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  • AutorenbildMichael Mutter

"We don't really need a snorkel."

In the early days of scuba diving, the snorkel was considered an essential piece of equipment for breathing at the surface before and after diving. Nowadays, however, many divers choose not to use a snorkel. This may be for various reasons, such as the belief that using a snorkel increases breathing resistance, possible fears of hypercapnia (CO2 intoxication) or simply because it gets in the way. Is this attitude justified?

Foto: Daniel Reumer. Tauchschule H2O

No "snorkelling studies"

While numerous studies exist that have investigated breathing through tubes, specific studies on snorkeling were lacking until recently. This shortcoming was addressed by Schellart in two studies.

The survey

First, diving physicians and divers were asked about their attitudes to snorkeling. They unanimously stated that, in their opinion, the snorkel significantly increases breathing resistance, which means that around one in four respondents do not use a snorkel. Personally, I have the impression that this percentage is much higher and that very few divers have a snorkel with them (let alone use one).

Measurement of maximum voluntary ventilation

The maximum voluntary ventilation of 19 test subjects was then measured over a period of 12 seconds, both with and without a snorkel. This means that the participants breathed through the snorkel as quickly and forcefully as they could. These measurements were taken on a commercially available J-shaped snorkel with a diameter of 20.5 mm, which had no additional features such as valves, and were carried out on land. The maximum respiratory minute volume with snorkel was on average 6% less than without snorkel. The calculated breathing resistance increased by an average of 6.5% with the snorkel, while the work of breathing remained the same in both groups.

Practical significance

So how does this affect diving? A snorkel with a sufficiently large diameter does not restrict breathing. Although breathing resistance increases, this does not appear to have any relevant significance in practice. The frequently expressed concern about hypercapnia is also refuted here. The tested snorkel increased the dead space, i.e. the part of the respiratory system that does not participate in gas exchange (physiologically e.g. trachea, bronchi), by 136 ml. This volume can be easily overcome by healthy people and is largely ventilated away during light to moderate exertion, such as swimming, so that it is practically negligible. There is therefore no risk of CO2 intoxication.

Favorable effect on swimming performance

The fact that the use of a snorkel has a positive effect on swimming performance, contrary to popular belief, was proven by the same author in another study. In this study, 12 test subjects completed a 12-minute crawl swimming test with and without a snorkel. The average swimming speed was 4.4% higher with a snorkel (in the range of +0.5% to +8.3%) compared to without. From this it could be calculated that without the snorkel 7.5% of the work had to be done for breathing, whereas with the snorkel this was only 2.7%. This means that about 5% more power was available for the swimming propulsion.

These numbers may or may not be correct. However, the additional effort involved in raising the head to catch breath without the snorkel obviously plays a significant role. The more relaxed swimming situation with a snorkel is also underlined by the fact that the heart rate was not higher when swimming with a snorkel than without a snorkel, despite the higher speed.

Swimming with diving equipment: very disadvantageous

The author emphasizes that the positive effect of the snorkel could be further enhanced when swimming with diving equipment. Although inflating the buoyancy compensation device (BCD) makes it easier to breathe at the surface, as the head does not have to be raised, it increases the cross-sectional area of the diver by around 15%, which impairs swimming. When swimming on the back with an inflated BCD, the cross-sectional area becomes even larger, which leads to even greater swimming resistance. These effects are even more detrimental in wind and waves. The use of a snorkel offers a clear advantage here, as the water position is smoother and more relaxed when you breathe through it.

Is a snorkel compulsory?

Schellart therefore recommends the regular use of a snorkel and even calls for it to be a mandatory piece of equipment when diving. However, this only applies to snorkels with a diameter of around 2 cm, as breathing resistance (with a smaller diameter) or dead space (with a larger diameter) could become too significant. In addition, unnecessary gimmicks such as exhalation valves or "wave deflectors" should not be used.

Conclusion for practical use

Snorkels are more useful than one might think. They can have a positive effect on breathing effort, breathing resistance and swimming on the surface. However, it is important to ensure that simple models with a diameter of approx. 2 cm are used without any superfluous accessories. It may be worth carrying (and using!) a snorkel, especially when diving in the sea, where swell is to be expected and where it may be necessary to cover longer distances to a diving boat.

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