University of Twente Student Theses


Dynamics of lung function and phase diagram.

Wijlens, K.A.E. (2019) Dynamics of lung function and phase diagram.

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Abstract:Rationale Clinical observations of respiratory distress resulting in imposed work of breathing, respiratory rate, heart rate, and oxygen saturation are currently used to provide feedback whether high flow nasal cannula (HFNC) therapy is effective for the subject. However, these parameters are biased by medication and oxygen supply and vulnerable to misinterpretation. Feedback using pressure to obtain a phase diagram reflecting changes in therapy could, besides clinical parameters, provide valuable information for the clinician to guide optimal therapeutic choices. Objective To compare the exercise induced changes in lung function to the changes in the phase diagram assessed with the squared perimeter divided by the area (Aex1), sphericity, and triangularity. The changes in lung function were measured with spirometry, forced expiration volume in 1 second (FEV1), and forced oscillatory technique (FOT) with the respiratory reactance (RRS) and resistance (XRS). In order to evoke a variation in lung function of subjects, a standard exercise challenge test (ECT) will be performed. Methods In this observational study 25 children were included and performed an ECT. The pressure was measured with an OMEGA pressure sensor and an OptiflowTM nasal cannula. Lung function was measured with spirometry and FOT. Preprocessing was performed with Matlab version R2018b, several parameters were determined, and data analysis methods were investigated. Results The mean decrease in FEV1 was 16.2% with a standard deviation of 8.6%. For the determination of the dot product, 21 Fourier terms should be taken into consideration. The parameters Aex1, sphericity and triangularity stabilize after 51 Fourier terms. Scaling the Fourier vector had no influence on the appearance of the phase diagram. The dispersion of the dot product values during the total measurement, influences the phase diagrams which should be included for the calculation of the mean phase diagram. A similar link between the FEV1 changes and the parameters has not been found yet for all subjects. 10 selected healthy and unhealthy phase diagrams were visual distinguishable, however, this was not found for the dot product or parameters. Discussion Further investigation is needed to determine a parameter that is able to distinguish healthy from unhealthy but also is able to indicate the therapy efficacy or lung function changes over time. As the parameters showed a greater discrimination between healthy and unhealthy when the mean of 10 phase diagrams was taken, the number of phase diagrams for average the parameter should be determined. To further improve the number of representative breaths, criteria can be added to prevent manipulations or unrepresentative breaths to result in phase diagrams. Conclusion A discrimination between healthy and unhealthy phase diagram is not yet assessed by a parameter. Further work is needed to determine a parameter that is able to indicate a correlate lung function changes to the appearance of the phase diagram.
Item Type:Essay (Master)
Medisch Spectrum Twente, Enschede, The Netherlands
Faculty:TNW: Science and Technology
Subject:44 medicine, 50 technical science in general
Programme:Technical Medicine MSc (60033)
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