No paradoxical bronchodilator response with forced oscillation technique in children with cystic fibrosis

Assessment of bronchodilator response in preschoolers: A systematic review

BACKGROUND

Several techniques can be used to assess bronchodilator response (BDR) in preschool-aged children, including spirometry, respiratory oscillometry, the interrupter technique, and specific airway resistance. However, there has not been a systematic comparison of BDR thresholds across studies yet.

METHODS

A systematic review was performed on all studies up to May 2023 measuring a bronchodilator effect in children 2-6 years old using one of these techniques (PROSPERO CRD42021264659). Studies were identified using MEDLINE, Cochrane, EMBASE, CINAHL via EBSCO, Web of Science databases, and reference lists of relevant manuscripts.

RESULTS

Of 1224 screened studies, 43 were included. Over 85% were from predominantly European ancestry populations, and only 22 studies (51.2%) calculated a BDR cutoff based on a healthy control group. Five studies included triplicate testing with a placebo to account for the within-subject intrasession repeatability. A relative BDR was most consistently reported by the included studies (95%) but varied widely across all techniques. Various statistical methods were used to define a BDR, with six studies using receiver operating characteristic analyses to measure the discriminative power to distinguish healthy from wheezy and asthmatic children.

CONCLUSION

A BDR in 2- to 6-year-olds cannot be universally defined based on the reviewed literature due to inconsistent methodology and cutoff calculations. Further studies incorporating robust methods using either distribution-based or clinical anchor-based approaches to define BDR are required.

Bronchodilator response assessment through impulse oscillometry system and spirometry in children and adolescents with cystic fibrosis

OBJECTIVE

To investigate the effect of bronchodilator on the respiratory mechanics and pulmonary function of children and adolescents with cystic fibrosis.

METHODS

Cross-sectional study on clinically stable children and adolescents with cystic fibrosis aged from six to 15 years. Participants underwent impulse oscillometry and spirometry evaluations before and 15 minutes after bronchodilator inhalation. The Kolmogorov-Smirnov test was applied to verify the sample distribution, and the Student's t-test and Wilcoxon test were used to compare the data before and after bronchodilator inhalation.

RESULTS

The study included 54 individuals with a mean age of 9.7±2.8 years. The analysis showed a statistically significant improvement in impulse oscillometry and spirometry parameters after bronchodilator inhalation. However, according to the American Thoracic Society (ATS) and European Respiratory Society (ERS) recommendations (2020 and 2021), this improvement was not sufficient to classify it as a bronchodilator response.

CONCLUSIONS

The use of bronchodilator medication improved respiratory mechanics and pulmonary function parameters of children and adolescents with cystic fibrosis; however, most patients did not show bronchodilator response according to ATS/ERS recommendations.

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.

Identifying pediatric lung disease: A comparison of forced oscillation technique outcomes

RATIONALE

Increasing evidence suggests the forced oscillation technique (FOT) has the capacity to provide non-invasive monitoring and diagnosis of respiratory disease in young children. However, which FOT outcomes provide the most pertinent clinical information is currently unknown. The aim of this study was to determine which FOT outcomes were most sensitive for differentiating between health and specific childhood respiratory disease.

METHODS

Respiratory impedance was measured using a commercial device (i2M, Chess Medical, Belgium) in children aged between 3 and 7 years, who had been diagnosed with either cystic fibrosis (N = 84), asthma (N = 99) or were born very preterm (N = 114). Z-scores were calculated for respiratory system resistance (Rrs) and reactance (Xrs) at 6, 8, and 10 Hz, the resonance frequency (Fres), frequency dependence (Fdep_4-24 ), and area under the reactance curve (AX). Pairwise comparisons of the area under the receiver operating characteristic (ROC) curve were used to determine the most relevant FOT variables.

RESULTS AND CONCLUSIONS

The FOT outcomes best able to discern between health and disease were Fres (P < 0.0001) in cystic fibrosis, Fres (P < 0.0001) in asthma and Xrs₈ (P < 0.0001) in children born preterm. These findings suggest the utility of specific FOT outcomes is dependent on the respiratory disease being assessed. It is hoped that a disease-specific approach to interpreting FOT data can help further refine the FOT technique to aid in the diagnosis of children with pediatric respiratory disease.

Defining 'healthy' in preschool-aged children for forced oscillation technique reference equations

BACKGROUND AND OBJECTIVE

Selecting 'healthy' preschool-aged children for reference ranges may not be straightforward. Relaxing inclusion criteria for normative data does not affect spirometry z-scores. We therefore investigated the effect of similarly relaxing inclusion criteria in preschoolers on reference ranges for respiratory impedance (Zrs) using a modified forced oscillation technique (FOT).

