Changes in lung function measured by spirometry and the forced oscillation technique in cystic fibrosis patients undergoing treatment for respiratory tract exacerbation

Beneficial short-term effect of autogenic drainage on peripheral resistance in childhood cystic fibrosis disease

Background

Airway clearance techniques are supposed to be a necessary adjunct for the enhancement of impaired peripheral clearance in cystic fibrosis (CF). The objective was to assess the effect of one physiotherapy session (autogenic drainage: AD) on mucus clearance (sputum wet weight) and impulse oscillometry system (IOS) indices, including those obtained from extended Resistance-Inertance-Compliance (eRIC) modelling, considering the degree of bronchial congestion.

Methods

Thirty children with CF (median age: 12.7 years) in a stable condition prospectively underwent IOS measurements at baseline and after AD. They were divided in two groups: with (visual analog scale of bronchial congestion by the physiotherapist ≥ 5/10) and without (scale < 5/10) bronchial congestion. Paired-comparison of the effects of AD on airway resistance measurements was done with Wilcoxon test.

Results

The congestion scale correlated with the wet weight of sputum production during the session (Pearson test: p < 0.0001, R = 0.66). Ten children had bronchial congestion and 20 were without congestion. In the whole group, R5–20 Hz significantly decreased after AD (P = 0.049), which was related to a decrease in the children with congestion (P = 0.025), whereas it was not significantly modified in the children without congestion (P = 0.327). The eRIC model allowed the calculation of the peripheral resistance of the respiratory system, which also decreased in the children with congestion (P = 0.037), however, not modified in the children without congestion (P = 0.390).

Conclusion

One session of autogenic drainage has the ability to decrease peripheral resistance obtained from IOS measurements, more specifically in children with CF with moderate to severe bronchial congestion.

Trial registration

ClinicalTrials.gov Identifier: NCT04094441.

Predictive value of impulse oscillometry and multiple breath washout parameters in pediatric patients with cystic fibrosis pulmonary exacerbation

BACKGROUND

Pulmonary exacerbations (PE) tend to complicate the course of cystic fibrosis (CF) and worsen the disease prognosis. One of the diagnostic criteria for an exacerbation is the forced expiratory volume in the first second (FEV₁ ) decline. Not all children, however, are able to perform spirometry. Therefore, the aim of this study was to evaluate alternative lung function tests in the diagnosis of PE.

METHODS

We assessed retrospectively the results of impulse oscillometry (IOS) and lung clearance index in multiple breath washout (MBW) during 259 visits in 47 CF paediatric patients. The differences in the results were compared between patients diagnosed with PE (ΔPE) and those in stable condition (ΔS).

RESULTS

Among the whole group of patients, we found significant differences between the changes during exacerbation (ΔPEs) and stable condition (ΔSs) values for lung clearance index (LCI), S_acin , R5Hz, R5-20Hz, X10Hz, AX, and Fres. The predictive values of Fres and X10Hz in IOS (AUC^ROC 0.71 both parameters) were higher than those of LCI (AUC^ROC 0.67). There was no difference in the predictive values (AUC^ROC ) of Δ LCI and IOS parameters in the subgroups of patients stratified based on FEV₁ z-score cut-off value of -1.64. In both groups of patients, predictive values of LCI were slightly lower than of IOS parameters (AUC 0.66 for LCI vs. 0.69 for both ΔX10Hz z-score and Δ Fres z-score in patients with FEV₁ z-score ≥-1.64 and AUC 0.67 for LCI vs 0.69 for both ΔX10Hz zscore and Δ Fres zscore in patients with FEV₁ <1.64.

CONCLUSIONS

Both IOS and MBW measurements are useful in the assessment of pediatric CF patients with PE. LCI has a similar predictive value to IOS in children with CF independently of their FEV₁ value.

Forced Oscillation Technique for Monitoring the Respiratory Status of Children with Cystic Fibrosis: A Systematic Review

Spirometry is considered the gold standard method for monitoring lung function of patients with cystic fibrosis (CF) but it requires patients’ cooperation and therefore it is not useful for the majority of preschool-aged children. Oscillometry is an alternative modality for lung function monitoring that requires minimal cooperation and can be applied in children as young as 3 years of age. Furthermore, it generates lesser aerosol compared to spirometry, an issue that is of considerable importance in the COVID-19 era. The aim of this review was to present the existing clinical data regarding the application of oscillometry in children and adolescents with CF. The method seems to have acceptable feasibility and repeatability. However, there is conflicting data regarding the correlation of oscillometry values with the clinical symptoms of CF patients either in clinically stable or in exacerbation periods. Furthermore, it is not clear to what extent oscillometry measurements correlate with the spirometry indices. Based on current evidence, spirometry cannot be substituted by oscillometry in the monitoring of the respiratory status of children and adolescents with CF.

