Relationships between specific airway resistance and forced expiratory flows in asthmatic children

Diagnostic accuracy of peripheral lung function measurements in paediatric asthma control assessment: a pilot study

Introduction

Recent studies have indicated the significance of the peripheral airways in asthma control. Methods estimating airway resistance, air trapping, and ventilation inhomogeneity are useful for assessing this area of the lung and have proven utility in the evaluation of asthma; however, it is unclear which method is most effective at characterising uncontrolled asthma.

Aim

To evaluate the diagnostic accuracy of various peripheral airway function measurements in the assessment of asthma control in children.

Material and methods

Children with controlled (n = 35) and uncontrolled (n = 29) asthma performed a sequence of pulmonary function tests (i.e. spirometry, body plethysmography, oscillometry, nitrogen washout test, and exhaled nitric oxide). The diagnostic accuracy of each peripheral airway measure was evaluated by an area under the receiver operating characteristic curve (AUC).

Results

Most peripheral airway parameters were significantly increased in children with uncontrolled asthma compared with children with controlled asthma. The measures with the highest diagnostic accuracy for asthma control were lung clearance index (LCI) (AUC = 0.76), with high specificity (0.97) and modest sensitivity (0.46), acinar ventilation heterogeneity (Sacin) (AUC = 0.73), with high sensitivity (0.85) and modest specificity (0.54), and resonance frequency (Fres) (AUC= 0.74), with perfect specificity (1.0) but low sensitivity (0.38).

Conclusions

LCI, Sacin and Fres had the highest discriminative capacity for distinguishing children with controlled and uncontrolled asthma among all evaluated peripheral airways measures. Discrepancies in the performance (i.e. sensitivity and specificity) of each parameter suggest that a combination may be most effective in determining asthma control status.

Changes in Pulmonary Functions of Adolescents with Pectus Excavatum Throughout the Nuss Procedure

BACKGROUND

We aimed to determine the longitudinal changes in pulmonary functions of adolescents with Pectus Excavatum who underwent the Nuss procedure, the minimally invasive repair of pectus excavatum (MIRPE).

METHODS

Lung function measurements were performed before bar implantation (T0), at least six weeks to ten months after implantation (T1a), at least eleven months to sixty-one months after bar implantation (T1b) and at least two weeks after bar explantation (T2).

RESULTS

Data of 114 patients (83.3% male) whose median age at implantation was 15.6 years and at explantation 18.7 years were analyzed. Shortly after implantation at T1a a significant decline of vital capacity (VC; n = 82), forced vital capacity (FVC; n = 78) and forced expiratory volume in 1 second (FEV1; n = 80) compared to T0 was seen. At T1b a significant decline for the residual volume (RV; n = 83), the residual volume/total lung capacity ratio (RV/TLC; n = 81), the total specific airway resistance (sRaw; n = 80) and the total airway resistance (Raw; n = 84) also compared to T0 was measured. In the comparison of T1b to T2 a significant increase of VC, FVC (n = 67), FEV1 (n = 69), TLC (n = 67) and a significant decrease of Raw (n = 66), sRaw, RV (n = 65) and the RV/TLC (n = 64) ratio could be observed. In the direct analysis between T0 and T2, after the explantation of the bar a significant increase in VC (n = 54), FVC (n = 52), and TLC (n = 55) and a significant decrease of RV (n = 51) and the RV/TLC index (n = 50), and in airway resistance parameters like Raw (n = 52) and sRaw (n = 51) could be detected.

CONCLUSIONS

Lung function values along with markers of airway resistance improve in patients after the complete procedure of MIRPE.

LEVEL OF EVIDENCE

Level II.

