Exhale is relaxed with no control at all. If the inhale comes via the nose then the exhale should exit the nose. If the inhale comes through the mouth then the exhale must travel out the mouth. Exhale and inhale need not be the same duration. In short don't stop at the top of the breath or at the bottom.
Breathing is one continuous loop.
Really feel your problem. Keep up your heart holding and breathing during your full experienceing. Spend as much time as you need to really feel this problem. Observe it and pay attention to its shape. As you notice its shape, allow your awareness to notice the area or space around this problem.