It is essential for you to remember, which nostril you exhaled from before you closed your both nostrils for 4 seconds breath hold. Please do remember this vital information, “the nostril you exhaled from is the nostril you inhale from to start the new breath cycle 4:2 : 4:2”.
Simplified version: Inhale for 4 counts and hold the inhalation for 2 counts with both nostril pinched; exhale for 4 counts and hold the exhalation for 2 counts with both nostril pinched. Just continue, inhale and hold; exhale and hold.
How long should I practise this breathing technique in one sitting? 5 minutes would be ideal or more when you can do it effortlessly.
People with high blood pressure, low pressure; if you have had a stroke or a heart attack; if you have any other medical condition(s). Be safe and seek advice first from your Doctor.
People with heart ailments should only practise calm rhythmic breathing with a 1 : 2 ratio. For example: Inhale through both nostrils gracefully, thoughtfully and rhythmically for 3 counts and then exhale through both nostrils gracefully, thoughtfully and rhythmically for 6 counts. Practise it for 5 minutes or more if you feel it is very calming and relaxing for your mind, body and heart. Then you can decide to do it for bit longer.