Structural characterization and anti-asthmatic effect of α-l-arabino(4-O-methyl-α-d-glucurono)-β-d-xylan from the roots of Rudbeckia fulgida

Many native plant biopolymers or derivatives thereof have interesting biological effects and therefore the search for additional biological activities is important to map their overall effects. A low molecular weight (M_w = 7600 g/mol) hemicellulose polymer α-L-arabino(4-O-methyl-α-D-glucurono)-β-D-xylan (AGX) was isolated from the crushed roots of the Rudbeckia fulgida medicinal plant by alkaline extractions and anion-exchange chromatography. Analysis of neutral sugars revealed a predominance of xylose (82.3 wt%) and arabinose (6.8 wt%), while other neutral sugars were found only in small amounts as contaminants. The uronic acid content in Rudbeckia AGX was determined to be 8.8 wt%. Pharmacological tests showed that Rudbeckia AGX effectively suppressed cough and the initial amplitude of histamine/methacholine-induced bronchoconstriction in healthy OVA-sensitive guinea pigs. In addition, its effect at a dose of 100 mg/kg was similar to or greater than that of the positive control bronchodilator salbutamol and the antitussive codeine agent. These findings support the fact that Rudbeckia AGX could be a suitable candidate for alternative treatment of allergic asthma.

Asthma control in children: Body plethysmography in addition to spirometry

BACKGROUND

There is a lack of agreement among measures of asthma control in children. In Central Europe, body plethysmography is additionally used for asthma monitoring. However, its value is still unclear.

OBJECTIVES

We investigated the possible additional value of body plethysmographic measures (specific resistance, residual volume-total lung capacity ratio [RV/TLC]) compared with spirometric measures forced expiratory volume in 1 second (FEV ₁ ), forced vital capacity (FVC), FEV ₁ /FVC, forced expiratory flow at 25% to 75% of forced vital capacity (FEF _25-75 ), and fraction of exhaled nitric oxide (FeNO) for assessment of asthma control.

METHODS

One hundred and forty-five asthmatic children aged 5 to 17 were included. All children performed measurements of FeNO, spirometry, and body plethymography. Asthma control was assessed by the asthma control test (c-ACT/ACT) and a doctor's assessment of asthma control.

RESULTS

Investigating single lung function parameters, FEV₁ , FEV ₁ /FVC, FEF _25-75 and RV/TLC differed between controlled and partly controlled asthma. However, we found no differences between controlled and uncontrolled asthma with regard to single lung function parameters or for any parameter if investigated in a multivariable approach. This was also true if we combined obtained parameters from spirometry (comparing pathologic vs normal spirometry). Investigating the combination of body plethysmography and doctor's assessment of asthma control a significant association was found ( P = 0.02). Furthermore, combined spirometry and body plethysmography showed a significant association with both doctor's assessed asthma control ( P = 0.009) and the c-ACT/ACT ( P = 0.04). The addition of FeNO did not improve the results.

CONCLUSIONS

The combination of body plethysmography and spirometry shows best agreement with asthma control in children compared with spirometry or body plethysmography alone. Further studies are needed to find out whether additional measurements of body plethysmography improve the outcome of children in asthma monitoring.

Tools in Asthma Evaluation and Management: When and How to Use Them?

The goals of asthma management are accurate diagnosis, prompt initiation of treatment and monitoring of disease progression to limit potential morbidity and mortality. While the diagnosis and management is largely based on history taking and clinical examination, there are an increasing number of tools available that could be used to aid diagnosis, define phenotypes, monitor progress and assess response to treatment. Tools such as the Asthma Predictive Index could help in making predictions about the possibility of asthma in childhood based on certain clinical parameters in pre-schoolers. Lung function measurements such as peak expiratory flow, spirometry, bronchodilator responsiveness, and bronchial provocation tests help establish airway obstruction and variability over time. Tools such as asthma questionnaires, lung function measurements and markers of airway inflammation could be used in combination with clinical assessments to assess ongoing asthma control. Recent advances in digital technology, which open up new frontiers in asthma management, need to be evaluated and embraced if proven to be of value. This review summarises the role of currently available tools in asthma diagnosis and management. While many of the tools are readily available in resource rich settings, it becomes more challenging when working in resource poor settings. A rational approach to the use of these tools is recommended.

Bronchodilator Response Assessment of the Small Airways Obstructive Pattern

Background:

A concomitant decrease in FEV₁ and FVC with normal FEV₁/FVC ratio and TLC defines small airways obstructive pattern (SAOP) and constitutes a classic pitfall of pulmonary-function-tests interpretation.

Objective:

To evaluate the prevalence of flow- (FEV₁ increase≥12% and 200 mL), volume- (FVC or inspiratory capacity [IC] increase≥12% and 200 mL), flow and volume-, and non-response to bronchodilation in patients with SAOP. An additional objective was to assess whether impulse oscillometry (IOS) parameters allow the diagnosis of SAOP and its reversibility.

