Values of Impulse Oscillometry in Healthy Mexican Children and Adolescents

Impulse oscillometry assessment of respiratory function in pediatric patients with a history of COVID-19

OBJECTIVE

While coronavirus disease 2019 (COVID-19) is generally considered to exhibit a less severe clinical course in children than in adults, studies have demonstrated that respiratory symptoms can endure for more than 3 months following infection in at least one-third of pediatric cases. The present study evaluates the respiratory functions of children aged 3-15 years within 3-6 months of their recovery from COVID-19 using impulse oscillometry (IOS) and compares them with the values of healthy children.

METHODS

Included in this prospective cross-sectional study were 63 patients (patient group) aged 3-15 years who contracted COVID-19 between December 2021 and May 2022, as well as 57 healthy children as a control group, matched for age and sex. The demographic, clinical, and laboratory data of the patients were recorded, and respiratory function was assessed based on airway resistance (zR5, zR20, R5-20) and reactance (zX5, zX20, reactance area [AX], resonant frequency [Fres]) using an IOS device.

RESULTS

There were no significant differences in the age, weight, height, and body weight z score values of the two groups (p > .05). While the zR5 and R5-20 levels of the patient group were higher (p = .008 and p < .001, respectively) than those of the controls, the zR20, AX, and Fres values did not differ significantly between the groups (p > .05). The parameters indicating the reactance, including zX5 and zX20, were significantly lower in the patient group than in the control group (p = .028 and p < .001, respectively).

CONCLUSION

Total and peripheral airway resistances were found to be elevated in children who had recovered from COVID-19 in the preceding 3-6 months.

Adding oscillometry to spirometry in guidelines better identifies uncontrolled asthma, future exacerbations, and potential targeted therapy

The objective of this review is to provide new advances in our understanding of the clinical importance of establishing peripheral airway impairment (PAI) by impulse oscillometry (IOS) and targeted therapy, which could result in better asthma outcomes. Data sources include PubMed and Google search, limited to English language and human disease, with key words IOS and asthma. Key findings include PAI being consistently associated with uncontrolled asthma across ethnicities, using IOS reference equations factoring Hispanic and White reference algorithms. It is noted that PAI is common even in patients considered well-controlled by asthma guidelines. In a large longitudinal analysis (Assessment of Small Airways Involved in Asthma or ATLANTIS study), a composite of R5-R20, AX, and X5 ordinal scores were independently predictive of asthma control and exacerbation in a multivariate analysis, but forced expiratory volume in 1 second was not significantly predictive of morbidities. However, combining forced expiratory volume in 1 second less than 80% with PAI resulted in greater odds of identifying uncontrolled asthma and exacerbations, than either alone. Applying an external validation method in children with asthma offers the clinician the IOS reference equations best fit for their own specific population. Several clinical phenotypes can also identify PAI with high probability, useful when IOS is not available. Poor asthma outcomes for obese patients with asthma are associated with dysanapsis and PAI, not obesity alone. Extrafine inhaled corticosteroids achieve better asthma control and improve peripheral airway function with fewer exacerbations at lower dosages than nonextrafine inhaled corticosteroid aerosols. In conclusion, these data support the benefit of adding IOS to spirometry in future asthma guidelines and suggest the potential benefit from targeted therapy.

Lung function is related to salivary cytokines and hormones in healthy children. An exploratory cross-sectional study

Pulmonary mechanics has been traditionally viewed as determined by lung size and physical factors such as frictional forces and tissue viscoelastic properties, but few information exists regarding potential influences of cytokines and hormones on lung function. Concentrations of 28 cytokines and hormones were measured in saliva from clinically healthy scholar children, purposely selected to include a wide range of body mass index (BMI). Lung function was assessed by impulse oscillometry, spirometry, and diffusing capacity for carbon monoxide, and expressed as z-score or percent predicted. Ninety-six scholar children (55.2% female) were enrolled. Bivariate analysis showed that almost all lung function variables correlated with one or more cytokine or hormone, mainly in boys, but only some of them remained statistically significant in the multiple regression analyses. Thus, after adjusting by height, age, and BMI, salivary concentrations of granulocyte-macrophage colony-stimulating factor (GM-CSF) in boys were associated with zR5-R20 and reactance parameters (zX20, zFres, and zAX), while glucagon inversely correlated with resistances (zR5 and zR20). Thus, in physiological conditions, part of the mechanics of breathing might be influenced by some cytokines and hormones, including glucagon and GM-CSF. This endogenous influence is a novel concept that warrants in-depth characterization.

Reference equations using segmented regressions for impulse oscillometry in healthy subjects aged 2.7-90 years

Background

Published reference equations for impulse oscillometry (IOS) usually encompass a specific age group but not the entire lifespan. This may lead to discordant predicted values when two or more non-coincident equations can be applied to the same person, or when a person moves from one equation to the next non-convergent equation as he or she gets older. Thus, our aim was to provide a single reference equation for each IOS variable that could be applied from infancy to old age.

Methods

This was an ambispective cross-sectional study in healthy nonsmokers, most of whom lived in Mexico City, who underwent IOS according to international standards. A multivariate piecewise linear regression, also known as segmented regression, was used to obtain reference equations for each IOS variable.

Results

In a population of 830 subjects (54.0% female) aged 2.7 to 90 years (54.8% children ≤12 years), segmented regression estimated two breakpoints for age in almost all IOS variables, except for R5-R20 in which only one breakpoint was detected. With this approach, multivariate regressions including sex, age, height and body mass index as independent variables were constructed, and coefficients for calculating predicted value, lower and upper limits of normal, percentage of predicted and z-score were obtained.

