Breathing of Humans and Its Simulation

Breathing of Humans and its Simulation Mina Nishi LSTM-Erlangen Institute of Fluid Mechanics Friedlich-Alexander-University Erlangen-Nuremberg Cauerstr.4, D-91058 Erlangen June 14, 2004 Abstract In this thesis, a breathing flow rate monitoring system and a mechanical breathing simulator are developed, constructed and tested for the experimental investigation of human breathing. Human breathing is a combination of three lung functions, ventilation, diffusion and circulation. In the present thesis, ventilation functioning is focused for the measurment and simulation. One of the most interesting features of ventilation functioning is its time varying volume flow rate. To measure this, the breathing mask which covers nose and mouth are used with cooperating with the thermal sensor. The sensor is called Time of Flight sensor, which is environmental condition, like temperature or humidity, independent and direction sensitive. The sensor gives two different information, one is the direction signal and the other signal is proportional to the mass flow rate. With this system, the ventilation volume flow rate can be precisely measured so that the exact human ventilation simulation will be realized. The sampled raw data of human ventilation will be analyzed to obtain the typical ventilation curve which is used for diagnosis of lung functioning defection. The second important part of this thesis is to simulate human ventilation with certain equipment which can reproduce any kind of ventilation curve. The simulation system is constructed with the mass flow contoroller which is applied for the exhalation simulation and for the inhalation simulation, volume flow controller, a proportional valve which is operated with vacuum pump and chamber. The whole ventilation simulation system is constructed and the result of the simulation is presented in this thesis. This work need to be developed further to make the breathing dummy or precise model of the human oropharynx so that it will provide the various possi- bilities, for example, to examine the particle deposition inside the human trachea etc. Contents 1 Introduction 2 2 A Brief Literature Survey 4 2.1 Breathing System of human being . 5 2.2 Measurement of the Human Breathing . 7 2.2.1 Parameters of Ventilation functioning tests . 9 2.2.2 Measurement Techniques of the Human Ventilation . 11 2.2.3 Analyzing Technique of the Human Ventilation . 14 2.3 Breathing Simulator . 16 3 Development of a Breathing Measurement System 23 3.1 Construction and Equipment for Breathing Flow Rate Measurements 23 3.1.1 Geometry of the breathing Mask . 23 3.1.2 Incorporation of Flow Sensors . 24 3.1.3 Calibration and Time response of the Sensor . 30 3.1.4 Signal Processing . 35 3.2 Final Measurements . 35 4 Realization of a Ventilation Simulator 39 4.1 Construction of ventilation Simulator . 39 4.1.1 Instrumentations . 39 4.1.2 Volume Flow Control System for Exhalation . 41 4.1.3 Volume Flow Control System for Inhalation . 42 4.2 Calibration of Combined Values . 43 4.3 Verification Test of the Simulator . 45 4.4 Application of mass flow rate control system as an exhalation unit 45 5 Conclusions, Final Remarks and Outlook 47 CONTENTS ii A numerical calculation of the three time components of the time of flight sensor 50 A.1 principle of Operation . 50 A.1.1 Response of the sending wire . 50 A.1.2 Time-of-flight calculations . 53 A.1.3 Response of the receiving wire . 58 A.2 Discussion of Responses of Sending and Receiving Wires . 60 List of Figures 2.1 Respiratory System . 5 2.2 Schematic Representation of Lung volumes . 10 2.3 Volume-Displacement Spirometer . 12 2.4 Various Spirometers . 13 2.5 Flow Volume Loop . 15 2.6 Classification of Abnormal Ventilation Functioning . 16 2.7 Mechanical Ventilator . 17 2.8 Digital Image of Active Servo Lung 5000 . 18 2.9 Experimental setup of the flow field in Humans’ Oropharynx . 20 2.10 Idealized Model geometry of human oropharynx . 20 2.11 Schematic aerosol experimental setup with Humans’ Inhaler . 21 2.12 3-D views of the oral airway model and bifurcation airway model . 22 2.13 Velocity and Non-dimensional temperature profiles . 22 3.1 Digital image and Schematic Figure of the mask with the sensor . 25 3.2 CTA Ventilation measurement . 27 3.3 Configuration of the Time of Flight Sensor . 28 3.4 Digital Image of the Time of Flight Sensor . 29 3.5 Schematic description of Time of Flight Sensor . 30 3.6 Measurement of time difference . 31 3.7 Time difference and the summation versus the flow velocity . 31 3.8 Calibration set up of the sensor for high velocity flow . 32 3.9 Calibration set up of the sensor for Low velocity flow . 33 3.10 Calibration curve of the extreme low velocity region . 33 3.11 Calibration curve of the Time of Flight Sensor . 34 3.12 Frequency response of the Time-of-Flight sensor . 36 3.13 Human Ventilation measurement with Time-of-Flight sensor . 38 LIST OF FIGURES 1 4.1 Configuration of the ventilation simulation system . 