A multimodal approach to detect and monitor early lung disease in cystic fibrosis

Introduction: In the early stages, lung involvement in cystic fibrosis (CF) can be silent, with disease progression occurring in the absence of clinical symptoms. Irreversible airway damage is present in the early stages of disease; however, reliable biomarkers of early damage due to inflammation and infection that are universally applicable in day-to-day patient management have yet to be identified.Areas covered: At present, the main methods of detecting and monitoring early lung disease in CF are the lung clearance index (LCI), computed tomography (CT), and magnetic resonance imaging (MRI). LCI can be used to detect patients who may require more intense monitoring, identify exacerbations, and monitor responses to new interventions. High-resolution CT detects structural alterations in the lungs of CF patients with the best resolution of current imaging techniques. MRI is a radiation-free imaging alternative that provides both morphological and functional information. The role of MRI for short-term follow-up and pulmonary exacerbations is currently being investigated.Expert opinion: The roles of LCI and MRI are expected to expand considerably over the next few years. Meanwhile, closer collaboration between pulmonology and radiology specialties is an important goal toward improving care and optimizing outcomes in young patients with CF.

Is Impulse Oscillometry System a Useful Method for the Evaluation and Follow-Up of Patients with Cystic Fibrosis?

Background: Although the impulse oscillometry system (IOS) is a noninvasive, easily accessible, well-tolerated, and alternative test, routine use of IOS in cystic fibrosis (CF) patients is not widespread. In our unit, IOS is routinely used for the evaluation and follow-up of patients with CF. We aimed to show that IOS may be utilized as a complement for measuring pulmonary function in CF patients. Materials and Methods: Retrospective data collection and analysis of pulmonary function tests on CF patients followed at our center between January 1, 2018 and February 1, 2019. IOS and spirometry data were compared as correlated with patients' clinical exacerbation, treatment response, bronchodilator response, and trends during follow-up intervals. Results: There was a significant correlation between spirometry and IOS parameters in 70 patients. In exacerbation, Z5, R5-R10, AX, Fres, and delta R5-R20 were significantly increased and X5-X20 was significantly decreased compared with baseline in 25 patients. After treatment, IOS parameters were observed to return to baseline values. In the evaluation of bronchodilator response in 33 patients, significant changes in IOS (decrease in Z5, R5-R10, AX, Fres, and delta R5-R20, and increase in X5-X10) and in spirometry [increase in forced expiratory volume in 1 s (FEV1) and forced expiratory flow during the middle half of forced vital capacity (FEF_25-75)] were found after bronchodilator. While there was no significant difference between spirometry values in follow-up visits in 31 patients, there was a significant increase in Z5% and R5%-R20%. Unlike other studies, there was a significant correlation between clinical scores and IOS. Conclusions: These results show that although IOS is not the gold standard method such as spirometry, it is an alternative method that can be used successfully in the evaluation and follow-up of CF patients. Clinical Trials.gov ID: 99166796-050.06.04.

The remaining barriers to normalcy in CF: Advances in assessment of CF lung disease

Despite early diagnosis of cystic fibrosis (CF) through newborn screening, a substantial proportion of infants and young children with CF still demonstrate physiologic and structural evidence of lung disease progression, such as obstructive airway disease and bronchiectasis. The growing availability of highly effective CF transmembrane conductance regulatory modulator therapy to the vast majority of people with CF has led to the potential to alter the natural history of CF lung disease, but to assess the full impact of these therapies on CF lung disease and to help guide treatment, sensitive measures of early and mild disease are needed. Chest imaging using computed tomography or magnetic resonance imaging is one approach, but technologic barriers and/or concern about exposure to ionizing radiation may limit its use. However, advances in physiologic measurement techniques and exhaled breath analysis offer another option for assessment of CF lung disease.

What Is Most Suitable for Children With Cystic Fibrosis-The Relationship Between Spirometry, Oscillometry, and Multiple Breath Nitrogen Washout

INTRODUCTION

In cystic fibrosis (CF), pathological lung changes begin early in life. The technological progress currently gives many diagnostic possibilities. However, pulmonary function testing in children remains problematic.

OBJECTIVES

Our study aimed to correlate the results of impulse oscillometry (IOS) with those of multiple breath nitrogen washout (MBNW) in our pediatric CF population. We also compared those parameters between the groups with and without spirometric features of obturation.

