| Modeling of Respiratory System by Forced Oscillation Technique
Forced Oscillation Technique (Forced Oscillation Technique - FOT) is a method of measuring respiratory system mechanics. This method involves the stimulation of the patient's respiratory system with low-amplitude oscillations. FOT system is a combination of two dynamic and non-linear oscillation sources: respiratory system and electro-mechanical vibrator which is usually generated by the speaker. Therefore, the statistical analysis of the linear dependence between FOT signals ( , and ) and loudspeaker drive signal should be the first step to investigate the FOT method. In this study, I designed and developed the new set up for the FOT system. The developed system includes both the hardware and the software for the data acquisition as well as for the system control.
For the measurements, six subjects were recruited and single sinusoidal signal was applied to the loudspeaker for the excitation of the system. Frequency of the sinusoidal signal was varied between 0.3 Hz-5 Hz. Airflow, airway pressure and breath temperature changes were measured with FOT oscillations for at least four breath cycle. After segmenting each measurement to one breath cycle, the set of correlation coefficient between airflow and breath temperature, airflow and mask pressure and airflow and excitation signal versus excitation frequency were calculated for each breath and for each subject.
Results showed that correlation coefficients depend on the involved signals. For example, the correlation coefficients between flow and pressure signals were always higher than the correlation coefficients between flow and the excitation signal. That is a strong evidence that loudspeaker has a nonlinear relation between excitation signal and resulted flow. Also, I observed that smokers have lower correlation coefficient between flow and temperature signals than the non-smoker.
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