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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.

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Resumen Introducción La oscilometría de impulso es una prueba que evalúa la mecánica respiratoria a través de la aplicación de pequeños pulsos de presión que producen oscilaciones de flujo a una frecuencia determinada. Su aplicación relevante es en el estudio de las enfermedades de la vía aérea pequeña. El software integrado al equipo que ejecuta esta prueba genera cálculos de valores predictivos para cada uno de los parámetros oscilométricos, los cuales se basan en datos de población alemana. Objetivo Estandarizar la prueba de oscilometría de impulso y obtener ecuaciones piloto para valores de referencia. Material y métodos Se realizó un estudio experimental, analítico, prospectivo y longitudinal con sujetos voluntarios sanos. Se llevaron a cabo pruebas de espirometría y oscilometría de impulso basales y, tras broncodilatador, se registraron las impedancias, resistencias y reactancias del sistema respiratorio a 5, 10, 15 y 20 Hz. Los resultados se analizaron por sexo, edad, talla y peso. Se de 127 participantes sanos ingresaron al estudio, 51.5% del sexo efectuó un modelo de regresión lineal múltiple. Resultados Un total masculino (68) y 48.5% (64) del femenino, con edad promedio de 39.65 ± 15.26 años; la talla tuvo un promedio de 1.63 ± 0.09 m. Se demostró que el sexo influye en los valores de la oscilometría en el volumen corriente (VT), la impedancia, las resistencias y el área de reactancia (p < 0.05), y no afecta las reactancias (XRs) (p > 0.05); este parámetro está mayormente asociado a la talla (r = 0.727, r2 = 0.528). La edad incide en los valores de la oscilometría, ya que las resistencias (Rrs) son menores en los grupos más jóvenes; el IMC y el peso no comprometieron los valores de IOS. Conclusiones Este estudio proporciona ecuaciones piloto de referencia para los índices comunes de oscilometría de impulso en sujetos mexicanos. Así, integra una prueba de función pulmonar para facilitar la detección de alteraciones funcionales en vía aérea pequeña. Sugerimos realizar más trabajos en población mexicana, sobre todo de edad avanzada, para confirmar nuestros resultados y proporcionar una base más sólida a las ecuaciones de referencia para IOS, con un fin clínico y epidemiológico.

Abstract Introduction Impulse oscillometry is a test that evaluates the respiratory mechanics by the application of small pulses of pressure, which produce flow oscillations to a certain frequency. Its main application is in the study of the illnesses of the small airline. The integrated software of the test equipment generates predictive values for each of the oscillometric parameters, based on German population data. Objective To standardize the impulse oscillometry test in order to design pilot equations for reference values in our population. Material and methods We performed a pilot, experimental, analytical, longitudinal study with healthy volunteer subjects. Spirometry and impulse oscillometry tests were performed, both basal impedances, resistances, and reactances of the respiratory system to and after bronchodilator application; we measured and registered the 5, 10, 15, and 20 Hz. The results were analyzed by sex, age, height, and weight. The analysis was performed using a model of multiple linear retrogression. Results A total of 127 healthy participants were recruited, 51.5% men (68) and 48.5% (64) women, with an average age of 39.65 ± 15.26 years; their height was an average of 1.63 ± 0.09 m. It was proved that the gender influences the oscillometry values of tidal volume (VT), the impedance, the resistances and reactance area (p < 0.05), but not the reactances (XRs) (p > 0.05); this parameter is mainly associated with the size (r = 0.727, r2 = 0.528). The age influences the oscillometry values since the resistances (Rrs) are lower in the youngest groups; the BMI and the weight had no influence on the values of IOS. Conclusions This study provides pilot reference equations for the common indexes of impulse oscillometry in Mexican subjects, in order to integrate this test of pulmonary function to facilitate the detection of functional alterations in the small airline. We suggest more studies should be done on Mexican population, and especially on people of advanced age, to confirm our results and to provide a more solid base for the equations of reference to IOS, with clinical and epidemiologic purposes.