METHODS

We collected 150 pulmonary function test sets, including spirometry, IOS, and MBNW in patients with CF aged 12.08 ± 3.85 years [6-18]. The study group was divided into two subgroups: IA (without obturation) and IB (with obturation). We also compared Sacin, Scond, and oscillometry parameters of 20 patients aged 14-18 years who reached the appropriate tidal volume (VT) during MBNW.

RESULTS

Statistical analysis showed a negative correlation between lung clearance index (LCI) and spimoetric parameters. Comparison of subgroups IA (n = 102) and IB (n = 48) indicated a statistically significant difference in LCI (p < 0.001) and FEV1z-score (p < 0.001), FEV1% pred (p < 0.001), MEF25z-score (p < 0.001), MEF50 z-score (p < 0.001), MEF75 z-score (p < 0.001), R5% pred (p < 0.05), and R20% pred (p < 0.01). LCI higher than 7.91 was found in 75.33% of the study group, in subgroup IB-91.67%, and IA-67.6%.

CONCLUSIONS

LCI derived from MBNW may be a better tool than IOS for assessing pulmonary function in patients with CF, particularly those who cannot perform spirometry.

Impulse oscillometry and spirometry measurements relative to personal best values at the time of acute exacerbations of cystic fibrosis in adults

BACKGROUND

Diagnosis of acute exacerbation (AE) of cystic fibrosis (CF) must be precise because both under- and over-prescription of antibiotics may be detrimental. How lung function tests contribute to diagnose AE is unclear. We aimed to describe variation of spirometry and oscillometry measurements, at Stable state and at AE in adults with CF.

METHODS

Patients were included in a retrospective single-centre study when both spirometry (FEV1, FVC) and oscillometry (X5, R5, R5-R20 and AX) data were available for at least one Stable and one AE visit between December 2016 and July 2019. For each visit, we calculated variation (Δ) in spirometry and oscillometry indices in comparison with personal best values. Measurements were expressed as % of predicted values and Z-scores when applicable. Areas under ROC curves (AUC) were computed.

RESULTS

Forty-two patients (28 ± 9 years, FEV1 64 ± 21%) were included; 80 AE and 104 Stable visits were analysed. FEV1 (L, %pred and Z-score) and FVC (%pred and Z-score) varied significantly between AE and Stable visits (p < .05), although differences were small (80 ml/2.7%pred for FEV1). Among oscillometry indices, X5 (kPa.s.L^-1 ), R5-R20 (kPa.s.L^-1 ) and AX (kPa/L) varied significantly. The AUCs for the variation in spirometry indices ranged from 0.601 (ΔFVC L) to 0.635 (ΔFEV1%pred). They were not significantly different from the AUCs for ΔX5 (0.589), ΔR5-R20 (0.649) and ΔAX (0.598).

CONCLUSIONS

Performance of both spirometry and oscillometry to discriminate AE from Stable state was poor. Variation of oscillometry indices (X5, R5-R20, AX) may be helpful when spirometry is unreliable or uncomfortable.

"Reactance inversion" at low frequencies in a child undergoing treatment of a cystic fibrosis exacerbation

INTRODUCTION

Impulse oscillometry (IOS) employs high frequency sinusoidal or impulse pressure and flow waveforms to interrogate the mechanical properties of the respiratory system. It has special applications to preschool and younger children who may have difficulty performing the repetitive forced expiratory maneuvers required for spirometry.

CASE PRESENTATION

We present a case illustrating improvements of respiratory system mechanics measured by IOS in a 6-year-old child with cystic fibrosis (CF) who demonstrated clinical and radiological improvement after a course of therapy with hospitalization and intravenous antibiotics, and initiation of a cystic fibrosis transmembrane regulator (CFTR) protein corrector/potentiator agent. We also report a new finding: observed lower than expected reactance at low compared to high frequencies ("reactance inversion").

CONCLUSION

Reactance inversion may reflect parallel pathway inhomogeneities in resistance and elastance or intrabreath airway inertance changes in young children with CF. Further study is needed in children with airway obstruction due to asthma, cystic fibrosis, and chronic lung disease of infancy to demonstrate the prevalence of this finding and whether it is specific to a measurement device.

Within-breath changes in respiratory system impedance in children with cystic fibrosis

BACKGROUND

The aim of this study was to assess within-breath respiratory system impedance by the forced oscillation technique (FOT) in children with cystic fibrosis (CF) and relate it to the underlying lung disease.

