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 really is fascinating that a simple instrument can take a measurement down to the molecular level without being stuck underneath the skin. This isn't the place to go into the smoke and mirrors physics, but it is something to do with absorbing light. Somehow, the machine to which the oximeter is attached can calculate the concentration of oxygen circulating in a patient's arterial blood.
While this is an excellent way of screening sick people from really sick people, a more accurate measurement is obtained by measuring oxygen directly from arterial blood. This is important in places like intensive care units or when a patient is under anesthesia having an operation.
This is a painful and invasive procedure and there needs to be a good reason for collecting this information. Patients who have their arterial blood sampled while they are awake describe the sensation as akin to having a needle stuck directly into their bone. Unfortunately, because one of the circumstances in which this information is important is while a patient is under an anesthetic, so the poor patient has to have the needle inserted while they are still awake.
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 categories of sleep apnea, neurological and obstructive. Obstructive sleep apnea (OSA) is more common than neurological sleep apnea, but no less dangerous. Treatments may include a device that is prescribed by a dentist to keep the mouth partially open at night, continuous positive airway pressure (CPAP) or, in extreme cases, surgery to correct an anatomic deformity that makes the airway unable to open.
The other kind of sleep apnea, neurological or central sleep apnea, is rarer and more serious than OSA. Rather than being unable to breathe, your brain doesn't bother to try. This is usually associated with a serious underlying condition affecting the brain stem, which is the part of the brain that controls breathing. Central sleep apnea may manifest itself alone or alongside OSA.
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 really is fascinating that a simple instrument can take a measurement down to the molecular level without being stuck underneath the skin. This isn't the place to go into the smoke and mirrors physics, but it is something to do with absorbing light. Somehow, the machine to which the oximeter is attached can calculate the concentration of oxygen circulating in a patient's arterial blood.
While this is an excellent way of screening sick people from really sick people, a more accurate measurement is obtained by measuring oxygen directly from arterial blood. This is important in places like intensive care units or when a patient is under anesthesia having an operation.
This is a painful and invasive procedure and there needs to be a good reason for collecting this information. Patients who have their arterial blood sampled while they are awake describe the sensation as akin to having a needle stuck directly into their bone. Unfortunately, because one of the circumstances in which this information is important is while a patient is under an anesthetic, so the poor patient has to have the needle inserted while they are still awake.
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 categories of sleep apnea, neurological and obstructive. Obstructive sleep apnea (OSA) is more common than neurological sleep apnea, but no less dangerous. Treatments may include a device that is prescribed by a dentist to keep the mouth partially open at night, continuous positive airway pressure (CPAP) or, in extreme cases, surgery to correct an anatomic deformity that makes the airway unable to open.
The other kind of sleep apnea, neurological or central sleep apnea, is rarer and more serious than OSA. Rather than being unable to breathe, your brain doesn't bother to try. This is usually associated with a serious underlying condition affecting the brain stem, which is the part of the brain that controls breathing. Central sleep apnea may manifest itself alone or alongside OSA.
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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