Patrick McKeown is doing something rare here. In a space crowded with enthusiastic converts and breathwork evangelists, he's offering a precise, physiological account of what the Wim Hof breathing technique actually does — and what it doesn't do.
The core claim: the method works not because it floods your blood with oxygen, but because it's a short-term stressor. The epinephrine and adrenaline surge are the mechanism. The immune modulation that follows — the same cascade documented in Radboud University's landmark 2014 PNAS study — comes from that stress response, not from any enhancement of blood oxygen saturation. Hemoglobin is already fully saturated at rest. You can't load it up further by breathing harder. What you can do is deplete your CO2 dramatically, and that has real physiological consequences.
Thirty seconds of hyperventilation halves your CO2. Every one millimeter drop in CO2 reduces cerebral blood flow by two percent. Run those numbers and you're reducing blood flow to the brain by up to forty percent. That light-headedness isn't oxygenation euphoria. It's your brain being starved of blood.
This is where McKeown's expertise as a Buteyko practitioner comes into sharp relief. His entire practice is built around CO2 tolerance — the understanding that carbon dioxide isn't just a waste gas, it's the primary driver of your breathing reflex and a critical regulator of oxygen delivery to tissues. The Bohr effect: when CO2 drops, hemoglobin holds onto oxygen more tightly. Paradoxically, hyperventilating can make it harder for your cells to actually use the oxygen in your blood.
Nobody disputes the benefits. The university studies, the self-reported outcomes, the measurable immune markers — the evidence is there. What McKeown is pushing back on is the narrative. "Hyper-oxygenation" is a compelling story. It just isn't what's happening. And the distinction matters, because once you understand the actual mechanism — controlled, voluntary stress response via adrenaline — you can work with it intelligently rather than chasing a physiological effect that doesn't exist.
Across our knowledge base, from Jesse James West's immersive 24-hour Wim Hof experience to the Tim Ferriss long-form interview, the pattern is consistent: the breathing technique is transformative when approached with discipline and respect. McKeown adds the physiological grammar that explains why.
Never, under any circumstances, combine the breathing technique with water. Not pools, not bathtubs, not the ocean. When your CO2 drops low enough, your brain stops sending the signal to breathe. Blood oxygen can fall to forty or fifty percent during the retention phase — lower than you'd see at the summit of Everest. In water, that means drowning. This isn't a theoretical risk. McKeown describes a supervised incident where a participant was unresponsive for three minutes.
The protocol itself is valuable. Done on dry land, in a controlled environment, with awareness of what you're actually triggering — a hormetic stress response that primes your immune system and rewires your stress tolerance — it belongs in the same category as sauna, cold plunge, and intermittent fasting. A deliberate stressor. Not a hack. A ritual.
Here's what strikes me most: the retention phase after hyperventilation — that extended, involuntary breath hold — produces blood oxygen levels that would be considered a medical emergency in any other context. And yet, this is precisely the signal that appears to trigger the immune cascade. The body interprets extreme hypoxia as a threat and responds with the same biological machinery it would deploy against an actual pathogen. You're essentially tricking your immune system into mobilizing without an actual infection. The dose, once again, is everything.