METHODS

The International Study of Asthma and Allergies in Childhood questionnaire classified 585 children into a healthy and five mutually exclusive groups. Zrs was measured between 4 and 26 Hz and resistance (R) and compliance (C) obtained by model fitting. Prediction models were determined using mixed effect models and z-scores compared between healthy children and the five groups.

RESULTS

Zrs data were obtained for 494 participants (4.30 ± 0.7 years) on 587 occasions. Comparison of the Zrs z-scores between the healthy children and the health groups found significant differences in children with asthma, current wheeze and respiratory symptoms, but not in children born preterm or with early-life wheeze. Adding these two groups to the healthy dataset had no significant effect on the distribution of z-scores and increased the size of the dataset by 22.3%.

CONCLUSION

Our data suggest that preschool-aged children born preterm or with early-life wheeze can be included in FOT reference equations, while those with asthma, current wheeze and respiratory symptoms within 4 weeks of testing should be excluded. This more inclusive approach results in more robust FOT reference ranges.

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.

Mechanical consequences of allergic induced remodeling on mice airway resistance and compressibility

The effect of remodeling on airway function is uncertain. It may affect airway compressibility during forced expirations differently than airflow resistance, providing a tool for its assessment. The aim of the current study was to compare the effects of acute and chronic antigen challenge on methacholine-induced bronchoconstriction assessed from resistance and maximal tidal expiratory flow. Balb/C mice were sensitized with ovalbumin (OVA) and challenged either daily for three days with intra-nasal OVA or daily for 5 days and three times a week for 5 subsequent weeks. Acute and chronic allergen challenge induced airway hyperresponsiveness (AHR) to methacholine. However the relationship between maximal tidal expiratory flow and resistance during methacholine challenge was different between the two conditions, suggesting that the determinants of AHR are not identical following acute and chronic allergen exposure. We conclude that the contrast of changes in maximal tidal expiratory flow and respiratory resistance during methacholine-induced bronchoconstriction may allow the detection of the mechanical consequences of airway remodeling.

Forced oscillations and respiratory system modeling in adults with cystic fibrosis

Background

The Forced Oscillation Technique (FOT) has the potential to increase our knowledge about the biomechanical changes that occur in Cystic Fibrosis (CF). Thus, the aims of this study were to investigate changes in the resistive and reactive properties of the respiratory systems of adults with CF.

Methods

The study was conducted in a group of 27 adults with CF over 18 years old and a control group of 23 healthy individuals, both of which were assessed by the FOT, plethysmography and spirometry. An equivalent electrical circuit model was also used to quantify biomechanical changes and to gain physiological insight.

Results and discussion

The CF adults presented an increased total respiratory resistance (p < 0.0001), increased resistance curve slope (p < 0.0006) and reduced dynamic compliance (p < 0.0001). In close agreement with the physiology of CF, the model analysis showed increased peripheral resistance (p < 0.0005) and reduced compliance (p < 0.0004) and inertance (p < 0.005). Significant reasonable to good correlations were observed between the resistive parameters and spirometric and plethysmographic indexes. Similar associations were observed for the reactive parameters. Peripheral resistance, obtained by the model analysis, presented reasonable (R = 0.35) to good (R = 0.64) relationships with plethysmographic parameters.

Conclusions

The FOT adequately assessed the biomechanical changes associated with CF. The model used provides sensitive indicators of lung function and has the capacity to differentiate between obstructed and non-obstructed airway conditions. The FOT shows great potential for the clinical assessment of respiratory mechanics in adults with CF.

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.

Novel end points for clinical trials in young children with cystic fibrosis

Cystic fibrosis (CF) lung disease commences early in the disease progression and is the most common cause of mortality. While new CF disease-modifying agents are currently undergoing clinical trial evaluation, the implementation of such trials in young children is limited by the lack of age-appropriate clinical trial end points. Advances in infant and preschool lung function testing, imaging of the chest and the development of biochemical biomarkers have led to increased possibility of quantifying mild lung disease in young children with CF and objectively monitoring disease progression over the course of an intervention. Despite this, further standardization and development of these techniques is required to provide robust objective measures for clinical trials in this age group.

Clinical investigation of respiratory system admittance in preschool children

INTRODUCTION

The upper airway shunt attenuates measurements of respiratory system impedance (Zrs), with greater impact in young children. Changes in respiratory system admittance, Ars (or Zrs(-1)), are theoretically independent of the shunt. This study compared the ability of Ars, to standard oscillatory outcomes, to determine respiratory disease and differentiate responses to inhaled bronchial challenges in the clinical setting.

