SpO2 vs. SaO2 ? | allnurses
What's the ddttrh.info one is from a pulse ox? thanks! pulse oximetry -- SaO2 with normal value >95% Quote from bubbly hypoxic inhalation and when SpO2 ¼ 85%. An HCT The PaO2 at altitude was estimated for each group using four published inverse relationship between oxygen partial pressure . from studies that quote feet and mmHg,9,10 thus the. book says that SaO2 denotes "invasively measured arterial oxygen saturation values, Quote from Daytonite Typically(in a healthy pt) SaO2 and SpO2 measure the same thing, but a difference can be found in patients with.
The measurement is given as a percentage.
Oxygen-Haemoglobin Dissociation Curve
PaO2 describes the amount of oxygen dissolved in arterial blood plasma. The measurement is given as a pressure value mmHg. There is a relationship between the two numbers, which is described in the oxyhemoglobin dissociation curve.
Without getting too far into it, roughly speaking all other things being equal PaO2 and SaO2 relate as follows: Jun 9, '10 Occupation: I thought it would be helpful to post the oxyhemoglobin dissociation curve pic from my slides Enjoy! Jun 9, '10 Joined: I believe that the SaO2 is an "assumed" value, meaning that it actually measures the hemes that are saturated, but only assumes they are saturated with O2. CO poisoning will artificially elevate the SaO2 level, because CO has more affinity to the hemes or vice versa, doesn't matter here for the sake of this argument than O2 does, and the measurement is not actually the number of O2 molecules that are bound, but how many "seats on the bus" are taken up.
Last edit by wannabHishands on Jun 9, '10 Sep 11, '11 Occupation: Looking for homecare Specialty: Since PaO2 is assumed during routine testing, how would it specifically be tested? Does an arterial blood sample need to be taken to get the ABGs?
Oxygen-Haemoglobin Dissociation Curve
This is such a key concept that we all must take pains to ensure our staff understands how to use this valuable monitoring tool. Some of the material below is from my book Anyone Can Intubate. What Is Oxygen Saturation?
Hemoglobin is a chemical molecule in the red blood cell RBC that carries oxygen on specific binding sites. Each Hgb molecule, if fully saturated, can bind four oxygen molecules.
Depending on conditions, Hgb releases some percentage of the oxygen molecules to the tissues when the RBC passes through the capillaries. We can measure how many of these binding sites are combined, or saturated, with oxygen. What Is Arterial PaO2 Pa02, put simply, is a measurement of the actual oxygen content in arterial blood.
Partial pressure refers to the pressure exerted on the container walls by a specific gas in a mixture of other gases. When dealing with gases dissolved in liquids like oxygen in blood, partial pressure is the pressure that the dissolved gas would have if the blood were allowed to equilibrate with a volume of gas in a container.
What’s The Difference Between Oxygen Saturation And PaO2?
In other words, if a gas like oxygen is present in an air space like the lungs and also dissolved in a liquid like blood, and the air space and liquid are in contact with each other, the two partial pressures will equalize.
The Oxygen-Hemoglobin Dissociation Curve Shows the Difference To see why this is relevant, look at the oxygen-hemoglobin dissociation curve. As the partial pressure of oxygen rises, there are more and more oxygen molecules available to bind with Hgb. As each of the four binding sites on an Hgb molecule binds to an oxygen molecule, its attraction to the next oxygen molecule increases and continues to increase as successive molecules of oxygen bind.
PaO2 vs SaO2 | allnurses
The more oxygen is bound, the easier it is for the next oxygen molecule to bind, so the speed of binding increases and the oxygen saturation percentage rises rapidly on the curve.
As all of the binding sites fill up, very little additional binding occurs and the curve levels out as the hemoglobin becomes saturated with oxygen. This tendency makes it easy for Hgb to rapidly pick up oxygen in the lungs as it passes through.
As PaO2 falls, the Hgb saturation also falls as Hgb releases oxygen to the tissues in the areas of lower oxygen supply. This is because Hgb binding sites become less attracted to oxygen as it is bound to fewer oxygen molecules.
This property allows Hgb to rapidly release oxygen to the tissues.