A comparison of linear and logarithmic auditory tones in pulse oximeters (2024)

FAQs

What are the two types of pulse oximetry? ›

Currently, the 2 basic types of pulse oximeter probes are transmission probes and reflectance probes.

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.

Excessive motion—shivering, shaking, or other movement—can also cause erroneous readings. Skin temperature and thickness can also reduce the accuracy of pulse pulse oximeters, and whether a person smokes tobacco can affect the device's accuracy.

3 types of waveforms

Waveform 1 is normal. 2. Waveform 2 is small and weak indicating decreased stroke volume, increased peripheral resistance and/or hypovolaemia as well as possibly cardiac failure. 3. Waveform 3 is large and bounding indicating decreased peripheral resistance and/or decreased compliance.

Blood oxygen readings are displayed in a percentage of SpO2 (peripheral oxygen saturation) and heart rates are displayed simply as BPM (beats per minute). According to the British Lung Foundation, your blood oxygen level should be around 95% to 100%. A healthy heart rate is 50 to 90 BPM.

Pulse oximeters may be prescribed by a doctor or purchased over the counter. The FDA recommends knowing the difference so that patients use pulse oximeters safely. Prescription oximeters are reviewed by the FDA; available by prescription only; have undergone clinical testing; and are used for medical purposes.

Principles of pulse oximetry

These two wavelengths are used because O₂Hb and Hb have differentabsorption spectra at these particular wavelengths. In the red region,O₂Hb absorbs less light than Hb, while the reverse occurs in theinfrared region.

The Waveform

A regular, repetitive waveform with obvious peaks and troughs is indicative of a good quality peripheral perfusion. A shallow, weak waveform would mean there is poor peripheral perfusion which could could indicate poor cardiac output or simply the casualty does not have great circulation in their fingers.

Your oxygen meter shows two numbers. Your oxygen level is labeled SpO2. The other number is your heart rate. For most people, a normal oxygen level is 95% or higher and a normal heart rate is generally below 100.

An SpO2 level of 92 percent is considered the lowest clinically acceptable level by established norms of clinical practice at any age, except in cases of chronic lung disease, where it is 88 percent. Death can occur due to hypoxemia at any level less than 88 percent.

What is the lowest oxygen level you can live with? ›

1 For most healthy adults and children, a normal oxygen saturation level is between 95% and 100%. 2 Hypoxemia occurs with lower levels of oxygen in the blood and can lead to complications or even death at dangerously low levels below 90%.

You could possibly be retaining CO2. If this is the case, you could still show high sats but still feel short of breath. In fact, high CO2 will trigger the feeling of shortness of breath long before you are actually low on breath.

The pleth waveform corresponds to blood flow. A well-defined pleth suggests a strong pulse and good perfusion at the probe site. With every cardiac contraction, during systole, the pulse ox pleth goes nearly straight up then starts to drop off. This is called the anacrotic limb.

Low-amplitude pulse oximetry wave tracings may be due to poor finger perfusion resulting from vasoconstriction and/or hypotension from a number of causes including distributive or hypovolemic shock, hypothermia, use of vasoconstrictor agents, and poor cardiac output due to pump failure or dysrhythmia.

Respiratory rate (RR) is an important early marker of respiratory deterioration, but is often inaccurately recorded. We have developed and validated a technique to derive RR from a standard pulse oximeter plethysmogram (pleth) trace.

SaO2 is the oxygen saturation of arterial blood, while SpO2 is the oxygen saturation as detected by the pulse oximeter.

In the briefest summary, Fractional saturation (FO₂Hb) is the fraction of total haemoglobin which happens to be oxygenated. Functional saturation (sO₂) is the fraction of effective haemoglobin which is oxygenated.

There are two styles of oxygen sensors, Narrowband and Wideband. Narrowband O2 Sensors typically have up to 4 wires coming out of them and as the name suggests only measure a very narrow window of Air to fuel mixtures – around 0.99 to 1.01 Lambda or 14.6 to 14.8:1 in the petrol scale.

Both of these non-invasive measurement techniques are simple and provide information continuously but their accuracy depends on skin blood flow. Pulse oximeters require pulsatile flow under the probe1 and transcutaneous monitors require adequate blood flow in the skin below the electrode2,3.