Excellent Pulmonary Resources

leslie :-D · May 14, 2004

I am a member of COPD-international, and a question was posted by a member who doesn't know how to explain the results of the pulseoximeter reading. Can you help me out. I just know that for me, when I'm active, my Po2 level is around 93, but after sitting down a few minutes, it drops back into the 80's. I would appreciate any feedback you could give me on this.
Thanks,

fran,

i don't put much stock in pulse oximeters for they don't always tell an accurate story. one time i had a pt. in acute heart failure, who was pale, diaphoretic with sob. the oximeter read 96% on ra. when the paras came, they complained to me "but his o2 sat is 96%!!!"..my point is that people tend to focus on machinery/equipment and not the pt. in terms of your own sat readings, your activity is increasing blood flow so more o2 is also increasing. at rest, circulation resumes its' normal flow and thus the reason for its' decrease. also with copd, with increased activity, you're ridding your body of retained co2, thus increasing o2 levels.

leslie

FranEMTnurse, CNA, LPN, EMT-I · May 14, 2004

fran,
i don't put much stock in pulse oximeters for they don't always tell an accurate story. one time i had a pt. in acute heart failure, who was pale, diaphoretic with sob. the oximeter read 96% on ra. when the paras came, they complained to me "but his o2 sat is 96%!!!"..my point is that people tend to focus on machinery/equipment and not the pt. in terms of your own sat readings, your activity is increasing blood flow so more o2 is also increasing. at rest, circulation resumes its' normal flow and thus the reason for its' decrease. also with copd, with increased activity, you're ridding your body of retained co2, thus increasing o2 levels.
leslie

Thanks for your reply, leslie. I have that very same problem, and most docs go by it too. It definitely aggravates me. Then the only real was to test a person's oxygen level is via ABG?

Havin' A Party!, ASN, RN · May 15, 2004

Temp of the extremities, dark nail polish, accuracy of the instrument, lighting in the room, and other conditions will affect the POx reading.

Always get different results (by several percent) when I check mine on two different machines at work.

leslie :-D · May 15, 2004

Then the only real was to test a person's oxygen level is via ABG?

fran, i am unsure as to whether you were posing this as a question but abg's stand for arterial blood gases, which is a blood draw through an artery, where all the o2 is leaving your left ventricle and before it gets deoxygenated in the venous return to the right side of your heart. as a rule i don't do o2 sats on copder's unless it's to establish a baseline and that's it. fran, don't hesitate to pm me for ANY info you need. truly i would do anything for you.

leslie

Home Health Columnist / Guide · May 15, 2004

little reminder about the :

oxygen transport and the oxyhemoglobin disassociation curve

lung diseases can effect any or all factors needed for oxygen transport.

http://asthma.about.com/cs/support/l/aa041701a.htm

the transport of [color=#236eb5]oxygen throughout the body is done by the blood stream and the red blood cells. factors that affect this transport include the available oxygen to the lungs, the ability of oxygen to get passed the [color=#236eb5]alveolar/capillary membrane, and the oxygen carrying capacity of the blood.

even after blood has received its load of oxygen, there are more factors that affect blood's willingness to release its cargo such as temperature and ph. these two factors effect what is known as the oxyhemoglobin disassociation curve.

lung diseases can affect any or all factors needed for oxygen transport. we treat a diminished ability to get oxygen into the alveoli and then into the capillaries by increasing the concentration of oxygen available to the patient. we can easily do that with [color=#236eb5]supplemental oxygen delivered by nasal cannula or mask, but this doesn't treat the cause of the disease. what it does is buy time for other treatments to work.

once oxygen has made its way past the lung it's up to the blood stream and red blood cells to deliver oxygen to all parts of the body. oxygen is carried two ways; bound to hemoglobin within the red blood cells and dissolved in the blood's plasma. the pao2 measured by an arterial blood gas (abg) looks at the dissolved portion of oxygen in the blood. this is a very small part but does give the clinician an idea of how much oxygen is making its way passed the alveolar/capillary membrane. the bulk of oxygen carried is bound to hemoglobin. the oxygen saturation or o2 sat. is a measurement of the amount of oxygen bound to hemoglobin.

the amount of hemoglobin available to oxygen, hemoglobin's ability to bind with oxygen, and then hemoglobin's ability to release its store of oxygen to the tissues are all important to oxygen transport. a low red blood cells count (anemia) reduces the amount of hemoglobin available. high oxygen saturations matter little since very little oxygen may be available to the body. this can be caused by bleeding, reduced red blood cell production, or other factors. other gasses binding with hemoglobin such as carbon monoxide, which has a 240 times greater affinity to hemoglobin than oxygen, can reduce oxygen delivered to the body but still show as high oxygen saturation.

