**6. Conclusions**

132 Practical Applications in Biomedical Engineering

Parameters for 2008 data.

*These selected parameters seem to be sensitive and reliable indices of lung function for respiratory* 

The correlation coefficient (r) between children Heights and these IOS and Model Parameters was also analyzed. The parameters showed a good correlation, the best correlation was observed for R5 with R = 0.764, and the lowest r value (0.542) was observed

> **Correlation with Height Parameters r**  R3 (kPa/l/s) 0.762 R5 (kPa/l/s) 0.764 X3 (kPa/l/s) 0.557 X5 (kPa/l/s) 0.542 R3-R20 (kPa/l/s) 0.688 R5-R20 (kPa/l/s) 0.62 AX (kPa/l/s) 0.741 Fres (1/s) 0.666 eRIC Cp (l/kPa) 0.762 Rp (kPa/l/s) 0.513 aRIC Cp (l/kPa) 0.717 Rp (kPa/l/s) 0.643

*disease classification using Impulse Oscillometric data, eRIC and aRIC Model Parameters.* 

**Table 15.** Correlation coefficients (r) between Height and IOS and respiratory system Model

**Figure 12.** Correlation between AX and eRIC Cp for Pre- and Post-B data.

for X5. In Table 15 the values for these correlations are presented.

While expert clinician diagnostic classification distinguished between children based on 4 levels of perceived normality or absence thereof of the visual patterns of IOS data, with the essential features characterizing the differences being associated with abnormalities group mean IOS and the aRIC model data appear to fall into two distinctly different groups: either Normal or Asthmatic, with the essential features characterizing the differences being associated with abnormalities of peripheral airways.

Our present and previous studies (52-61, 75), have demonstrated that equivalent electrical circuit Model Parameters of the human respiratory system are able to track changes in the respiratory system function after bronchodilation. Both the eRIC and aRIC models clearly distinguished between children who were Normal (Healthy) or possibly had mild SAI, who showed no significant changes with bronchodilation-BD), and those who were Asthmatic with SAI, both at baseline and at Pre- to Post-BD conditions. The eRIC model showed an apparently larger peripheral airway compliance (Cp) than the aRIC model, probably because it might include some of the "extrathoracic airway compliance" (Ce). On the other hand, the eRIC model is more parsimonious, and the parameter, Ce, that may be difficult for physicians to understand, appears to show no significant change Post-BD in the Asthmatic group.

It can be observed that children classified as Normal (Healthy) or possible SAI were relatively similar in both IOS and the aRIC model parameters. However, they showed clear increases in R3, R5, R3-R20, R5-R20, AX, Fres, and Rp, and a clear decrease in X3, X5 and Cp going from Normal to PSAI.

Going to increasingly abnormal levels of "diagnostic classification," R3, R5, R5-R20, AX, Fres and Rp continue to increase from Healthy to PSAI to SAI to Asthma, while X3, X5 and Cp decrease in this progression. Differences between SAI and Asthmatic children were modest.

The features used in this work seem to be sensitive and reliable indices for automatic respiratory disease classification using Impulse Oscillometry data. The correlation between AX and the eRIC Cp was the best correlation in both Pre-B and Post-B work.

Our expert clinician confirmed that the range of values of all analyzed features: R3, R5, R3- R20, R5-R20, X3, X5, AX, Fres, eRIC Cp, eRIC Rp, aRIC Cp and aRIC Rp obtained for the

SAD and Asthmatic groups were comparable to those values he has observed over many years in other asthmatic children of the same age range.

Impulse Oscillometric Features and Respiratory System Models Track Small Airway Function in Children 135

**Author details** 

*Universidad Autónoma de Ciudad Juárez, Mexico* 

Lidia Rascón Madrigal and Nelly Gordillo Castillo *Universidad Autónoma de Ciudad Juárez, Mexico* 

Homer Nazeran, Carlos Ramos and Liza Rodriguez

[1] American Lung Association Asthma and Allergy, Asthma &Children.

Children Aged 2-7 Years. Pediatric Pulmonology 1998; 25, 322-331.

Children. Am J Respir Crit Care Med 2000; 162, 1500-1506.

Fails to Improve. J Allergy and Clin Immun 2003; 111, S135.

