Vital Signs: Puls Oximetry study: A study of chest based pulse oximetry and respiration rate as an early warning system.
Pulse Oximetry and respiration rate are often used as important vital signs during the monitoring of a patient during recovery or to access wellbeing. This study will examine the relationship between these two parameters and determine key algorithms, trending, device geometries and hence model and set-up a set of trials to understand how future protocols could be designed to allow implementation of this combination of sensors.
The project will involve further research on how impedance based RR can be optimised as a robust sensing technique and how optical based transmissive SpO2 can be positioned within the chest area. Statistical and data analysis will be utilised and eventually trending will be modelled building up patterns that can be assessed via techniques such as PCA.
Respiratory rate (Vf, Rf or RR) is also known by respiration rate, pulmonary ventilation rate, ventilation rate, or breathing frequency is the number of breaths taken within a set amount of time, typically 60 seconds.
Human respiration rate is measured when a person is at rest and involves counting the number of breaths for one minute by counting how many times the chest rises. Respiration rates may increase with fever, illness, or other medical conditions. Inaccuracies in respiratory measurement have been reported in the literature.
Average respiratory rate reported in a healthy adult at rest is usually given as 12-18 breaths per minute (Vf)but estimates do vary between sources, e.g., 12–20 breaths per minute, 10–14, between 16–18,etc. With such a slow rate, more accurate readings are obtained by counting the number of breaths over a full minute.
The value of respiratory rate as an indicator of potential respiratory dysfunction has been investigated but findings suggest it is of limited value. One study found that only 33% of people presenting to an emergency department with an oxygen saturation below 90% had an increased respiratory rate.
A blood-oxygen monitor displays the percentage of arterial haemoglobin in the oxyhemoglobin configuration.
Acceptable normal ranges for patients without COPD with a hypoxic drive problem are from 95 to 99 percent, those with a hypoxic drive problem would expect values to be between 88 to 94 percent, values of 100 percent can indicate carbon monoxide poisoning. 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 SpO2reading.
Pulse oximetry is a particularly convenient noninvasive measurement method. Typically it utilises 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, 905, 910, or 940 nm. Absorption at these wavelengths differs significantly between oxyhemoglobin and its deoxygenated form; therefore, the oxy/deoxyhemoglobin ratio can be calculated from the ratio of the absorption of the red and infrared light. The absorbance of oxyhemoglobin and deoxyhemoglobin is the same (isosbestic point) for the wavelengths of 590 and 805 nm; earlier equipment used these wavelengths for correction for hemoglobin concentration.
The monitored signal bounces in time with the heart beat because the arterial blood vessels expand and contract with each heartbeat. 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, (though black nail polish tends to distort readings) and discern only the absorption caused by arterial blood. Thus, detecting a pulse is essential to the operation of a pulse oximeter and it will not function if there is none.
Personnel Involved
First Supervisor: McLaughlin, JAD Prof
Second Supervisor: Escalona, OJ Prof
Collaboration: This project does not involve collaboration with another establishment