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 Table of Contents  
ORIGINAL ARTICLE
Year : 2013  |  Volume : 26  |  Issue : 2  |  Page : 151-158

Study on the use of impulse oscillometry in the evaluation of children with asthma


Department of Pediatrics, Menoufia Faculty of Medicine, Menoufia University, Menoufia, Egypt

Date of Submission09-Jul-2013
Date of Acceptance15-Jul-2013
Date of Web Publication31-Jan-2014

Correspondence Address:
Mohamed I Al-Ghndour
MB, BCh, Alsharkia-Dyarb Negm-Abu-Eid Port said st. 1st, floor 3
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1110-2098.126149

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  Abstract 

Objective
The aim of this study was to determine the use of impulse oscillometry in the evaluation of children with asthma and to analyze lung parameters, order effect, and utility, compared with spirometry.
Background
Asthma is a disease characterized by ongoing inflammation of the airway, overproduction of mucus, and airway constriction due to tightened muscles, which results in permanent structural changes in the lungs, a condition often called airway remodeling. In turn, these changes usually lead to accelerated declines in lung function, including irreversible decreases in airflow because of narrowed air passages. The Impulse Oscillometry System measures respiratory impedance using short pulses (impulses) of air pressure. Impulse oscillometry has been used with success to assess lung function in healthy and asthmatic children, as well as in adolescents.
Materials and methods
This case-control study was carried out on 66 children divided into two groups: group 1 included 46 children who were previously diagnosed as asthmatic, and group II (control group) included 20 children without a history of asthma. All studied children were subjected to full history taking; clinical evaluation, including general examination and local chest examination; pulmonary function testing; impulse oscillometry before and after spirometry. Pulmonary function testing (impulse oscillometry and spirometry) was repeated in group 1 after bronchodilator administration.
Results
Asthma prevalence was increased among children with a family history of atopy and among those with family members who smoked. Postbronchodilator impulse oscillometry results were significant, especially R5% and X5pred.-X5. Performing forced expiratory maneuvers during spirometry causes a marked decrease in lung function, detected using impulse oscillometry.
Conclusion
Impulse oscillometry is useful in the evaluation of children with asthma.

Keywords: Bronchodilator response, childhood asthma, impulse oscillometry, lung function, spirometry


How to cite this article:
El-Nemr FM, Al-Ghndour MI. Study on the use of impulse oscillometry in the evaluation of children with asthma. Menoufia Med J 2013;26:151-8

How to cite this URL:
El-Nemr FM, Al-Ghndour MI. Study on the use of impulse oscillometry in the evaluation of children with asthma. Menoufia Med J [serial online] 2013 [cited 2017 Oct 24];26:151-8. Available from: http://www.mmj.eg.net/text.asp?2013/26/2/151/126149


  Introduction Top


Asthma one of the most prevalent chronic childhood conditions and the most frequent cause of hospitalization among children [1] . Asthma is a disease characterized by ongoing inflammation of the airway, overproduction of mucus, and airway constriction due to tightened muscles, which results in permanent structural changes in the lungs, a condition often called airway remodeling. In turn, these changes usually lead to accelerated declines in lung function, including irreversible decreases in airflow due to narrowed air passages [2] . Persistent reductions in baseline airway function and increased airway responsiveness during childhood are associated with the development of asthma in adult life [3] . In children, as in adults, tests of airflow obstruction, airway responsiveness, and airway inflammation may provide support for a diagnosis of asthma [4] . The ability to objectively diagnose and assess the severity of asthma is crucial for the selection of appropriate therapy by the skilled provider for the management of pediatric asthma. Current guidelines recommended by the Expert Panel Report of the National Asthma Education and Prevention Program include the use of spirometry in 5-year-old children to determine airway obstruction and reversibility [5] . Although the use of spirometry to assess lung function is of great value, many studies have indicated that only 21% of medical practitioners use spirometry in the diagnosis of asthma in children [6] . This may be because of a number of factors, including lack of access to spirometry, difficulty in interpretation of results in a younger age group, and technical difficulties in performing spirometry among young and handicapped children, as it requires the performance of effort-dependent lung maneuvers [7] . In 1993, a system based on amodification of the forced oscillation technique, impulse oscillometry system, was introduced by Jaeger as a user-friendly, commercialized apparatus that could be used to measure respiratory system resistance (R) and reactance (X) at a number of frequencies [8] . Impulse oscillometry has been introduced as an alternative technique to assess lung function with particular application to younger children with asthma. This is because impulse oscillometry is noninvasive, easy to perform, and requires only minimal patient cooperation. Impulse oscillometry is based on the production of small pressure oscillations that are applied at the mouth and transmitted to the lungs, which in turn permits the measurement of the resistance and reactance to the impedance of the respiratory system during spontaneous quiet breathing, thus providing an indirect analysis of lung function [9] .


