CCRN Resources giving different answers!

[RNexplorer]

For the following basic question, elite reviews and Barron's are giving different answers:

What vent settings would be important to have for a patient with asthma?

- Elite reviews: "a longer inspiratory time" or an "inverse I:E ratio" to keep the alveoli inflated...

- Barron's: "a longer expiratory time to decrease auto PEEP."

I'm really worried because I've been studying a lot of questions from elite reviews, and I'm thinking that if they are wrong on this question they may have been wrong on many others!!

Can anyone advise about these resources? Thanks! I'm so nervous because my exam is coming up.

[PaSSiNGaS, MSN]

COPD and things like asthma you want a longer than normal I:E ratio. Normal I:E ratio is 1:2, so for a 60 second or 1 minute time period you are inhaling for say 2 seconds and exhaling for 4 seconds for 10 breaths. Give it a try and make this ratio 2:1 and try taking a breath in for 4 and only exhaling for 2. You will not be able to do this for very long.

Asthma causes constriction of smooth muscle in the airways and increased peak inspiratory pressures which decreases the amount of tidal volume you can deliver. By making the I:E higher you will maybe be able to get in a little extra volume but then run the risk of air trapping. Patients with asthma and COPD are already at an increased risk of air trapping and by making the I:E high like 2:1 or 3:1 you will increase whats called auto-peep and make things worse.

So short answer is go with a longer expiratory phase on the vent. If I see a bad COPD pattern on the ETCO2 I will change the I:E to 1:2.5 or 1:3 to prevent that auto peep. Since I'm in trouble and have to be moderated to be able to post this may take a while for you to see.