POLITECNICO DI MILANO SCUOLA DI INGEGNERIA INDUSTRIALE E DELL’INFORMAZIONE CORSO DI LAUREA IN INGEGNERIA BIOMEDICA Design of a new function for mechanical ventilators to optimize PEEP in preterm infants Tesi di Laurea di: Amedeo Bussi Matr. 813388 Relatore: Prof. Raffaele Dellacà Correlatore: Dott.ssa Chiara Veneroni Anno Accademico 2014 - 2015 ii Table of contents Table of contents ............................................................................................................................................ iii List of Figures ................................................................................................................................................... v List of Tables ................................................................................................................................................... ix Sommario ........................................................................................................................................................ x Summary ....................................................................................................................................................... xvii Introduction ..................................................................................................................................................... 2 1 The infant respiratory system and respiratory treatments ....................................................................... 5 Anatomy and function of the respiratory system ................................................................................. 5 Biomechanical modelling....................................................................................................................... 7 1.2.1 Pressure ............................................................................................................................................. 7 1.2.2 Volume .............................................................................................................................................. 7 1.2.3 Static behaviour ................................................................................................................................ 8 1.2.4 Dynamic behaviour ......................................................................................................................... 12 Infants’ respiratory system .................................................................................................................. 17 1.3.1 Neonatal respiratory disorders ....................................................................................................... 19 Respiratory treatments ....................................................................................................................... 24 1.4.1 Mechanical ventilation .................................................................................................................... 25 1.4.2 Ventilator settings ........................................................................................................................... 32 Optimization of Mechanical Ventilation .............................................................................................. 35 1.5.1 Ventilation parameters Optimisation ............................................................................................. 35 1.5.2 Oscillatory mechanics: Forced Oscillation Technique (FOT) ........................................................... 36 1.5.3 PEEP Optimisation ........................................................................................................................... 39 2 System Overview .................................................................................................................................... 43 Objective and Requirements ............................................................................................................... 43 Mechanical Ventilator – Fabian HFO ................................................................................................... 44 Bluetooth Adapter ............................................................................................................................... 48 2.3.1 Communication protocol ................................................................................................................ 48 2.3.2 Electronic board .............................................................................................................................. 49 Tablet ................................................................................................................................................... 51 Software .............................................................................................................................................. 53 2.5.1 Bluetooth communication Android ................................................................................................. 54 2.5.2 Android application description – User Interface ........................................................................... 59 3 Data processing ...................................................................................................................................... 67 Algorithms ........................................................................................................................................... 67 3.1.1 Impedance computation ................................................................................................................. 67 3.1.2 Impedance selection : quality control and end expiration determination ..................................... 70 Algorithm optimisation and sensor correction .................................................................................... 88 3.2.1 In vitro test for sensors correction .................................................................................................. 88 3.2.2 Parameters Optimisation ................................................................................................................ 97 iii 4 Validation ............................................................................................................................................. 101 In vitro Test ........................................................................................................................................ 101 In vivo Test ......................................................................................................................................... 107 5 Conclusions .......................................................................................................................................... 112 Future development .......................................................................................................................... 112 APPENDIX A: Android Apps Development .................................................................................................... 113 Android Application ....................................................................................................................................... 113 OS Android .................................................................................................................................................. 113 Intents ......................................................................................................................................................... 115 Android Activity .......................................................................................................................................... 116 Android Service .......................................................................................................................................... 118 Handler ....................................................................................................................................................... 120 Thread ......................................................................................................................................................... 120 AsyncTask ................................................................................................................................................... 122 Dialog and Toast ......................................................................................................................................... 123 BIBLIOGRAFY ................................................................................................................................................ 126 iv List of Figures Fig. 1: Respiratory Volume ...................................................................................................................................... 7 Fig. 2: Surface tension attraction forces in a liquid. ................................................................................................ 8 Fig. 3 Laplace law applied to alveoli ........................................................................................................................ 9 Fig. 4: Static inflation and deflation pressure-volume curves (Karcz, Vitkus, Papadakos, Schwaiberger, & Lachmann, 2012) ................................................................................................................................................... 10 Fig. 5 Relaxation pressure-volume curve of the lung and chest wall. ................................................................... 11 Fig. 6 Two-spring