A pulse oximeter is a medical device that indirectly measures the oxygen saturation of a patient's blood (as opposed to measuring oxygen saturation directly through a blood sample) and changes in blood volume in the skin, producing a photoplethysmograph. A medical device is an object which is useful for diagnostic or therapeutic purposes Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells €”such as nutrients and oxygen—and transports Waste products A photoplethysmograph (PPG is an optically obtained Plethysmograph, a volumetric measurement of an organ It is often attached to a medical monitor so staff can see a patient's oxygenation at all times. A medical monitor is an automated Medical device that senses a patient's Vital signs and displays the results Most monitors also display the heart rate. Portable, battery operated pulse oximeters are also available for home blood oxygen monitoring. The original oximeter was made by Milliken in the 1940s. In the 1970s designs were based on Aoyagi's ability to relate arterial hemoglobin saturation to vessel bed pulsation; the prototype for future pulse oximeters was invented in 1978 by Dr. William New. William Herbert New, OC, FRSC (born 28 March 1938) is a Canadian Poet and Literary critic. The device did not see wide adoption in the United States until the 1980's.
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Function
A blood-oxygen monitor displays the percentage of arterial hemoglobin in the oxyhemoglobin configuration. Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein Acceptable normal ranges are from 95 to 100 percent, although values down to 90% are common. For a patient breathing room air, at not far above sea level, an estimate of arterial pO2 can be made from the blood-oxygen monitor SpO2 reading. The term above mean sea level ( AMSL) refers to the Elevation (on the ground or Altitude (in the Air) of any object relative to the
A pulse oximeter is a particularly convenient non-invasive measurement instrument. The term non-invasive in Medicine has two meanings A Medical procedure which does not penetrate mechanically, nor break the Skin Typically it has 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. A photodiode is a type of Photodetector capable of converting Light into either current or Voltage, depending upon the mode of operation One LED is red, with wavelength of 660 nm, and the other is infrared, 905, 910, or 940 nm. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of Absorption at these wavelengths differs significantly between oxyhemoglobin and its deoxygenated form, therefore from the ratio of the absorption of the red and infrared light the oxy/deoxyhemoglobin ratio can be calculated. Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein The absorbance of oxyhemoglobin and deoxyhemoglobin is the same (isosbestic point) for the wavelengths of 590 and 805 nm; earlier oximeters used these wavelengths for correction for hemoglobin concentration. In Spectroscopy, an isosbestic point is a specific Wavelength at which two (or more chemical species have the same Molar absorptivity (&epsilon [1]
The monitored signal bounces in time with the heart beat because the arterial blood vessels expand and contract with each heartbeat. Measuring heart rate The Pulse rate (which in most people is identical to the heart rate can be measured at any point on the body where an Artery 's pulsation The blood vessels are part of the Circulatory system and function to transport Blood throughout the body By examining only the varying part of the absorption spectrum (essentially, subtracting minimum absorption from peak absorption), a monitor can ignore other tissues or nail polish[2] and discern only the absorption caused by arterial blood. A material's absorption spectrum shows the fraction of incident Electromagnetic radiation absorbed by the material over a range of Frequencies. Thus, detecting a pulse is essential to the operation of a pulse oximeter and it will not function if there is none.
