Kapalbhati is a yoga breathing technique that involves rapid and forceful exhalations, followed by passive inhalations. It is typically safe for most people to practice, but it can be contraindicated in certain medical conditions. If you have a herniated stomach, it is important to consult with your doctor or a qualified yoga teacher before beginning this or any other yoga practice. They can advise you on whether or not kapalbhati is appropriate for you and if any modifications need to be made to protect your herniated stomach.