Conclusions

Our study provides IOS reference equations that include the major determinants of lung function, i.e. sex, age, height and body mass index, that can be easily implemented for subjects of almost any age.

In young children with asthma, obesity, and uncontrolled disease are highly associated with peripheral airway impairment

BACKGROUND

Despite the fact that impulse oscillometry (IOS)-determined peripheral airway impairment (PAI) phenotype is a major risk factor for uncontrolled asthma, IOS is seldom used clinically.

OBJECTIVE

To identify clinical characteristics that can best identify the PAI phenotype.

METHODS

Clinical characteristics and spirometry results were compared in 227 patients with asthma with the PAI phenotype determined by resistance and reactance values that exceeded IOS‑predictive normal values using Gochicoa-Rangel equations. Logistic regression analyses determined factors associated with PAI phenotype, with risk classification based on predicted probability from the final adjusted model.

RESULTS

Analysis for identifying PAI, present in 37% of our population, revealed statistically significant odds ratio (OR) for age (4-7 years), of 3.75 (1.47-9.55) (P = .006), obesity OR of 2.59 (1.36-4.96) (P = .004), uncontrolled asthma OR of 2.77 (1.34-5.74) (P = .006), and abnormal forced expiratory flow between 25% and 75% (FEF25%-75%) (<65%) OR of 4.22 (1.59-11.20) (P = .004). For identifying PAI in those considered well controlled, key characteristics were age (4-7 years), OR of 2.81 (1.10-7.18) (P = .03), and obesity, OR of 2.18 (1.09-4.39) (P = .03). For those 4 to 7 years old, who were obese and had uncontrolled disease, probability of PAI was greater than or equal to 80%, regardless of FEF 25%-75%. Probabilities from logistic regression analyses to identify PAI were associated with an area under the curve of 0.750, and applying standard threshold of greater than or equal to 0.50 probability for identification produced sensitivity at 49.4%, specificity at 85.3%, positive predictive value at 66.1%, negative predictive value at 74.4%, and accuracy at 72.1%.

CONCLUSION

Clinical characteristics of age at 4 to 7 years, obesity, uncontrolled asthma, and FEF 25%-75% (<65%) identify PAI with high specificity and accuracy. This approach offers the clinician a practical method for strongly considering the presence of PAI when IOS is not available.

External validation can provide the clinician with IOS equations that best predict the risk of uncontrolled asthma in their population

BACKGROUND

Peripheral airway impairment (PAI) has been shown to have a close association to risk of uncontrolled asthma in children. However, clear methods have not been established for the clinician to select impulse oscillometry (IOS) reference equations best suited for their population. Our study aimed to develop a practical external validation analytic approach for the clinician to determine which of the available reference equations best predicts uncontrolled asthma for their patients.

METHODS

This is a post hoc analyses of data collected at baseline in a randomized controlled study that occurred from March 2016 to 2018. The study population consisted of 227 children, ages 4-18 years, with moderate to severe asthma. Discrimination and calibration predictive performance of available and suitable IOS equations were assessed by using uncontrolled asthma as the criterion outcome. Discrimination statistics of accuracy, sensitivity, and specificity served as the primary performance indicators. Rank scores were determined by the number of acceptable limit thresholds met for these measures (≥60%, ≥50%, and ≥60%, respectively) across IOS metrics (R5, R5-R20, AX, and X5) resulting in a total possible score of 12.

RESULTS

External validity assessment determined the rank order of best to worst equations as being Gochicoa-Rangel (rank score = 10) > Nowowiejska (rank score = 9) > Assumapcao (rank score = 6) > Amra (rank score = 2). Gochicoa-Rangel reference equations provided the best option for universal application with accuracy of 73.1%, 72.2%, 76.7%, and 66.2% for R5, R5-R20, AX, and X5, respectively.

CONCLUSIONS

External validation, particularly discrimination in asthmatic children, offers the clinician a practical approach to selecting the most suitable predictive equations for their patients.

Oropharyngeal obstruction and respiratory system compliance are linked to ventilatory control parameters in pediatric obstructive sleep apnea syndrome

Instable ventilatory control is an endotypic trait of obstructive sleep apnea syndrome (OSAS). This study aimed to evaluate the relationships between the anatomical compromise of the upper (oro- and naso-pharynx) and lower airways and ventilatory control (measured by chemical loop gain) in otherwise healthy children suffering from moderate to severe OSAS (apnea hypopnea index ≥ 5/hour). The children underwent ear, nose and throat examination, measurement of impedance of the respiratory system that allowed characterizing peripheral lung mechanics using the extended Resistance-Inertance-Compliance model. Physiologically constrained analytical model based on tidal breathing analysis allowed for the computation of steady-state plant gain, steady-state controller gain (CG0) and steady-state loop gain (LG0). Medium-frequency components of the feedback control system were then deduced. Fifty children (median age 11.2 years) were enrolled. Oropharyngeal obstruction was associated with decreased CG0 (0.6 [0.2; 1.0] vs 1.5 [0.5; 6.6] L.s^- 1.mmHg^- 1, p = 0.038) and LG0 (0.4 [0.2; 1.1] vs 1.2 [0.4; 9.3], p = 0.027), while nasal obstruction did not modify ventilatory control parameters. In a multivariate analysis Medium-Frequency PG was negatively related to minute ventilation and respiratory system compliance. Both upper (tonsil hypertrophy) and lower (compliance of respiratory system) airways are linked to ventilatory control in children with moderate to severe OSAS.