the [color=#236eb5]oxyhemoglobin disassociation curve describes how oxygen interacts with hemoglobin. the curve itself is based on a comparison of pao2 and oxygen saturation. as pao2 drops, so does oxygen saturation, but the relationship is not linear, the curve is more "s" shaped. oxygen saturations will stay in the 90 and above percent range until the pao2 drops to about 60mmhg. below that the curve drops drastically along with oxygen saturations. variations in ph, carbon dioxide, 2,3-dpg, and temperature can cause the curve to shift to the right or left. a shift to the right means it will take higher pao2s to maintain a high oxygen saturation, where a shift to the left will have high saturations even with normally low oxygen levels.

this helps explain why people drowning in cold water can be saved with little or no brain damage even when they've been submerged to long periods of time. hypothermia and an acidotic blood chemistry shift the curve to the left maintaining high oxygen levels in the blood. hypothermia also lowers the body's metabolic rate so it uses less oxygen. the flip side of the curve is that shifts to the left means hemoglobin has an increased affinity for oxygen and releases less of it to the body. a shift to the right, even with lower oxygen saturations, means hemoglobin releases its supply of oxygen more easily.

factors and how the curve is affected:

variation of the hydrogen ion concentration. this changes the blood's ph. a decrease in ph shifts the standard curve to the right, while an increase shifts it to the left. this is known as the bohr effect.
effects of carbon dioxide. carbon dioxide affects the curve in two ways: first, it influences intracellular ph (the bohr effect), and second, co2 accumulation causes carbamino compounds to be generated through chemical interactions. low levels of carbamino compounds have the effect of shifting the curve to the right, while higher levels cause a leftward shift.
effects of 2,3-dpg. 2,3-diphosphoglycerate, or 2,3-dpg, is an organophosphate, which are created in erythrocytes during glycolysis. the production of 2,3-dpg is likely an important adaptive mechanism, because the production increases for several conditions in the presence of diminished peripheral tissue o2 availability, such as hypoxemia, chronic lung disease, anemia, and congestive heart failure, among others. high levels of 2,3-dpg shift the curve to the right, while low levels of 2,3-dpg cause a leftward shift, seen in states such as septic shock and hypophosphatemia.
temperature. temperature does not have so dramatic effect as the previous factors, but hyperthermia causes a rightward shift, while hypothermia causes a leftward shift.
carbon monoxide. hemoglobin binds with carbon monoxide 240 times more readily than with oxygen, and therefore the presence of carbon monoxide can interfere with the hemoglobin's acquisition of oxygen. in addition to lowering the potential for hemoglobin to bind to oxygen, carbon monoxide also has the effect of shifting the curve to the left. with an increased level of carbon monoxide, a person can suffer from severe hypoxemia while maintaining a normal po2.
effects of methemoglobinemia (a form of abnormal hemoglobin). methemoglobinemia causes a leftward shift in the curve.
fetal hemoglobin. fetal hemoglobin (hbf) is structurally different from normal hemoglobin (hb). the fetal dissociation curve is shifted to the left relative to the curve for the normal adult. typically, fetal arterial oxygen pressures are low, and hence the leftward shift enhances the placental uptake of oxygen.

http://asthma.about.com/gi/dynamic/offsite.htm?site=http://www.ventworld.com/resources/oxydisso/dissoc.html

----------

when you have less that 88% saturation, you can see how steeply the percent of oxygen in the body drops.

what do the readings indicate?

[color=#660066]as a guide:

[color=#660066]95% - 99% - normal

[color=#660066]91% - 94% - mild hypoxia

[color=#660066]86% - 91% - moderate hypoxia

[color=#660066]85% and lower - severe hypoxia

supplemental o2 is indicated for

oximetry should always be measured: at rest and with activity (often drops with activity).

medicare guidelines for oxygen payment is standard most insurance companies use for oxygen payment.

for patients that don't qualify, a doctor can still write a rx for oxygen and patient pay for rental of an e tank--costs less than $75.00/month.

if a person does not meet the following guidelines, medicare may not pay for home oxygen therapy:

arterial oxygen pressure is less than or equal to 55 mm hg (millimeters of mercury, a measure of pressure).
arterial oxygen saturation is less than or equal to 88%.
arterial oxygen pressure is between 56 mm hg and 59 mm hg or oxygen saturation is 89% and the person has:
- evidence of right-side heart failure due to breathing problems (cor pulmonale).
- heart failure.
- an increased number of red blood cells (erythrocytosis).
[*]arterial oxygen saturation is greater than 88% when the person is resting but becomes less than or equal to 88% when the person is exercising or sleeping.

hope this helps!

leslie :-D · May 15, 2004

Karen, that was very informative....I'm keeping this one for my books. Thanks!

