Practise seated or lying down in a safe place. Never practise while driving, operating machinery, cycling, walking in traffic, or in or near water. Do not change your natural breathing pattern or hold your breath during pregnancy. Consult a qualified healthcare professional first if you have a serious cardiovascular, neurological, respiratory, eye or mental-health condition, uncontrolled high blood pressure, recent major surgery or injury, or a history of fainting. Stop and return to relaxed breathing if you feel unwell, distressed, dizzy or in pain.