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Chapter 6 – High Frequency Percussive Ventilator characterization 1:1 and a percussive frequency from 300 to 900 cycles per minute with work pressure of 20 cm H 2 O and free expiratory flow. The selected cut-off frequency of the on-board low-pass Butterworth filter was of 500 Hz. Fig. 6.4 shows the acquired pressure and flow curves together with the estimated volume during a respiration cycle. Fig. 6.4 VDR-4-Measured Pressure (top), Flow (middle) and computed (bottom) Volume during a high percussive respiration cycle. 82
Chapter 6 – High Frequency Percussive Ventilator characterization 6.5 Results and discussion Table 6.1 shows the reference set values of resistance (R FLUKE) and elastance (E FLUKE) used in the Servo-I test, with the corresponding resistance (R mean ± 1SD) and elastance (E mean ± 1SD) estimated values together with their respective % relative estimation errors (∆R% and ∆E%) and the normalized mean square error between measured and estimated pressure (NMSE). The mean and SD values are computed on 12 successive respiration cycles by the procedure implemented in the device. Table 6.1 Resistance and compliance estimated during inflation by the Servo-I ventilator. Pressure and flow measures were carried out for 60 seconds, setting up on the ventilator a respiratory frequency of 12 breaths per minute with I/E 1:1 and a work pressure of 30 cm H 2 O. R FLUKE cm H 2 O/(l/sec) E FLUKE cm H 2 O/l R mean±1SD cm H 2 O/(l/sec) ∆R% E mean±1SD cm H 2 O/l ∆E% 5 20 5.9±0.02 18.9% 24.4±0.07 22.0% 0.03 20 20 22.2±0.25 11.1% 19.9±0.06 -0.2% 0.12 50 20 67.1±0.83 34.2% 18.6±0.14 -7.1% 0.94 5 50 5.1±0.04 2.3% 60.1±0.12 20.2% 0.09 20 50 17.4±0.04 -13.2% 58.5±0.12 17.0% 0.18 50 50 60.5±0.75 21.0% 51.2±0.28 2.3% 1.02 5 100 3.4±0.09 -33.0% 125.7±0.31 25.7% 0.22 20 100 14.6±0.11 -26.8% 118.7±0.64 18.7% 0.23 50 100 46.4±0.10 -7.2% 111.2±0.35 11.2% 0.38 NMSE In conventional ventilation case, the estimated values of the parameters are very similar to those set on the lung simulator, with a good repeatability and a low NMSE. In this case, the hypothesized model adequately estimates the behaviour of the lung simulator. The accuracy of resistance and elastance measurements by a monitoring system has also been described in some studies. A similar level of accuracy (i.e. 20% of set values) was reached in measurement of respiratory mechanic compared to known values of a neonatal lung simulators [Jackson EA et al 1995]. Lower accuracy in a monitoring system (Bicore, SensorMedics 2600, Babylog) for the resistance and compliance estimation of a lung model by means of the occlusion technique has been also reported [Hauschild M et al 1994]. The graphs of Figure 6.5 show the relations between the lung simulator set parameters and the corresponding estimated parameters. 83
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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 35 and 36: Chapter 2 - Intensive care: mechani
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Page 39 and 40: Chapter 3 - The pulmonary function
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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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