Denitrogenation in pregnant women

Forty-five pregnant females were studied with respect to the effectiveness of denitrogenation by the 3, 5, 7 and 9 rapid vital capacity breaths, and 3 to 5 minutes of normal breathing. It was found that 3 to 9 vital capacity breaths cannot effectively denitrogenate a pregnant patient when a circle breathing system with a gas flow of 8 litres/min is used. At least 3 minutes of normal tidal volume breathing should be given for proper denitrogenation or preoxygenation if the circle system is used for such a purpose.