If you just need something to take the edge off your contractions you may find it helpful to use gas and air (properly called Entonox). This is administered through a mouthpiece or a face mask and, in most hospitals, is centrally supplied to each delivery room. At home, the gas comes from a cylinder that the midwife brings with her.
To get the best from gas and air, put the mouthpiece into your mouth at the very beginning of your contraction and breathe deeply and evenly to operate the valve. It takes about 20 seconds for the gas to build up in your bloodstream and dampen down your pain. If you use it as soon as you feel a contraction starting, it will have taken effect by the time the wave is at its peak. The gas will eventually make you feel a little light-headed and your grasp on the mouthpiece will loosen so that you stop breathing through it. By the end of the contraction, your head will have cleared.
You should hold the mask or mouthpiece yourself because when you have had enough you will start to feel slightly light-headed and will automatically let go. If someone holds the mask for you, you run the risk of inhaling too much gas.
The advantages of Entonox are that it usually works well and its effects are short-lived. You are also in control of your own pain relief. However, it is only a mild pain-killer. If you use Entonox for a long time, you may find that your mouth gets very dry. (Your birth partner could give you sips of water between contractions.) Some women say that Entonox makes them feel sick. If you don't like the mask, ask for a mouthpiece to use instead.