Reference values for respiratory sinusoidal oscillometry in children aged 3 to 17 years

BACKGROUND

New oscillometry devices allowing quantification of respiratory function using tidal breathing are commercially available, but reference equations are lacking for the multiethnic Canadian pediatric population.

METHODS

We conducted a prospective cross-sectional study of healthy children carefully selected for absence of asthma, atopy, tobacco smoke, obesity, prematurity, and recent respiratory infection. Triplicate measures were obtained of respiratory system resistance (Rrs) and reactance (Xrs), area under the reactance curve (AX) and resonant frequency (Fres) on four signals, whose testing order was randomized: two signals on the Resmon Pro Full (8 Hz and 5-11-19 Hz) and two signals on the tremoflo C-100 (5-37 Hz and 7-41 Hz). Feasibility was defined as the ability to obtain valid reproducible results. Prediction equations and 95% confidence intervals were derived for whole- and within-breath Rrs and Xrs and for AX and Fres, using linear regression or Generalized Additive Models for Location, Scale and Shape.

RESULTS

Of 306 children randomized, valid and reproducible results on ≥1 signal were obtained in 299 (98%) multiethnic (69% Caucasians: 8% Black: 23% Others) children aged 3-17 years, 91-189 cm tall. Standing height was the strongest predictor with no significant effect of sex, age, body mass index or ethnicity. Significant within-patient differences were observed between Resmon Pro and tremoflo C-100 measurements, justifying the derivation of device-specific reference equations.

CONCLUSION

Valid reproducible oscillometry measurements are highly feasible in children aged 3 years and older. Device-specific reference equations, valid for our multiethnic population, are derived.

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.

Impulse Oscillometry System for the Diagnosis of Wheezing Episode in Children in Office Practice

Background and Objective

Objectively differentiating between wheezing episodes and other respiratory disorders will be helpful in treatment in office practice. The impulse oscillometry system has been useful in assessing airway resistance in children 3–6 years old. As the reference values are different in geographical regions the use of the impulse oscillometry is still limited. Comparison between the percent change in IOS parameters as compared to reference standards and changes in actual IOS parameters was done to diagnose wheezing episodes.

Methodology

Three to six years old children with a history of fever, cough, cold, and/or breathlessness with noisy breathing and who were not on any regular medications, whose parents gave consent were recruited in the study. The children underwent an impulse oscillometry system examination as per the guidelines. The test was repeated after they were given nebulization by salbutamol (2.5 mg) (before COVID 19 pandemic). Final diagnosis was done by following patients for 7 days.

Results

About 106 children were recruited in the study. Five children could not perform the IOS test. Eighteen children did not complete the follow-up. Hence, 83 children were analyzed. There were 47 males and 36 female patients. The change in actual values of AX, R5, and X20 showed statistically significant difference in wheezing episode group (p-value<0.001). The percentage change as compared to predicted values of R5 and X20 also showed a statistically significant difference in the wheezing episode group and the others group (p-value<0.001).

Conclusion

The change in actual values of AX, R5, X20, and resonant frequency may help to differentiate wheezing episode from other respiratory diseases.

Lung Function in Preschool Children in Low and Middle Income Countries: An Under-Represented Potential Tool to Strengthen Child Health

BACKGROUND

The burden of respiratory disease is high in low-middle income countries (LMIC). Pulmonary function tests are useful as an objective measure of lung health and to track progression. Spirometry is the commonest test, but its use is limited in preschool children. Other lung function methods have been developed but their use in LMIC has not been well described.

AIM

To review the use of preschool lung function testing in children in LMIC, with particular reference to feasibility and clinical applications.

METHODS

Electronic databases "PubMed", "Scopus"," Web of Science", and "EBSCO host" were searched for publications in low and middle income countries on preschool lung function testing, including spirometry, fractional exhaled nitric oxide (FeNO), oscillometry, interrupter technique, tidal breathing and multiple breath washout (MBW), from 1 January 2011 to 31 January 2022. Papers in English were included and those including only children ≥6 years were excluded.

RESULT

A total of 61 papers from LMIC in Asia, South America, Africa, Eurasia or the Middle East were included. Of these, 40 included spirometry, 7 FeNO, 15 oscillometry, 2 interrupter technique, and 2 tidal breathing. The papers covered test feasibility (19/61), clinical application (46/61) or epidemiological studies (13/61). Lung function testing was successful in preschool children from LMIC. Spirometry was the most technically demanding and success gradually increased with age.

CONCLUSION

Preschool lung function testing is under-represented in LMIC for the burden of respiratory disease. These tests have the potential to strengthen respiratory care in LMIC, however access needs to be improved.

Impulse oscillometry indices to detect an abnormal lung clearance index in childhood cystic fibrosis

The objective of our cross-sectional study was to assess the relationships between indices of multiple breath washout (MBW) and impulse oscillometry system (IOS) in cystic fibrosis in forty consecutive children (median age 8.1 years) in stable conditions and to evaluate whether cut-off values of IOS indices may help to avoid MBW, which is time-consuming. IOS measurements took a median duration of 3 min, while MBW measurements took a median duration of 49 min. Lung Clearance Index (LCI_2.5% ) depicted significant linear correlations with z-scores of R5Hz, R5-20Hz, X5Hz, AX, and Fres (r²  = 0.27 to 0.51). Receiver-operator characteristic curves were constructed and showed that the best compromise was obtained with the z-score of Fres, with a cut-off value of -1.37 that had a sensitivity of 0.966, a specificity of 0.636, and a negative predictive value of 0.875. This z-score is useful for excluding increased LCI_2.5% when below -1.37 using the reference set of Gochicoa et al. In conclusion, IOS measurement is easily and rapidly obtained in children and may be clinically useful for excluding increased LCI_2.5% , thus allowing the time-consuming MBW test to be avoided.

