we found an excellent correlation between the two-minute test and the six-minute test. We did not observe a training effect when the test was repeated.

CONCLUSIONS

The two minute walking test has a high reproducibility and we propose this test, because it is shorter and more comfortable for pediatric patients with cystic fibrosis, in order to evaluate the evolution, progressive deterioration of the of the patient and the response to different types of treatments.

[Assessment of lung function using forced impulse oscillometry in cystic fibrosis patients]

The aim of this study was to evaluate the usefulness of forced impulse oscillometry to measure airway resistance in patients with cystic fibrosis. Thirty-four patients (20 men) with a mean age of 15 +/- 4 years were studied. All patients underwent forced impulse oscillometry, forced spirometry and body plethysmography. Correlations among spirometric, plethysmographic and oscillometric variables were analyzed. We found a statistically significant relation between both forced expiratory volume in one second (FEV1) and total airway resistance (Raw) and the following oscillometric variables: impedance (Zrs), resonance frequency (Fres), resistance to 5 hertz (Rrs5) and reactance to 5 hertz (Xrs5). The measurements that correlated most highly with classical pulmonary function tests were Zrs and Xrs5. Both resistance (Rrs) and reactance (Xrs) of the respiratory system were dependent on frequency. Their correlation with FEV1 and Raw were therefore lower when frequencies above 5 hertz were used. We conclude that airway resistances of cystic fibrosis patients can be adequately estimated by forced impulse oscillometry. This technique is a promising test of pulmonary function in such patients.

[Eosinophil cationic protein in the asthmatic infant: correlation with the clinic and pulmonary function]

PATIENTS AND METHODS

Serum eosinophil cationic protein (ECP) was measured in 99 chronic asthmatic patients (51 males and 48 females) with a mean age of 10.59 years and correlated with the number of eosinophils, lung function, symptoms in the last 6 months and clinical scoring (that reflecting the clinical situation during the last 15 days).

RESULTS

Serum ECP showed a significant correlation with the total number of eosinophils (p < 0.001, R = 0.44), clinical scoring (p < 0.05, R = 0.26), number of inhaled beta 2-agonist doses needed in the last 15 days (p < 0.05, R = 0.26), forced expiratory volume during 1 second (FEV1; p < 0.01, R = -0.27), forced vital capacity (FVC; p < 0.05, R = -0.23), maximal mid-expiratory flow (FEF25-27; p < 0.001, R = -0.37). However, there was no significant correlation between the total number of eosinophils and the clinical situation of the children or the FEV1, but we found a significant correlation with the FEF25-27. Patients with ECP < 20 had better results on lung function tests than patients with ECP > 20 (FEV1: 108.89 +/- 17.7 vs 100.5 +/- 22 (p < 0.05), FEF25-27: 93.81 +/- 24.4 vs 75.21 +/- 24.5 (p < 0.001).

CONCLUSIONS

The findings of this study suggest that the ECP level is a good marker of the situation of asthma in childhood. The levels of ECP will probably be able to help us to evaluate the degree of bronchial inflammation that neither the clinical state nor the lung function define completely.

[Secretory IgA and infantile respiratory pathology]

Secretory component of IgA is the major class of immunoglobulin in secretions and mucous membranes. Many causes have been involved in etiopathogenesis of respiratory tract disease in children, one of them the possible deficit of secretory component of IgA. Authors have studied 191 children with respiratory tract disease secondary to infections and/or allergy and a control group of 35 healthy children. In all of them the secretory IgA non stimulated sputum was measured. In the group with respiratory disease serum IgA, IgG, IgM and IgE were also measured. Levels of secretory IgA were greater in group with respiratory disease than in control; also serum level of IgA was above normal for their ages. Level of secretory IgA was greater in children with "wheezing respiratory disease". These findings do not agree with theory of existence of an IgA secretory deficit as a cause or respiratory tract disease in children.