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?