METHODS

Thirty-three children with CF (median [range] age 12.0 [6-17] years) underwent FOT at 8 Hz during tidal breathing, multiple breath nitrogen washout (LCI), spirometry (FEV1), body plethysmography (RV/TLC), and magnetic resonance imaging (MRI). FOT outcomes included: mean inspiratory, expiratory, and whole breath resistance (R8_INSP , R8_EXP , R8_TOT ) and reactance (X8_INSP , X8_EXP , X8_TOT ), and the differences between X8_INSP and X8_EXP (ΔX8). Morphological changes were evaluated by MRI using CF-specific morphological scores. Spearman correlation was performed to examine the correlation between FOT indices and other parameters.

RESULTS

FEV1 was negatively correlated with R8_EXP (r = -0.52, P = 0.002) and ΔX8 (r = -0.55, P = 0.001), and positively correlated with and X8_EXP (r = 0.56, P < 0.001). RV/TLC was positively correlated with R8_EXP (r = 0.43, P = 0.013), and ΔX8 (r = 0.54, P = 0.001) and negatively correlated with X8_EXP (r = -0.54, P = 0.001). We found poor correlation between FOT parameters and LCI and no correlation between FOT parameters and MRI scores.

CONCLUSION

In children with CF, changes in within-breath FOT parameters are consistent with peripheral obstruction and dynamic airway compression, while they are not associated with ventilation heterogeneities and morphological alterations.

Pediatric pulmonology year in review 2016: Part 2

Pediatric Pulmonology continues to publish research and clinical topics related to the entire range of children's respiratory disorders. As we have done annually in recent years, we here summarize some of the past year's publications in our major topic areas, as well as selected literature in these areas from other core journals relevant to our discipline. This review (Part 2) covers selected articles on neonatology, asthma, physiology and lung function testing, and infectious diseases.

Sleep and pulmonary outcomes for clinical trials of airway plexiform neurofibromas in NF1

OBJECTIVE

Plexiform neurofibromas (PNs) are complex, benign nerve sheath tumors that occur in approximately 25%-50% of individuals with neurofibromatosis type 1 (NF1). PNs that cause airway compromise or pulmonary dysfunction are uncommon but clinically important. Because improvement in sleep quality or airway function represents direct clinical benefit, measures of sleep and pulmonary function may be more meaningful than tumor size as endpoints in therapeutic clinical trials targeting airway PN.

METHODS

The Response Evaluation in Neurofibromatosis and Schwannomatosis functional outcomes group reviewed currently available endpoints for sleep and pulmonary outcomes and developed consensus recommendations for response evaluation in NF clinical trials.

RESULTS

For patients with airway PNs, polysomnography, impulse oscillometry, and spirometry should be performed to identify abnormal function that will be targeted by the agent under clinical investigation. The functional group endorsed the use of the apnea hypopnea index (AHI) as the primary sleep endpoint, and pulmonary resistance at 10 Hz (R10) or forced expiratory volume in 1 or 0.75 seconds (FEV1 or FEV0.75) as primary pulmonary endpoints. The group defined minimum changes in AHI, R10, and FEV1 or FEV0.75 for response criteria. Secondary sleep outcomes include desaturation and hypercapnia during sleep and arousal index. Secondary pulmonary outcomes include pulmonary resistance and reactance measurements at 5, 10, and 20 Hz; forced vital capacity; peak expiratory flow; and forced expiratory flows.

CONCLUSIONS

These recommended sleep and pulmonary evaluations are intended to provide researchers with a standardized set of clinically meaningful endpoints for response evaluation in trials of NF1-related airway PNs.

Evaluation of children with cystic fibrosis by impulse oscillometry when stable and at exacerbation

BACKGROUND

Pulmonary function tests are important in the diagnosis and follow-up of airway disease in cystic fibrosis (CF). Conventional spirometry for which repeated forced expiration maneuver are needed is considered as the main method. Impulse oscillometry (IOS) is a non-invasive method, which needs minimal cooperation. We performed a prospective cross-sectional study to determine the pulmonary function in CF children with IOS, and evaluate the IOS measurements during acute exacerbation. We hypothesized that IOS can detect lung function impairment in CF patients and detect changes during acute exacerbations.

METHODS

CF patients aged 3-18 years were included as the study group and healthy children of the same age formed the control group. The patients were evaluated three times at 3-month intervals. Patients aged >6 years performed both spirometry and IOS while patients aged ≤6 years performed only IOS. In patients with acute exacerbation, spirometry and IOS were performed both at and after the exacerbation.

