To give you a better understanding of PowerShell, we should first define what a shell is. No, we're not talking about a turtle's shell. :) In computer science, a shell is a user interface that gives you access to various services of an operating system.
SaO2 can be measured either by ABG analysis or by pulse oximetry. SaO2 refers to the amount of oxygen bound to hemoglobin in arterial blood. SpO2 simply means that the SaO2 was measured using pulse oximetry.aO2 is an invasive measure of the % of Oxyhemoglobin (oxygen saturated hemoglobin) in the blood using lab tests on arterial blood. SpO2 noninvasive measure the % of saturated hemoglobin in the capillary bed and does not identify what is saturating the hemaglobin.
The 2's on the right side mean that *two* atoms of hydrogen and *two* atoms of chlorine are produced as a result. Now let's look at subscripts. Subscripts always *follow* the symbol for an element, like in H2O which is, of course, water. The subsript means that *two* atoms within *one* whole water molecule are hydrogen. Subscripts are always used in this way--in the middle or at the end of a compound. You could also have something like CaCl2, which is calcium chloride--one atom of calcium and *two* atoms of chlorine for every *molecule* of calcium chloride.