Hypercapnia (from the Greek hyper = "above" and kapnos = "smoke"), also known as CO₂ Poisoning, is a condition where there is too much carbon dioxide (CO₂) in the blood. Carbon dioxide is a gaseous product of the body's metabolism and is normally expelled through the lungs. Smoke from a wildfire Smoke is the airborne solid and liquid particulates and gases evolved when a material undergoes pyrolysis or combustion, together with the quantity of air that is entrained or otherwise mixed into the mass. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms, and is in a gaseous state in the atmosphere of the Earth. ... This article does not cite any references or sources. ... The human body is the entire physical structure of a human organism. ... A few of the metabolic pathways in a cell. ... Human respiratory system The lungs flank the heart and great vessels in the chest cavity. ...

Causes

Hypercapnia is generally caused by hypoventilation, lung disease, or diminished consciousness. It may also be caused by exposure to environments containing abnormally high concentrations of carbon dioxide (usually due to volcanic or geothermal causes), or by rebreathing exhaled carbon dioxide. In medicine, hypoventilation (also known as respiratory depression) occurs when ventilation is inadequate (hypo means below) to perform needed gas exchange. ... Human respiratory system The lungs flank the heart and great vessels in the chest cavity. ... Consciousness is a quality of the mind generally regarded to comprise qualities such as subjectivity, self-awareness, sentience, sapience, and the ability to perceive the relationship between oneself and ones environment. ... Inspiration Closed Circuit Diving Rebreather Description A rebreather is a type of breathing equipment that provides a breathing gas containing oxygen and recycles exhaled gas. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms, and is in a gaseous state in the atmosphere of the Earth. ...

Can also be an initial effect of administering supplemental oxygen on a patient with sleep apnea. In this situation the hypercapnia can also be accompanied by respiratory acidosis. ^[1] Respiratory acidosis is acidosis (abnormal acidity of the blood) due to decreased ventilation of the pulmonary alveoli, leading to elevated arterial carbon dioxide concentration. ...

Symptoms

Symptoms of early hypercapnia, where arterial carbon dioxide pressure, PaCO₂, is elevated but not extremely so, include flushed skin, full pulse, extrasystoles, muscle twitches, hand flaps, reduced neural activity, and possibly a raised blood pressure. In severe hypercapnia (generally PaCO₂ greater than 10 kPa or 75 mmHg), symptomatology progresses to disorientation, panic, hyperventilation, convulsions, unconsciousness, and eventually death. For other uses, see Pulse (disambiguation). ... Extrasystole Systole is a medical name for a contraction most often used in the description of the way the heart beats. ... A sphygmomanometer, a device used for measuring blood pressure. ... The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ... One way of defining pressure is in terms of the height of a column of fluid that may be supported by that pressure; or the height of a column of fluid that exerts that pressure at its base. ... Panic is the primal urge to run and hide in the face of imminent danger. ... In medicine, hyperventilation (or hyperpnea) is the state of breathing faster or deeper (hyper) than necessary, and thereby reducing the carbon dioxide concentration of the blood below normal. ... This article is about the medical condition. ... Unconsciousness is the absence of consciousness. ... This article or section does not adequately cite its references or sources. ...

During diving

Reasons

There are a variety of reasons for carbon dioxide not being expelled completely when the diver exhales: CO2 retention is a pathophysiological state in which too much carbon dioxide is accumulated in the blood. ...

• The diver is exhaling into a vessel that does not allow all the CO2 to escape to the environment, such as a long snorkel, full face diving mask, or diving helmet. The diver then re-inhales from that vessel.
• The carbon dioxide scrubber in the diver's rebreather is failing to remove sufficient carbon dioxide from the loop.
• The diver is over-exercising, producing excess carbon dioxide due to elevated metabolic activity.
• The density of the breathing gas is higher at depth, so the effort required to fully inhale and exhale has increased, making breathing more difficult and less efficient. The higher gas density also causes gas mixing within the lung to be less efficient, thus increasing the deadspace (wasted breathing).
• The diver is deliberately hypoventilating, known as "skip breathing" (see below).

Snorkel A snorkel (also spelled schnorkel or schnorchel) is a tube that allows a person, vehicle, or vessel to draw air while submerged under water. ... A diver in a pool wearing an AGA full face mask A diver wearing an Ocean Reef full face mask A full-face diving mask is a type of diving mask worn by SCUBA divers so that they can talk with the surface or other divers. ... Diving helmets are worn by divers who need to speak and hear underwater. ... // Soda lime is a mixture of chemicals, used in granular form in closed breathing environments, such as general anaesthesia, submarines, rebreathers and recompression chambers, to remove carbon dioxide from breathing gases to prevent CO2 retention and carbon dioxide poisoning. ... A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycles exhaled gas. ... In physics, density is mass m per unit volume V. For the common case of a homogeneous substance, it is expressed as: where, in SI units: ρ (rho) is the density of the substance, measured in kg·m-3 m is the mass of the substance, measured in kg V is... Air is the most common and only natural breathing gas. ... In medicine, hypoventilation (also known as respiratory depression) occurs when ventilation is inadequate (hypo means below) to perform needed gas exchange. ...

Skip breathing

Skip breathing is a controversial technique to conserve breathing gas when using open-circuit scuba, which consists of briefly holding one's breath between inhalation and exhalation (i.e. "skipping" a breath). It leads to CO₂ not being exhaled efficiently. There is also an increased risk of burst lung from holding the breath while ascending. Air is the most common and only natural breathing gas. ... Open circuit can mean: In electronics, where there is nothing connected to a load and no current can flow. ...

Skip breathing is counter productive with a rebreather where the act of breathing pumps the gas around the "loop" pushing carbon dioxide through the scrubber and mixing freshly injected oxygen.

Rebreathers

In closed circuit SCUBA (rebreather) diving, exhaled carbon dioxide must be removed from the breathing system, usually by a scrubber containing a solid chemical compound with a high affinity for CO₂, such as soda lime. If not removed from the system, it may be re-inhaled, causing an increase in the inhaled concentration. A scuba diver in usual sport diving gear SCUBA is an acronym for Self-Contained Underwater Breathing Apparatus. ... A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycles exhaled gas. ... The word scrubber can mean:- The part of a rebreather breathing set which absorbs the carbon dioxide which the individual using the breathing set breathes out. ... // Soda lime is a mixture of chemicals, used in granular form in closed breathing environments, such as general anaesthesia, submarines, rebreathers and recompression chambers, to remove carbon dioxide from breathing gases to prevent CO2 retention and carbon dioxide poisoning. ...

See also

• Permissive hypercapnia
• hypocapnia, decreased level of carbon dioxide
  
• Respiratory Physiology
• Ocean acidification

Permissive hypercapnia is hypercapnia, (i. ... Hypocapnia, also sometimes known as acapnia, is a state in which the level of carbon dioxide in the blood is lower than normal. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Change in sea surface pH caused by anthropogenic CO2 between the 1700s and the 1990s Ocean acidification is the name given to the ongoing decrease in the pH of the Earths oceans, caused by their uptake of anthropogenic carbon dioxide from the atmosphere. ...

References

• CO₂ Effects on Humans

Footnotes