There are indeed air bubbles in amber. And these have been examined for their chemical content. The air became trapped at the same time as the insects and other items found in the "frozen" (or dried) tree sap.
Consistently, there is a higher percentage of oxygen in these amber samples from before the Great Flood. A higher percentage of oxygen would mean a lower percentage of at least one other gas, of course. Some of the repercussions have not been thoroughly researched. But we know that oxygen is necessary for respiration.
(Image shows air bubbles trapped in amber.)
Here are links to two related articles regarding this:
Dinosaur Breath, by John G. Cramer http://www.npl.washington.edu/av/altvw27.html
Air Bubbles, Amber, and Dinosaurs http://minerals.cr.usgs.gov/gips/na/amber.html
Note in the second article (from the USGS) that the original pre-Flood atmosphere appears to have had about 35% oxygen. (Along with higher air pressure, for other reasons.) But post-Flood levels (down to modern times) is only at 21%. During the "age of the dinosaurs", i.e. the pre-Flood era, each breath would have contained about 50% more life-giving oxygen! (Ignore their fictious evolutionary dating beliefs; just focus on the scientific facts - air bubbles in ancient amber contain much more oxygen.)
The fossil record includes huge insects which "breathe" through their skin (spiracles). Beetles and roaches grew to 9 inches long! Dragonfly remains show that they grew to an 18 inch wingspan! Dinosaurs (terrible lizards) also grew much larger and probably lived a lot longer. Increased oxygen in the environment was a part of their ability to grow larger than their weaker, smaller descendants of today. We are going down, not up. Evolution is a fictional account that ignores the scientific evidence.
(Every time they state "millions of years ..." or "prehistoric" - instead
mentally insert the meaning of: - "pre-flood" as from about 5,000 years ago,
as the accurate time frame.)