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Chapter 6 – High Frequency Percussive Ventilator characterization The graphs of Figure 6.6 show the relations between the lung simulator set parameters and the corresponding estimated parameters at the four diffferent percussive frequencies. Fig.6.6 VDR-4 : R mean and E mean values at different percussive frequencies From the results it appears necessary to distinguish the case where the resistance is less than 50 cm H 2 O/(l/sec) from that in which the resistance is equal to 50 cm H 2 O/(l/sec). In the first case, the mean square errors are kept low (Table 6.3) and the graphs of figure 6.6 show dependence on the frequency of lung simulator parameters. Again, until the resistance remains at reasonable values from a clinical point of view, the hypothesized simple respiratory model can adequately simulate the situation even if the mean square errors are 86
Chapter 6 – High Frequency Percussive Ventilator characterization higher than in the case of conventional ventilation. The introduction of more sophisticated models for high frequency [Dorkin et al 1988] seems to be necessary in order to explain the found differences. On the other hand, in case of resistance equal to 50 cm H 2 O/(l/sec), the model does not seem valid anymore (Table 6.3, Figure 6.6). Moreover, Figure 6.7 shows that the mean square error (NMSE) reaches unacceptable values for R=50 cm H 2 O/(l/sec). Fig.6.7 VDR-4 : NMSE versus R at different percussive frequency Figure 6.8 shows the flow curves at different resistance values. A high frequency disturbance, which dramatically increases as the resistance rises, is well evident and this negatively influences the volume calculation. It seems reasonable to assume that this phenomenon could be due to a turbulent motion present in the pneumotachograph, caused by frequency dependent effects [Patrick F and Allan MD 2010]. This turbulence is less negligible as load resistance increases. Moreover, Figure 6.8 compares the acquired pressure curve against the estimated one when resistance changes, highlighting the effect of the error during the estimation of volume parameters. 87
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UNIVERSITÀ DEGLI STUDI DI TRIESTE
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Index 2.2.7 Pressure-Controlled Ven
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Introduction Introduction The lungs
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Introduction The study was carried
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Physiology of the respiratory syste
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Chapter 2 - Intensive care: mechani
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Page 39 and 40: Chapter 3 - The pulmonary function
Page 47 and 48: Chapter 4 - State of the art of met
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Page 97 and 98: Conclusions and future developments
Page 99 and 100: References References Annane D, Orl
Page 101 and 102: References Lucangelo U, Antonaglia
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UNIVERSITÀ DEGLI STUDI DI TRIESTE - OpenstarTs - Università ...

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