A less common occurrence is what is known as reverse block. This occurs when an air space closes off during a dive, perhaps as a result of inflammation or mucus forming. As you ascend, the expanding air will cause discomfort if it cannot escape. If this happens, try descending, equalizing, and starting to ascend very slowly. Repeat if needed. The expanding air will typically find an escape route if you ascend slowly enough. If pain persists after the dive, seek immediate medical advice.