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P E Morozoff

Publications and source records attributed to P E Morozoff.

3 recordsLinked to original sources
PubMedDate not supplied

Real-time display of flow-pressure-volume loops.

Graphic display of respiratory waveforms can be valuable for monitoring the progress of ventilated patients. A system has been developed that can display flow-pressure-volume loops as derived from a patient's respiratory circuit in real time. It can also display, store, print, and retrieve ventilatory waveforms. Five loops can be displayed at once: current, previous, reference, "ideal," and previously saved. Two components, the data-display device (DDD) and the data-collection device (DCD), comprise the system. An IBM 286/386 computer with a graphics card (VGA) and bidirectional parallel port is used for the DDD; an eight-bit microprocessor card and an A/D convertor card make up the DCD. A real-time multitasking operating system was written to control the DDD, while the DCD operates from in-line assembly code. The DCD samples the pressure and flow sensors at 100 Hz and looks for a complete flow waveform pattern based on flow slope. These waveforms are then passed to the DDD via the mutual parallel port. Within the DDD a process integrates the flow to create a volume signal and performs a multilinear regression on the pressure, flow, and volume data to calculate the elastance, resistance, pressure offset, and coefficient of determination. Elastance, resistance, and offset are used to calculate Pr and Pc where: Pr[k] = P[k]-offset-(elastance.V[k]) and Pc[k] = P[k]-offset-(resistance.F[k]). Volume vs. Pc and flow vs. Pr can be displayed in real time. Patient data from previous clinical tests were loaded into the device to verify the software calculations. An analog waveform generator was used to simulate flow and pressure waveforms that validated the system.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer Graphics↗
PubMedDate not supplied

Closed-loop control of SaO2 in the neonate.

A microprocessor-based device has been designed to control oxygen saturation (SaO2) in neonates by adjusting the inspired air-oxygen mixture (FiO2) delivered by a mechanical blender. The user sets a target SaO2, which the controller attempts to maintain. Alarms are actuated if the neonate's SaO2 is outside predefined limits. SaO2 levels are extracted from a commercial pulse oximeter and analyzed by an eight-bit microprocessing unit (MPU). Delivered percentages of FiO2 are adjusted by a motorized air-oxygen blender. The controller has a menu-driven user interface and can graphically present four-hour trends of the SaO2, FiO2, or blender setting. Sixteen hours of collected data can be stored and later downloaded to a personal computer. A real-time multitasking operating system forms the nucleus of the controller's software. Major tasks that share MPU time are control, filtering, user display, data collection, data archiving, alarm monitoring, and user input. Analog SaO2 levels are read and converted to digital values, which are then filtered to extract noise. A differential control algorithm is used to determine the required FiO2 blender setting. The blender is then adjusted to the new setting, after which the controller waits to repeat the process of sampling SaO2 and adjusting FiO2. System response time and blender increments are adjustable to allow a user to tune the controller to the patient's needs. Alarm conditions of concern within the device are SaO2 and FiO2 sensor disconnection, blender disconnection, and SaO2 limiting errors. In preliminary trials, for a target of 92.0% SaO2, a prototype controller maintained an average of 91.6% with a standard deviation of 5.0% over a one-hour period.(ABSTRACT TRUNCATED AT 250 WORDS)

Analog-Digital Conversion↗