Respiratory function in children with nephrotic syndrome: Comparative evaluation of impulse oscillometry and spirometry

AIM

To evaluate the respiratory functions of children with nephrotic syndrome (NS) by impulse oscillometry (IOS) and its correlation with spirometry.

METHODS

Fifty-five NS patients aged 3-18 years were included as the study group and 40 healthy children of the same age formed the control group. Patients were divided into nephrotic phase (first attack and relapse) and remission. Demographic, anthropometric, and laboratory data of the children were recorded. Respiratory functions were evaluated by IOS and spirometry. Children over 6-years old performed both IOS and spirometry while children under 6 years performed only IOS.

RESULTS

The R (R5%, R10%, R5-20), AX and Z5% values of IOS in patients with nephrotic phase were higher than remission patients and control group while spirometry indices of PEF% and MEF25-75% were lower. Z scores of MEF25-75 were significantly negatively correlated with z scores of R5, R10, Z5, and Fres while they were significantly positively correlated with z scores of X values (5, 10, 15, and 20 Hz). Z scores of forced expiratory volume in 1 /forced vital capacity significantly negatively correlated with z scores of R values (R5, R10), Z5 and AX and positively correlated with z scores of X values (X5, X10, X15 Hz).

CONCLUSION

Our study demonstrated that respiratory functions measured by IOS and spirometry were affected at the time of nephrotic phase in NS patients. IOS, a novel method easily applicable even in small children, is a potentially valuable tool to detect this condition; given its good correlation with spirometry.

Peripheral Airway Impairment and Dysanapsis Define Risk of Uncontrolled Asthma in Obese Asthmatic Children

BACKGROUND

Factors that determine the relationship between obesity and poor outcomes in asthmatic children are not well understood. Dysanapsis and peripheral airway impairment (PAI) could provide an explanation in the obese asthmatic patient.

OBJECTIVES

To determine the effect of obesity on increased dysanapsis and PAI and establish the effect of obesity, dysanapsis, and PAI on increased risk of uncontrolled asthma.

METHODS

We evaluated 206 children with moderate to severe asthma, aged 4-18 years, to determine the relationship of body mass index (BMI) to increased dysanapsis and PAI, using reference values. We examined the probability of obesity, dysanapsis, and PAI increasing the risk of uncontrolled asthma by BMI categorically and BMI z scores using generalized linear model analyses.

RESULTS

Compared with normal-weight children, overweight and obese children had increased forced vital capacity % predicted and obesity increased odds of dysanapsis by 2.32 (P = .04), while PAI showed an age-dependent effect, with increased odds of 2.09 for children younger than 12 years (P = .08) and 54.14 for those 12 years and older (P = .003). For each unit increase in BMI z score, there was an increased odds ratio of 1.57 for dysanapsis (P = .009), greater in males, OR of 3.10, P = .009, and of 1.39 for PAI for those younger than 12 years (P = .042) and of 4.60 for those 12 years and older (P = .002). Obesity's relationship to uncontrolled asthma was indirect, as not significant when adjusted for the direct effect of dysanapsis and PAI, which were highly significant predictors, with increased odds of 28.01 for dysanapsis for those younger than 12 years (P < .001) and of 3.09 for PAI (P = .005).

CONCLUSIONS

Overweight and obesity significantly increase odds of dysanapsis and PAI, in an age and gender-specific manner, increasing the probability of uncontrolled asthma.

Reference values of respiratory impedance with impulse oscillometry in healthy Chinese adults

Background

Impulse oscillometry (IO) is a non-invasive pulmonary function test for measuring respiratory impedance. Available reference equations of IO indices for adults are limited. The aim of this study was to develop reference equations of IO indices for Chinese adults.

Methods

In a multicentral, cross-sessional study of IO in Chinese adults, IO data from healthy subjects were collected from 19 general hospitals across China between 2016 and 2018. Oscillometry measurements were conducted in accordance with recommendations of the European Respiratory Society (ERS). Multiple linear regression was performed to develop sex-specific reference equations of IO indices.

Results

IO measurements were performed in 1,318 subjects, of which 567 subjects were defined as healthy individuals with acceptable IO data and were included in the final analysis. Reference equations and limits of normal [lower limit of normal (LLN)/upper limit of normal (ULN)] of IO indices were developed separately for males and females. Height but not age was shown to be the most influential contributor to IO indices. The reference equations currently used in lung function laboratories predicted higher R5 and X5. Normal ranges of R5 and X5 recommended by the equipment manufacturer were clearly different from the ULN/LLN derived from the reference equations.

Conclusions

Reference equations of IO indices for Chinese adults from a wide region were provided in this study. It is necessary to update new IO reference equations and adopt ULN/LLN as normal ranges of IO indices.

Trial Registration

This study was registered at www.clinicaltrials.gov as part of a larger study NCT03467880.

Assessment of airway reversibility in asthmatic children using forced oscillation technique - A single-center experience from North India

Background:

Lung function testing is recommended for the management of asthma. Due to certain limitations of conventional spirometry in vulnerable patients, forced oscillation technique (FOT) has been studied with promising results. As there is a paucity of data from developing world, we planned to conduct this study in children using FOT. To assess airway reversibility after inhaled salbutamol in asymptomatic children with suspected asthma.