Leslie :)

FranEMTnurse, CNA, LPN, EMT-I · May 15, 2004

fran, i am unsure as to whether you were posing this as a question but abg's stand for arterial blood gases, which is a blood draw through an artery, where all the o2 is leaving your left ventricle and before it gets deoxygenated in the venous return to the right side of your heart. as a rule i don't do o2 sats on copder's unless it's to establish a baseline and that's it. fran, don't hesitate to pm me for ANY info you need. truly i would do anything for you.
leslie

Thanks, leslie, but I do know about ABG's I should. When I had pneumonia the first time in 2002, I had to have one every single day for ten days straight.

Here's a (((HUG)))

FranEMTnurse, CNA, LPN, EMT-I · May 15, 2004

little reminder about the :
oxygen transport and the oxyhemoglobin disassociation curve
lung diseases can effect any or all factors needed for oxygen transport.
http://asthma.about.com/cs/support/l/aa041701a.htm

the transport of [color=#236eb5]oxygen throughout the body is done by the blood stream and the red blood cells. factors that affect this transport include the available oxygen to the lungs, the ability of oxygen to get passed the [color=#236eb5]alveolar/capillary membrane, and the oxygen carrying capacity of the blood.

even after blood has received its load of oxygen, there are more factors that affect blood's willingness to release its cargo such as temperature and ph. these two factors effect what is known as the oxyhemoglobin disassociation curve.

lung diseases can affect any or all factors needed for oxygen transport. we treat a diminished ability to get oxygen into the alveoli and then into the capillaries by increasing the concentration of oxygen available to the patient. we can easily do that with [color=#236eb5]supplemental oxygen delivered by nasal cannula or mask, but this doesn't treat the cause of the disease. what it does is buy time for other treatments to work.

once oxygen has made its way past the lung it's up to the blood stream and red blood cells to deliver oxygen to all parts of the body. oxygen is carried two ways; bound to hemoglobin within the red blood cells and dissolved in the blood's plasma. the pao2 measured by an [color=#236eb5]arterial blood gas (abg) looks at the dissolved portion of oxygen in the blood. this is a very small part but does give the clinician an idea of how much oxygen is making its way passed the alveolar/capillary membrane. the bulk of oxygen carried is bound to hemoglobin. the oxygen saturation or o2 sat. is a measurement of the amount of oxygen bound to hemoglobin.

the amount of hemoglobin available to oxygen, hemoglobin's ability to bind with oxygen, and then hemoglobin's ability to release its store of oxygen to the tissues are all important to oxygen transport. a low red blood cells count (anemia) reduces the amount of hemoglobin available. high oxygen saturations matter little since very little oxygen may be available to the body. this can be caused by bleeding, reduced red blood cell production, or other factors. other gasses binding with hemoglobin such as carbon monoxide, which has a 240 times greater affinity to hemoglobin than oxygen, can reduce oxygen delivered to the body but still show as high oxygen saturation.

the [color=#236eb5]oxyhemoglobin disassociation curve describes how oxygen interacts with hemoglobin. the curve itself is based on a comparison of pao2 and oxygen saturation. as pao2 drops, so does oxygen saturation, but the relationship is not linear, the curve is more "s" shaped. oxygen saturations will stay in the 90 and above percent range until the pao2 drops to about 60mmhg. below that the curve drops drastically along with oxygen saturations. variations in ph, carbon dioxide, 2,3-dpg, and temperature can cause the curve to shift to the right or left. a shift to the right means it will take higher pao2s to maintain a high oxygen saturation, where a shift to the left will have high saturations even with normally low oxygen levels. this helps explain why people drowning in cold water can be saved with little or no brain damage even when they've been submerged to long periods of time. hypothermia and an acidotic blood chemistry shift the curve to the left maintaining high oxygen levels in the blood. hypothermia also lowers the body's metabolic rate so it uses less oxygen. the flip side of the curve is that shifts to the left means hemoglobin has an increased affinity for oxygen and releases less of it to the body. a shift to the right, even with lower oxygen saturations, means hemoglobin releases its supply of oxygen more easily.