METHODS

The forced oscillation technique (FOT) was used to establish reference equations for Ars in healthy preschool children, compare the change in Ars to standard oscillatory outcomes during bronchial challenge with inhaled adenosine-5'-monophosphate (AMP) and to inhaled bronchodilator in healthy children and those with respiratory disease.

RESULTS

Children with respiratory disease had lower baseline Ars than healthy children (P < 0.05). However, there was no improved ability for Ars to differentiate between bronchodilator responses in healthy and disease populations. In contrast, the response to inhaled AMP occurred at a lower concentration, [25 (3.12-400) mg ml(-1); median (10th-90th centile)], as measured by Ars when compared to respiratory system resistance [225 (6.25-400) mg ml(-1); P = 0.016].

CONCLUSION

This study supports the use of Ars during inhaled challenges, but not in response to bronchodilation.

Lung function testing in preschool-aged children with cystic fibrosis in the clinical setting

In cystic fibrosis (CF) lung function testing is a means of monitoring progression of lung disease. The preschool years have often been referred to as the "silent years" due to the previous lack suitable measures of lung function testing in this age group. This review outlines the various techniques of lung function testing in preschool children with CF in the clinical setting. This includes measures requiring tidal breathing including the forced oscillation technique, the interrupter technique, plethysmography, and multiple breath washout, as well as spirometry that requires respiratory maneuvers. We describe the feasibility and variability of different lung function methods used in preschoolers and report measurements made during tidal breathing have greater feasibility, although greater variability compared to spirometry. We also report associations with lung function and markers of CF lung disease. In the preschool age group measurements made during tidal breathing may be more appropriate in the clinic setting than those that require a higher degree of cooperation and specific respiratory maneuvers.maneuvers.

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.

Early detection of lung disease in children with cystic fibrosis using lung function

Measurement of lung function is routine in older children and adults with cystic fibrosis (CF) but not in infants and preschool children. Pulmonary infection, neutrophil-dominated inflammation and clinical exacerbations in young children similar to those seen in older subjects have been identified and highlight the urgent need to evaluate lung function in early life. Mounting evidence suggests lung function techniques sensitive to changes in peripheral lung function may be required to detect the early functional abnormalities in infants and preschool children with CF. In addition, the majority of studies in young children with CF have not reported longitudinal data and therefore the prognostic potential of existing lung function methods to track disease progression is poorly understood. This review aims to describe recent research findings in infants and preschool children and to outline currently available lung function techniques, issues around their standardization and their relative advantages and disadvantages in young children with CF.

Identification of bronchodilator responsiveness by forced oscillation admittance in children

The upper airway wall motion may be responsible for significant error when measuring respiratory resistance (Rrs) with the forced oscillation technique (FOT), particularly in young children with airway obstruction. Assessing the response to methacholine from the change in respiratory admittance (Ars, the reciprocal of respiratory impedance, Zrs) avoids the artifact. The aim of the study was to explore the possibility of assessing the response to a bronchodilator from the change in Ars. FOT measurements were performed at 12 Hz in 36 young children before and after salbutamol. Transrespiratory pressure was varied in two ways: directly at the mouth (standard generator, SG) and around the head (head generator, HG), a variant nearly free of upper airway artifact. Salbutamol induced significantly lower Rrs and Zrs change with SG than HG (respectively, p = 0.0003 and 0.05). The relative change in Ars was not significantly different with SG and HG. Both estimates were significantly correlated (p < 0.0001). The change in Ars may thus be useful to avoid the upper airway artefact when assessing the response to salbutamol using the FOT in young children.

Mucoviscidose : du bon usage des explorations fonctionnelles respiratoires

INTRODUCTION

Neonatal screening for cystic fibrosis (CF) leads to early dedicated specialist care for all patients.

BACKGROUND

Pulmonary function tests (PFT) are mandatory for routine monitoring of CF patients. The aim of this article is to review the current guidelines for PFTs in CF, particularly the type of test, the age and the clinical status of the patient.

VIEWPOINT

The regular use of spirometry is generally accepted. Many other tests are used but their clinical value in the routine follow-up of CF patients remains to be established.

CONCLUSION

Further efforts should be made to evaluate the value of PFTs in CF, particularly in very young children.

