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Impulse oscillometry reference values in Anglo and Hispanic children.


Asthma is one of the most chronic respiratory conditions that is prevalent in and currently affects approximately 550,000 Texas children [1]. Detection of lung function within the early developmental stages of the pulmonary system is extremely critical in the intervention and treatment of asthmatic children [2,3]. Conventional detection methods of airway impairments are conducted using a pulmonary function test known as Spirometry, which requires strenuous breathing maneuvers [4]. This makes measuring lung function in the pediatric population a challenge. In addition, multiple studies have shown that Spirometry lacks the sensitivity to diagnose patients with asthma [5,6].

Impulse Oscillometry (IOS) provides an alternative patient-friendly lung function test that only requires passive patient cooperation [7-9]. The impulse oscillometric method is a Forced Oscillation Technique (FOT) that is capable of measuring respiratory impedance in terms of the Resistance (R) and Reactance (X) of the lungs at frequencies between 5 Hz-25 Hz [10].

As previous research conducted by our group has indicated, parameters of the equivalent electrical circuit models of the human respiratory system along with those of the IOS measurements have proven to be valuable in the diagnosis of patients with central and peripheral airway obstruction [11-13]. The purpose of this study was to develop predictive IOS equations for 112 asthmatic and non-asthmatic Anglo and Hispanic children in order to provide an original frame of reference for different IOS model parameters within this population.


Impulse Oscillometry data were collected in 2006-2008 at Western Sky Medical Research Clinic from 112 Anglo and Hispanic asthmatic and non-asthmatic children residing in the El Paso, Texas area. To avoid airflow leak, all subjects were asked to breathe normally while wearing a nose clip through a mouthpiece. Three to five repeat IOS measurements were recorded for each child to ensure accuracy in data collection. The data were then quality assured by our expert clinician and pulmonologist, and categorized into 4 classes as follows: Normal (N), Possible Small Airway Impairment (PSAI), Small Airway Impairment (SAI), or Asthmatic (A).

The average values of the following parameters were used for data analysis: Resistance of the respiratory system at 5 Hz [R5], Resistance at 5Hz-20Hz [R5-R20] or frequency-dependence of resistance, Reactance Area/"the Goldman Triangle" (AX), Resonant Frequency (Fres), and Peripheral (small airway) Compliance (eRIC_Cp). To identify any correlations, we employed statistical analyses of the IOS parameters. Linear prediction equations were developed by regression analysis with measuring (R5, R5R20, AX, Fres, eRIC_CP) as dependent variables regressed against height (H).


The predictive equations of the following parameters, R5, R5-R20, AX, and eRIC Cp were calculated. These are shown in Table 1. Previous studies conducted by our research group established correlations between the IOS parameters and height to correctly diagnose patients as Normal (N), PSAI, and SAI, and Asthmatic (A), and we conducted these calculations using algorithms that we developed in our research lab [14]. The results obtained by this study and other similar studies show that AX is considered a relevant indicator in the proper diagnosis of asthma in children.


Impulse Oscillometry is a patient-friendly test that has been proven to be more sensitive than Spirometry in clinical settings. It has also been proven to be of valuable and clinical significant due to the fact that it can track pulmonary function over a period of time [12, 13, 15]. Here we were able to successfully develop predictive IOS equations for 112 asthmatic and non-asthmatic Anglo and Hispanic children in order to provide an original frame of reference for different IOS model parameters within this population. This study and our previous work showed that the AX parameter is a relevant indicator in the proper diagnosis of asthmatic children. As such, Impulse Oscillometry may serve as a viable candidate for consideration for integration into clinical settings where a child-friendly approach to the reliable treatment of children with asthma is of paramount interest.


The data collection for this research was supported by NIH grant #1 S11 ES013339-01A1: UTEPUNM HSC ARCH Program on Border Asthma.


[1] Texas Department of State Health Services (2014, December). 2012 Child Asthma Fact Sheet--Texas [Online] Available: https://www. LinkIdentifier=id&ItemID=8589994054.

[2] Martinez FD, Morgan WJ, Wright AL, Holberg CJ, Taussig LM. Diminished lung function as a predisposing factor for wheezing respiratory illness in infants. N Engl J Med 1988; 319: 1112-1117.

[3] Young S, Sherrill DL, Arnott J, Diepeveen D, LeSouef PN, Landau LI. Parental factors affecting respiratory function during the first year of life. Pediatr Pulmonol 200; 29:331-340.

