Oxygen sensors are used to measure and monitor oxygen concentration levels, the oxygen inhaled and exhaled by a patient connected to a ventilator or anesthesia machine.
The oxygen sensor in a respiratory gas monitor (RGM) measures the oxygen concentration (or) oxygen partial pressure in the breathing gas mixture.
Oxygen sensors are also known as FiO2 sensors or O2 batteries, and the fraction of inhaled oxygen (FiO2) is the concentration of oxygen in the gas mixture. The inspired oxygen fraction of the gas mixture in the atmospheric room air is 21%, which means that the oxygen concentration in the room air is 21%.
Why do RGMs need an oxygen sensor?
All breathing gas monitoring is designed to move a mixture of air and oxygen into and out of a patient’s lungs to assist with breathing, or in some cases, to provide mechanical respiration for a patient whose breathing is insufficient or whose body is unable to breathe.
During ventilation, precise measurement of the breathing gas mixture is required. In particular, measuring oxygen during ventilation is critical due to its importance in metabolism. In this case, an oxygen sensor is used to control and detect the patient’s calculated oxygen supply. The main requirement is to provide high accuracy measurement of oxygen content in breathing gases. Different Mechanisms of Medical Oxygen Sensors
Electrochemical sensors
Fluorescent oxygen sensor
1. Electrochemical oxygen sensor
Electrochemical oxygen sensing elements are mainly used to measure the oxygen content in ambient air. These sensors are integrated in the RGM machine to measure the concentration of the oxygen supply. They leave chemical changes in the sensing element, resulting in an electrical output proportional to the oxygen level. Electrochemical sensors convert chemical energy into electrical energy through oxidation and reduction processes. It provides an electrical output to the device proportional to the percentage of oxygen in the cathode and anode. The oxygen sensor acts as a current source, so the voltage measurement is made through the load resistor. The output current of the oxygen sensor is proportional to the rate of oxygen consumption by the oxygen sensor.
2. Fluorescent oxygen sensor
Optical oxygen sensors are based on the principle of fluorescence quenching of oxygen. They rely on the use of light sources, light detectors and luminescent materials that react to light. Luminescence-based oxygen sensors are replacing electrochemical oxygen sensors in many fields.
The principle of molecular oxygen fluorescence quenching has long been known. Some molecules or compounds fluoresce (ie, emit light energy) when exposed to light. However, if oxygen molecules are present, the light energy is transferred to the oxygen molecules, resulting in less fluorescence. By using a known light source, the detected light energy is inversely proportional to the number of oxygen molecules in the sample. Therefore, the less fluorescence is detected, the more oxygen molecules must be present in the sample gas.
Post time: Aug-05-2022