Air–Oxygen Blenders for Mechanical Ventilators: A Literature Review

Abstract

Respiratory diseases are one of the most common causes of death in the world and this recent COVID-19 pandemic is a key example. Problems such as infections, in general, affect many people and depending on the form of transmission they can spread throughout the world and weaken thousands of people. Two examples are severe acute respiratory syndrome and the recent coronavirus disease. These diseases have mild and severe forms, in which patients gravely affected need ventilatory support. The equipment that serves as a basis for operation of the mechanical ventilator is the air–oxygen blender, responsible for carrying out the air–oxygen mixture in the proper proportions ensuring constant supply. New blender models are described in the literature together with applications of control techniques, such as Proportional, Integrative and Derivative (PID); Fuzzy; and Adaptive. The results obtained from the literature show a significant improvement in patient care when using automatic controls instead of manual adjustment, increasing the safety and accuracy of the treatment. This study presents a deep review of the state of the art in air–oxygen benders, identifies the most relevant characteristics, performs a comparison study considering the most relevant available solutions, and identifies open research directions in the topic.

A Pneumatic Proportional Constant Flow Valve With Mechanical Feedback

“…Therefore, according to the force analysis diagram in Fig. 3(b), the motion equation of the spool can be written as (1), in which the mass m is the sum of all the moving parts.…”

“…For occasions where the inlet pressure fluctuates significantly, although there is a small nonlinear segment in the pressure-flow curve, the percentage of flow rate change also has a similar magnitude to the percentage of pressure change. This is fatal for occasions that require high constant flow characteristics such as the proportional adjustment of chemical reaction gasses and medical oxygen concentration [1] [2].…”

A New Model of Air–Oxygen Blender for Mechanical Ventilators Using Dynamic Pressure Sensors

“…Tasked with regulating the air and O 2 proportions for patients, thereby controlling the inspiratory oxygen fraction (FiO 2 ), it can be constructed in various ways, such as a Venturi tube, Poppet-configuration area asset variation, three-terminal solenoid valves, or electronic devices. Typically, a blender includes an air inlet, an O 2 inlet, a bypass system for excessive pressures, a gas equilibrium stage, and a mixing stage [ 9 , 10 , 11 , 12 ]. Previous studies have evaluated similar aspects on Venturi, turbine, or mixer systems for non-invasive ventilation [ 13 , 14 ].…”