[2] AAAAI. American Academy of Allergy Asthma and Inmunology.

diagnosis-and-treatment.html (accessed June 18 2012).

http://www.lung.org/lung-disease/asthma/learning-more-about-asthma/symptoms-

[3] COMPEDIA. Colegio Mexicano de Pediatras Especialistas en Inmunología Clínica y Alergias. http://www.compedia.org.mx/archivos/docs/6\_asma\_bron.pdf. (accessed June

[4] Klug, B and Bisgaard, H. Specific Airway Resistance, Interrupter Resistance, and Respiratory Impedance in Healthy Children, and Respiratory Impedance in Healthy

[5] Nielsen, KG and Bisgaard, H. The Effect of Inhaled Budesonide on Symptoms, Lung Function, and Cold Air and Methacholine Responsiveness in 2- to 5-year-old Asthmatic

[6] Gaylor, P B, et al. Forced Oscillation using Impulse Oscillometry (IOS) Provides Objective Responses to Inhaled Corticosteroids (ICS) in Asthmatic Patients when FEV1

[7] Marotta, A, et al. Impulse Oscillometry provides an effective measure of lung dysfunction in 4-year-old children at risk for persistent asthma. J Allergy Clin Immunol

[8] Ortiz, G and Mendez, R. The Effects of Inhaled Albuterol and Salmeterol in 2- to 5-Year-Old Asthmatic Children as Measured by Impulse Oscillometry. Journal of Asthma 2002;

[9] Goldman, M D, et al. Within- and Between-Day Variability of Respiratory Impedance, Using Impulse Oscillometry in Adolescent Asthmatics. Pediatric Pulmonology 2002; 34,

[10] Klug, B and Bisgaard, H. Measurement of Lung Function in awake 2-4 Year-Old Asthmatic Children During Methacholine Challenge and Acute Asthma: A Comparison of the Impulse O Technique, the Interrupter Technique, and Transcutaneous

http://www.aaaai.org/about-the-aaaai/newsroom/asthma-statistics.aspx (accessed June

*University of Texas at El Paso, USA* 

*University of Texas at El Paso, USA* 

Erika G. Meraz

**7. References** 

18 2012).

18 2012).

2003; 112, 317-321.

39(6), 531-536.

312-319.

Comparing all the IOS parameters for Pre- and Post-B data and the eRIC and aRIC Model Parameters in the Normal group, no significant differences were observed. Also comparing Pre- and Post-B parameters for the PSAI group only R3, R5 and the eRIC Rc showed significant differences. Similarly evaluating Pre- and Post-B values for the SAI group, the following parameters showed significant differences: R3, R5, X3, X5, X10, X15, R3-R20, R5- R20, AX, the aRIC Rp, eRIC Rp, eRIC I and eRIC Cp. Finally evaluating Pre- and Post-B values for the Asthmatic group all of the parameters showed significant differences with the exception of the aRIC Ce and eRIC I.

The selected IOS and model derived parameters (R3, R5, R3-R20, R5-R20, X3, X5, AX, Fres, the eRIC Cp, eRIC Rp, aRIC Cp and aRIC Rp) showed a good correlation with children Heights.

In this research study focusing on children with and without SAI (Healthy), the eRIC Model Parameters showed to be consistent and to some extent more closely correlated with IOS measures compared to the aRIC model parameters. As eRIC is more intuitive, less complex and a more parsimonious model (75), it may be considered a more suitable diagnostic tool for clinical applications than the aRIC model.

IOS lung function data are similarly well-modeled by the eRIC (without upper airway shunt compliance) and aRIC models (with upper airway shunt compliance), which are reduced versions of the popular Mead's model developed at Harvard several decades ago, based on the close correlations of their corresponding parameters excluding Ce. The eRIC model is a more parsimonious and equally powerful model in capturing the differences between SAI and H children, therefore it is recommended as a clinically-preferred model of lung function based on IOS data.

In summary, we conclude that the IOS parameters AX and the eRIC model-derived parameter Cp are the most reliable parameters to track small airway function in children before and after bronchodilation. AX (the "Goldman Triangle"), representing the integrated low frequency respiratory reactance magnitude between 5 Hz and Fres, and the eRIC Cp corresponding to the peripheral (small airway) compliance demonstrated superior diagnostic discrimination compared to all other parameters analyzed and emerged as useful and reliable indices of small airway function in children.

Further work in a larger number of H and SAI children is required to establish normal values for these sensitive indices and enable researchers in this field to perform more effective and timely evaluation, detection, diagnosis, and treatment of different respiratory diseases. Also future work should be performed in order to collect data from a larger sample of children and perform a statistical analysis in order to evaluate IOS parameters and both models (eRIC and aRIC) performances to evaluate these changes in lung function. A definitive choice between the eRIC and aRIC models will require further assessments in a larger sample of children.