RESULTS

Forty-nine CF patients and 45 healthy children were enrolled to the study. Sixteen patients were admitted with acute exacerbation during the study. The resistance values (R5-10-15-20 Hz) as well as Z5, Fres, and AX values of the patients were higher than those of the control group, while reactance values (X5-10-15-20 Hz) were lower. R values as well as Z5, Fres, and AX values increased during exacerbation and decreased after treatment; X (10-15 Hz) values decreased during exacerbation and increased after recovery (P < 0.05).

CONCLUSIONS

IOS may be useful to evaluate pulmonary functions and detect acute exacerbations in CF patients. Pediatr Pulmonol. 2016;51:1151-1158. © 2016 Wiley Periodicals, Inc.

The Forced Oscillation Technique in Paediatric Respiratory Practice

The Forced Oscillation Technique (FOT) is a lung function modality based on the application of an external oscillatory signal in order to determine the mechanical response of the respiratory system. The method is in principal noninvasive and requires minimal patient cooperation, which makes it suitable for use in young paediatric patients. The FOT has been successfully applied in various paediatric respiratory disorders, such as asthma, cystic fibrosis, and chronic lung disease of prematurity, in order to assess airway obstruction, bronchodilator response, and airway responsiveness after bronchoprovocation challenge. This technique may be more sensitive than spirometry in identifying disturbances of peripheral airways and assessing the level of asthma control or the effectiveness of therapy at the long term. Further research is required to determine the exact role of the FOT in paediatric lung function testing and to incorporate the method in specific diagnostic and management algorithms.

An impulse oscillometry system is less efficient than spirometry in tracking lung function improvements after intravenous antibiotic therapy in pediatric patients with cystic fibrosis

A literature search identified one retrospective study on the responsiveness of impulse oscillometry (IOS) in pediatric patients with cystic fibrosis. The aim of this prospective observational study was to assess this property in an adequately powered study after intravenous antibiotic therapy (IVAT) administered for an acute episode of pulmonary exacerbation. Spirometry and IOS were done on the same day as the start and the end of IVAT. Data from 34 patients' of mean age 11.9 years (range, 5-17 years) were studied. The mean FEV1 at the start and at the end of the IVAT was 73.1 ± 23.8% (range, 23.4-122%) and 88.3 ± 21.3% (range, 29.4-131%), respectively. The mean relative change (mean ± SD) was 20.2 ± 14.2% for FEV1 (ΔFEV1 ), -21.9 ± 23.8% for reactance at 5 Hz (ΔX5) and -13.4 ± 18.9% for resistance at 5 Hz (Δ R5) (all P-values <0.05). There was a weak but significant correlation between ΔFEV1 and ΔX5 (r =-0.473; p = 0.01). The magnitude of improvement of ΔX5 was not statistically different between patients with normal versus abnormal lung function at the start of IVAT. Furthermore, using ΔX5 alone as an outcome measure of IVAT efficiency resulted in a significant improvement in 44% of the patients, while it was 79% with ΔFEV1 . These results indicate that IOS may track changes after IVAT, but that this improvement may be insufficiently evaluated using IOS alone.

Lung Function Tests in Preschool Children

The measurement of lung function by spirometry is routinely used to monitor and adequately treat children with asthma. The assessment and evaluation of lung function in children aged 3-5 years has been neglected for a long time because of the difficulty to perform forced expiratory maneuvers. However, the use of techniques such as the interrupter technique and the forced oscillation technique, which only require passive collaboration and where the only request to the child is to breathe at tidal volume, has overcome this limitation. Other techniques such as the measurement of specific airway resistance by plethysmography or the measurement of the lung clearance index using the multiple-breath washout might be helpful in this regard, although these techniques are less standardized in preschool children.

Impact of lung disease on respiratory impedance in young children with cystic fibrosis

This study aimed to evaluate the ability of the forced oscillation technique (FOT) to detect underlying lung disease in preschool children with cystic fibrosis (CF) diagnosed following newborn screening.184 children (aged 3-6 years) with CF underwent lung function testing on 422 occasions using the FOT to assess respiratory resistance and reactance at the time of their annual bronchoalveolar lavage collection and chest computed tomography scan. We examined associations between FOT outcomes and the presence and progression of respiratory inflammation, infection and structural lung disease.Children with CF who had pronounced respiratory disease, including free neutrophil elastase activity, infection with pro-inflammatory pathogens and structural lung abnormalities had similar FOT outcomes to those children without detectable lung disease. In addition, the progression of lung disease over 1 year was not associated with worsening FOT outcomes.We conclude that the forced oscillation technique is relatively insensitive to detect underlying lung disease in preschool children with CF. However, FOT may still be of value in improving our understanding of the physiological changes associated with early CF lung disease.

