Yes. Nitrogen hypoxia is something our body doesn’t naturally have a system to detect.

With drowning, the body knows that it’s not getting air, you choke on the fluid as it tries to enter your lungs. The body detects and rejects the incoming fluid.

Nitrogen is a natural part of the atmosphere, it’s the majority of the air we breathe, making up over three quarters of the gases we breathe in and out in normal atmosphere. Nitrogen doesn’t harm the body in this context, or any breathing context, to my knowledge.

Our “suffocating” reaction is typically based on CO2 concentrations. Basically, if we can’t get rid of CO2 through breathing and it builds up in our bodies, we get a suffocation reaction.

Interestingly, the body has no mechanism for monitoring O2. So as O2 levels drop, our body has no reaction to it.

So what happens with nitrogen hypoxia, is that the atmosphere can still accept CO2, and that can leave our system perfectly fine, and it doesn’t build up, which robs us of any biological detection that we are suffocating. Meanwhile since the atmosphere is absent of any concentration of O2, we don’t get any oxygen to add to our system. Since we don’t have a biological way to detect that, it goes largely unnoticed. In the case of nitrogen hypoxia, your CO2 concentration in your blood is never more than what is expected, but your blood O2 saturation falls. Typically, your blood O2 (or SpO2) is somewhere around 95% for a healthy person. Most people can survive unassisted with an SpO2 down to about 85-90%. When you start to dip below 85%, in a medical situation, like a hospital, you would be placed on oxygen to raise it back up, but you probably won’t die from low SpO2 alone at this level. You start risking death below 60% or so.

So what’s happening to the subject in the example above is that you get light headed as your brain and body are deprived of oxygen, this is one of the first signs. You may feel weak and tired. You may even get a bit delirious or giddy. As the SpO2 falls further and further, eventually your brain won’t have enough oxygen to continue, and you will lose consciousness. If the condition continues, then your body will shut down and cease it’s normal functions (like your heart beating, or breathing); and you will discontinue living.

We know these effects in detail because many people have both intentionally and unintentionally experienced this. The effects are well known, and more than a few people have unintentionally died from it. Nitrogen hypoxia is basically undetectable by your body. Nothing feels different about the air you breathe, and you simply get light headed, and eventually fall asleep to die. People get trained to recognise the symptoms if they work with nitrogen products, and if they’re ever in situations where nitrogen hypoxia is possible, and likely, as an effect of their work, for safety. I believe high altitude pilots get this same kind of training. I don’t believe commercial airliners count, since they’re not exactly skimming the atmosphere, and if they have any decompression of the cabin, they’ve been trained to drop to a lower altitude for this exact reason. Anyone climbing very tall mountains may also get training like this.

It’s a very dangerous situation to be in, but not scary when you experience it (unless you recognize what’s happening - which most people won’t).

There was no indication or biological function that caused him to feel the need to hold his breath. He only intellectually knew that he was going to be terminated in this manner a chose to hold his breath. He had no other reason to do it. His body wouldn’t have sent him any danger signals to hold his breath, nor did he have any discomfort that could have indicated that he should have. Only because the mask (or whatever apparatus) was placed on him with the nitrogen flowing. It’s tragic that he chose to fight against it in this way. His decisions made his experience a very unpleasant one. But make no mistake, they were conscious decisions on his part. By holding his breath, he would have had a build up of CO2 which would have felt like suffocating. He induced that in himself, and eventually when his SpO2 dropped to the point where he passed out, he breathed normally and perished anyways.

He make a conscious effort to survive in a situation he would not survive through, and created his own suffering in that moment.