Settings:

This study was conducted at pediatric asthma clinic of a tertiary care referral hospital in North India.

Design:

This was a prospective interventional study over 1-year period.

Subjects and Methods:

Asymptomatic children between 2 and 18 years of age, with history suggestive of asthma, were eligible for participation. Baseline and postbronchodilator pulmonary functions were assessed using FOT. Airway resistance and reactance were monitored at various frequencies. SPSS version 17 was used for statistical analysis.

Results:

Among the 345 enrolled children, baseline mean ± standard deviation total airway resistance (R₅), central airway resistance (R₁₉), peripheral airway resistance (R₅–R₁₉), reactance (X₅), and resonant frequency (Fres) were 6.85 ± 2.60, 5.23 ± 1.93, 1.6 ± 1.16, and − 2.54 ± 1.36 cmH₂O/L/s and 17.28 ± 3.06 Hz. The median (interquartile range) percentage change after inhaled salbutamol was 19.9 (11.40, 29.12), 22.86 (6.88, 38.76), 14.08 (3.40, 22.62), 39.20 (8.20, 62.39), and 15.79 (8.33, 27.27) in respective parameters. All changes were statistically significant. The studied respiratory variables were in maximum negative correlation with height, followed by body mass index.

Conclusions:

FOT is a simple technique for monitoring lung functions in children during asthma management.

Assessment of pulmonary function by impulse oscillometry and spirometry in children with type 1 diabetes mellitus

AIM

To assess the lung functions with impulse oscillometry (IOS) and spirometry in children with type 1 diabetes mellitus (T1DM).

METHODS

Fifty-one children with T1DM, and sex- and age-matched 53 healthy control (HC) subjects were included in this study. Demographic, clinical, and laboratory characteristics of the subjects were recorded and their pulmonary functions were analyzed by IOS and spirometry.

RESULTS

In IOS, zR5, zR10, and zR20 levels were higher in children with T1DM compared with HCs (P = .019, P = .017, and P = .002, respectively). In spirometry, zFEF75 and zFEF25-75 were lower in children with T1DM compared with HCs (P = .025, P = .001, respectively). In IOS, zR5-20 (P = .008, P = .005, respectively) and zAX (P = .013, P = .009, respectively) were significantly lower in good-controlled group compared with moderate- and poor-controlled group. In spirometry, zFEF25-75 was significantly higher in good-controlled group compared with moderate- and poor-controlled group (P = .005, P = .009, respectively). HbA1c was positively correlated with zR5-20 value (r = .339; P = .017) in male children with T1DM. The duration of the disease was positively correlated with zR5-20 (r = .290; P = .043) and zFres (r = .358; P = .010). According to the receiver operating characteristic curve analysis to estimate optimal cut-offs to discriminate good control level of T1DM (HbA1c < 7%), a zR5-20 ≤ 2.28 demonstrated a 75.0% sensitivity and 82.9% specificity, with an area under the curve of 0.805 ([confidence interval, 0.615-0.995]; P = .007).

CONCLUSIONS

This study showed subclinical impairment of lung functions which is associated with disease duration and the degree of metabolic control in children with T1DM.

Reference equations for parameters of impulse oscillometry in Egyptian children and adolescents

Background

Impulse oscillometry (IOS) is important in diagnosing respiratory functions in non-cooperative children. Studies are rising nowadays to establish reliable reference values of IOS for children of different ethnicities. No available data about the regression equations for parameters of IOS for Egyptian children and adolescents. So, our study aimed to develop regression equations for parameters of IOS in Egyptian children and adolescents in relation to their age, weight, height, and body mass index.

Results

Height and age affected the regression equation of impedance at 5 Hz (Z5 Hz) and resistance at 5 Hz (R5 Hz) in both males and females, resistance at 20 Hz (R20 Hz) in males and reactance at 5 Hz (X5 Hz) in females. Height affected the regression equation of R20 Hz in females, resonant frequency (Fres) in males, and the area of reactance (AX) in both males and females. While age affected the equation of X5 Hz in males and Fres in males.

Conclusions

Height and age were the most predictive values affecting the regression equation of IOS in Egyptian children and adolescents.

Standardized IOS Reference Values Define Peripheral Airway Impairment-Associated Uncontrolled Asthma Risk Across Ethnicity in Children

BACKGROUND

Although clinically useful in identifying peripheral airway impairment (PAI), impulse oscillometry (IOS) has not received universal acceptance. This may be due to variable cutoff points, and the perception that available standardized reference values may not be clinically relevant in all populations.

OBJECTIVE

To establish the relationship between PAI, based on standardized IOS reference values, and uncontrolled asthma as well as interchangeability between Hispanic and white reference algorithms.

METHODS

IOS reference values were established for upper and lower limits of normal (>95th and <5th percentile, respectively) using published algorithms in Hispanic and white children. Values exceeding normal limits (PAI) were compared in those uncontrolled and controlled for significance of differences. Probability estimates and odds ratio of uncontrolled asthma were determined for R5, R5-R20, AX, and X5 using adjusted generalized estimating equation analyses. Intraclass correlation coefficients determined interchangeability of Hispanic and white reference algorithm values.

RESULTS

Those with uncontrolled asthma had significantly greater PAI and a higher frequency of PAI than those well controlled (P < .05), whereas odds of uncontrolled asthma increased with increasing PAI (P < .001) for all IOS measures, particularly for X5, where odds ratios ranged from 2.70 to 11.01.There was good to excellent (>70%) agreement between Hispanic and white algorithms, except for R5-R20 (<70%).