  Materials and methods Top


This study is a case-control study carried out at the Pediatric Department of Zagazig University Hospitals on children attending either the outpatient clinic, the emergency room, or admitted to the inpatient ward.

The children were classified into two groups: group 1 (case group) included 46 patients. All patients were previously diagnosed as being asthmatic. Children below the age of 5 years, children above the age of 15 years, and patients with localized wheezing, fever, or a history of cardiac, renal, or hepatic dysfunction were excluded from this study. Group 2 (control group) included 20 apparently healthy nonasthmatic children of the same age, sex, and socioeconomic status.

Children personal data, residence, socioeconomic status according to Fahmy and El Sherbini classification [10] were collected. Special habits of family members and a family history of asthma or atopy were taken into account. A modified American Thoracic Society symptom questionnaire (ATS-B) was administered before lung function testing to assess respiratory symptoms in the 12 months preceding the interview. On obtaining a positive response to four of five questions, a diagnosis of asthma was made by the physician [11] . Pulmonary function testing included impulse oscillometry before and after spirometry for both groups. In group I, pulmonary function measurements (impulse oscillometry and spirometry) were repeated 15 min after a bronchodilator (200 μg salbutamol) was administered through a spacer device.

A Jaeger Master Screen Impulse Oscillometry system (Jaeger Co., Wurzburg, Germany) was used. The system was calibrated with a single volume of air (3l) at different flow rates, which were verified with a reference resistance device. The machine was also calibrated for body temperature and pressure of saturated gas. The children used nose clips, and the parent or guardian gently held the sides of each child's face to decrease the shunt compliance of the cheeks. Multifrequency impulses were applied over a 30-s interval to the airway through the mouthpiece during tidal breathing. Pulmonary impedance was measured and reported as resistance (R), the energy required to propagate the pressure wave through the airway, and reactance (X), which reflects the viscoelastic properties of the respiratory system. The mean values of reactance and resistance were calculated at frequencies from 5 to 20 Hz, specifically R5%, R20%, and X5. Each observation consisted of an optimum of three reproducible maneuvers, which did not have artifacts caused by coughing, breath holding, swallowing, or vocalization. An average of three adequate measurements was analyzed and graphically represented.

A Jaeger Master Screen Spirometry system (Jaeger Co.) was used. This system was also calibrated for body temperature and pressure and volume of saturated gas, as per ATS standards. The children used nose clips and were coached through standard forced expiratory maneuvers. The child was encouraged to produce the greatest expiratory flow he/she was capable of. Each data set consisted of at least three reproducible attempts, with no more than six attempts made. If the operator determined that the effort was suboptimal or expiration could not be maintained until close to the residual volume, the test was discarded. The best effort was defined as the greatest sum of forced vital capacity (FVC) and forced expiratory volume during the first second (FEV 1 )and was used in statistical analysis.

Spirometry and impulse oscillometry were performed by one researcher who was trained in both procedures. All results were transferred onto an associated computer program, abstracted into spread sheets, and presented to the statistician, who analyzed the data among and within diagnostic criteria for statistical differences without bias.


  Results Top


In the current study, the majority of participants belonged to the age group of 8.28± 2.86 years, with a higher prevalence of asthma among boys. However, there was no statistically significant difference between patients and controls as regards sex, height, and weight. There was increased asthma prevalence in rural areas compared with urban areas, but with no statistically significant difference. In addition, there was increased asthma prevalence among children of low socioeconomic status, with a statistically significant difference. The majority of patients had a family history of atopy. In addition, increased asthma prevalence was reported among children who were subject to passive smoking. Most patients were diagnosed on the basis of assessments made through questionnaires administered to the parents, with a statistically significant difference.

