![]() ![]() When you insert your fingertip into a pulse oximeter, it uses two non-invasive LED lights-one red to measure deoxygenated blood and the other infrared to measure oxygenated blood. If all the binding sites on the hemoglobin molecule have oxygen, the hemoglobin is 100% saturated. Pulse oximetry measures the percent of hemoglobin saturated by oxygen, which is called oxygen saturation and is expressed as a percentage. Oxygen is attached to hemoglobin, an iron-rich protein in red blood cells. Pulse oximetry is a quick and painless indicator as to how well your body is working to move the oxygen from your heart to your extremities. Best Pulse Oximeters For Seniors Of 2023Ī pulse oximeter is a device that measures your pulse rate (or heart rate) and the percentage of oxygen in your blood, showing digital readings for both in a matter of seconds. While we work hard to provide accurate and up-to-date information that we think you will find relevant, Forbes Health does not and cannot guarantee that any information provided is complete and makes no representations or warranties in connection thereto, nor to the accuracy or applicability thereof. The compensation we receive from advertisers does not influence the recommendations or advice our editorial team provides in our articles or otherwise impact any of the editorial content on Forbes Health. Second, we also include links to advertisers’ offers in some of our articles these “affiliate links” may generate income for our site when you click on them. This site does not include all companies or products available within the market. The compensation we receive for those placements affects how and where advertisers’ offers appear on the site. First, we provide paid placements to advertisers to present their offers. This compensation comes from two main sources. To help support our reporting work, and to continue our ability to provide this content for free to our readers, we receive compensation from the companies that advertise on the Forbes Health site. I assume there would be some atmospheric stratification, as suggested by Ville Nieme, but I don't know for sure.The Forbes Health editorial team is independent and objective. I don't know what the likely total pressures are - which could help us narrow down the range - but it seems like you've got a decent amount of wiggle room, in your gas dwarf scenario. At 70% oxygen, effects start to appear at total pressures of about 45 kPa at 0% oxygen, humans can't survive (the minimum should be 10%-20%, depending on the total pressure). The atmospheres are likely to be 30%-100% hydrogen and helium, meaning that they can be 70%-0% oxygen (and other heavy gases, which can be just as dangerous if their partial pressures are increased). I've boxed in the area between $2M_$, the area where we're likely to see gas dwarfs, at some likely envelope radii. In a gas dwarf, how much of the atmosphere is likely to be oxygen? Here's (a modified) Figure 9 from Lopez & Fortney (2013): Below 0.5 atmosphere of inspired oxygen, indefinite exposure appears to be safe between 0.5 and approximately 2 atmospheres, pulmonary toxicity occurs after prolonged exposures but CNS effects are not detectable above 2 atmospheres, CNS toxicity appears before pulmonary effects are detectable. The safe duration of exposure becomes shorter as the inspired PO2 increases. The occurrence of toxicity depends upon both the inspired oxygen pressure (PO2) and the duration of exposure. The two areas most affected are the CNS and the lungs. See the Apollo 1 disaster.ĭuration is also a necessary factor, as this university page explains: However, note that in atmospheres that are almost entirely oxygen, combustion becomes an issue. For example, at a total pressure of 90 Kpa, you can have at most an oxygen concentration of about 50%, though effects will begin at about 35%. Really, the limits depend on the rest of the atmosphere. Tobias (1967) came up with the following graph of the limits of the percent of oxygen vs. ![]() ![]() One NASA page reviews many studies on the limits. ![]() There are many good studies on oxygen toxicity. ![]()
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