A recent use has been found for the pulse oximeter, in the area of detecting blood loss. Kirk ÂShelley, a Yale University anesthesiologist, through gathering pulse oximeter data for over seven years, developed an algorithm that turns absorption changes into accurate estimates of blood volume. Technology Review
Advantages
Because of their simplicity and speed (they clip onto a finger and display results within a few seconds), pulse oximeters are of critical importance in emergency medicine and are also very useful for patients with respiratory or cardiac problems. Emergency Medicine is a speciality of Medicine that focuses on the Diagnosis and treatment of acute illnesses and injuries that require immediate medical attention Portable, battery operated pulse oximeters are useful for pilots operating in a non-pressurized aircraft above 10,000 feet (12,500 feet in the US[3]), where supplemental oxygen is required. Prior to the oximeter's invention, many complicated blood tests needed to be performed. A blood test is a laboratory analysis performed on a Blood sample that is usually extracted from a Vein in the arm using a needle, or via Portable pulse oximeters are also useful for mountain climbers and athletes whose oxygen levels may decrease at high altitudes or with exercise. Altitude is the Elevation of a point or object from a known level or datum (plural data
Drawbacks
Oximetry is not a complete measure of respiratory sufficiency. A patient suffering from hypoventilation (poor gas exchange in the lungs) given 100% oxygen can have excellent blood oxygen levels while still suffering from respiratory acidosis due to excessive carbon dioxide. In Medicine, hypoventilation (also known as respiratory depression) occurs when ventilation is inadequate ( hypo means "below" to perform needed Gas exchange or respiration takes place at a respiratory surface—a boundary between the external environment and the interior of the body lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive Respiratory acidosis is Acidosis (abnormally increased acidity of the blood due to decreased ventilation of the pulmonary Alveoli, leading to Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single
It is also not a complete measure of circulatory sufficiency. If there is insufficient bloodflow or insufficient hemoglobin in the blood (anemia), tissues can suffer hypoxia despite high oxygen saturation in the blood that does arrive. This is an article about the rock music band "Circulatory System" Anemia ( AmE) or anæmia/anaemia ( BrE) (from the Ancient Greek grc-Latn anaîmia, meaning “without blood” is defined as a qualitative Chronic Hypoxia is a pathological condition in which the body as a whole ( generalized hypoxia) or region of the body ( tissue hypoxia) is deprived of adequate Oxygen saturation is a relative measure of the amount of Oxygen that is Dissolved or carried in a given medium
A higher level of methemoglobin will tend to cause a pulse oximeter to read closer to 85% regardless of the true level of oxygen saturation. Methemoglobin (British English Methaemoglobin (pronounced "MET-hemoglobin" is a form of the Oxygen -carrying Protein Hemoglobin (British English It also should be noted that the inability of two-wavelength saturation level measurement devices to distinguish carboxyhemoglobin due to carbon monoxide inhalation from oxyhemoglobin must be taken into account when diagnosing a patient in emergency rescue, e. Carboxyhemoglobin (British English Carboxyhaemoglobin) (COHb is a stable complex of Carbon monoxide and Hemoglobin that forms in red Blood Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. g. , from a fire in an apartment. A CO-oximeter measures absorption at additional wavelengths to distinguish CO from O2 and determines the blood oxygen saturation more reliably. A CO-oximeter is a device for of detecting hypoxia, a medical condition relating to Oxygen deficiency at Tissue level. In 2005 Masimo Corporation introduced the first FDA-approved pulse oximeter to monitor carbon monoxide levels noninvasively. [4]
Further development
The latest generation pulse oximeters use digital signal processing to make accurate measurements in clinical conditions that were otherwise impossible. Digital signal processing ( DSP) is concerned with the representation of the signals by a sequence of numbers or symbols and the processing of these signals These include situations of patient motion, low perfusion, bright ambient light, and electrical interference. Because of their insensitivity to non-pulsate signals, it is also possible to build reflectance probes that place the photodiode beside the LEDs and can be placed on any flat tissue. These can be used on non-translucent body parts, to measure pulses in specific body parts (useful in plastic surgery), or when more convenient sites are unavailable (severe burn victims). Plastic surgery is a medical specialty interested in the correction of form and function A burn is a type of Injury that may be caused by Heat, cold, Electricity, Chemicals, Light, Radiation, or They are commonly applied to the forehead of patients with poor peripheral perfusion. In Human anatomy, the forehead or brow is the bony part of the head above the Eyes Cultural Aspects A popular Stereotype In Physiology, perfusion is the process of nutritive delivery of Arterial Blood to a Capillary bed in the Biological tissue.
See also
- Arterial blood gas
- Medical equipment
- Medical monitor
- Pulse oximetry
- Capnography, measuring of carbon dioxide (CO2) in the respiratory gases
Pulse oximetry is the most important safety development in anesthesia. An arterial blood gas ( ABG) is a Blood test that is performed specifically on Blood from an Artery. Medical equipment is designed to aid in the diagnosis monitoring or treatment of medical conditions A medical monitor is an automated Medical device that senses a patient's Vital signs and displays the results Pulse oximetry is a non-invasive method allowing the monitoring of the Oxygenation of a patient's Hemoglobin. Capnography is the monitoring of the concentration or partial pressure of Carbon dioxide (CO2 in the respiratory gases
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