CONCLUSIONS

PAI, defined by IOS reference values, not central airway markers (R20), is consistently related to the risk of uncontrolled asthma. This is true whether using Hispanic or white reference algorithms. Thus, standardized reference values in children offer the clinician readily available IOS cutoff points that are clinically relevant across ethnicity.

Regression Equations of Respiratory Impedance Measured by Forced Oscillation Technique for Indian Children

OBJECTIVE

To develop regression equations of within and whole-breath respiratory impedance for Indian children aged 5 to 17 y.

METHODS

A prospective cross-sectional study was carried out in 5 to 17 y old school children of Bhopal, India. Healthy children were identified by physical examination and by administering questionnaire. The respiratory system resistance (Rrs) and reactance (Xrs) were measured at frequency of 5, 11, and 19 Hz by forced oscillation technique (FOT). The regression equations of within and whole-breath Rrs and Xrs were developed separately for boys and girls by multiple linear regression models.

RESULTS

Total 336 children were recruited and data of 320 healthy children (boys - 159), standing height of 146.1 ± 16.6 cm and body mass index of 17.2 ± 2.9 kg/m² were included in the analysis. The mean respiratory system resistance at 5 Hz (R5) and respiratory system reactance at 5 Hz (X5) of the children, irrespective of gender were 5.46 ± 2.10 cmH₂O/L/s and - 1.43 ± 0.85 cmH₂O/L/s respectively. Boys of age 16 y and older had significantly smaller Rrs as compared to girls of corresponding age (p < 0.05). The standing height of children had the highest predictive power, followed by age in the regression model. With an increase in standing height, the magnitude of both Rrs and Xrs values of children decrease. The bodyweight of children had a negligible contribution to the regression models.

CONCLUSIONS

The regression equations of within- and whole-breath Rrs and Xrs of Indian children aged 5 to 17 y are presented for the first time. The R5 values of Indian children were comparable to children of other ethnicities.

Technical standards for respiratory oscillometry

Oscillometry (also known as the forced oscillation technique) measures the mechanical properties of the respiratory system (upper and intrathoracic airways, lung tissue and chest wall) during quiet tidal breathing, by the application of an oscillating pressure signal (input or forcing signal), most commonly at the mouth. With increased clinical and research use, it is critical that all technical details of the hardware design, signal processing and analyses, and testing protocols are transparent and clearly reported to allow standardisation, comparison and replication of clinical and research studies. Because of this need, an update of the 2003 European Respiratory Society (ERS) technical standards document was produced by an ERS task force of experts who are active in clinical oscillometry research.The aim of the task force was to provide technical recommendations regarding oscillometry measurement including hardware, software, testing protocols and quality control.The main changes in this update, compared with the 2003 ERS task force document are 1) new quality control procedures which reflect use of "within-breath" analysis, and methods of handling artefacts; 2) recommendation to disclose signal processing, quality control, artefact handling and breathing protocols (e.g. number and duration of acquisitions) in reports and publications to allow comparability and replication between devices and laboratories; 3) a summary review of new data to support threshold values for bronchodilator and bronchial challenge tests; and 4) updated list of predicted impedance values in adults and children.

Impulse oscillometry reference values and bronchodilator response in three- to five-year old children living at high altitude

Introduction

Impulse oscillometry (IOS) is used to measure airway impedance. It is an effective tool for diagnosing and treating respiratory diseases, and it has the advantage that it does not require forced respiratory maneuvers. IOS reference values are required for each population group.

Objective

This study aimed to determine the IOS reference values and bronchodilator response in healthy preschool children living in Bogotá, Colombia.

Methods

We performed a cross-sectional study in preschool children who had no history of respiratory disease; 96 children fit the parameters for testing to determine normal values according to the American Thoracic Society and European Respiratory Society criteria.

Results

Values for respiratory resistance (Rrs) and reactance (Xrs) at 5, 10, and 20 Hz, respiratory impedance (Zrs, and resonance frequency (Fres) were established. Height was the most influential independent variable for IOS values; an increase in height led to a reduction in Rrs5 and Rrs20 and an increase in Xrs5. After the administration of 400 mcg of salbutamol the values for Rrs5(−17.48%), Rrs20(−8.63%), Fres (−10.68%), and area of reactance (−35.44%) were reduced, meanwhile Xrs5 (15.35%) was increased.

Conclusions

Normal IOS values before and after the administration of 400 mcg of salbutamol were determined for a population of children aged 3–5 years at 2,640 m. Reference IOS equations for these children are presented. A relative change of up to −28% and 36% after the use of salbutamol for respiratory resistance and reactance, respectively, should be considered as an upper limit of the normal range, and possible appropriate cut-off values for defining significant response for evaluating therapeutic interventions.

Virus-Induced Asthma/Wheeze in Preschool Children: Longitudinal Assessment of Airflow Limitation Using Impulse Oscillometry