Methods:

Fifty consecutive adult patients with SAOP (FEV₁ and FVC < lower limit of normal, FEV₁/FVC and TLC > lower limit of normal) diagnosed on spirometry and plethysmography underwent the assessment of reversibility (400 µg salbutamol) on FEV₁, FVC, IC and IOS parameters.

Results:

The diseases most frequently associated with SAOP were COPD and asthma (26 and 15 patients, respectively). Six patients were flow-responders, 20 were volume-responders, 9 were flow and volume-responders and 15 patients were non-responders. Overall, 26 patients had a significant improvement of IC, and 35 / 50 (70%, 95%CI: 57-83) exhibited a significant bronchodilator response. The difference between Rrs_5Hz and Rrs_20Hz was increased in 28/50 patients (56%, 95%CI: 42-70 with value higher than upper limit of normal) and its decrease after bronchodilator significantly correlated to FEV₁ increase only, suggesting proximal airway assessment.

Conclusion:

A significant reversibility, mainly assessed on IC increase, is frequent in Small Airways Obstructive Pattern. Impulse oscillometry is of limited value in this context because of its low sensitivity.

Relationship between pre-anesthetic and intra-anesthetic airway resistance in patients undergoing general anesthesia: A prospective observational study

Surgery patients in Japan undergo routine spirometry testing prior to general anesthesia. The use of a flow sensor during general anesthesia has recently become common. However, it is not certain whether the information derived from flow-volume curves is being adequately used for mechanical ventilation management during general anesthesia. So far, there have been no attempts to calculate airway resistance using flow-volume curves. Therefore, we performed a prospective, observational study to investigate the relationship between pre-anesthetic and intra-anesthetic airway resistance in patients scheduled for surgery under general anesthesia. We calculated pre-anesthetic and intra-anesthetic airway resistance in each patient, based on the slopes of flow-volume curves obtained prior to and during general anesthesia. We also calculated endotracheal tube resistance to correct the intra-anesthetic airway resistance values calculated. A total of 526 patients were included in the study, and 98 patients had a forced expiratory volume in the first second/forced vital capacity ratio of < 70%. Pre-anesthetic airway resistance was significantly higher in patients with airflow obstruction than in those without airflow obstruction (p < 0.001), whereas no significant difference in intra-anesthetic airway resistance was found between patients with and without airflow obstruction during mechanical ventilation (p = 0.48). Pre-anesthetic and intra-anesthetic airway resistance values were closer to each other in patients without airflow obstruction, with a mean difference < 1.0 cmH2O L-1s-1, than in those with airflow obstruction, although these respiratory parameters were significantly different (p < 0.001). Intra-anesthetic airway resistance was not related to the FEV1/FVC ratio, regardless of the degree to which the FEV1/FVC ratio reflected pre-anesthetic airway resistance. As compared with patients with airflow obstruction, the mean difference between pre-anesthetic and intra-anesthetic airway resistance was small in patients without airflow obstruction.

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.

Pharmacodynamic evaluation of RP3128, a novel and potent CRAC channel inhibitor in guinea pig models of allergic asthma

The increase in intracellular Ca(2+) levels through the activation of Ca(2+) release-activated Ca(2+) (CRAC) channels is essential for mediating a wide scale of immune cell responses. Emerging evidence indicates an involvement of abnormal CRAC channel activity in human diseases such as certain types of immunodeficiency, autoimmunity and allergic disorders. This objective of this study was to evaluate the therapeutic potency of a novel CRAC channel inhibitor, RP3128, in experimental models of allergic asthma using guinea pigs. Ovalbumin-induced allergic airway inflammation was determined upon acute and long-term (14 days) oral administration of RP3128. In vivo changes in specific airways resistance (sRaw) and amplitude of isometric contraction (mN) of ASM (in vitro) were estimated to evaluate bronchodilatory effect upon acute and long-term administration of RP3128 or salbutamol. Exhaled nitric oxide (eNO), immunohistochemical and histological analysis of cellular infiltration in airways tissue, and levels of cytokines in plasma as well as bronchoalveolar lavage fluid (BALF), were determined using Bio-Plex® 200 System (BIO-RAD, USA). Ciliary beat frequency (CBF, in Hz) was estimated using a high-speed video camera and LabVIEW™ Software. Additionally, the impact of RP3128 and budesonide on mucociliary clearance was determined. Acute and long-term administration of RP3128 resulted in significant bronchodilation. Long-term administration of RP3128 exceeded the bronchodilatory effect of salbutamol and significantly decreased eNO and cytokine levels in plasma and BALF, which together with histological and immunohistochemical analysis validated its anti-inflammatory effect compared to budesonide. Data demonstrate the therapeutic potential of RP3128 in respiratory diseases causally associated with allergic inflammation.

