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It disperses across the thin membranes of the alveoli, entering the capillaries, where it dissolves into the bloodstream. So the process goes like this: We breathe oxygen into our lungs. Four oxygens per hemoglobin is maximum occupancy. Each site can bind one oxygen, and only one. We have zillions of them in our blood, and they like to cluster into donut-shaped discs called red blood cells (or erythrocytes).Įach hemoglobin has four binding sites where oxygen molecules like to attach. Hemoglobin are little iron-based proteins. (The kinds of life that can survive on dissolved oxygen alone are the lumpy ones that just kind of roll around from place to place.) So animals like humans have developed a method of carrying far more oxygen in their blood than the fluid itself can absorb. The trouble is that amount of oxygen you breathe in can only produce a very low PaO2 - nowhere near enough bloodborne oxygen to sustain human life. Just like in the Pepsi, the amount of oxygen your blood can dissolve is limited by the PO2 of the gas surrounding it. Breathing faster and breathing higher concentrations of oxygen will both achieve this.

(This is referred to as PO2, or the partial pressure of oxygen.) In other words, the more oxygen you breathe in, the more will cross over into the blood. The concentration of oxygen present in arterial blood is a concentration called PaO2, and is directly related to the concentration of oxygen inhaled into the alveoli. (At the same time, carbon dioxide is diffusing in the other direction, from the blood out into the alveoli, to be exhaled out as waste.) This oxygen “dissolves” into the blood in the same way that fizzy CO2 is dissolved in a can of Pepsi. Oxygen in the ambient air is inhaled into the thin-walled sacs called aveoli, where they easily diffuse across the membrane wall into tiny capillaries filled with blood. Most can survive briefly without oxygen, but not for long and not well.ĭelivering oxygen to the cells is a process that starts in the lungs. The cells of the human body use oxygen molecules (two oxygen atoms forming an O2) as a vital component of their basic metabolism. Don’t worry - we’ll get to the good stuff soon enough. In order to get there, though, we should really start with some basics of pulmonology and respiration. What’s this device all about, and how should we be using it? We brought up pulse oximetry several weeks ago, and it seems like a topic worth exploring in detail.