: Several researchers have assessed the utility of Impulse Oscillometry System (IOS) in diagnosing and evaluating the severity of respiratory diseases in childhood, but none has investigated the impact of the fluctuations of IOS parameters in an individualized manner. In this two-year prospective study, we aimed to longitudinally evaluate changes in airflow limitation and bronchodilator responsiveness in steroid-naïve four- to six-year-old children during a virus-induced wheezing episode, with IOS pulmonary resistance parameters set at 5 (R5) and 20 (R20) Hz. Moreover, feasibility and reproducibility, in addition to the diagnostic properties of these parameters were examined. Lung function was assessed every six weeks (baseline), within the first 48 hours following an acute wheezing episode (Day 0), after 10, and after 30 days. Forty-three out of 93 recruited children (4.5 ± 0.4 years old) experienced a wheezing episode during the study period. All children were able to perform the IOS effort in an acceptable and highly reproducible manner. R5 and R20 fluctuated independently of atopy, age, height, and weight. On Day 0, R5 values were significantly lower than the respective baseline values and returned to individual baseline levels within 10 days. Post-bronchodilation R5 values were similar to the baseline ones, reflecting a reversible airway obstruction on Day 0. Response to bronchodilation (ΔR5) was significantly more pronounced on Day 0. ΔR5 values lower than -20.5% had a sensitivity of 70% and a specificity of 76% and could accurately identify up to 75% of the examined preschoolers. This study provides evidence in favor of the objective utility of IOS as an easy, highly reproducible, and sensitive technique to assess clinically significant fluctuations and bronchodilation responses suggestive of airflow limitation. Reference values although necessary are suboptimal, utilizing the personal best values as personal reference is useful and reliable.

Impulse oscillometry in the assessment of children's lung function

PURPOSE

To review available evidence in the literature on impulse oscillometry in the assessment of lung function in children with respiratory diseases, especially asthma.

DATA COLLECTION

Research in the Medline, PubMed, and Lilacs databases, with the keywords forced oscillation, impulse oscillometry, asthma and impulse oscillometry.

RESULTS

The Impulse Oscillometry System (IOS) allows the measurement of resistance and reactance of airways and is used as a diagnostic resource. A significant association between the findings of the IOS and those of spirometry is observed. In asthma, the IOS has already been used to assess the bronchodilator response and the therapeutic response to different drugs and has shown to be a sensitive technique to evaluate disease control. There are limitations to this assessment, such as children with attention deficit and in some cases it is difficult to interpret the results from a clinical point of view.

CONCLUSION

The IOS is a useful tool for the measurement of the lung function of children. It is an easy test, although its interpretation is not straightforward.

Recognition of the peripheral airway impairment phenotype in children with well-controlled asthma

BACKGROUND

Peripheral airway impairment, although frequently unrecognized, is a risk factor for poor asthma control, loss of control, increased exacerbations, airway hyperresponsiveness, and loss of lung function with age, even in patients with well-controlled asthma.

OBJECTIVE

To determine the presence of peripheral airway impairment by impulse oscillometry and forced expiratory flow between 25% and 75% (FEF_25%-75%) in children whose asthma is well controlled by National Asthma Education and Prevention Program (NAEPP) guidelines.

METHODS

In this retrospective, cross-sectional analysis, outcomes were evaluated across 192 encounters in 139 patients with moderate to severe asthma, ages 4-18 years. Receiver operator characteristic curves were created and oscillometry thresholds determined by maximizing the sum of sensitivity and specificity to identify those whose condition is not well controlled. Impairment was then identified for those whose condition was well controlled when these age-dependent oscillometry thresholds were met for each IOS measure or FEF_25%-75% < 65% of predicted.

RESULTS

Reactance at 5 Hz (X5) appeared most robust to identify peripheral airway impairment. In 96 well-controlled asthma encounters, impairment was identified by X5 in approximately 20% and 45% for those younger than 12 years and adolescents, respectively, compared with a maximum of 10% with FEF_25%-75% in the adolescent cohort (P < .05).

CONCLUSION

We conclude that peripheral airway impairment, determined by oscillometry, is common in patients with well-controlled asthma across age cohorts. X5 with optimal cut points ≤ -3.8, ≤ -2.5, and ≤ -1.5 cmH₂O/L/s for ages 4-7, 8-11, and >12 years, provides the clinician with a practical tool to identify the presence of the peripheral airway impairment phenotype that is consistently superior to FEF_25%-75%. This recognition, if confirmed, may reduce the risk of asthma-associated consequences with earlier and more targeted therapy.

Impulse oscillometry and obesity in children

OBJECTIVE

To compare impulse oscillometry system parameters of normal-weight children with overweight and obese children.

METHOD

All participants were submitted to the evaluation of lung function (spirometry and impulse oscillometry) following the American Thoracic Society standards. The evaluation of respiratory mechanics was performed using the Jaeger™ MasterScreen™ Impulse Oscillometry System (Erich Jaeger, Germany), three tests were recorded, with acquisition for at least 20seconds.

RESULTS

The study included 81 children (30 in the control group, 21 in the overweight group, and 30 the in obesity group), matched for age and sex. Regarding spirometry data, obesity group showed higher numerical values in relation to the control group; however, there were no significant differences among the three groups. For impulse oscillometry parameters, there was a difference between control group and obesity group for respiratory impedance (p=0.036), resistance at 5hertz (p=0.026), resonant frequency (p=0.029), and reactance area (p=0.014). For the parameters expressed in percentage of predicted, there were differences in resistance at 5 hertz, resonant frequency, and reactance area between control group and obesity group.

CONCLUSIONS

Obese children showed increased oscillometry parameters values representative of airway obstruction, compared to normal-weight children. Changes in some oscillometry parameters can already be observed in overweight school-aged children.

Respiratory impedance is correlated with airway narrowing in asthma using three-dimensional computed tomography

BACKGROUND

Respiratory impedance comprises the resistance and reactance of the respiratory system and can provide detailed information on respiratory function. However, details of the relationship between impedance and morphological airway changes in asthma are unknown.

OBJECTIVE

We aimed to evaluate the correlation between imaging-based airway changes and respiratory impedance in patients with asthma.

