We called these 'breathing exercises in 80'. We learned them in school. It was 4-4-4. 4 seconds or count breathe in, 4s hold and 4s exhale. There were no rules

We called these 'breathing exercises in 80'. We learned them in school. It was 4-4-4. 4 seconds or count breathe in, 4s hold and 4s exhale. There were no rules on timings. Do it as long as needed to come to 'normal'. They work for me when needed.