VQ mismatch?

[jeyre1847]

I'm on a peds floor for preceptorship.

This week, we had an 8 month old girl with RSV getting nebulizer treatments. She would always drop to like 82% right after the treatments, even after she had been fine on room air otherwise. The RT said it was probably a VQ mismatch, and the doctor discontinued the nebs, and she was fine.

I know the general meaning of a VQ mismatch, but I've only heard of it with things like COPD and ventilator management. I was trying to find something about it but nothing that explains it really well.

How would a nebulizer treatment cause a VQ mismatch in an infant? Any input would be greatly appreciated!

[GilaRRT]

Was the baby angry, crying and moving about during the treatment? If so, you really cannot rely on pulse oximetry all that much. If she was not having clear indications of an obstructive deficit (wheezing and so on), inhaled beta agonists are really not indicated anyway.

[CRNA1982]

I'm on a peds floor for preceptorship.

This week, we had an 8 month old girl with RSV getting nebulizer treatments. She would always drop to like 82% right after the treatments, even after she had been fine on room air otherwise. The RT said it was probably a VQ mismatch, and the doctor discontinued the nebs, and she was fine.

I know the general meaning of a VQ mismatch, but I've only heard of it with things like COPD and ventilator management. I was trying to find something about it but nothing that explains it really well.

How would a nebulizer treatment cause a VQ mismatch in an infant? Any input would be greatly appreciated!

Hmmm....I'm assuming they were albuterol/atrovent nebs. There are many reasons why VQ mismatches occur; in fact I have books that pertain to this stuff alone. Remember the V stands for ventilation. Is the pt. being ADEQUATELY ventilated (either mechanically or own their own). Tidal volume, Fio2, obstruction and secretions can all affect inadequate ventilation. The Q stands for perfusion. Remember atelectic lung segments may be perfused but they don't participate in gas exchange due to alveolar collapse; this is dead spacing. She probably dropped her sats transiently after her nebs because her nebs were given at a higher Fi02 per RT. Her lungs were "liking" the higher Fi02 and when her nebs were finished, she began breathing room air again. Shortly after the nebs were discontinued her sats dropped due to a gradual decline in her Pa02. After some time, she probably would have compensated and you would have seen her Sa02 increase back to baseline. Again, this is just a hunch; I'm not a pulmonologist.

[jeyre1847]

This didn't happen as much when she was on continuous oxygen, it started after she was on room air. This explains how her lungs "liked" the higher FiO2 like you said. Also, it was an albuterol nebulizer because she had been wheezing when she was admitted, but by the time she didn't need O2 anymore, she wasn't really wheezing anymore and just had some fine crackles left.

That explains a lot! Thanks for all your help!

[GilaRRT]

This didn't happen as much when she was on continuous oxygen, it started after she was on room air. This explains how her lungs "liked" the higher FiO2 like you said. Also, it was an albuterol nebulizer because she had been wheezing when she was admitted, but by the time she didn't need O2 anymore, she wasn't really wheezing anymore and just had some fine crackles left.

That explains a lot! Thanks for all your help!

Fine crackles indicates the potential presence of atelectasis. The crackling is often the sound of collapsed alveoli being forced open. This can cause V/Q mismatch.