The Lunge Flow has some tips and tricks so that breathing and alignment are perfected. Here are a few:
1. When you step forward make sure your foot is aligned straight before you lift.
2. Wait a little moment when you raise up before breathing in. For some reason breathing in with too much haste causes you to run out of breath before the motion is over.
3. When you come out of the Lunge Pose take your hands down and exhale. But when you step back take a quick breath before you drop down and do the Chatruranga UpWard Dog flow. Most yoga flows try to do it with one breath but you have to be a real expert for that and use special tricks otherwise your gasping for air before entering Cobra or Upward Dog.