Inhalation Sedation (Nitrous Oxide)

Medically reviewed by Gordon Laurie BDS MPH, a specialist in Special Care Dentistry, on September 8, 2019 – Written by the Dental Fear Central Team

Drawing by Emma Laurie depicting a girl using inhalation sedation
Inhalation sedation, laughing gas, relative analgesia, happy air, nitrous, nitrous oxide, N2O-O2… this one has more names than any other sedation technique! And deservedly so.

What is nitrous oxide? And what does it feel like?

Nitrous is a great drug – it makes most people feel lovely and relaxed and maybe a bit floaty. It’s very controllable and just gets increased a step at a time until you’re comfy.

After 5 minutes or so of breathing in the gas, you should feel a warm and fuzzy feeling spread throughout your body. In the following video, Gregor (a patient at the Berkeley Clinic in Glasgow) explains what inhalation sedation feels like for him:

First-hand accounts of inhalation sedation from our forum

“I had nitrous when I had a tooth extracted because I was extremely nervous about it. I also briefly considered IV but that gave me more anxiety than the thought of the extraction itself (loss of control). The nitrous was fine. I felt completely aware the whole time. No nausea or vomiting. Since it’s just a cup over your nose you can tell them if you feel unwanted side effects and they can adjust the dose quickly or remove it entirely. It also wears off quickly. I found it helped me relax and occasionally let my mind drift away from the procedure. I also listened to relaxing music during. The nitrous did not make me feel drunk or high or giddy. I felt just like myself but not super-stressed and anxious as I would have been otherwise.”

“You start with O2 and a few minutes later he asked how i was doing and basically nothing happened so he had to increase it a couple of times and finally I started to relax a bit. No real loopiness but just a sense of yeah I can get thru this. The biggest sensation was my legs felt kinda heavy as if to say maybe I want to stay here a while. Thinking like that I knew the gas was definitely working!! I WANTED TO STAY AT THE DENTIST!!!! Can you believe this.”

How does nitrous oxide work?

Pure nitrous oxide (N2O) on its own can only safely be used for short periods of time. But when mixed with oxygen (O2), it’s safe to use for longer periods of time. Hence, the “laughing gas” used by dentists nowadays is N2O-O2.

Depending on the concentration and how long it’s breathed in for, four levels of sedation can be experienced:

  1. a tingling sensation, especially in the arms and legs, or a feeling of vibration, quickly followed by
  2. warm sensations, and
  3. a feeling of well-being, euphoria and/or floating.
  4. At a deeper level of sedation, sleepiness, difficulty to keep one’s eyes open or speak (“dream”) can occur. This stage would mean that the N2O concentration is too high, and it can be associated with side effects such as nausea.

With inhalation sedation, your dentist will want you to stay within the first three levels.

I had a bad experience with laughing gas in the past – have things changed?

Nowadays, the vast majority of dentists who use nitrous oxide are aware of the need to gradually increase (“titrate”) the N2O concentration, because everyone is unique and reacts differently, and people’s tolerance can vary from day to day.

Perhaps this wasn’t always the case – many years ago, dentists were allowed to use nitrous oxide with very little in the way of training (and such training wasn’t readily available back then). As a result, some people ended up with too much sedation and nausea, dizziness or vertigo.

In medicine and especially in labour, sometimes a mix of 50% oxygen to 50% nitrous oxide is used. This is known as entonox or, more commonly, “gas and air”. 50% nitrous tends to be too much for most patients, and nausea is quite common. The mix given to most dental patients on the other hand is only 30% nitrous oxide (and 70% oxygen).

Don’t confuse dizziness with the normal feeling of lightheadedness which many people who’ve never had N2O before experience after maybe 60 or 90 seconds. The feeling of lightheadedness will pass as the concentration of N2O is increased.

Of course, if you do experience any unwanted side effects, just let your dentist know so they can adjust the concentration of N2O – the effects are almost immediate!

What is the mechanism of action of nitrous oxide?

Interestingly, the actual mechanism of action of N2O is still unknown (it appears that there are quite a few different mechanisms at work)! However, it’s been observed that N2O depresses almost all forms of sensation – especially hearing, touch and pain. It also reduces anxiety. The ability to concentrate and perform intelligent acts is only minimally affected, as is memory.

How is it administered?

The equipment used for inhalation sedation is quite simple. It consists of a supply of compressed gases and an apparatus which delivers the gases to the patient. The administrator can produce the desired mix of N2O-O2 in the desired quantities.

