Fingertip oxygen monitor, an incredible invention at the end of the 20th century, provides an inexpensive alternative to drawing blood to find the oxygen content of blood at the periphery of the human body.

Vital sign monitors since then have included saturation of peripheral oxygen monitors (SpO2 monitors) as blood oxygen monitor of choice in their device complex. Come to think of it, the effective distribution of oxygen is the single most crucial component in patients in critical condition. Therefore, all the vital sign monitor devices, blood pressure sensors, heart pulse rate sensors, and oxygen saturation sensors, are provided to give insight into the effectiveness of oxygen distribution. Let's see how vital sign monitoring works.

Heart pulse rate sensors

Heart muscle is designed as a pump to repeatedly push the freshly oxygenated blood from the lungs into all other parts of the body. The hear pulse rate determines how often the oxygen depleted blood is replaced by the fresh, presumably oxygen saturated blood from the lungs. With low heart pulse rate, the oxygen transport to the body cells will be low. Therefore, heart pulse rate monitor is always included in any vital signs monitor complex.

Blood pressure sensors

Intuitively, the higher the blood pressure, the more power the heart will exert on the blood, and the more oxygen will reach the remote (peripheral) body organs and cells. Since these cells are crucial for person's activities (think finger movements, etc.), there has to be sufficient blood pressure generated for (presumably) highly oxygenated blood to reach the remotest cells in the body. Therefore, blood pressure sensors are just as important as the heart rate sensors as vital sign sensors. Sure enough, there are caveats to this. While the blood pressure is important in delivery of oxygen, high blood pressure could mean that the arteries are clogged, and therefore present more resistance than usual, forcing the heart to compensate, which is not a good thing as the heart muscle must work much harder than normal.

Oxygenation probes or blood oxygen saturation monitor

Finally, what does it help to have powerful (high pressure) blood flow, with sufficiently high frequency (heart pulse) when the blood itself carries little oxygen? That is where saturation of peripheral oxygen probes (SpO2 probes), or a finger oxygen saturation monitor come in. When the blood pressure sensors have established that the blood is pumped in forcefully, and the heart rate monitors confirm that the heart is beating with sufficient frequency, blood oxygen saturation probe will confirm that red blood cells, or hemoglobin, is actually sufficiently laden with oxygen molecules for blood to actually be supplying the all-important oxygen to the cells. That way, by confirming with all three probes at the same time, a nurse can be reasonably sure that the patient's body is sufficiently supplied with oxygen to assure the patient's livelihood.

Of course, these are just the basic requirements for sufficient delivery of energy-providing oxygen to the cells in the patient's body. Other, more complex vital sign monitors will feature additional vital sign probes, such as ECG monitors, respiration monitors, and more.