Features of mechanical ventilation are selected by input devices such as touch pads and potentiometers on the control panel ( Fig 1). Analog signals from the control panel and from gas pressure and flow sensors are 'digitized' by means of an analog-to-digital converter. Digitized signals are transmitted to the microprocessor, which interprets and executes program instructions and performs arithmetical and relational operations. Digital output from the microprocessor is converted to analog signals by means of a digital-to-analog converter in order to control various operations of the mechanical ventilator.
A microprocessor offers the ability to provide rapid and precise control of inspiratory and expiratory valve events while running the user interface (control panel), acquiring data, and monitoring ventilator performance. Microprocessor control is designed as either an open- or a closed-circuit system. In an open-circuit system, input is not influenced by output. In a closed-circuit system, commonly called servocontrol, input is affected by output. Servosystems are designed to prevent any difference (error) between the reference value, represented by control panel settings, and the quantified output, represented by sensor measurements. Strategies in mechanical and software design contribute greatly to the optimal performance of a mechanical ventilator.
Was this article helpful?