Abstract
Rationale
It has been shown that NIV causes internal airflow redistribution in COPD patients recovering after exacerbation [Int J COPD, 2011;6 615-24]. This work tries to use functional respiratory imaging (FRI) to develop a method to predict the amount of redistribution that can be achieved in a patient specific manner.
Methods
10 persistent hypercapnic COPD GOLD III patients underwent a HRCT scan at FRC and TLC. From these scans airway tree and initial internal flow distribution (IFD) were obtained. Using computation fluid dynamics (CFD), and by setting tracheal pressure ptrach=0, this data was used to calculate lobar pressure (plobe). Different PEEP levels (p'trach) were simulated by adapting plobe (p'lobe) using the formula below:
p'lobe=plobe[(Σlobe=RULLLL(p'trach-plobe)Alobe)/(Σlobe=RULLLL(ptrach-plobe)Alobe)]
Using this new lobar pressure in the CFD calculations resulted in values for IFD in function of the PEEP level.
Results
It was observed that in some patients increasing PEEP levels did not result in a change in IFD, where as in other patients a complete shift from predominant upper lobe breathing to lower lobe breathing was seen. The shift in IFD happened for all patients in the PEEP range [0-10]cmH2O.
Conclusions
FRI predicts PEEP to have an influence on IFD. This influence is observed in a range of PEEP that is clinical achievable. These findings have to be confirmed in a prospective clinical trial.
This study was funded by AirLiquide.
- © 2014 ERS