40 4.2 Digital image of the proportional valve . 41 4.3 Calibration Curve for the Exhalation Simulation . 42 4.4 Calibration Curve for the Inhalation Simulation . 43 4.5 Averaged Calibration Curve for Combined Condition . 44 4.6 Simulation of the Human Ventilation . 46 4.7 Simulation of the Human Ventilation with Mass Flow Controller . 46 A.1 Sketch of the time of flight wires of sensor . 51 A.2 Theoretical prediction of sending wire time constant . 54 A.3 Theoretical prediction of fluid time of flight . 56 A.4 Fluid time of flight plotted on log scales . 57 A.5 Theoretical prediction of fluid time of flight as a function of Peclet number ................................ 57 A.6 Detected time of flight versus the flow velocity . 58 A.7 Theoretical prediction of receiving wire time constant . 59 Chapter 1 Introduction In various fields of medicine like physiology or Aerosol medicine, investigations related to the breathing of human beings have gained an increasing interest. Mainly this work is concentrated on the instantaneous volume flow rate through the mouth and nose of different individuals. Breathing is a physiological function which is a combination of three functions, ventilation, perfusion (diffusion) and circulation. For this thesis work, the ventilation function is the target of the monitoring and simulation. The monitoring ventilation is interesting especially for the people who work in medical field to diagnose the lung disease etc. as well as the people who try to simulate the human ventilation mechanically or numerically. There are two different kinds of Human Breathing simulator; one is used for the patients who have the breathing problem, this can be called mechanical ventilator (Machine aided breathing system) and the other is the pure breathing simulator for the measurements in e.g., Human Toxicology field. Some researchers[13] have already developed the mechanical model of human oropharynx to investigate the deposition of the particulate matters on the wall of it. Once one develops the mechanical ventilation system and it is possible to cooporate with such oropharynx system so that one can examine the particle deposition. In Chapter 2, the measurement of the breathing in the clinics or medical laboratory is mainly discussed. The purpose of the measurement for the medical doctors is, for example, diagnosis of the disease. In the first section of this chapter, the breathing system of humans is briefly explained and in the second section, the measurement technique for the Human breathing, how to analyze the result of the measurement and the parameter of them are introduced. The human breathing simulator which is available in the world is introduced in the 3 last section. In chapter 3, the monitoring system of the human ventilation volume flow rate is discussed. The monitoring system including the breathing mask with mass flow rate sensor is developed so that time varying human ventilation of different individuals will be accurately sampled. For the sampling, firstly CTA is applied, however, the result has considerable error thus the time of flight sensor is applied for the necessity since it is not sensitive of the environmental condition like temperature and humidity of the exhaled air. In chapter 4, the experimental investigation of a mechanical ventilation simulator is described. Firstly, two proportional valves, which are incorporated either with vacuum chamber for the inhalation simulation or with pressurized air for the exhalation simulation, are operated by the program of the soft ware Lab view with data acquisition card to simulate the human ventilation. However, the exhalation simulation does not suit the original ventilation curve because the ventilation is time varying flow and simple proportional valve is not suitable for that simulation. Thus a mass flow controller with pressure transducer is applied for the ventilation simulation. The data line of real human ventilation curve is applied for this mechanical simulation. The whole simulation system and the result are presented in this chapter. The conclusions and final remarks are written in chapter 5. Chapter 2 A Brief Literature Survey In this chapter, the work which is relevant to the breathing monitoring and simulation, is briefly explained in three sections as human breathing system, the measurement of the human ventilation and the human breathing simulator. Human breathing is a combination of the lung functions of ventilation, perfusion and circulation. There are many kinds of breathing functioning test, however, one of the test, ventilation functioning test is a great interest for the medical doctors and researchers since it gives the direct diagnosis of the lung disease. In the second section of this chapter, the measurement technique for the ventilation function which is mainly used in the clinics are referred and anlysing technique of the sampled data are briefly explained.

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