Baseline measurements from spirometry and impulse oscillometry for both groups showed statistically significant differences in R5%, X5 predicted -X5, R5-R20%, FEV 1 %, and FEV 1 /FVC%, whereas they showed no statistically significant differences in R20% and FVC% between groups. Spirometry results before and after bronchodilator administration showed a statistically significant difference in FEV 1 % and FEV 1 /FVC%. Impulse oscillometry results before and after bronchodilator administration show a statistically significant difference in R5%, X5pred. -X5, and R5-R20%. In addition, impulse oscillometry results before and after spirometry showed a marked increase and statistically significant differences in R5%, X5 predicted -X5, and R5-R20%.


  Discussion Top


Asthma, one of the most prevalent chronic childhood conditions, is the most frequent cause of hospitalization among children [1] . It is a chronic inflammatory disorder of the airway, in which many cells and cellular elements play a role. Chronic inflammation causes an associated increase in airway hyper-responsiveness, which leads to recurrent episodes of wheezing, breathlessness, chest tightness, and coughing, particularly at night or early in the morning. These episodes are usually associated with widespread but variable airflow obstruction, which is often reversible either spontaneously or with treatment [12] . Impulse oscillometry has been introduced as an alternative technique to assess lung function, which is particularly applicable to younger children with asthma. This is because impulse oscillometry is noninvasive, easy to perform, and requires only minimal patient cooperation. Impulse oscillometry is based on the production of small pressure oscillations that are applied at the mouth and transmitted into the lungs, which in turn permits the measurement of the resistance and reactance to the impedance of the respiratory system during spontaneous quiet breathing, thus enabling indirect analysis of lung function [9] .

Our study was carried out at the Pediatrics Department of Zagazig University Hospitals on children attending either the outpatient clinic, the emergency room, or admitted to the inpatient ward. The study included 46 patients (31 boys and 15 girls) previously diagnosed as being asthmatic and 20 healthy control children (11 boys and nine girls); their ages ranged from 5 to 15 years, with mean ages of 8.28 ± 2.86 years among patients and 8.15 ± 2.52 years among controls.

Patients and controls were compared as regards the analysis of lung parameters and order effect, aiming at evaluating children with asthma using impulse oscillometry and addressing the concern that performing spirometry may cause transient bronchospasm.

In the current study, asthma was reported to be more common among boys than among girls (67.4 and 32.6%, respectively). These results were in concordance with the findings of Almgvist et al. [13] , who stated that boys have a higher prevalence of wheezing and asthma than girls. Hassane et al. [14] in their study reported that asthma was more common among boys than among girls.

In our study, asthma was more common among children living in rural areas (52.2%) compared with urban areas (47.8%). This is in agreement with the findings of Yawn [15] , who reported that the rural environment has a rich mixture of allergens from seasonal crops, abundant wildflower, weed growth, dust and animal dander in barns and soils, air pollution (e.g. ozone and methane gas from manure), and noxious odors from landfills, which are frequently located in rural areas. Among the Egyptian studies, Amer et al. [16] in their study found that asthma was more common in urban areas (60.2%) compared with rural areas (39.8%). In contrast, Shaaban et al. [17] reported that asthma was more in rural areas (62.2%) compared with urban areas (37.8%). However, Magdy et al. [18] did not find a significant difference in the prevalence of childhood asthma between urban and rural areas, which can be explained by the similarity in environmental conditions in both areas because of their close proximity to each other in the crowded Nile delta region.

In this study, the majority of asthmatic children had a positive family history of atopy (58.7%). This result was in accordance with the findings of El Saify et al. [19] , who reported that 58.5% of asthmatic children had a positive family history of atopy, as well as with those of Moustafa et al. [20] , who reported that 48.6% of asthmatic children had a positive family history of atopy. Al-Mousawi et al. [21] found that sensitization to allergens, a family history of asthma, and a history of whooping cough increased the risk for asthma.

In the current study, 63% of asthmatic children were exposed to passive smoke. This means that exposure to tobacco smoke is one of the most consistent risk factor in the development and exacerbation of asthma. This result is in accordance with the findings of Vagras et al. [22] , who found that environmental tobacco smoke exposure is associated with an increased use of the Emergency Department for acute asthma care.

In the current study, as regards the diagnosis of asthma on the basis of the ATS-B questionnaire, parental assessment of asthma correctly identified 76.1% of patients with asthma. This result is in accordance with the findings of Komarow et al. [23] , who stated, on the basis of a questionnaire, that parental assessment of asthma correctly identified 78% of patients with asthma. This finding is remarkably consistent with that on using the International Study of Asthma and Allergies in Childhood (ISAAC)-based questionnaire, administered to the parents of 6295 children aged between 1 and 6 years, in which parental assessment of asthma identified 77% of the children with asthma, thus highlighting the important consideration of parental appraisal of childhood asthma [24] .

