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Investigation of non-uniform airflow signal oscillation during high frequency chest compression.

Sohn K, Warwick WJ, Lee YW, Lee J, Holte JE - Biomed Eng Online (2005)

Bottom Line: The simulation results indicated that lung capacitance or the inertance of air is also not a factor in the non-uniformity of HFCC airflow signals.Although not perfect, our circuit analogue model allows us to effectively simulate the nonlinear characteristics of the respiratory system.We found that the amplitudes of HFCC airflow signals behave as a function of spontaneous airflow signals.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, USA. sohn0015@umn.edu

ABSTRACT

Background: High frequency chest compression (HFCC) is a useful and popular therapy for clearing bronchial airways of excessive or thicker mucus. Our observation of respiratory airflow of a subject during use of HFCC showed the airflow oscillation by HFCC was strongly influenced by the nonlinearity of the respiratory system. We used a computational model-based approach to analyse the respiratory airflow during use of HFCC.

Methods: The computational model, which is based on previous physiological studies and represented by an electrical circuit analogue, was used for simulation of in vivo protocol that shows the nonlinearity of the respiratory system. Besides, airflow was measured during use of HFCC. We compared the simulation results to either the measured data or the previous research, to understand and explain the observations.

Results and discussion: We could observe two important phenomena during respiration pertaining to the airflow signal oscillation generated by HFCC. The amplitudes of HFCC airflow signals varied depending on spontaneous airflow signals. We used the simulation results to investigate how the nonlinearity of airway resistance, lung capacitance, and inertance of air characterized the respiratory airflow. The simulation results indicated that lung capacitance or the inertance of air is also not a factor in the non-uniformity of HFCC airflow signals. Although not perfect, our circuit analogue model allows us to effectively simulate the nonlinear characteristics of the respiratory system.

Conclusion: We found that the amplitudes of HFCC airflow signals behave as a function of spontaneous airflow signals. This is due to the nonlinearity of the respiratory system, particularly variations in airway resistance.

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Ptp-volume curves of the lung model during use of HFCC. Although the initial LV (FRC) is 2700 ml, LV during use of HFCC is smaller. The curves became jagged due to HFCC pulses.
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Figure 2: Ptp-volume curves of the lung model during use of HFCC. Although the initial LV (FRC) is 2700 ml, LV during use of HFCC is smaller. The curves became jagged due to HFCC pulses.

Mentions: which implies that represents Cas. It can be obtained by equation (1); however, the equation did not consider the hysteresis of Ptp-volume curves that is caused by several proposed reasons [1]. To overcome this, we defined Cas as *k (k<0), and k was continuously changed over the time course of the simulation. The values of k were empirically determined to achieve the acceptable shape of the hysteresis, which is shown in fig. 2.


Investigation of non-uniform airflow signal oscillation during high frequency chest compression.

Sohn K, Warwick WJ, Lee YW, Lee J, Holte JE - Biomed Eng Online (2005)

Ptp-volume curves of the lung model during use of HFCC. Although the initial LV (FRC) is 2700 ml, LV during use of HFCC is smaller. The curves became jagged due to HFCC pulses.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1173124&req=5

Figure 2: Ptp-volume curves of the lung model during use of HFCC. Although the initial LV (FRC) is 2700 ml, LV during use of HFCC is smaller. The curves became jagged due to HFCC pulses.
Mentions: which implies that represents Cas. It can be obtained by equation (1); however, the equation did not consider the hysteresis of Ptp-volume curves that is caused by several proposed reasons [1]. To overcome this, we defined Cas as *k (k<0), and k was continuously changed over the time course of the simulation. The values of k were empirically determined to achieve the acceptable shape of the hysteresis, which is shown in fig. 2.

Bottom Line: The simulation results indicated that lung capacitance or the inertance of air is also not a factor in the non-uniformity of HFCC airflow signals.Although not perfect, our circuit analogue model allows us to effectively simulate the nonlinear characteristics of the respiratory system.We found that the amplitudes of HFCC airflow signals behave as a function of spontaneous airflow signals.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, USA. sohn0015@umn.edu

ABSTRACT

Background: High frequency chest compression (HFCC) is a useful and popular therapy for clearing bronchial airways of excessive or thicker mucus. Our observation of respiratory airflow of a subject during use of HFCC showed the airflow oscillation by HFCC was strongly influenced by the nonlinearity of the respiratory system. We used a computational model-based approach to analyse the respiratory airflow during use of HFCC.

Methods: The computational model, which is based on previous physiological studies and represented by an electrical circuit analogue, was used for simulation of in vivo protocol that shows the nonlinearity of the respiratory system. Besides, airflow was measured during use of HFCC. We compared the simulation results to either the measured data or the previous research, to understand and explain the observations.

Results and discussion: We could observe two important phenomena during respiration pertaining to the airflow signal oscillation generated by HFCC. The amplitudes of HFCC airflow signals varied depending on spontaneous airflow signals. We used the simulation results to investigate how the nonlinearity of airway resistance, lung capacitance, and inertance of air characterized the respiratory airflow. The simulation results indicated that lung capacitance or the inertance of air is also not a factor in the non-uniformity of HFCC airflow signals. Although not perfect, our circuit analogue model allows us to effectively simulate the nonlinear characteristics of the respiratory system.

Conclusion: We found that the amplitudes of HFCC airflow signals behave as a function of spontaneous airflow signals. This is due to the nonlinearity of the respiratory system, particularly variations in airway resistance.

Show MeSH