Choosing the Right Pulse Oximeter

Hemoglobin is a biological pigment found in red blood cells. When hemoglobin combines with oxygen during the oxygenation of blood in the lungs, it becomes oxyhemoglobin.

Oxyhemoglobin is a molecule that absorbs a large amount of infrared light when the latter passes through it. The principle of pulse oximetry measurement is therefore based on the absorption of infrared radiation by oxyhemoglobin.

In practice, a light-emitting diode emits infrared light to a photodiode through a capillary. The amount of infrared light absorbed by this capillary will therefore be proportional to the oxyhemoglobin concentration.

Huntleigh Diagnostics pulse oximeter with separate sensor

There are primary selection criteria when purchasing a pulse oximeter, such as the measurement reliability, and secondary selection criteria, such as the readability.

• Main selection criteria:
  • Application: pulse oximeters can be used in hospitals and at home as well as in the neonatal/pediatric, sports and veterinary fields, among others.
  • The type of oximeter desired: there are essentially two types of pulse oximeters:
    • Fingertip pulse oximeters: the monitor is integrated directly into the clip-on sensor. This type of pulse oximeter is practical and easily transportable. They are widely used by individuals as well as in hospitals.
    • Pulse oximeters with separate sensor: in this type, the monitor is connected by a cable to the sensor. These devices are more cumbersome and complex, making them less practical for use by individuals. They provide more reliable measurements however and are more suitable for hospital wards.
  • Measurement reliability: it is recommended to choose a pulse oximeter that has obtained CE certification and meets the ISO 8061-2-61 standard. The user should also refer to the instruction manual for the exact margin of error stated by the manufacturer. Measurement reliability also depends on the number of sensors present on the device.
  • Autonomy: this is very important if the pulse oximeter will be used several times a day. Most devices are battery operated. Autonomy depends on the presence or absence of certain features, such as powerful backlighting of the display screen which will consume more energy, or the existence of an automatic shutdown function of the device which will save battery use.

• Secondary selection criteria:
  • Readability: there are several features that make reading a pulse oximeter easier, such as powerful backlighting, a multi-directional display, anti-reflective glass, a large and contrasting number display, etc.
  • Complementary measures: a pulse oximeter can be associated with a capnograph or a heart rate monitor and also allow heart rate measurement.
  • Device reliability: resistance to shocks, dust or water is particularly important when the device is used by certain professions such as firefighters or mountaineers.

Using a pulse oximeter has several advantages, such as its non-invasiveness, as well as some disadvantages, such as the fact that it cannot warn of a respiratory problem before it occurs. Here is a list of the main advantages and disadvantages:

• Advantages:
  • Non-invasive
  • Quick and easy installation
  • Painless
  • Instantaneous
  • Regular monitoring of certain vital signs made simple
• Disadvantages:
  • The results indicate  respiratory problems late
  • The relative reliability of the results

Beurer pulse oximeter

Using a pulse oximeter is simple and generally similar for each device. The main steps to follow are as follows:

• Check that the sensor and the LED transmitter are clean. If not, they should be cleaned with an alcohol or soap solution.
• Place the sensor on one finger (usually the index finger, but another finger can be used if the patient feels more comfortable). Check for the absence of nail polish and grease on the finger.
• A normal oxygen saturation in the blood should be between 95% and 100%. Below 95%, the patient’s condition should be considered worrying. Below 90%, it becomes critical.
• After taking the measurement, be sure to put the device back in its case, in a dry place, not overexposed to light and at room temperature in order to prevent the batteries from losing their charge and avoid the risk of less reliable measurements.

Lepu Medical pediatric pulse oximeter

Certain factors can influence the measurement and distort the results of a pulse oximeter, such as a patient’s low blood pressure or heart rhythm disorders. The following is a non-exhaustive list of these factors:

• High blood pressure
• Hypothermia
• Heart rhythm disorders, such as arrhythmia or tachycardia
• The sensor not positioned properly
• Nail polish on the finger on which the sensor is placed
• Excessive patient movement
• Anemia
• Patient morphology (size and thickness of fingers)
• Measurement performed at a higher altitude (the oxyhemoglobin level will be lower due to the lack of oxygen in the environment)
• If the oximeter is single-sensor and the same device is used to perform neonatal/pediatric and adult measurements.