In our study, the baseline measurements of spirometry for the control group were as follows: mean FEV1%, 93.20 (± 9.55 SD); mean FVC%, 95.10 (± 10.23 SD); and mean FEV1/FVC%, 97.80 (± 7.88 SD). Baseline measurements of impulse oscillometry for the control group were as follows: mean R5%, 108.95 (± 19.90 SD); mean R20%, 97.15 (± 9.95 SD); mean X5pred.-X5, 0.062 (± 0.058 SD); mean R5-R20%, 14.05 (± 16.86 SD). These results are similar to those of Ashmawi et al. [25] ; in their study, baseline spirometry measurements for the control group (including 25 participants: 23 boys and two girls) were as follows: mean FVC%, 97.98 (± 12.18 SD); mean FEV1%, 96.09 (± 10.07 SD); mean FEV1/FVC%, 82.79 (± 6.206 SD); and mean MMEF, 76.84 (± 22.64 SD). Baseline impulse oscillometry measurements in their study were as follows: mean R5%, 117.82 (± 23.57 SD); mean R20%, 120.96 (± 18.94 SD); and mean X5, −0.063 (± 0.162 SD).

In our study, the baseline spirometry measurements for patients were as follows: mean FEV1%, 67.19 (± 14.74 SD); mean FVC%, 93.17 (± 14.08 SD); and mean FEV1/FVC%, 71.17 (± 10.58 SD). Baseline impulse oscillometry measurements for patients were as follows: mean R5% (elevated), 201.11 (± 43.28 SD); mean R20%, 98.41 (± 12.48 SD); mean X5pred.-X5, 0.28 (± 0.13 SD); and mean R5-R20% 102.69 (± 42.60 SD). These results are in concordance with those of Olaguνbel et al. [26] , who assessed the baseline repeatability and bronchodilator response of impulse oscillometry indices in preschool children and their correlation with spirometry. The study reported a mean R5% of 196.60 (± 39.28 SD) and a mean R20% of 89.55 (± 18.28 SD). These results are not in accordance with the findings of Song et al. [27] , who investigated the correlation between impulse oscillometry and spirometry in 48 children with asthma. Our results were inconsistent with the findings of Farid et al. [28] as regards impulse oscillometry data: the mean R5% was high, being 303 (± 88 SD), and the mean R20% was also high, being 186.80 (± 50 SD).

In this study, on comparing patients with controls, highly statistically significant differences between the two groups were found as regards spirometry parameters, specifically FEV 1 % and FEV 1 /FVC%, being much lower patients compared with controls. However, there were no statistically significant differences between the two groups as regards FVC%. In the same context, as regards impulse oscillometry parameters, there were highly statistically significant differences between both groups as regards R5%, X5pred.-X5, and R5-R20%, being higher in patients compared with controls. However, there were nonsignificant statistical differences between the two groups as regards R20%. Thus, impulse oscillometry measurements (R5%, X5pred.-X5, and R5-R20%) were able to accurately discriminate asthmatic patients from controls. However, R20% was indistinguishable between the two groups. These results are in concordance with those of Cavalcanti et al. [29] , who in their study of 29 asthmatic patients and 24 healthy individuals to evaluate bronchodilator response by impulse oscillometry in healthy individuals compared with asthmatic patients found that resistance and reactance were higher in asthmatic patients than in controls. This result contradicts that of Marotta et al. [11] , who in their study found that there were nonsignificant statistical differences in R5% and X5 between asthmatic children and controls.

In the current study, on comparing response before and after bronchodilator administration in asthmatic children through spirometry parameters, a highly statistically significant difference between the degree of reversibility in FEV 1 % and FEV 1 /FVC% was found; however, the degree of reversibility in FVC% showed no statistically significant difference. The percentage increase in FEV 1 % after bronchodilator administration was 15%. These results are in concordance with the findings of Bussamra et al. [30] , who in their study on children with asthma for the evaluation of the magnitude of bronchodilator response concluded that cutoff values established for the assessment of bronchodilator response in asthmatic children were more than 12%, which represents a good bronchodilator response. Although there was no significant difference in the percent predicted values of FVC%, the percent predicted values of FEV 1 % and the FEV 1 /FVC% ratio were increased significantly in asthmatic children, representative of good reversibility after bronchodilator administration. These results are also in agreement with those of Zerah et al. [31] , who found a highly statistically significant increase in FEV 1 % and FEV 1 /FVC% among 22 asthmatic patients after inhalation of 200 μg salbutamol.