factors and how the curve is affected:
variation of the hydrogen ion concentration. this changes the blood's ph. a decrease in ph shifts the standard curve to the right, while an increase shifts it to the left. this is known as the bohr effect.
effects of carbon dioxide. carbon dioxide affects the curve in two ways: first, it influences intracellular ph (the bohr effect), and second, co2 accumulation causes carbamino compounds to be generated through chemical interactions. low levels of carbamino compounds have the effect of shifting the curve to the right, while higher levels cause a leftward shift.
effects of 2,3-dpg. 2,3-diphosphoglycerate, or 2,3-dpg, is an organophosphate, which are created in erythrocytes during glycolysis. the production of 2,3-dpg is likely an important adaptive mechanism, because the production increases for several conditions in the presence of diminished peripheral tissue o2 availability, such as hypoxemia, chronic lung disease, anemia, and congestive heart failure, among others. high levels of 2,3-dpg shift the curve to the right, while low levels of 2,3-dpg cause a leftward shift, seen in states such as septic shock and hypophosphatemia.
temperature. temperature does not have so dramatic effect as the previous factors, but hyperthermia causes a rightward shift, while hypothermia causes a leftward shift.
carbon monoxide. hemoglobin binds with carbon monoxide 240 times more readily than with oxygen, and therefore the presence of carbon monoxide can interfere with the hemoglobin's acquisition of oxygen. in addition to lowering the potential for hemoglobin to bind to oxygen, carbon monoxide also has the effect of shifting the curve to the left. with an increased level of carbon monoxide, a person can suffer from severe hypoxemia while maintaining a normal po2.
effects of methemoglobinemia (a form of abnormal hemoglobin). methemoglobinemia causes a leftward shift in the curve.
fetal hemoglobin. fetal hemoglobin (hbf) is structurally different from normal hemoglobin (hb). the fetal dissociation curve is shifted to the left relative to the curve for the normal adult. typically, fetal arterial oxygen pressures are low, and hence the leftward shift enhances the placental uptake of oxygen.
http://asthma.about.com/gi/dynamic/offsite.htm?site=http://www.ventworld.com/resources/oxydisso/dissoc.html

----------
when you have less that 88% saturation, you can see how steeply the percent of oxygen in the body drops.
what do the readings indicate?

[color=#660066]as a guide:
[color=#660066]95% - 99% - normal
[color=#660066]91% - 94% - mild hypoxia
[color=#660066]86% - 91% - moderate hypoxia
[color=#660066]85% and lower - severe hypoxia
supplemental o2 is indicated for

oximetry should always be measured: at rest and with activity (often drops with activity).

medicare guidelines for oxygen payment is standard most insurance companies use for oxygen payment.
for patients that don't qualify, a doctor can still write a rx for oxygen and patient pay for rental of an e tank--costs less than $50.00/month.

if a person does not meet the following guidelines, medicare may not pay for home oxygen therapy:
arterial oxygen pressure is less than or equal to 55 mm hg (millimeters of mercury, a measure of pressure).
arterial oxygen saturation is less than or equal to 88%.
arterial oxygen pressure is between 56 mm hg and 59 mm hg or oxygen saturation is 89% and the person has:
evidence of right-side heart failure due to breathing problems (cor pulmonale).
heart failure.
an increased number of red blood cells (erythrocytosis).
[*]arterial oxygen saturation is greater than 88% when the person is resting but becomes less than or equal to 88% when the person is exercising or sleeping.
hope this helps!

awesome karen. thank you so very much!!

JSouba · Mar 27, 2006

I'm a student nurse in my second semester of school, and I'm a little stumped on continuous versus intermittent suctioning. I was taught to always use intermittent in class, and the nurses on my unit say to use intermittent, because it decreases the risk of damaging the airway. However, when I used intermittent suctioning in front of a respiratory therapist, she told me to always use continuous because it's more effective, and every other respiratory therapist I've talked to agrees.

So, now I have to change my method depending on who is watching me!

I've found two articles on the topic (references below). Glass and Grap say to use continuous, as there's no evidence that intermittent reduces trauma. Czarnik et al. found that both methods were equally damaging to the airways of dog, but they were using suction pressures of 200 mmHg...

What do you think? Which do you use, and why? Have you found one to be more effective/damaging?

I've posted this same question in the pulmonary and student nursing forums, but I'm going to write a paper on this for my theory class, so I'm looking for a few more opinions.

Thank you!

Glass, C., & Grap, M. (1995). Ten tips for safe suctioning. American Journal of Nursing, 5(5), 51-53.

Czarnik, R., Stone K., Everhart, Jr. C., and Preusser, B. (1991). Different effects of continuous versus intermittent suction on tracheal tissue. Heart and Lung, 20(2), 144-151.

perfectbluebuildings, BSN, RN · Mar 30, 2006

So... is NP suctioning considered a sterile or clean procedure; how about OP suctioning? I've seen nurses I work with do it both ways, and I'm not sure. I try to keep sterile when I do this, but have not always. Seems like the risk for resp. infections would increase if not done w/sterile technique, but that's just my thoughts not backed up w/any kind of research. What do you all think?

meownsmile, BSN, RN · Mar 30, 2006

NP suction should be sterile or a new sterile catheter used each time because you are moving lower into the respiratory track. OP suction is not sterile because you are going through the mouth and only suctioning into the mouth and upper pharyngeal cavity with yankar.

However, the newer evidence based practice may change that in the near future for pnemonia prevention