A gas delivery unit for delivering a respiratory gas of a subject is disclosed herein. The gas delivery unit includes an expiratory limb for an expiratory gas, and an inspiratory limb for inspiratory gas. The gas delivery unit also includes a common limb connecting at a branching point with the expiratory and inspiratory limb for delivering the expiratory and inspiratory gas, and at least one port for a fluid dispenser. The port opens into at least one of the inspiratory limb, the expiratory limb, the common limb and the branching point. The port is along an opening direction forming an angle δ, which is less than 90° degrees, with one of the inspiratory limb, the expiratory limb and the common limb, and which inspiratory limb can form an angle β, which is at an angle of 100°-180° degrees, with the common limb.
