Breath control

Breath control (also called breath play) is the intentional restriction of breathing for sexual gratification. When performed specifically to restrict oxygen to the brain, this is called erotic asphyxiation (or when performed alone, autoerotic asphyxiation). Breath control is a high-risk kink and the most common cause of fatalities in solo-play scenes [citation needed].

Background

Humans must breathe to survive. Breathing serves two essential purposes:

• Deliver oxygen to the body
• Remove carbon dioxide from the body

Dysfunction of either can rapidly cause serious injury or death.

Respiratory physiology

Human lungs exchange oxygen for carbon dioxide and store additional oxygen, which allows for brief periods of apnea (pauses in breathing) without harm. The amount of gas stored in the lungs at a given time is described by "lung volumes", and varies depending on what the person is doing. If breathing is paused, adequate oxygenation will be provided to the body until the remaining oxygen stored in the lungs is consumed, after which the person's oxygen saturation will rapidly decrease followed shortly by loss of consciousness.

Importantly, the body's sense of urgency to breathe is almost entirely driven by the ability to exhale carbon dioxide rather than the level of oxygen in the blood. This means that in certain circumstances (e.g. inhaling breaths of nitrous oxide continuously), the person will never feel short of breath despite low oxygen levels which can rapidly lead to unconsciousness.

The following table demonstrates how much gas remains in the lungs and how long that gas can supply enough oxygen to the body for a number of different circumstances for an average adult. Note that while the average volumes of gas vary greatly between individuals based upon their lean body weight, there is a reciprocal change in the rate of oxygen consumption meaning that the calculated times until desaturation occurs remain roughly the same.

Amount of gas stored in the lungs

	Normal breathing	Inhaling the largest breath possible	Exhaling as much gas as possible
Terminology	Functional residual capacity (FRC)	Total lung capacity (TLC)	Residual volume (RV)
Volume of gas	2 liters	5 liters	1 liter
Volume of oxygen (if breathing room air)	420 milliliters	1,050 milliliters	210 milliliters
When resting calmly
Rate of oxygen consumption	280 milliliters per minute
Time until oxygen is depleted	90 seconds	3 minutes, 45 seconds	45 seconds
During vigorous sexual activity
Rate of oxygen consumption	1,600 milliliters per minute
Time until oxygen is depleted	15 seconds	1 minute	<10 seconds

Hypoxia (Low oxygen)

Hypoxia is the term used to describe inadequate oxygen delivery to the body. When oxygen is completely depleted:

• Consciousness is lost within seconds
• Permanent brain damage occurs within minutes
• Death is all but certain after 10 minutes

When only breathing is restricted, the amount of time until oxygen is depleted is largely determined by how much oxygen remains in the lungs and the rate at which the body is using oxygen (see table above). However, in certain forms of breath play, oxygen depletion can occur much faster. For example:

• When other gases are being inhaled that significantly displace air (e.g. nitrous oxide)
• During carotid compression, which immediately completely restricts oxygen delivery to the brain

Loss of consciousness

Examples of decorticate and decerebrate posturing.

An example of rapid loss of consciousness and onset of posturing due to bilateral carotid compression.
0:11 - Consciousness is lost
0:14 - Decorticate posturing begins
0:21 - Posturing transitions to decerebrate features. Note the right arm attempting to extend outward blocked by legs.
0:35 - Posturing ceases, consciousness begins to return

When consciousness is lost due to hypoxia, the brain no longer communicates with the body normally and the body enters a reflexive state called posturing. Posturing results in the extreme tension of specific groups of muscles, which depend on the parts of the brain being denied oxygen. However, in all types of posturing the fingers close tightly into a fist. This has several extremely important implications:

• It is highly likely that a person will not let go of something they are holding when they lose consciousness
  • Depending on releasing an object in order to restore normal airflow is NOT a safe risk-mitigation strategy
• This grip may not release until brain death occurs
• To people unfamiliar with the appearance of posturing, it may not be apparent that loss of consciousness has occurred
  • This may delay or prevent assistance being provided, leading to further injury or death

Hypercarbia (high carbon dioxide)

Hypercarbia is the term used to describe the inability to eliminate carbon dioxide from the body by exhalation. When carbon dioxide cannot be eliminated, an increasingly urgent sensation to breathe develops. If airflow is not restricted, the rate and depth of breathing reflexively increase. At very high levels of carbon dioxide, a person can become unresponsive and the pH of the blood can become dangerously acidic.

During breath play, unless oxygen supplementation and/or a carbon dioxide scrubber are used, hypoxia will generally present a life-threatening problem before hypercarbia becomes dangerous.