Echinacea complex--chemical view and anti-asthmatic profile

ETHNOPHARMACOLOGICAL RELEVANCE

Echinacea purpurea (L.) Moench is one of the mostly used herbs in the traditional medicine for the treatment of respiratory diseases. Modern interest in Echinacea is directed to its immunomodulatory activity. Recent studies have shown that secretion of asthma-related cytokines in the bronchial epithelial cells can be reversed by Echinacea preparations.

AIM OF THE STUDY

To examine the pharmacodynamics profile of Echinacea active principles, a complex has been isolated from its flowers by alkaline extraction and has been tested using an animal model of allergic asthma.

MATERIAL AND METHODS

The structural features of Echinacea purpurea complex was determined using chemical and spectroscopic methods. Allergic inflammation of the airways was induced by repetitive exposure of guinea pigs to ovalbumin. Echinacea complex was then administered 14 days in 50mg/kg b.w. daily dose perorally. Bronchodilatory effect was verified as decrease in the specific airway resistance (sRaw) in vivo and by reduced contraction amplitude (mN) of tracheal and pulmonary smooth muscle to cumulative concentrations of acetylcholine and histamine in vitro. The impact on mucociliary clearance evaluated measurement of ciliary beat frequency (CBF) in vitro using LabVIEW™ Software. Anti-inflammatory effect of Echinacea complex was verified by changes in exhaled NO levels and by Bio-Plex® assay of Th2 cytokine concentrations (IL-4, IL-5, IL-13 and TNF-alpha) in serum and bronchoalveolar lavage fluid (BALF).

RESULTS

Chemical and spectroscopic studies confirmed the presence of carbohydrates, phenolic compounds and proteins, as well as the dominance of rhamnogalacturonan and arabinogalactan moieties in Echinacea complex. The significant decrease in sRaw values and suppressed histamine and acetylcholine-induced contractile amplitude of isolated airways smooth muscle that were similar to effects of control drug salbutamol confirmed Echinacea complex bronchodilatory activity. The anti-inflammatory effect was comparable with that of control agent budesonide and was verified as significantly reduced exhaled NO levels and concentration of Th2 cytokines in serum and BALF. The values of CBF were changed only insignificantly on long-term administration of Echinacea complex suggested its minimal negative impact on mucociliary clearance.

CONCLUSION

Pharmacodynamic studies have confirmed significant bronchodilatory and anti-inflammatory effects of Echinacea complex that was similar to effects of classic synthetic drugs. Thus, results provide a scientific basis for the application of this herb in traditional medicine as a supplementary treatment of allergic disorders of the airways, such as asthma.

