Breathe through your nose! The science of breathing & nasal nitric oxide
Luke breathing on top of an iceberg during a film project in Greenland.

Breathe through your nose! The science of breathing & nasal nitric oxide

This article is about the importance of nasal breathing and the production of nasal nitric oxide in the nasal cavity. We’ll explore some ideas and questions around the benefits of nasal nitric oxide and whether we leave those benefits behind if we wear a full diving mask.

You will understand why:

  • Why nasal breathing is so important?
  • Nasal Nitric Oxide: a powerful molecule and vaso-dilator.
  • Is diving with a mask actually “choking” us?
  • Why Nitric Oxide is an active ingredient in viagra?
  • Implications after the COVID-19 pandemic?

Reading Time: 10 minutes

“Nitric oxide is a ubiquitous molecule that is involved in regulating virtually every biological process.”

Rakesh C. Kukreja, Ph.D

Background: Understand the Science

The chemical compound nitric oxide (NO) is a gas present in high concentrations in healthy persons in the nasal airways. We all produce this gas with cells that line the paranasal cavity, and it is often referred to as ‘nasal nitric oxide’ (NNO).

If we breathe through the nose, we breathe in nasal nitric oxide and there are quite some benefits to this. After all, a diving mask restricts the flow of nitric oxide through the respiratory system and during long diving sessions may do so for hours at a time.

The chemical compound nitric oxide is created in the nasal cavity and has a positive effect on the respiratory system, leading to better oxygenated tissues. 

Thus, a smart question any freediver can ask themselves is:

Does breathing through your mouth during a diving session because you have a diving mask affect your dives?

The effects of nitric oxide in the respiratory system

Nitric oxide is a potent vasodilator, meaning that it widens your blood vessels and thus promotes good blood circulation. The body produces nitric oxide molecules, and those molecules help blood vessels to relax.


Guess what ingredient is in viagra?

In the environment, nitric oxide is a potentially toxic gas that is formed in lightning strikes and car exhaust, creating air pollution and irritating lungs. But, inside the body, nitric oxide plays a very different role.

Nitric oxide in higher concentrations can kill parasites that cause diseases, and indeed it has been shown that nitric oxide concentrations rise in sick individuals.

No, you don’t need to take Viagra, the point here is to outline the connection between Nasal Nitric Oxide produced in your body and the pharmacological use if it.

A study worth reading

A great study performed by Lundberg et al. in 1996 has quantified some of the effects of NO in the lungs on the respiratory system:

They found that during periods of 5 minutes of nasal breathing, the transcutaneous oxygen pressure was 10% higher than during 5 minutes of mouth breathing.

In lay man terms:

  1. Transcutaneous oxygen pressure (TcpO2) is a measure for the oxygenation of your skin (but not the oxygenation of your blood).

Lundberg et al. also found that arterial oxygen tension (more oxygen in the arteries) significantly rose, and the pulmonary vascular resistance index (the resistance to blood flow in the lungs) significantly lowered in intubated persons (somebody that breathes with the help of a tube in the trachea, bypassing the nose) when administering nasal air.

The timespan in which they did so?

Ten minutes.

Lundberg et al. (1996) found positive effects of nasal breathing on 1) blood flow in the lungs, 2) on oxygenation of the arteries and 3) on oxygenation of tissues under the skin. The positive effects took place within 5 – 10 minutes.

Now ask yourself: how long do you breathe only through your mouth in a freediving session? 

As freedivers, are we missing out if we dive with a diving mask?

This is where we can start speculating. Aside from the obvious equalization issue, is there another reason we naturally gravitate to use a nose clip in deeper dives?

From the study, it is fair to say that; “the increase in subcutaneous pressure of healthy subjects indicates that something is significantly improving the respiratory system.”

After all, getting the blood through arteries and capillaries to oxygenate tissues is [in the study] an indirect way to measure the effect of NO on the respiratory system.

The time lag associated with the oxygenation appears to be less than a minute (fig. 2 in Lundberg et al., 1996). Also, the time lag associated with a decrease in oxygenation is less than a minute.

As soon as you put your diving mask on and start breathing through your snorkel, are you effectively de-oxygenating your tissue?

For transcutaneous oxygenation the answer appears to be yes, but for deep tissues this may be different.

All in all, it appears that simply by breathing through your nose you will be better oxygenated. That means, you would be in better freediving condition if you can breathe-up through your nose.

Why is this important post-COVID-19?

Whether you are a professional freediver, an amateur or simply enjoy meditation and breath-work, nasal breathing has obvious health benefits.

We’ve known this for a long time now, but it’s the science that gives us a new perspective on the importance of this.

The simple fact that some positive health effects of nasal breathing are:

  1. Increased blood flow in the lungs,
  2. Oxygenation of the arteries,
  3. Oxygenation of tissues under the skin, and
  4. The positive effects took place within 5 – 10 minutes.

This is quite obvious as to why focusing on proper, deep and slow nasal breathing (like we do in freediving) is so beneficial.


  1. Lundberg at al., 1999.
  3. Breathe, by James Nestor.
  4. Kmjec, M. et al. National Library of Medicine. 2018.

Luca Malaguti

Luca Malaguti is a former engineer turned freediving professional athlete and founded Sea to Sky Freediving. He lives in Vancouver, Canada among other places including Dahab, Dominica and Philippines.

This Post Has 5 Comments

  1. Dave Forcucci

    I tried diving with goggles for my dynamic (monofin) pool training the last couple times in the pool. Noticed a difference but not sure if it is only from nasal breath up? I find I like the googles better than a mask though and I don’t use a nose clip for dynamics.

    1. Jaap

      thanks for sharing!

    1. Jaap

      That’s really interesting. That must also be one of the bigger effects of using a mantra while meditating (the roots of the ommmm….?).

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