When doctors, nurses or paramedics need a quick estimate of a patient's oxygen levels, they use technology called CMS pulse oximeters. These little gadgets can be easily clipped onto a finger or an earlobe and indirectly measure oxygen levels by determining the percentage of hemoglobin, a respiratory pigment, that is saturated with the life-giving gas. Normal values in most people are 95 percent or more.
It isn't obvious how a non-invasive instrument can measure with any degree of accuracy something down to the molecular level. Without getting too technical, oximetry works on the principle that different substances absorb light differently. Two different wavelengths of light are passed through the patient and the instrument is able to determine the absorbance, and therefore the concentration, of oxygen in pulsating arterial blood.
While this is a decent method of measuring oxygen saturation, it gives no information about the actual level of oxygen in the blood. More accurate measurements of blood oxygen levels may be obtained by measuring arterial blood flow. The best method of doing this is by sticking a needle directly into an accessible artery.
Jamming a needle into an artery, which are by design very thick, is very painful for the patient. Because of this, it is not routinely done unless it is really necessary. The feeling of having a needle pierce into an artery has been compared to having a sharp implement poking directly into a bone.
One of the circumstances where pulse oximetry is employed is during sleep studies. These investigations require an overnight stay in the hospital and are done for the purpose of finding out if someone has a condition called sleep apnea. This is when a person periodically stops breathing during the night. At best, they wake up drowsy and fuzzy-headed. At worst, it is a risk factor for life-threatening conditions like heart attack and stroke.
There are two main types of sleep apnea, obstructive and neurological. Obstructive sleep apnea (OSA) is the more common of the two and is also the easiest to treat. Therapies include surgery, continuous positive airway pressure (CPAP) or prescribing a device that the patient puts in their mouth when they go to bed that helps them to keep their airway open.
The other form of sleep apnea, central, is less common and potentially more serious than OSA. This is because the center of the brain that regulates physiological processes like heart rate and breathing, malfunctions to the point where the body won't try to breathe. Either type of apnea may occur on its own or in conjunction with the other form.
Although anyone can have any type of sleep apnea, the major risk factors are male gender over the age of 40 and being overweight. Sleep apnea is particularly dangerous in infants, who can stop breathing for as long as twenty seconds. This is a very daunting prospect for new parents. Fortunately, there are apnea alarms available that will alert the parents when a baby stops breathing for a set number of seconds. It is also possible to obtain CMS pulse oximeters for home use.
It isn't obvious how a non-invasive instrument can measure with any degree of accuracy something down to the molecular level. Without getting too technical, oximetry works on the principle that different substances absorb light differently. Two different wavelengths of light are passed through the patient and the instrument is able to determine the absorbance, and therefore the concentration, of oxygen in pulsating arterial blood.
While this is a decent method of measuring oxygen saturation, it gives no information about the actual level of oxygen in the blood. More accurate measurements of blood oxygen levels may be obtained by measuring arterial blood flow. The best method of doing this is by sticking a needle directly into an accessible artery.
Jamming a needle into an artery, which are by design very thick, is very painful for the patient. Because of this, it is not routinely done unless it is really necessary. The feeling of having a needle pierce into an artery has been compared to having a sharp implement poking directly into a bone.
One of the circumstances where pulse oximetry is employed is during sleep studies. These investigations require an overnight stay in the hospital and are done for the purpose of finding out if someone has a condition called sleep apnea. This is when a person periodically stops breathing during the night. At best, they wake up drowsy and fuzzy-headed. At worst, it is a risk factor for life-threatening conditions like heart attack and stroke.
There are two main types of sleep apnea, obstructive and neurological. Obstructive sleep apnea (OSA) is the more common of the two and is also the easiest to treat. Therapies include surgery, continuous positive airway pressure (CPAP) or prescribing a device that the patient puts in their mouth when they go to bed that helps them to keep their airway open.
The other form of sleep apnea, central, is less common and potentially more serious than OSA. This is because the center of the brain that regulates physiological processes like heart rate and breathing, malfunctions to the point where the body won't try to breathe. Either type of apnea may occur on its own or in conjunction with the other form.
Although anyone can have any type of sleep apnea, the major risk factors are male gender over the age of 40 and being overweight. Sleep apnea is particularly dangerous in infants, who can stop breathing for as long as twenty seconds. This is a very daunting prospect for new parents. Fortunately, there are apnea alarms available that will alert the parents when a baby stops breathing for a set number of seconds. It is also possible to obtain CMS pulse oximeters for home use.
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