[4] Rodriguez, L.; Nazeran, H.; Meraz, E.; Estrada, E.; Rodriguez, C.; Edalatpour, R., "Discriminative Capacity of Impulse Oscillometry in Diagnosis and Treatment of Asthmatic Children," Biomedical Engineering Conference (SBEC), 2013 29th Southern, vol., no., pp.13,14, 3-5 May 2013.

[5] Centers for Disease Control and Prevention (2012, Mar. 6). Asthma [Online]. Available:

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[8] U. Frey, "Forced Oscillation Technique in infants and young children," Paediatric Respiratory, vol. 6, pp. 246-254, 2006.

[9] M. Goldman, E. Meraz, B. Diong and H. Nazeran, "Airflow perturba-tion analyses using simplified models can assess upper airway shunt during resting breathing Biomedical Engineering: Recent Developments, Washington, DC, Apr 2007

[10] Dencker M, Malmberg LP, Valind S, Thorsson O, Karlssonmk, Pelkonen A. Reference values for respiratory system impedance by using impulse oscillometry in children aged2-11 years. Clin Physiol funct imaging 2006; 26(4):247-50.

[11] Diong, B., H. Nazeran, P. Nava, and M. Goldman. "Modeling Human Respiratory Impedance." IEEE Engineering in Medicine and Biology Magazine 26.1 (2007): 48-55.

[12] Meraz et al.: Analysis of impulse oscillometric measures of lung function and respiratory system model parameters in small airway-impaired and healthy children over a 2-year period. BioMedical Engineering OnLine 2011 10:21.

[13] Meraz E, Nazeran H, Goldman M, Diong B: Respiratory System Model Parameters Track Changes in Lung Function after Bronchodilation. In proceedings of the 25th Southern Biomedical Engineering Conference, Miami, Florida. ; 2009:319-322.

[14] E.G. Meraz Ph.D. dissertation, Dept. Elect. Eng., Univ. of TX at El Paso, El Paso, TX, 2011

[15] H. D. Komarow, J. Skinner, M. Young, D. Gaskins, C. Nelson, P. J. Gergen and D. D. Metcalfe, "A Study of the Use of Impulse Oscillometry in the Evaluation of Children with Asthma: Analysis of Lung Parameters, Order Effect, and Utility Compared with Spirometry," Pedi-atric Pulmonology, 2011.

Roya Edalatpour (1), Karla Montano (1), Erika Meraz (2), Carlos Rodriguez (1), Christopher Aguilar (1), Homer Nazeran (1)

(1) Department of Electrical and Computer Engineering, The University of Texas at El Paso, El Paso, Texas, USA

(2) Universidad Autonoma de Ciudad Juarez, Cd. Juarez, Chihuahua, Mexico
Table 1: IOS Reference Equations for Pre-Bronchodilator Subjects

IOS Reference Equations


           Reference Equations        SEE          [r.sup.2]
                                      ([dagger])   ([double

R5         1.4280--0.0063 x height      0.057        0.645

R5-R20     0.3635--0.0018 x height      0.027        0.432

AX         1.2128--0.0052 x height      0.110        0.245

eRIC_Cp    -0.3268 + 0.0031 x           0.058        0.301


           Reference Equations           SEE       [r.sup.2]

R5         1.3280--0.0049 x height      0.110        0.432

R5-R20     0.7039--0.0033 x height      0.063        0.511

AX         5.9360--0.0295 x height      0.481        0.592

eRIC_Cp    -0.0763 + 0.0010 x           0.019        0.506


           Reference Equations         SEE    [r.sup.2]

R5         1.2493-0.0049 x height    0.069     0.646

R5-R20     0.5299-0.0025 x height    0.049     0.487

AX         4.4259-0.0232 x height    0.272     0.725

eRIC_Cp    -0.1412 + 0.0016 x
              height                 0.024     0.628


           Reference Equations         SEE    [r.sup.2]

R5         1.6843-0.0067 x height     0.112     0.559

R5-R20     1.0039-0.0049 x height     0.074     0.610

AX         8.7637-0.0448 x height     0.528     0.720

eRIC_Cp    -0.0348 + 5.8503e-04 x     0.008     0.675

([dagger]) SEE = Standard Error of the Estimate

([double dagger]) [r.sup.2] = Coefficient of Determination
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Author:Edalatpour, Roya; Montano, Karla; Meraz, Erika; Rodriguez, Carlos; Aguilar, Christopher; Nazeran, Ho
Publication:Journal of the Mississippi Academy of Sciences
Article Type:Report
Date:Apr 1, 2015
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