The Respiratory System

This chapter addresses upper airway physiology for the pediatric intensivist, focusing on functions that affect ventilation, with an emphasis on laryngeal physiology and control in breathing. Effective control of breathing ensures that the airway is protected, maintains volume homeostasis, and provides ventilation. Upper airway structures are effectors for all of these functions that affect the entire airway. Nasal functions include air conditioning and protective reflexes that can be exaggerated and involve circulatory changes. Oral cavity and pharyngeal patency enable airflow and feeding, but during sleep pharyngeal closure can result in apnea. Coordination of breathing with sucking and nutritive swallowing alters during development, while nonnutritive swallowing at all ages limits aspiration. Laryngeal functions in breathing include protection of the subglottic airway, active maintenance of its absolute volume, and control of tidal flow patterns. These are vital functions for normal lung growth in fetal life and during rapid adaptations to breathing challenges from birth through adulthood. Active central control of breathing focuses on the coordination of laryngeal and diaphragmatic activities, which adapts according to the integration of central and peripheral inputs. For the intensivist, knowledge of upper airway physiology can be applied to improve respiratory support. In a second part the mechanical properties of the respiratory system as a critical component of the chain of events that result in translation of the output of the respiratory rhythm generator to ventilation are described. A comprehensive understanding of respiratory mechanics is essential to the delivery of optimized and individualized mechanical ventilation. The basic elements of respiratory mechanics will be described and developmental changes in the airways, lungs, and chest wall that impact on measurement of respiratory mechanics with advancing postnatal age are reviewed. This will be follwowed by two sections, the first on respiratory mechanics in various neonatal pathologies and the second in pediatric pathologies. The latter can be classified in three categories. First, restrictive diseases may be of pulmonary origin, such as chronic interstitial lung diseases or acute lung injury/acute respiratory distress syndrome, which are usually associated with reduced lung compliance. Restrictive diseases may also be due to chest wall abnormalities such as obesity or scoliosis (idiopathic or secondary to neuromuscular diseases), which are associated with a reduction in chest wall compliance. Second, obstructive diseases are represented by asthma and wheezing disorders, cystic fibrosis, long term sequelae of neonatal lung disease and bronchiolitis obliterans following hematopoietic stem cell transplantation. Obstructive diseases are defined by a reduced FEV1/VC ratio. Third, neuromuscular diseases, mainly represented by DMD and SMA, are associated with a decrease in vital capacity linked to respiratory muscle weakness that is better detected by PImax, PEmax and SNIP measurements.

Non specific pattern of lung function in a respiratory physiology unit: causes and prevalence: results of an observational cross-sectional and longitudinal study

Background

ATS/ERS Task Force has highlighted that special attention must be paid when FEV₁ and FVC are concomitantly decreased (<5^th percentile) and the FEV₁/FVC ratio is normal (>5^th percentile) because a possible cause of this non specific pattern (NSP) is collapse of small airways with normal TLC measured by body plethysmography (>5^th percentile). Our objectives were to determine the main lung diseases associated with this pattern recorded prospectively in a lung function testing (LFT) unit, the prevalence of this pattern in our LFT and among the diseases identified, and its development.

Methods

Observational study of routinely collected data selected from our Clinical Database Warehouse.

Results

The prevalence of NSP was 841/12 775 tests (6.6%, 95% CI: 6.2 to 7.0%). NSP was mainly associated with seven lung diseases: asthma (prevalence of NSP among asthmatics: 12.6%), COPD/emphysema (prevalence 8.6%), bronchiectasis (12.8%), sarcoidosis (10.7%), interstitial pneumonia (4.0%), pulmonary hypertension (8.9%) and bilateral lung transplantation for cystic fibrosis (36.0%). LFT measurements were described in 185 patients with NSP and indisputable nonoverlapping causes. A moderate defect (FEV₁: 66 ± 9% predicted) with mild lung hyperinflation (FRC: 111 ± 27%, RV: 131 ± 33% predicted: suggesting distal airway obstruction) was evidenced whatever the underlying cause. A long term stability of NSP was evidenced in 130/185 patients (70% 95% CI: 64 to 77%).

Conclusions

NSP is observed in asthma, COPD/emphysema, bronchiectasis, sarcoidosis, pulmonary hypertension, interstitial pneumonia and after bilateral lung transplantation and remains stable in the majority of patients.

Baseline and post-bronchodilator interrupter resistance and spirometry in asthmatic children

