S.D. Solnushkin - Senior Research Scientist, Pavlov Institute of Physiology, Russian Academy of Sciences, St.-Petersburg
V.N. Chikhman - Ph.D. (Eng.), Head of Laboratory, Pavlov Institute of Physiology, Russian Academy of Sciences, St.-Petersburg
Efficiency of lung ventilation function is affected by the functional state of respiratory muscles; its estimation requires modern methods and advances in information technology. The aim of our work was to organize computing processes in problem-oriented hardware and software package that enables diagnosis of functional impairment of the respiratory muscles by detecting respiratory parameters in different modes and calculating the relevant estimations. A previously developed device MD245 is used to input respiratory parameters in hardware and software system. The pressure measurement is carried out using a sigma-delta ADC AD7192 (Analog Devices) with the subsequent digital input via USB to the computer. Device MD245 management, including elec-tromagnetic valve control the overlap of the respiratory tract, is carried out using a computer with a USB 2.0 full-speed interface.
The developed software runs on the basis of the device MD245 and performs the following functions: measure of the air pressure in the respiratory tract, controls the electromagnetic valve overlap of the respiratory tract, allows graphical display of the recorded pressure with time, calculates various timing parameters of the respiratory cycle, saves the experimental parameters and signals in a database, calculates a number of specific parameters. It is believed that the most comprehensive estimation of the condition of respiratory muscles is achieved by measuring pressure in the respiratory tract when the air flow is stopped during the first 100 ms of the natural inhalation (occlusion stage), and by creation of special respiratory conditions (Mueller maneuver) to calculate specific parameters. Mueller maneuver is referred to an attempt of maximal breath with close mouth and nose - in our case it is provided by the overlap of the respiratory tract solenoid valve at certain times.
The program performs computational processes in the three modes of operation: "experiment", "measurement process" and "work with the archive." In the "experiment" mode, the registration of the experimental data in real time is carried out: the pressure in the respiratory tract is measured during free breathing phase, or during the phase of occlusion (overlapping airflow in the first 100 ms of inhalation), or under conditions of special breathing (Mueller maneuver).
The subject breathes through a tube device for medical and physiological respiratory research. The experimenter initiates regis-tration of inspiratory signal during a specified period of time ("record" button); the phase of quiet breathing also is measured and displayed on the screen in the upper field of the graphic input of the inspiratory signal. At the stage of "breath with break" (occlusion) program provides control signals to the valve mechanism that occludes the inspiratory channel (after 50ms from the beginning of exhalation the valve closes and after 100 ms the valve opens). During the Mueller maneuver the valve closes after 50 ms from the beginning of exhalation and opens after 50 ms from the moment of maximal inspiratory pressure in the channel. When all three phases are over, a separate graphic field appears on the screen showing the overall picture of the measurement of signal of inspiratory breath during all stages of research.
The experimenter decides whether to save the results in a database for further processing by reviewing the general picture of in-spiratory signal obtained in the "experiment" mode. The database keeps a record that contains a registered inspiratory signal at all stages of respiratory research, time values of the moments of opening and closing the valve, and accompanying information (date, time, comment).
At the stage "processing of measurement" mathematical calculations of functional respiratory evaluation of the data accumulated in the database is performed. When calling from a database entry corresponding to a particular subject and a particular experiment with the subject of the overall picture appears inspiratory measurement signal at all stages of research with marked moments of time and the table calculated changes.
The program allows delayed possibility of data processing by transferring OLE experimental media into standard modules (eg, EXCEL, MATHLAB). In the mode "work with the archive" an option exists which allows to save the current state of the database and selection of an archive database as a current database. The present software is developed in the environment of Delphi v.6.0 c using the Windows API library functions; for graphics output a component of the SL Scope library of visual components is used. The library is distributed freely by Mitov Software. The tests confirmed a possibility of using the device in the clinic for functional diagnostics of breathing in patients with respiratory diseases, as well as for the study of respiration in healthy people engaged in specific types of work and sports activities.