Chest Physiotherapy in the Pediatric Intensive Care Unit

Despite widespread practice, there is very little, high-level evidence supporting the indications for and effectiveness of cardiopulmonary/chest physiotherapy (CPT) in critically ill infants and children. Conversely, most studies highlight the detrimental effects or lack of effect of different manual modalities. Conventional CPT should not be a routine intervention in the pediatric intensive care unit, but can be considered when obstructive secretions are present which impact on lung mechanics and/or gaseous exchange and/or where there is the potential for long-term complications. Techniques such as positioning, early mobilization, and rehabilitation have been shown to be beneficial in adult intensive care patients; however, little attention has been paid to this important area of practice in pediatric intensive care units. This article presents a narrative review of chest physiotherapy in pediatric critical illness, including effects, indications, precautions, and specific treatment modalities and techniques.

Putting lung function and physiology into perspective: cystic fibrosis in adults

Adult cystic fibrosis (CF) is notable for the wide heterogeneity in severity of disease expression, both between patients and within the lungs of individuals. Although CF airways disease appears to start in the small airways, in adults there is typically widespread bronchiectasis, increased airway secretions, and extensive obstruction and inflammation of the small airways. The complexity and heterogeneity of airways disease in CF means that although there are many different methods of assessing and describing lung 'function', none of these single-dimensional tests is able to provide a comprehensive assessment of lung physiology across the spectrum seen in adult CF. The most widely described measure, the forced expiratory volume in 1 s, remains a useful and simple clinical tool, but is insensitive to early changes and may be dissociated from other more detailed assessments of disease severity such as computed tomography. In this review, we also discuss the use of more sensitive novel assessments such as multiple breath washout tests and impulse oscillometry, as well as the role of cardiopulmonary exercise testing. In the future, hyperpolarized gas magnetic resonance imaging techniques that combine regional structural and functional information may help us to better understand these measures, their applications and limitations.

Correlation between impulse oscillometry and spirometry parameters in Indian patients with cystic fibrosis

Impulse oscillometry (IOS) is an emerging tool to assess lung function in chronic respiratory diseases, more often in preschool children and patients who are unable to perform spirometry. We conducted a prospective cross-sectional study on patients with cystic fibrosis (CF). Primary objective was to evaluate correlation between IOS and spirometry parameters. Secondary objective was to evaluate the ability of IOS parameters to discriminate patients with airflow limitation at various forced expiratory volume in 1 second (FEV1) cutoffs. Patients with CF above 6 years of age, who were following up on a routine visit, were enrolled in the study. Patients underwent IOS and spirometry as per guidelines. A total of 39 patients (34 children and 5 adults) were enrolled in the study. There was a significant moderate negative correlation between spirometry parameters (FEV1, forced vital capacity, and peak expiratory flow rate) and IOS parameters, that is, impedance at 5 Hz (Z5), resistance at 5 Hz (R5), and reactance area, both between raw values and percent predicted values. Of the various IOS parameters, Z5 percent predicted had the maximum area under the curve (AUC) of 0.8152 and 0.8448 for identifying children with FEV1 <60% and <80%, respectively. R5 percent predicted had an AUC of 0.8185 for identifying children with FEV1 <40%. IOS can be used as an alternative pulmonary function test in patients with CF more so in patients who are unable to perform spirometry.

Spirometry and forced oscillations in the detection of airway hyperreactivity in asthmatic children

BACKGROUND

Provocation tests are routinely used to detect airway hyperreactivity (AH) in the diagnosis of asthma. We compared the sensitivities of the forced oscillation technique (FOT) and spirometry in the detection of AH in asthmatic children.

METHODS

FOT and spirometry were performed in 20 asthmatic children (aged 5-18 years) following aerosolized histamine and methacholine at an interval of 2 weeks. The respiratory system input impedance was measured by FOT; the resistance at 6 Hz (R(6) ), the average resistance between 4 and 24 Hz, the area under the reactance curve (AX) and the resonant frequency were extracted from these recordings. Spirometry was used to obtain forced expiratory volumes and flow parameters.

RESULTS

Following provocation with the two agonists, the FOT detected the airway response as early as spirometry. When the greater variability of the impedance parameters was taken into account, the two methods were observed to have similar sensitivities. Among the lung function parameters studied, AX and R(6) were the most sensitive for the demonstration of AH.