METHODS

Respiratory impedance and spirometric data were evaluated in 72 patients with asthma and 29 reference subjects. We measured the intraluminal area (Ai) and wall thickness (WT) of third- to sixth-generation bronchi using three-dimensional computed tomographic analyses, and values were adjusted by body surface area (BSA, Ai/BSA, and WT/the square root (√) of BSA).

RESULTS

Asthma patients had significantly increased respiratory impedance, decreased Ai/BSA, and increased WT/√BSA, as was the case in those without airflow limitation as assessed by spirometry. Ai/BSA was inversely correlated with respiratory resistance at 5 Hz (R5) and 20 Hz (R20). R20 had a stronger correlation with Ai/BSA than did R5. Ai/BSA was positively correlated with forced expiratory volume in 1 second/forced vital capacity ratio, percentage predicted forced expiratory volume in 1 second, and percentage predicted mid-expiratory flow. WT/√BSA had no significant correlation with spirometry or respiratory impedance.

CONCLUSIONS & CLINICAL RELEVANCE

Respiratory resistance is associated with airway narrowing.

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.

Small airway oscillometry indices: Repeatability and bronchodilator responsiveness in young children

INTRODUCTION

The impulse oscillometry (IOS) indices absolute and relative difference between respiratory resistance at 5 and 20 Hz (R5-20 and R5-20%, respectively) and the area under the reactance curve (AX) are postulated to reflect small airway function. Data on their cutoff values to evaluate bronchodilator responsiveness (BDR) or between-visit changes after interventions are limited in young children.

METHODS

We evaluated the BDR of 103 healthy children aged 2-7 years, who received either salbutamol (n = 84) or placebo (n = 19) in order to determine cutoff values for BDR of R5-20, R5-20%, and AX. We then determined the repeatability within and between two IOS measurements 7-14 days apart in young children aged 4-8 years with asthmatic symptoms (n = 43), including cutoff values for significant between-visit changes.

RESULTS

The investigated IOS parameters showed marked BDR (fifth percentile cutoff of 75-110% of the baseline value) in healthy children, whereas no significant changes were seen after inhalation of placebo. The agreement within the triplicate IOS measurement was excellent (ICC > 0.80), and the agreement of results between visits was good (ICC > 0.60). A change in R5-20, R5-20%, and AX of 0.65, 1.08, and 0.84 z-scores, respectively, would exceed 95% confidence intervals for between-visit variability.

CONCLUSION

We introduce cutoff values for BDR of R5-20, R5-20%, and AX, and their repeatability indices and cutoff limits for significant between-visit changes. These IOS parameters may show greater variability than the conventional IOS indices during follow-up, but the between-visit agreement remains good, providing potentially useful endpoints for monitoring lung function in young children.

The case for impulse oscillometry in the management of asthma in children and adults

OBJECTIVE

To provide a clinical rationale for including impulse oscillometry (IOS) as a part of standard office-based asthma assessment.

DATA SOURCES

PubMed and Google search, limited to English language and human disease, with the keywords IOS and asthma.

STUDY SELECTIONS

Articles included in this review were based on the expert opinion and previous publications by the authors.

RESULTS

In children, IOS was more useful than spirometry in identifying asthma and uncontrolled asthma and predicting loss of control and exacerbations. IOS predicts young children at risk for loss of lung function with age and the potential for early intervention to prevent further sequelae. In adults, peripheral airway impairment detected by IOS or spirometry (ie, forced expiratory flow between 25% and 75%) commonly occurs across severity, and each measure may be complementary in predicting loss of control even with normal forced expiratory volume in 1 second. Extrafine inhaled corticosteroids with or without long-acting β-agonists proved superior to standard particle aerosols in improving IOS-detected peripheral airway obstruction. Our data also suggest that currently available commercial reference values for lung resistance at 5 Hz and lung reactance at 5 Hz are applicable across diverse populations, but further studies are needed.

CONCLUSION

The findings of this review suggest that IOS can add value to traditional clinical and spirometric assessment and thus improve management of asthma in children and adults, as well as have the potential to detect early dysfunction of the peripheral airways, which may result in better outcomes.

Sensitivity of newly defined impulse oscillometry indices in preschool children

INTRODUCTION

Early origins of chronic obstructive pulmonary disease have been recognized. Impulse oscillometry (IOS) is suitable for assessment of lung function also in preschool children, and some novel indices have been connected to assessment of small airway function. However, limited data exist on the sensitivity of these new indices to detect lung function deficits in young symptomatic children.

METHODS

IOS measurements of 103 healthy preschool children were evaluated to establish reference equations for the difference between respiratory resistance at 5 and 20 Hz (R5-20), the relative difference of R5-20 (R5-20%), and area under the reactance curve (AX). Thereafter, IOS results of children with late-onset troublesome lung symptoms (n = 20), a history of early wheeze (n = 37), or a history of bronchopulmonary dysplasia (BPD, n = 8) were compared to healthy children.

RESULTS

None of the patient groups differed from healthy regarding respiratory resistance at 5 Hz (R5), and only children with a history of BPD differed from healthy regarding respiratory reactance at 5 Hz (X5). In contrast, z-scores of R5-20, R5-20%, and AX were significantly higher in all patient groups than in healthy children (P < 0.001), showing improved sensitivity (20-55%) compared to R5 and X5 (5-6%).

CONCLUSION

R5-20, R5-20%, and AX are superior to conventional IOS parameters in distinguishing children with current or past lower respiratory tract symptoms from healthy, and may prove valuable for screening early lung function deficits. Pediatr Pulmonol. 2017;52:598-605. © 2016 Wiley Periodicals, Inc.