What you can do is use a closed system, which will eliminate all noise but still allow some of the carbogen to enter the solutions without movement. What I did in the past was bubble the solutions for a couple minutes. Fill a urine bag (i know it sounds weird but it works) with 95%O2/5%CO2. While full, don't overfill it or the bag will start to leak. Have some tubing go from the end of the urine bag to a corning pyrex storage bottle. The bottle will have to have two holes drilled into it where you can put the ends of a 1 ml syringe through the bottles (make sure that there is tubing around the syringe so that it doesn't leak. The tip of the syringe needs to face out of the bottle while the bottom needs to go into the bottle. You will then need to have a second syringe coming from the bottle to a flow system so that it is gravity driven. You can see from the picture a couple examples. You'll notice blue tubing in the bottles. One of the tubes will allow bubbles to enter from the urine bag, while the other will extract the liquid from the bottle, go into the syringes on the outside and down the tubing into the slices. Let me know if this helps at all. If you have questions (i'm sure you might since it's not the best explanation), please let me know and I can give you further guidance. 

I'm not sure about recirculating the compound. What you can always do is in an interface system if you are doing fEPSPs, you can keep the flow rate low. 

Eric:

This seems like a nice solution to the bubbing roblem. I may contact you in the near future for more details.

Kevin, No problem at all. It works really well and simplifies everything. It also makes transferring to other solutions very simple. We have used this type of flow system for both patch and fields. Feel free to contact me at any point. 

Finally I managed to get these experiments working. I use a Petri dish to maintain 50 ml of regular ACSF recirculating during the experiment using two lines of the pump: one to take the ACSF into the recording chamber, and the other one to return it into the Petri dish. As Michel Herde said there seem not be a big problem to recirculate the ACSF, but the main challenge was the lack of oxygen during the experiment. So, by using a Petri dish of 100 mm, I create a big surface area of the ACSF for potential oxygen capture. In the Petri dish cap I inserted a tube for the carbogen. Once inside the chamber, this tube branches off to two tubes, one is open and the other one is located inside a folded tissue wet with ACSF. In this way, I try to create an atmosphere with the carbogen, which would get into the ACSF by the big area of interchange (see Figures attached).

Experiments were tested under these conditions and the fEPSP responses from the slices were stable for at least two hours.

In my case, I needed to maintain such a conditions (recirculation and no bubbles) because I am working right now with a compound highly sensitive to mechanical interference. Moreover, the production of this substance is quite limited, so we need to use as less as possible in our experiments. Hope that this simply resolution can help others with the same requeriments.