CONCLUSIONS

Our findings demonstrate that FOT is as suitable as spirometry for the measurement of bronchoconstriction and thus it may be considered for the detection of AH in asthmatic children. Since its application requires minimal cooperation, this approach imposes less stress and may be particularly favorable in the diagnosis of asthma at a young age.

Clinical applications of lung function tests: a revisit

The development and clinical application of lung function tests have a long history, and the various components of lung function tests provide very important tools for the clinical evaluation of respiratory health and disease. Spirometry, measurement of the diffusion factor, bronchial provocation tests and forced oscillation techniques have found diverse clinical applications in the diagnosis and monitoring of respiratory diseases, such as chronic obstructive pulmonary disease, interstitial lung diseases and asthma. However, there are some practical issues to be resolved, including the establishment of reference values for individual test parameters and the roles of these tests in preoperative risk assessment and pulmonary rehabilitation. Novel measurements, including negative expiratory pressure, the fraction of exhaled nitric oxide and analysis of exhaled breath condensate, may provide new insights into physiological abnormalities or airway inflammation in respiratory diseases, but their clinical applications need to be further evaluated. The clinical application of lung function tests continues to face challenges, which may be overcome by further improvement of conventional techniques for lung function testing and further specification of new testing techniques.

Lung function and inflammation during murine Pseudomonas aeruginosa airway infection

BACKGROUND

Following any acute irritation lung function declines rapidly. Reasons for pulmonary deterioration in humans had been attributed to the action of either interleukin-6 or interleukin-8 in the lungs.

OBJECTIVES

The present study investigates the association between immune response and decline in lung function in a murine bacterial lung infection model.

METHODS

Upon intratracheal inoculation of C57BL/6J mice with a sublethal dose of Pseudomonas aeruginosa lung function, cytokine, chemokine and cytometry in bronchoalveolar lavage fluid, bacterial counts and lung histology was assessed at 2, 4, 6, 8, 10, 12, 18, 24, 48, 72, 96 and 120 h post inoculation.

RESULTS

Lung function measured by non-invasive head-out spirometry decreased most strongly between 6 and 10 h post inoculation and required up to 72 h to recover for selected parameters. CFU counts in the lungs peaked at 4h post inoculation with subsequent decline until at 24-48 h post inoculation background levels were reached. Cytokine and chemokine responses could be separated into an early pro-inflammatory phase (2-8h post inoculation; mainly tumor-necrosis factor α (TNFα) and interleukin-1α driven) and a late anti-inflammatory resolution phase (starting at 24h post inoculation; mainly interleukin-10 and interleukin-4 driven). Interleukin-6 levels correlated with the deterioration of lung function. Lung histology showed maximal changes in terms of inflammation and edema between 24 and 48 h post inoculation.

CONCLUSIONS

In summary, elevated interleukin-6, high local neutrophil counts and lung edema were found to be the most characteristic signs of the transient period of deterioration of lung function.

Respiratory impedance and bronchodilator response in healthy Italian preschool children

OBJECTIVE

To define normal values for respiratory resistance (R(rs)) and reactance (X(rs)) and bronchodilator response (BDR) in a population of healthy Italian preschool children using a commercially available forced oscillation device.

METHODS

R(rs) and X(rs) were measured in kindergartens in Viterbo, Italy. Regression analysis was performed taking into account height, weight, age, gender, and reference equations calculated. The coefficient of repeatability (CR) between two tests performed 15 min apart was calculated in a subset of children. BDR was assessed by repeating the measurements 15 min after the administration of 200 µg of inhaled salbutamol and calculated as an absolute change in R(rs) and X(rs) at 8 Hz, as a percent change in baseline, and as a change in Z-score calculated from the reference equations.

RESULTS

Lung function was attempted in 175 healthy children and successful in 163 (81 male, median age 4.8, range 2.9-6.1 years). R(rs) and X(rs) at 6, 8, and 10 Hz were related to height but not other variables. The CR was 1.53 hPa s L(-1) for R(rs8) and 0.91 hPa s L(-1) for X(rs8). The 5th percentile for absolute R(rs8) BDR was -3.16 hPa s L(-1), whereas the 95th percentile for absolute X(rs8) BDR was 2.25 hPa s L(-1). These cut-off values corresponded to a change in the Z-score of -1.88 and 2.48, respectively.

CONCLUSIONS

We have established reference equations for R(rs) and X(rs) in healthy Italian preschool children using forced oscillations. We recommend a change in Z-score of -1.88 for R(rs8) and 2.48 for X(rs8) as cut-off values for a positive BDR.