In children unable to perform reliable spirometry, the interrupter resistance (R(int) ) technique for assessing respiratory resistance is easy to perform. However, few data are available on the possibility to use R(int) as a surrogate for spirometry. We aimed at comparing R(int) and spirometry at baseline and after bronchodilator administration in a large population of asthmatic children. We collected retrospectively R(int) and spirometry results measured in 695 children [median age 7.8 (range 4.8-13.9) years] referred to our lab for routine assessment of asthma disease. Correlations between R(int) and spirometry were studied using data expressed as z-scores. Receiver operator characteristic curves for the baseline R(int) value (z-score) and the bronchodilator effect (percentage predicted value and z-score) were generated to assess diagnostic performance. At baseline, the relationship between raw values of R(int) and FEV(1) was not linear. Despite a highly significant inverse correlation between R(int) and all of the spirometry indices (FEV(1) , FVC, FEV(1) /FVC, FEF(25-75%) ; P < 0.0001), R(int) could detect baseline obstruction (FEV(1) z-score ≤ -2) with only 42% sensitivity and 95% specificity. Post-bronchodilator changes in R(int) and FEV(1) were inversely correlated (rhô = -0.50, P < 0.0001), and R(int) (≥35% predicted value decrease) detected FEV(1) reversibility (>12% baseline increase) with 70% sensitivity and 69% specificity (AUC = 0.79). R(int) measurements fitted a one-compartment model that explained the relationship between flows and airway resistance. We found that R(int) had poor sensitivity to detect baseline obstruction, but fairly good sensitivity and specificity to detect reversibility. However, in order to implement asthma guidelines for children unable to produce reliable spirometry, bronchodilator response measured by R(int) should be systematically studied and further assessed in conjunction with clinical outcomes.

T2-T3 sympathectomy versus sympathicotomy for essential palmar hyperhidrosis: comparison of effects on cardio-respiratory function

OBJECTIVES

The aim of this study was to determine cardio-respiratory changes after endothoracic sympathetic denervation and their correlation with the extent of denervation.

METHODS

A total of 45 patients with essential palmar hyperhidrosis were randomized into two groups: the conventional group (CG; 23 patients) and the simplified group (SG; 22 patients). In the CG, excision of T2 and T3 ganglia was performed, whereas in the SG only separation of the sympathetic chain was performed at the same level. Patients underwent respiratory and cardiovascular exercise tests before, at 2 weeks and again at 6 months after the procedure. The postoperative values were then compared with the preoperative values to assess the statistical difference.

RESULTS

Twenty-one patients in each group completed the study. In the SG, forced expiratory volume in 1 s (FEV 1; P < 0.01) and forced vital capacity (FVC; P < 0.01) were significantly reduced at 2 weeks, but returned to similar baseline values 6 months after the procedure. No significant cardiac changes were observed. In the CG, both FEV 1 and FVC were significantly reduced at 2 weeks (P < 0.01) and at 6 months after operation (P < 0.05). A significant reduction in forced expiratory flow between 25 and 75% of vital capacity (P < 0.01) and a relevant increase in airway resistance (P < 0.05) during the entire postoperative course were also observed. Heart rates at rest and at peak exercise were significantly reduced at 2 weeks (P < 0.01) and significantly decreased 6 months after the procedure (P < 0.05). No other changes were registered. The cardio-respiratory alterations remained at a sub-clinical level; all patients completed the exercise test without symptoms.

CONCLUSION

Sympathectomy may result in a disturbance of bronchomotor tone and cardiac function. Such changes remained at a sub-clinical level and seemed directly correlated with the extension of denervation.

Relationships between respiratory and airway resistances and activity-related dyspnea in patients with chronic obstructive pulmonary disease

Background

The aims of the study were: (1) to compare numerical parameters of specific airway resistance (total, sRaw_tot, effective, sRaw_eff and at 0.5 L · s⁻¹, sRaw_0.5) and indices obtained from the forced oscillation technique (FOT: resistance extrapolated at 0 Hz [Rrs_{0 Hz}], mean resistance [Rrs_mean], and resistance/frequency slope [Rrs_slope]) and (2) to assess their relationships with dyspnea in chronic obstructive pulmonary disease (COPD).

Methods

A specific statistical approach, principal component analysis that also allows graphic representation of all correlations between functional parameters was used. A total of 108 patients (mean ± SD age: 65 ± 9 years, 31 women; GOLD stages: I, 14; II, 47; III, 39 and IV, 8) underwent spirometry, body plethysmography, FOT, and Medical Research Council (MRC) scale assessments.

