Best Pulse Oximeters
A pulse oximeter is a simple and widely used piece of medical device which can be highly valuable in a number of areas of medicine. A pulse oximeter is a portable device that measures oxygen saturation and pulse rate. Pulse oximeters can be used for monitoring medical conditions such as COPD and asthma, or by certain sports participants who are interested in measuring oxygen saturation or pulse rate after running or other activities.
Best Pulse Oximeters in UK 2020
How does a finger pulse oximeter work?
A finger pulse oximeter uses the red color of blood to measure the percent of oxygen that is saturated within an individual’s blood. Red blood cells are red because they contain protein chemical called hemoglobin. Hemoglobin contains iron, which is utilized for transporting oxygen and carbon dioxide. When blood passes through the lungs, oxygen molecules attach to the hemoglobin making them oxyhemoglobin. Hemoglobin releases oxygen while blood passes through the body’s tissue becoming deoxyhemoglobin. The empty hemoglobin molecules then bond with the tissue’s carbon dioxide or other waste gases, transporting it away.
During this process, the color of blood changes. The finger pulse oximeter detects these changes through two light emitting diodes and two sensors on the opposite side of the finger. One diode sends out red light while the other sends out infrared light. Oxygenated blood absorbs light at 660nm (red light), whereas deoxygenated blood absorbs light preferentially at 940nm (infra-red). The relative absorption of light by oxyhemoglobin (HbO) and deoxyhemoglobin is processed by the device and an oxygen saturation level is reported.
The body naturally delivers oxygenated blood in arteries and returns deoxygenated blood in veins. To ensure only the oxygenated blood levels are measured, Finger pulse oximeters are programmed to detect pulsetile blood, which only occurs in veins.
Using Pulse Oximeter
Pulse oximeters are designed to measure the percentage of oxygen molecules which are being carried by each hemoglobin molecule. A normal reading of oxygen saturation in the blood typically ranges from 95-100%. However, certain medical conditions and health related variables can reduce the threshold of a normal reading to as low as 90%. To determine what a normal blood oxygen level is for yourself, it is best to consult a physician.
The heart rate, or pulse rate, is determined by a pulse oximeter by measuring the expansion and contraction of blood vessels with each heartbeat. Nearly all oximeters on the market that measure blood oxygen also measure heart rates. Combined, this data is especially useful for athletes, those monitoring themselves that have health conditions and of course by medical professionals.
The majority of pulse oximeters are attached to a finger, which is typically the index finger. To obtain an accurate reading, it is important to be aware of certain conditions that may exist which distort readings. To obtain an accurate reading, the finger to which the pulse oximeter is attached should be free from nail polish. Black nail polish, for example, can prevent accurate readings. If the subject has cold hands and fingers, this too can prevent an accurate reading. Providing that neither of the aforementioned conditions exist, to obtain an accurate measurement the pulse oximeter must be securely clipped onto the finger.
While the cost of pulse oximeters has fallen in recent years, their availability should never replace an accurate reading in a professional medical office with qualified physicians overseeing the treatment of a patient. Self monitoring pulse oximeters are used not only for those monitoring their own blood oxygen and heart rate levels, but athletes in training, pilots in high altitudes and other applications.
Finger Pulse Oximeter Limitations
- Poor positioning of the finger pulse oximeter.
- Nail polish can give readings are capable false low readings
- Any issues which may cause poor tissue perfusion such as hypovoliemia, hypotension, cold extremities, hypothermia, or cardiac arrest.
- Some Cardiac valvular defects can cause venous pulsation resulting in a finger pulse oximeter reading venous blood and recording low SpO2 levels. Tricuspid regurgitation is one defect.
- Finger pulse oximeters accuracy decreases as the value decreases. Readings below 70% are not reliable.
- Cardiac arrhythmias that alter arterial pulsation can disrupt the finger pulse oximeter from recording an accurate reading.
- Carbon monoxide poisoning causing carboxyhaemoglobin cannot be distinguished from oxygen resulting in finger pulse oximeters giving false readings of 100%. Finger pulse oximeters should not be utilized when carbon monoxide poisoning is suspected
- Abnormal haemoglobins such as methaemoglobinaemia, for example following overdose of prilocaine, cause readings to tend towards 85%.
- Age, sex, or skin color does not have a significant effect on finger pulse oximeter readings