Decreased CO2 during breathwork: emergence of altered states of consciousness

Mechanisms and Physiology

• Several commenters affirm the OP’s “secular” summary: hyperventilation → lower CO₂ (respiratory alkalosis), plus rhythmic diaphragmatic movement and focused attention → euphoria, trance‑like states, cognitive shifts.
• More detailed explanations: low CO₂ causes vasoconstriction and respiratory alkalosis; albumin binds calcium more, altering neuronal excitability and producing tingling and muscle cramps (tetany), especially in hands/face.
• Key distinction made between:
  • Hyperventilation‑driven low CO₂ (breathwork).
  • Apnea/freediving‑driven low O₂/high CO₂.
• One thread notes that lower end‑tidal CO₂ in exhaled air isn’t a direct readout of tissue CO₂, and CO₂ has important physiological roles (Bohr effect), not just “waste gas.”

Safety and Risks

• Tetany is described as uncomfortable but generally transient; explicit warning that people with epilepsy should avoid this kind of breathwork.
• Freediving studies are cited suggesting possible mild, persistent cognitive impairments after years of extreme apnea training; commenters stress this is a different mechanism from hyperventilation‑based practices.
• Strong warnings from divers and freedivers against pre‑dive hyperventilation: it delays the CO₂‑driven urge to breathe without increasing O₂ much, increasing risk of blackout.
• Some worry about nitrous oxide use and hypoxia; others counter that nitrous’ primary effects are pharmacologic, not just from oxygen deprivation.

Subjective Effects and Use Cases

• Many anecdotes of holotropic, Wim Hof, and yogic breathwork producing intense states: euphoria, trance, emotional release, “not far off psychedelics.”
• Others report primarily unpleasant effects (lightheadedness, cramps, insomnia, “hard to think”) or find it difficult to sustain intense breathing outside guided group settings.
• Surfers and freedivers describe training to remain calm and control breathing under extreme stress (hold‑downs, “washing machine” sets), framing it as almost “ego death.”

Meditation, Rationality, and Tradition

• Debate on why breathwork/meditation are popular in atheist circles: some see tension with “rationality,” others emphasize strong empirical support (especially for meditation) for mood, attention, and executive function.
• Clarifications that meditation/breathwork are not inherently religious; they can be treated as “exercise for the brain.”
• Multiple comments connect breathwork to long‑standing practices: pranayama, tummo, Vipassana, and Buddhist psychology; several assert that modern science is “catching up.”

Indoor Air and Environment

• A substantial subthread argues that chronic exposure to stale, high‑CO₂/poor‑quality indoor air subtly worsens mood and cognition.
• CO₂ is framed mainly as a proxy for overall ventilation; commenters also stress VOCs, PM₂.₅, mold, and radon.
• Discussion of consumer air‑quality monitors (CO₂, VOC, particulates), their cost, sensor quality, and calibration, with disagreement over how much CO₂ itself matters at typical household levels.