Using index of ventilation to assess response to treatment for acute pulmonary exacerbation in children with cystic fibrosis

BACKGROUND

The use of alternative more sensitive measures has become a focus of research in CF. The utility of indexes of ventilation, Lung Clearance Index (LCI) and peak aerobic capacity (peak VO(2)), were studied as assessment tools in gauging response to intravenous (IV) therapy in acute pulmonary exacerbation, in comparison to the more commonly used index of forced expiratory volume in 1 sec (FEV(1)). The utility of a previously published clinical score was further explored.

METHODS

Patients aged 8-18 years admitted for IV antibiotic treatment of a pulmonary exacerbation were recruited. Spirometry, plethysmography, multiple breath nitrogen washout, exercise testing, and Cystic Fibrosis Clinical Score (CFCS) were performed on admission and prior to discharge.

RESULTS

Twenty-eight patients were recruited, with a mean (range) age of 13.7 (8; 17) years, 16 female and 12 male. Mean (range) admission FEV(1) was 61.4 (28; 92)% predicted, or z-score -3.09 (-6.15; -0.52), FVC 83.0 (38; 120)% predicted, or z-score -1.71 (-5.66; -1.17), and Shwachman-Kulczycki 68.9 (50; 90). FEV(1) increased by 7.0% (P < 0.01) from admission to discharge. Mean (range) admission LCI, 10.10 (6.87; 14.83), decreased by 3.8% (P = 0.03). Mean (range) admission peak VO(2) (ml/kg/min), 31.2 (23.4; 45.4), increased on discharge by 6.6% (P < 0.01). Proposed clinical thresholds, based on the available variability data, highlighted the heterogeneity of response in lung function tests. Mean (range) admission CFCS, 26.5 (19; 39), decreased to 19.9 (13; 31) on discharge, a 25.2% improvement (P < 0.01). CFCS demonstrated improvement in 27 of 28 patients. Changes in peak VO(2) (r = -0.50, P = 0.02) and LCI (r = 0.48, P = 0.01) correlated with CFCS change.

CONCLUSIONS

In children with mild-to-moderate CF, whilst statistically significant improvement in both LCI and peak VO(2) were seen, heterogeneity of response was evident. The most consistent improvement was seen in CFCS. Correlation of LCI and peak VO(2) with change in clinical score (CFCS) was seen. The full clinical significance of these changes in LCI and peak VO(2) needs to be evaluated further with additional variability data. The CFCS may be useful in the assessment of response to treatment in CF but requires formal validation.

Relationship between impulse oscillometry and spirometric indices in cystic fibrosis children

BACKGROUND

The aim of our retrospective study was to determine the relationship between impulse oscillometry (IOS) data and spirometric tests in cystic fibrosis (CF) children. methods: Thirty CF children aged 4-19 years have performed lung function tests (LFT). A subset of 15 patients repeated LFT on five separate occasions. IOS parameters were respiratory resistance (Rrs), reactance (Xrs) and impedance at 5 Hz (R5, X5, Zr) and the resonant frequency (Fres). Spirometry indices (SI) included forced expiratory volume in 1 sec (FEV(1)), forced expiratory flow during the middle half of FVC (FEF(25-75)) and forced vital capacity (FVC).

RESULTS

An inverse relationship was observed between raw values of R5, Zr, Fres and SI respectively, and X5 correlated positively with SI. Although significant, these correlations were poor. Receiver operating characteristic curves (ROC) were constructed to identify cutoff points for IOS parameters to discriminate between children according to predefined FEV(1) thresholds (percent predicted), generally used to categorize the level of lung function impairment. No acceptable cutoff points can be found for IOS parameters. Trends analyses in the subgroup of 15 patients showed a significant decline of FEV(1) between the first and the fifth evaluation. None of the IOS indices demonstrated a consistent tendency, apart from a slight decrease of Fres.

CONCLUSION

IOS measurements presented an insufficient sensitivity to detect and follow bronchial obstruction in CF patients.

Assessment and monitoring of cystic fibrosis lung disease in infants and young children

Chronic airway infection and inflammation are the hallmarks of cystic fibrosis (CF) lung disease. As these events occur early in life, it is critical to develop techniques for the assessment and monitoring of early-CF lung disease in infants and young children. In the last several years, there have been major advances in the development of imaging technology to assess structural damage in CF lung disease, noninvasive markers of CF airway inflammation and measurement of lung function in infants and young children with CF. In this article, we will review these advances and techniques, and discuss future directions for research and clinical applications.