eBooks 
SKY Breath Meditation is an abbreviation of Sudarshan Kriya Yoga (SKY) Breathwork, which aims at greater mental and physical health, increased productivity, and higher life satisfaction. It was developed by Gurudev Sri Sri Ravi Shankar (mind that the repeated “Sri” is not a typo).
eBook | More info here
Sky Breathwork is believed to improve sleep quality, concentration, and respiratory functions, balance heart rate and blood pressure, regulate emotions, stimulate the immune system, and counteract anxiety, stress, fears, depression, and Post-Traumatic Stress Disorder (PTSD).
It’s based on Yogic Pranayamas and involves breathing exercises in a variety of different patterns ranging from slow and calming to fast and stimulating.
SKY Breathing actually consists of four steps i.e. four exercises, which can be carried out lying down or sitting with your back straight: Ujjayi Breathing (Victorious Breath), Bhastrika Pranayama (Bellows Breath), Om Chanting (AUM Chanting), and Sudarshan Kriya (Purifying Breath, which is form of rhythmic, cyclical breathing with slow, medium, and fast cycles).
The whole cycle takes about forty-five minutes, and can be practiced at any time of the day.