Results

Principal component analysis determined that the functional parameters were described by three independent dimensions (airway caliber, lung volumes and their combination, specific resistance) and that resistance parameters of the two techniques were not equivalent, obviously. Correlative analyses further showed that Raw_tot and Raw_eff (and their specific resistances) can be considered as equivalent and correlated with indices that are considered to explore peripheral airways (residual volume (RV), RV/ total lung capacity (TLC), Rrs_slope), while Rrs_mean and Raw_0.5 explored more central airways. Only specific resistances taking into account the specific resistance loop area (sRaw_tot and sRaw_eff) and Rrs_slope were statistically linked to dyspnea.

Conclusion

Parameters obtained from both body plethysmography and FOT can explore peripheral airways, and some of these parameters (sRaw_tot, sRaw_eff, and Rrs_slope) are linked to activity-related dyspnea in moderate to severe COPD patients.

Use of specific airway resistance to assess bronchodilator response in children

BACKGROUND AND OBJECTIVE

Changes in specific airway resistance (ΔsRaw) after bronchodilation, as measured by plethysmography and FEV(1) , are frequently considered to be interchangeable indices of airway obstruction. However, the baseline relationship between these two indices is weak, and the value of ΔsRaw that best predicts FEV(1) reversibility in children has yet to be determined. The aim of this study was (i) to establish the sRaw cut-off value that best distinguishes between positive and negative bronchodilator responses, as measured by FEV(1) reversibility; (ii) to determine whether the discrepancy between ΔsRaw and ΔFEV(1) might be explained by independent correlations between ΔFEV(1) and both ΔsRaw (mainly airway obstruction) and ΔFVC (airway closure); and (iii) to assess the effect of height and age on the relationship between ΔsRaw and ΔFEV(1) .

METHODS

A retrospective study was performed in 481 children (median age 10.5years, range 6.1-17.6) with actual or suspected asthma, for whom sRaw and spirometry data were obtained at baseline and after administration of a bronchodilator.

RESULTS

The sRaw cut-off value that best predicted FEV(1) reversibility was a 42% decrease from baseline (P=0.0001, area under the curve 0.70, sensitivity 55%, specificity 77%) and was independent of height and age. Changes in FEV(1) were significantly but independently related to ΔsRaw and ΔFVC (index of air trapping) (r=0.40, P<0.0001 and r=0.39, P<0.0001, respectively).

CONCLUSIONS

A 42% decrease in sRaw predicted FEV(1) reversibility reasonably well, whereas a smaller decrease in sRaw failed to detect approximately one out of two positive responses detected by FEV(1) , with no influence of height or age.

Lung function impairment evidenced by sequential specific airway resistance in childhood persistent asthma: a longitudinal study

BACKGROUND

Specific airway resistance (sRaw) is virtually independent of lung growth, height, and gender, thus facilitating longitudinal follow-up.

OBJECTIVE

To assess whether a specific phenotype of asthmatic children with a decline in lung function can be evidenced using sRaw.

METHODS

The authors hypothesized that sequential sRaw measurements over a long period would detect subtle trends. Clinical and functional data of children with persistent asthma under inhaled corticosteroids, evaluated at least three times per year for at least 4 years, were retrieved from a database.

RESULTS

One hundred fourteen children (30 girls) were followed for (median [interquartile range]) 6.9 years [5.6-7.9]. Data from 1699 measurements of sRaw (median 14/child) allowed the calculation of individual slopes of sRaw plotted against time demonstrating stable values in the group as a whole between 4 and 18 years. A positive correlation between individual slopes and the degree of intraindividual variation of sRaw was observed (R(2) = .16; p < .0001). Children with more than one positive skin test showed larger intrasubject variation of sRaw (p = .011). In 19/114 children (17%), a significant increase in sRaw of 12.3% per year (median) was observed. As compared to children without, those with a significant increase in sRaw were boys (p < .0001), had a lower initial (p = .008) and a higher final resistance (p = .025) but did not differ in terms of inhaled corticosteroid dose.

CONCLUSION

This retrospective study identifies a specific phenotype of asthmatic children that develops an impairment of lung function, confirming the results of a post hoc analysis of the Childhood Asthma Management Program study.

