Radial A line trace...why is it like that?!

This is a newborn baby with PA-VSD, MAPCAs.
Postop day#2 after RVOT patch (transannular).
Generally, doing well.

And, one day later...the same arterial line trace looks like this!!!

Possible explanations: (i) Papaverine was started or (ii) Tubing for the transducer was changed to a rigid, "pressure-tubing" (from a more compliant, "non-pressure" tubing).

This improvement in waveform may also occur when the arterial catheter is changed to a larger caliber.

Description & study of the above distortion in arterial line is illustrated below:

(From Cardiovascular Dynamics by Robert F. Rushmer MD. 3rd ed.1970. W.B.Saunders. page 162)