The desired N2O-O2 mix is fed through a tube to which a nasal hood or cannula is attached. This hood is put over your nose. All you have to do now is breathe normally through your nose – bingo!

Photo of a mask used for administering inhalation sedation

There is a sort of double mask (see photo) where the outside mask is connected to a vacuum machine to suck away the waste gas – you wouldn’t want your dentist to get a face full of nitrous… The white inside mask, which is placed over your nose, may come in scents – such as vanilla, strawberry, and mint! The one pictured to the left is scented with vanilla…
Gordon's nurse Maire wearing an RA mask

The twin tubes running to the mask are for “gas in” and “gas out”. The “gas out” line is attached to the vacuum machine, while the “gas in” line is attached to the inhalation sedation machine. The inner mask is attached to the “line in”, you breathe out through a one-way valve in the inner mask, and the exhaust gas is collected inside the outer grey mask (pictured to your right) and sucked into the vacuum machine.

What are the advantages of inhalation sedation?

  • It works very rapidly – it reaches the brain within 20 seconds, and relaxation and pain-killing properties develop after 2 or 3 minutes.
  • The person who administers the nitrous is able to deepen or lessen the level of sedation almost instantly (unlike with IV sedation, where it’s easy to deepen the level but not to lessen the level of sedation).
  • Other sedation techniques have a fixed duration of action (because the effects of pills or intravenous drugs last for a specific time span), whereas nitrous can be given for the exact time span it’s needed for.
  • There’s no “hangover” effect – the gas is eliminated from the body within 3 to 5 minutes after the gas supply is stopped. You can safely drive home and don’t need an escort.
  • With inhalation sedation, it’s easy to give incremental doses until the desired action is obtained. This prevents the possibility of accidental overdoses.
  • For certain procedures – those involving gums rather than teeth (e. g. deep cleaning) – it may be possible to use nitrous instead of local anaesthesia. N2O acts as a painkiller on soft tissues such as gums. However, its pain-relieving effects vary a lot from person to person and can’t be relied upon.
  • No injection is required. In cases of very severe needle phobia, if you decide on sedation, using inhalation sedation first can help you feel relaxed enough to allow the needle required for IV sedation to be put in your arm or hand. The very deep state of sedation that can be achieved through IV sedation will then allow you to accept local anaesthetic.
  • Inhalation sedation is very safe. It has very few side effects and the drugs used have no ill effects on the heart, lungs, liver, kidneys, or brain.
  • Inhalation sedation has been found to be very effective in eliminating or at least minimising severe gagging.

Are there any disadvantages?

  • Some people are not comfortable with the effects of inhalation sedation (either because they’re afraid they might lose control or because they had a bad experience with it in the past).
  • Some people will not be sedated deeply enough with permissible levels of oxygen.
  • If you can’t breathe through your nose (e.g. because you’re a pure mouth breather, or because you have a cold and your nose is blocked), it can’t be used.
  • If you feel claustrophobic or panicky when something is put over your nose, it may not be for you.
  • Depending on where you live, a dentist who offers inhalation may be hard to come by.
  • The cost of the equipment and gases is high, so you’ll probably have to contribute to the cost – but it’s quite a bit cheaper than IV sedation.
  • Apart from that, most of the disadvantages of inhalation sedation won’t affect you personally: there’s training required, the equipment is quite bulky and takes up a lot of space, and nitrous oxide is a greenhouse gas (though it makes up a very small percentage of total greenhouse gases).

Are there any contraindications to inhalation sedation?

There aren’t many major contraindications, except for emphysema and some exotic chest problems.

It also hasn’t been proven to be safe during the first trimester of pregnancy.

If you have a vitamin B12 deficiency and receive injections, nitrous oxide is contraindicated because the gas inactivates the B12 in your blood so that your body can’t use it. This can make you very sick quite quickly. It only applies to people who have a problem with absorbing B12 from their diet – most people have a good store of B12 in their liver.

You can’t be allergic to N2O. It’s also safe to use if you suffer from epilepsy, liver disease, heart disease, diabetes, or cerebrovascular disease. It is used quite successfully in many people with respiratory disease – but it depends on the exact nature of the disease, so check with your dentist!

How do I know if it’s for me?

Why not ask if you can have a 5 minute ‘sample’ so that you know what to expect on the day of your procedure?

Many thanks to Gordon Laurie for his help with writing this page, and for the photos.

Related Pages

What Can Help? Strategies for tackling dental anxiety and fear

Is dental sedation right for me?

Oral Sedation

IV sedation

Artwork © Emma Laurie. All rights reserved.