Lumen areas and homothety factor influence airway resistance in COPD

The remodelling process of COPD may affect both airway calibre and the homothety factor, which is a constant parameter describing the reduction of airway lumen (h(d): diameter of child/parent bronchus) that might be critical because its reduction would induce a frank increase in airway resistance. Airway dimensions were obtained from CT scan images of smokers with (n=22) and without COPD (n=9), and airway resistance from plethysmography. Inspiratory airway resistance correlated to lumen area of the sixth bronchial generation of right lung, while peak expiratory flow correlated to the area of the third right generation (p=0.0009, R=0.57). A significant relationship was observed between h(d) and resistance (p=0.036; R(2)=0.14). A modelling approach of central airways (5 generations) further described the latter relationship. In conclusion, a constant homothety factor can be described by CT scan analysis, which partially explains inspiratory resistance, as predicted by theoretical arguments. Airway resistance is related to lumen areas of less proximal airways than commonly admitted.

The link between exhaled NO and bronchomotor tone depends on the dose of inhaled steroid in asthma

BACKGROUND

Exhaled NO (FE(NO)) is a steroid dose dependent eosinophilic inflammometer, but also a mediator of bronchomotor tone, but statistically significant relationships have infrequently been obtained with pulmonary function tests (PFT). The aim was to test the hypothesis that the relationships between FE(NO) and PFT could be uncovered by inhaled corticosteroid (ICS) treatment, namely that a link between FE(NO) and bronchodilator response (an index of bronchomotor tone) would appear under ICS.

METHODS

Exhaled NO, forced expiratory flows and lung volumes were measured in atopic asthmatic children without recent (one month) respiratory symptoms.

RESULTS

Two hundred and thirty children (mean + or - SD, age: 11.2 + or - 2.5 years, 69 girls) were included (% predicted, FEV(1): 100 + or - 14; FEF(50%): 76 + or - 23; RV: 107 + or - 29). The relationship between ICS dose (GINA classification) and FE(NO) plateaued in children with an ICS dose higher than 200 microg beclomethasone equipotent daily dose: FE(NO) (median [25th-75th percentiles]), 43 ppb [15-105] (no treatment, n=65), 33 ppb [15-77] (low dose, n=70), 23 ppb [12-57] (medium dose, n=57) and 26 ppb [9-49] (high dose, n=38). Statistically significant relationships between FE(NO) and PFT were only observed in children receiving more than 200 microg/day ICS: with FEV(1) (medium ICS dose: rho=0.43, p=0.001; high dose: rho=0.32, p=0.052) and bronchodilator (400 microg salbutamol) response (medium dose: rho=0.54, p=0.001; high dose: rho=0.65, p=0.002).

CONCLUSIONS

A positive correlation between FE(NO) and bronchomotor tone appears with increasing ICS doses in atopic children with clinically controlled asthma, which further suggests that children depicting the highest FE(NO) values may have lesser steroid sensitivity.

Abnormalities of plethysmographic lung volumes in asthmatic children

BACKGROUND

While lung hyperinflation is frequent in asthma, measurement of lung volumes is not recommended in current guidelines. The aim of this descriptive functional study was to assess whether systematic measurement of volumes by plethysmography may detect isolated hyperinflation with normal expiratory flows.

METHODS AND PATIENTS

One hundred sixty asthmatic children (mean age + or - SD: 10.8 + or - 2.7 years; 50 girls) receiving inhaled corticosteroid underwent lung function tests before and after bronchodilation (BD). To avoid the problem of dysanaptic lung growth on predicted values in childhood, airflow limitation and hyperinflation were defined by ratios (FEV(1,%pred)/FVC(%pred) for the former, RV/TLC for the latter) and values below and above the 5th or 95th percentiles of reference values, were chosen as cut-off values.

RESULTS

Different functional phenotypes were evidenced, mainly normal lung function (142/160 [89%] after BD), but also isolated airflow limitation (35/160 [22%] before and 7/160 [4%] after BD) and isolated hyperinflation (17/160 [11%] before and 11/160 [7%] after BD), while the combination of both impairments before BD (13/160 [8%]) was never observed after BD. There was no statistical relationship between airflow limitation and hyperinflation, either before or after BD. Indices of spirometry (FEV(1), FEF(50%)) were unable to predict isolated hyperinflation that corresponds to small airway obstructive syndrome.

CONCLUSION

Isolated hyperinflation is not infrequent in asthmatic children (7-11%) and small airway obstruction is not detected by forced expiratory flows.