An algorithm for automatic control of O2 and CO2 in artificial ventilation

Analysis of parameters affecting blood oxygen saturation and modeling of fuzzy logic system for inspired oxygen prediction

BACKGROUND AND OBJECTIVE

Fraction of Inspired Oxygen is one of the arbitrary set ventilator parameters which has critical influence on the concentration of blood oxygen. Normally mechanical ventilators providing respiratory assistance are tuned manually to supply required inspired oxygen to keep the oxygen saturation at the desired level. Maintaining oxygen saturation in the desired limit is so vital since excess supply of inspired oxygen leads to hypercapnia and respiratory acidosis which lead to increased risk in cell damage and death. On the other side a sudden drop in oxygen saturation will lead to severe cardiac arrest and seizure. Hence intelligent real time control of blood oxygen level saturation is highly significant for patients in intensive care units.

METHODS

This paper gives statistical pair wise analysis for finding out deeply correlated physiological parameters from clinical data for fixing fuzzy variables. An advisory fuzzy controller using Mamdani model is developed with R programming to predict FiO₂ which is to be delivered from the ventilator to maintain SaO₂ with in required levels.

RESULTS

Fuzzy variables for the fuzzy model is fixed using 75% of the clinical data collected. Remaining 25% of the data is used for checking the system. Compared the predictive output of the system with physicians' decisions and found to be accurate with less than five percentage error.

CONCLUSIONS

Based on the comparison the system is proved to be effective and can be used as assist mode for physicians for effective decision making.

A microcomputer oxygen control system for ventilatory therapy

A computer-based feedback system has been developed to adjust the concentration of oxygen in the inspired gas of a patient under artificial respiration. The system uses a proportional plus integral controller and feedback of arterial oxygen saturation to adjust the inspired oxygen fraction. The effectiveness of the controller has been tested using a dynamic, mathematical model of the human respiratory system. This relatively sophisticated model has been developed and examined in the past, and it has been shown that it can realistically describe the human respiratory system for a wide variety of test conditions. The performance of the oxygen control system has been evaluated using the simulation model. The response of the controller to different disturbances is always stable, with arterial pressure of oxygen returning to normal in less than 12 minutes. Some of the simulation results are presented to illustrate the dynamic behavior and robustness of the controller.

Closed-loop control for anesthesia breathing systems

Numerous medical applications of closed-loop control have been developed over the past 40 years. For the patient breathing system, appropriate sensors are available. Feedback controllers have been developed and tested. Gas and vapor delivery devices seem ready for use. With the sensors, controllers, and delivery devices developed and tested, it seems likely that closed-loop control will be an integral part of future anesthesia workstations. The convenience and improved stability and response time will be important advantages in future anesthesia delivery systems.

Closed-loop control of blood pressure, ventilation, and anesthesia delivery

Closed-loop control systems have been in use for over 4,000 years, yet applications in medicine have developed only recently. When compared with manual control, closed-loop controllers for blood pressure, ventilation, and anesthesia delivery provide more rapid and more precise control of mean pressure, end-tidal CO2, and end-tidal anesthetic concentrations. Closed-loop control systems perform better in almost all situations. It must be remembered however, that the best anesthesiologist may perform better than the controller, particularly in his ability to anticipate clinical events which effect control. Although the convenience, precision of control, and immunity to distractions are reason enough to further pursue their development, their final application to clinical care will depend on the inclusion of appropriate safeguards and supervisory software algorithms to protect the systems from failure.

Fundamentals of feedback control applied to microcomputer instrumentation design

Feedback control is widely used in applications which range from simple control of room temperature to very sophisticated control of space flight. This paper describes some fundamentals of feedback control as they apply specifically to microcomputer based medical devices. A classical controller is described in its analog and digital implementations. Reference is made to methods for adjusting or tuning the controller for specific applications. Successful applications of adaptive or self-tuning control are discussed. Examples of feedback control include systems to control arterial blood pressure by the infusion of sodium nitroprusside, systems to control arterial carbon dioxide concentration by mechanical ventilation and systems to control depth of anesthesia by controlled anesthesia delivery.