Cause of uneven pulse/ox wave form

Published

I took care of a child recently who did not have any invasive monitoring. Just standard EKG and pulse/ox. I noticed that the waveform on the pulse/ox would show one high, strong wave, followed by one slightly lower, and then one lower than that. Then it would start all over again in groups of three from tall to medium to low. I was unable to determine why and the RN's I asked were also unsure why it was happening. Other VS were stable in the child. Any thoughts?

rnkaytee

219 Posts

I don't know if I've seen it necessarily in that pattern but the most frequent causes are low temp of the extremity, poor perfusion or needing a new pulse ox/position change.

Pediatric Critical Care Columnist

NotReady4PrimeTime, RN

16 Articles; 7,358 Posts

Specializes in NICU, PICU, PCVICU and peds oncology. Has 25 years experience.

Does your display look like this?

images?q=tbn:ANd9GcS_FBPoSZHCBB_RhYym6I4Z-DUW7tL6rkIxr4ywThepXTHnL4jrIQ

This waveform represents pulsus paradoxus. It's the physical manifestation of a drop in systolic BP >10 mmHg with inspiration. It may be caused by such things as pericardial effusion, cardiogenic shock, pulmonary embolus, tension pneumothorax, asthma, chronic lung disease, anaphylactic shock, SVC syndrome or obesity. If the patient had an arterial line a similar pattern to the waeform would be seen. Without more information about the patient it's hard to guess as to which cause is present, but given the likelihood of chronic lung disease in certain segments of the pediatric ICU population, that's where I'd go.

anon456, BSN, RN

7 Articles; 1,144 Posts

Thank you! That actually makes sense considering their history and what we were doing for the patient. I have never seen that in "real life" before.

brewski09

34 Posts

Was the patient having bigeminal PVC or PAC (really any premature beats)? I've seen something similar to what you described in adult patients where the second beat does not produce as big of a pulseox waveform because of the decreased preload caused by premature second contraction of the heart. I would make sure the MD was aware of this, but they may not do anything if the patient is otherwise stable.

cinlou, BSN, MSN, RN

1 Article; 221 Posts

Specializes in Emergency and Critical Care. Has 45 years experience.

remember that with peds most cardiac issues are based on their respiratory status and does no necessarily mean that there is anything that is wrong with their cardiac status. Remember when you were taught to always count respirations and pulse on little ones for a full minute, irregularities are normal in the young population. But the Doc should be notified, they may want to check out other things CXR etc. Peds triangle, what do they look like?

anon456, BSN, RN

7 Articles; 1,144 Posts

remember that with peds most cardiac issues are based on their respiratory status and does no necessarily mean that there is anything that is wrong with their cardiac status. Remember when you were taught to always count respirations and pulse on little ones for a full minute, irregularities are normal in the young population. But the Doc should be notified, they may want to check out other things CXR etc. Peds triangle, what do they look like?

This patient was a known cardiac case with systemic symptoms of heart failure and pulmonary congestion. We were treating accordingly and the patient was improving a bit. In this case reporting it would not have really changed the treatment plan. Now I know that if I see that again, to call the MD and look for other signs related to it. Love these boards, I learn so much! :-)

aCRNAhopeful

261 Posts

Specializes in CVICU.

Not a PICU nurse but I had a couple thoughts. I am an anesthesia student with experience mostly in adult CVICU and now anesthesia FYI but I think the concept is relevant in pediatrics as well. I agree with the previous poster regarding the pulsus paradoxus. To go a little further you will see it anytime positive intrathoracic pressure causes significant decrease in venous return. If the pt is intubated the decrease in the pulse ox waveform or art line tracing will occur during inspiration and if spontaneously breathing it will occur during expiration due to positive pressure collapsing the vena cava and thus decreasing venous return/pre-load, thus decreasing stroke volume and blood pressure for those brief periods. With adults (and for the life of me I cant think why it wouldnt be the same for peds) this is a sign that someone is VOLUME responsive. Is the patient hypotensive with significant variability in the aline and/or pulse ox waveform with risk factors for hypovolemia: the BP will likely respond to a fluid challenge. This is the concept that the vigileo/flowtrack monitors use to calculate stroke volume variance (SVV). Other terms are systolic pressure variation, pulse pressure variation, SVV and they all refer to this phenomenon. So all the other causes like superior vena cava syndrome, tamponade, etc are all things you have to think about but I would say that the most common cause for this (at least in adults and surgical patients) is hypovolemia. Final caveat: seeing this on the monitor is not necessarily a bad thing, if everything else checks out OK then just note it and move on, maybe patient is just a tad on the dry side but still perfusing well, if so just leave it alone.

anon456, BSN, RN

7 Articles; 1,144 Posts

Not a PICU nurse but I had a couple thoughts. I am an anesthesia student with experience mostly in adult CVICU and now anesthesia FYI but I think the concept is relevant in pediatrics as well. I agree with the previous poster regarding the pulsus paradoxus. To go a little further you will see it anytime positive intrathoracic pressure causes significant decrease in venous return. If the pt is intubated the decrease in the pulse ox waveform or art line tracing will occur during inspiration and if spontaneously breathing it will occur during expiration due to positive pressure collapsing the vena cava and thus decreasing venous return/pre-load, thus decreasing stroke volume and blood pressure for those brief periods. With adults (and for the life of me I cant think why it wouldnt be the same for peds) this is a sign that someone is VOLUME responsive. Is the patient hypotensive with significant variability in the aline and/or pulse ox waveform with risk factors for hypovolemia: the BP will likely respond to a fluid challenge. This is the concept that the vigileo/flowtrack monitors use to calculate stroke volume variance (SVV). Other terms are systolic pressure variation, pulse pressure variation, SVV and they all refer to this phenomenon. So all the other causes like superior vena cava syndrome, tamponade, etc are all things you have to think about but I would say that the most common cause for this (at least in adults and surgical patients) is hypovolemia. Final caveat: seeing this on the monitor is not necessarily a bad thing, if everything else checks out OK then just note it and move on, maybe patient is just a tad on the dry side but still perfusing well, if so just leave it alone.

Great explanation! Have you ever considered teaching?