Assessment of bronchodilator responsiveness in preschool children using forced oscillations

BACKGROUND

The forced oscillation technique (FOT) requires minimal patient cooperation and is feasible in preschool children. Few data exist on respiratory function changes measured using FOT following inhaled bronchodilators (BD) in healthy young children, limiting the clinical applications of BD testing in this age group. A study was undertaken to determine the most appropriate method of quantifying BD responses using FOT in healthy young children and those with common respiratory conditions including cystic fibrosis, neonatal chronic lung disease and asthma and/or current wheeze.

METHODS

A pseudorandom FOT signal (4-48 Hz) was used to examine respiratory resistance and reactance at 6, 8 and 10 Hz; 3-5 acceptable measurements were made before and 15 min after the administration of salbutamol. The post-BD response was expressed in absolute and relative (percentage of baseline) terms.

RESULTS

Significant BD responses were seen in all groups. Absolute changes in BD responses were related to baseline lung function within each group. Relative changes in BD responses were less dependent on baseline lung function and were independent of height in healthy children. Those with neonatal chronic lung disease showed a strong baseline dependence in their responses. The BD response in children with cystic fibrosis, asthma or wheeze (based on both group mean data and number of responders) was not greater than in healthy children.

CONCLUSIONS

The BD response assessed by the FOT in preschool children should be expressed as a relative change to account for the effect of baseline lung function. The limits for a positive BD response of -40% and 65% for respiratory resistance and reactance, respectively, are recommended.

Reference values for respiratory system impedance by using impulse oscillometry in children aged 2-11 years

The forced oscillation technique makes it possible to evaluate the mechanical properties of the respiratory system with a minimum of cooperation. The method is therefore especially useful in children. Impulse oscillometry (IOS) is a commercially available version of this technique. There is, as yet, limited information on reference values for IOS in children. The aim of this study was to extend the reference values for IOS variables and to study their correlation with height, weight and age in healthy children. A sample (n = 360) of children (age 2.1-11.1 years) was measured by using impulse oscillometry (IOS; Jaeger, Würzburg, Germany). The sample was based on children attending kindergarten in Finland and children attending primary school in Sweden. Measurements of respiratory resistance (Rrs) and reactance (Xrs) at 5, 10, 15 and 20 Hz, total respiratory impedance (Zrs) and the resonance frequency (Fr) were made. All variables were related to body height. Most of them were also weakly related to weight. Reference equations for children (height 90-160 cm) are presented.

Adenovirus pneumonia in infants and factors for developing bronchiolitis obliterans: a 5-year follow-up

To describe clinical, pulmonary function, and chest tomography profiles in a 5-year follow-up of infants with adenovirus pneumonia and determine the factors that potentially contributed to the development of bronchiolitis obliterans (BO). We prospectively assessed 45 hospitalized infants with adenovirus pneumonia with additional follow-up for 5 years. At the end of the study, pulmonary function by impulse oscillometry technique (IOS) and chest tomography were performed in the 38 surviving patients (mean 5.7 years of age). We divided the population between those who developed chest tomography evidence of BO and those who did not. Most of the children developed adenovirus infection before 2 years of age. During the 5 years of follow-up, almost half (47.4%) developed BO. Children who developed BO had significantly more respiratory compromise (intensive care admission, need for mechanical ventilation and for oxygen therapy, and systemic corticosteroid and beta agonist use) during their adenovirus pneumonia episode than those who did not develop BO. Only 33.3% of children with BO had normal impedance compared with 85% in the no BO group. Children who developed BO had significantly higher levels of Zrs, R5, X5 and predicted Zrs, R5, and X5 and frequency. However, there were no differences in the beta 2 agonist response between the children with and without BO (94% vs. 80%, respectively). This study represents the spectra of adenovirus pneumonia ranging from relatively mild to severe and fatal cases. Children with severe pulmonary compromise are usually more prone to develop BO.

[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.

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

Objective measures of lung function are critical for the treatment and study of lung diseases such as cystic fibrosis (CF). Spirometry is the most widely used and accepted method of pulmonary function testing in CF, but not all patients can perform the maneuvers required to obtain valid results from spirometry. The forced oscillation technique (FOT) requires less cooperation than spirometry. The goals of this study were to determine if FOT could detect changes in lung function in CF patients receiving inpatient treatment of respiratory tract exacerbations (RTEs), and to gather preliminary data on the magnitude of these changes and the variability of FOT data in such patients. We performed a retrospective chart review of CF patients admitted to the hospital for RTEs. We identified 14 patients who had both spirometry and FOT performed at the beginning and end of their treatment course. Their mean age was 15.9 years (range, 8-18). The mean forced expiratory volume in 1 sec (FEV1) on admission was 62.57% predicted. FEV1 increased by 27.1 +/- 33.15% (mean +/- SD, P = 0.008). The absolute value of reactance at 5 Hz (X5) decreased by 22.3 +/- 25.1% (P = 0.005), while resistance at 5 Hz decreased by 11.6 +/- 17.3% (P = 0.025). There was a significant relationship between changes in FEV1 and X5 (P = 0.003, r2 = 0.54). Our study demonstrates that FOT can detect significant changes in lung function in CF patients receiving treatment for RTEs. We speculate that FOT can serve as an alternative method to measure lung function in CF patients unable to perform spirometry, such as young children.

