We are all narced

April 2024

Scuba divers are well aware that nitrogen (N₂), which accounts for 78% of the air we breathe and is otherwise inert and not metabolized, is narcotic at depth. Its inebriating effects while diving on standard air are felt as early as 30 m deep and are colloquially referred to as "being narced" or "the Martini effect" (i.e., one cocktail for every 10 m below a depth of 20 m). While generally mild and innocuous at the depths involved in recreational diving, nitrogen-related impairment is directly involved in up to 6% of all deaths in divers (Clark, 2015). For deep dives (generally defined as 40 m and below), safety dictates that N₂ must be replaced (at least in part) by some other diluent gas.

Unexpectedly, I came across fascinating anesthesiology research that N₂ is slightly narcotic even at surface pressure. This is not new research; it was published in 1975. Yet, even as a scuba instructor myself, I had never heard of this effect. In this study, 18 young healthy volunteers who had not consumed alcohol nor psychoactive substances for a week were subjected to an experiment. They were tasked with signaling pattern changes in audio and visual stimuli by pressing a button while inhaling two different gas mixtures. The first group inhaled normoxic nitrox (78% N₂, 21% O₂) while the second inhaled normoxic heliox (78% He, 21% O₂). Both groups' reaction times were recorded while executing the performance task, and then their gas mixtures were switched, so that each group acted both as control and test in turn. Helium was chosen as the control diluent as it is considered to be non-narcotic at any pressure.

A highly statistically significant result (P < 0.001) was observed whereby test subjects inhaling the helium-oxygen mixture reacted within .95–.99 seconds of stimuli changes, a 9.3% mean improvement over the nitrogen-oxygen group who reacted within 1.02–1.12 seconds. There was no meaningful difference between groups based on the order in which they breathed each mixture; as they both equilibrated for 20 minutes with each gas before attempting the performance task.

The conclusion of the study is delightfully thought-provoking:

“that the 'nitrogen blanket' effect [...] is a real phenomenon, and that human history has proceeded under partial narcosis. Perhaps this explains the current state of world affairs.”

Based on this research, you, me, and everyone else alive is constantly and ever-so-slightly narced, and blissfully unaware of it. Conversely, the implication is that if you want a quick cognitive boost for situations where reaction time is crucial, you should breathe pure O₂ for 20 minutes prior and throughout.

In The Maltese Falcon (1941), Humphrey Bogart famously declares “the problem with the world is that everyone is a few drinks behind”. A few drinks behind, perhaps, but not too far behind thanks to nitrogen.

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