Mr. Harikrishna Arya said - Yes, it is true and it can happen. Pulse Oximeter will show SpO2 (oxygen level) and pulse rate of every semi-transparent objects whether it is a biscuit (of any brand) or any other non-living semi-transparent thing. (One can try out for different things, shoot a video, then upload to social media, saying it measures oxygen level and pulse rate of non-living materials, so oximeter is a big fraud.) But, in fact, it is not so. Actually, it works on principle of light absorption.
Let us understand the whole process of Oximeter.
• The oximeter utilizes an electronic processor and a pair of small light-emitting diodes (LEDs) facing a photodiode through a translucent part of the patient's body, usually a fingertip or an earlobe.
• One LED is red, with wavelength of 660 nm, and the other is infrared with a wavelength of 940 nm.
• Absorption of light at these wavelengths differs significantly between blood loaded with oxygen and blood lacking oxygen.
• Oxygenated hemoglobin absorbs more infrared light and allows more red light to pass through.
• Deoxygenated hemoglobin allows more infrared light to pass through and absorbs more red light.
• The LEDs sequence through their cycle of one on, then the other, then both off about thirty times per second.
• The amount of light that is transmitted (in other words, that is not absorbed) is measured.
• These signals fluctuate in time because the amount of arterial blood that is present increases (literally pulses) with each heartbeat.
• By subtracting the minimum transmitted light from the peak transmitted light in each wavelength, the effects of other tissues is corrected for allowing for measurement of only the arterial blood.
• The ratio of the red light measurement to the infrared light measurement is then calculated by the processor (which represents the ratio of oxygenated hemoglobin to deoxygenated hemoglobin).
• This ratio is then converted to SpO2 by the processor via a lookup table based on the Beer–Lambert law.
But the question remains Why would a pulse oximeter give a reading when used with a Biscuit, Pakoda, Pen or Pencil etc.?
Pulse oximeter is detected oxygen level based on the sensitivity of the amount of red and infrared light falling on the sensor of the pulse oximeter. When these obstructs are inserted in Oximeter it increasing the distance between the LED and the detector, or by inserting some object inside the probe, the module will think the finger is inserted and will start searching for a pulse. In this condition, the varying intensity of diffused light falling on the detector can cause a pulsating effect and lead to a reading on the pulse oximeter. The pulse oximeter is a very sensitive device. However, if the gap between the LED and the sensor is closed fully, so that no light falls on the detector, the pulse oximeter will sense no pulse and there won’t be any reading.
Small beams of light pass through the blood in the finger, measuring the amount of oxygen. It does this by measuring changes in light absorption in oxygenated or deoxygenated blood. The pulse oximeter will thus be able to tell you your oxygen saturation levels.
CAUTION: Please do not insert any objects like a pencil, pen, buiscuit, pakodas etc in the pulse oximeter to check the readings. This may damage the sensor of the device and can lead to malfunctioning.
Pulse Oximeter क्या है? हिंदी में जानने के लिए Pulse Oximeter पर क्लिक कीजिए