In the current study, comparing response before and after bronchodilator administration in asthmatic children using impulse oscillometry showed that there was a highly statistically significant difference in response as regards the degree of reversibility, represented by R5%, X5pred.-X5, and R5-R20%; however, R20% showed a nonsignificant statistical difference. The percentage of decline in R5% after bronchodilator administration was 23%. These results are in concordance with those of Meraz et al. [32] , who in their study compared impulse oscillometry parameters before and after bronchodilator administration and showed that there was a larger decrease, with significant differences in R5%, R5-R20%, and X5, indicating improved lung function and small airway function. These results are also consistent with those of Marotta et al. [11] , who stated that significant differences in the percentage change of resistance at 5 Hz were observed after bronchodilator use. Nearly significant differences were observed for reactance at 5 Hz. A bronchodilator response of 20-25% at a resistance of 5 Hz helps identify young children with asthma. In contrast to our study, Hellinckx et al. [33] evaluated bronchodilator response in 3-6.5-year-old asthmatic children and found that a drop in the R5% value by 40% was necessary to consider bronchodilator response as positive.

In the current study, comparing impulse oscillometry parameters before and after spirometry in asthmatic children showed a marked decline in pulmonary functions, represented by increases in R5%, X5pred.-X5, and R5-R20% and highly statistically significant differences in R5%, X5pred.-X5, and R5-R20%. However, R20% was found to have a nonsignificant statistical difference. These results agree with those of Komarow et al. [23] , who concluded that when impulse oscillometry and spirometry are performed sequentially, impulse oscillometry should be performed first as performing forced expiration during spirometry for multiple trials may cause bronchospasm, detected by impulse oscillometry.

As regards sensitivity, specificity, positive predictive value, and negative predictive value, impulse oscillometry was able to diagnose 42 asthmatic children of the 46 children previously diagnosed with asthma; in addition, one normal child of the 20 normal children was diagnosed with asthma. In contrast, spirometry was able to diagnose 36 asthmatic children of the 46 children previously diagnosed with asthma, and two normal children of the 20 normal children were diagnosed as being asthmatic.

The sensitivity and specificity of impulse oscillometry were 91 and 95%, respectively, which were higher than those of spirometry (78 and 90%). Positive and negative predictive values of impulse oscillometry were 97.6 and 83%, respectively, which were also higher than those of spirometry (94.7 and 64%). These results are in accordance with those of Ashmawi et al. [25] , who reported that the calculated sensitivity of impulse oscillometry in detecting cases of bronchial asthma was as high as 94.1%. However, these results are not in accordance with the findings of Al-Mutairi et al. [34] , who reported that the sensitivity of impulse oscillometry was only 31.3% and the specificity was 80.5%. However, impulse oscillometry can discriminate between diseased and nondiseased individuals.


  Conclusion Top


This study supports the objective utility of impulse oscillometry in the evaluation of children with asthma. When analyzing independent impulse oscillometry lung parameters and comparing them with FEV1%, R5% best differentiated asthmatic individuals from nonasthmatic individuals. The high sensitivity and specificity of impulse oscillometry shown in this study, in addition to its broad application in young or physically compromised children, merits the consideration of incorporation of impulse oscillometry into future standard guidelines for the treatment of children with asthma [Figure 1],[Figure 2],[Figure 3],[Figure 4],[Figure 5],[Figure 6],[Figure 7],[Figure 8] and [Figure 9] and [Table 1],[Table 2],[Table 3],[Table 4] and [Table 5].
Figure 1:

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Figure 2:

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Figure 5:

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Figure 8:

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Table 1: Distribution of the studied groups on the basis of general data

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Table 2: Baseline measurements of both impulse oscillometry and spirometry

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Table 3: Comparison of impulse oscillometry results before and after bronchodilator administration for all patients (n = 46)

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Table 4: Comparison of spirometry results before and after bronchodilator administration for patients (n = 46)

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Table 5: Comparison of impulse oscillometry results before and after spirometry for patients (n = 46)

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  Acknowledgements Top


Conflicts of interest

None declared.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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  In this article
Abstract
Introduction
Materials and me...
Results
Discussion
Conclusion
Acknowledgements
References
Article Figures
Article Tables

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