If you're doing the Valsalva maneuver during deadlifts, then it is possible to get light headed during. Overcoming it will come with experience. Though, it's common for people to hold their breath during the entire set which is not what you want to do. This is especially true for those that "bounce" the bar (disengage and immediately pull).
To make sure you have enough oxygen throughout the set:
- Perform a few really deep breaths before grabbing the bar.
- Grab the bar
- Deep breath in to the stomach and hold
- Pull the lift
Repeat 3 - 6 until set is complete.
Do not rush the set. Do not bounce. It's not a race. Take as many breaths between reps as you need. Reset each rep if you have to.