Serial Lung Function and Responsiveness in Cystic Fibrosis during Early Childhood

In a 4-year prospective study, we evaluated specific airway resistance (sRaw) by whole-body plethysmography, respiratory resistance by the interrupter technique, and respiratory resistance and reactance at 5 Hz by the impulse oscillation technique combined with measurement of responsiveness to bronchodilators and cold air in 30 children (mean [range] age 5.7 [2 to 8] years) with cystic fibrosis (CF). Spirometry was done at school age. Mean sRaw was consistently abnormal: the mean z score (SD) was 2.52 (2.02) (p < 0.001) at the start and was unchanged 36 months later at 2.74 (2.02). Mean z score (SD) for FEV(1) at first satisfactory measurement, at a mean age (range) of 6.1 (4.9-7.5) years was -1.2 (1.2) and was further reduced to -1.85 (1.2) 4 years from inclusion at a mean age (range) of 9.9 (6.8-12) years. Neither respiratory resistance by the interrupter technique nor the impulse oscillation technique demonstrated consistent abnormal levels. Patients with CF as a group did not differ from healthy subjects in responsiveness to bronchodilators and cold air. sRaw may be a useful tool in CF during early childhood. Reduced lung function was documented from consistently abnormal levels of sRaw and FEV1 during the study. Bronchodilator responsiveness and response to cold air challenge were normal.

Pulmonary function tests in preschool children with cystic fibrosis

Pulmonary function tests have rarely been assessed in preschool children with cystic fibrosis (CF). The objective of this multicenter study was to compare pulmonary function in 39 preschool children with CF (height, 90-130 cm; 16 homozygous Delta F508) and in 79 healthy control children. Functional residual capacity (helium dilution technique) and expiratory interrupter resistance (Rint(exp)) (interrupter technique) were measured. As compared with control children, children with CF had significantly higher Rint(exp), expressed as absolute values and as Z-scores (1.05 +/- 0.36 versus 0.80 +/- 0.20 kPa.L(-1). second, p < 0.0001; and 1.31 +/- 1.72 versus 0.19 +/- 0.97, p < 0.0001), and significantly lower specific expiratory interrupter conductance (1.29 +/- 0.34 versus 1.63 +/- 0.43 kPa(-1). second, p < 0.0001). The effect of the bronchodilator salbutamol on Rint(exp) was not significantly different between children with CF and control children. Rint(exp) Z-scores were significantly higher in children with CF who were exposed to passive smoke (n = 8) (p < 0.03). Children with CF and with a history of respiratory symptoms (n = 31) had significantly higher functional residual capacity Z-scores (p < 0.02) and lower specific expiratory interrupter conductance Z-scores (p < 0.04). Genotype did not influence the data. We conclude that Rint(exp) and functional residual capacity measurements may help to follow young children with CF who are unable to perform reproducible forced expiratory maneuvers.

Clinical application of forced oscillation

This review summarizes current clinical use of the forced oscillation technique (FOT) for analysis of lung function. It presents an intuitive approach to FOT pattern recognition for interpretation of results in human subjects, and the view that FOT is now well established and, clinically, eminently useful in patients with airflow obstruction. The focus of this review is on findings that relate directly to clinical utility, with less emphasis on theoretical mechanisms. The major thrust for clinical application of FOT derives from a number of European clinical research centers. Farre and Navajas and their colleagues in Barcelona, Harf and the Lorinos and their coworkers in Paris, Peslin and Duvivier and their coworkers in Vandoeuvre-les-Nancy, Pride and coworkers in London, and Van de Woestijne, Clement, Demedts, Landser, Van Noord, and their colleagues in Leuven have essentially been responsible for clinical development of FOT over the past 25 years. Publishing space does not permit an exhaustive listing of the many contributions of these investigators, but it is intended that the present review will provide a useful infrastructure from which the reader may progress to other research citations as desired.