Hypoventilation (also known as respiratory depression) occurs when ventilation is inadequate (''hypo'' meaning "below") to perform needed respiratory gas exchange. By definition it causes an increased concentration of

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

(

hypercapnia Hypercapnia (from the Greek ''hyper'' = "above" or "too much" and ''kapnos'' = "smoke"), also known as hypercarbia and CO2 retention, is a condition of abnormally elevated carbon dioxide (CO2) levels in the blood. Carbon dioxide is a gaseous p ...

) and

respiratory acidosis Respiratory acidosis is a state in which decreased ventilation ( hypoventilation) increases the concentration of carbon dioxide in the blood and decreases the blood's pH (a condition generally called acidosis). Carbon dioxide is produced contin ...

. Hypoventilation is not synonymous with respiratory arrest, in which breathing ceases entirely and death occurs within minutes due to hypoxia and leads rapidly into complete anoxia, although both are medical emergencies. Hypoventilation can be considered a precursor to hypoxia and its lethality is attributed to hypoxia with carbon dioxide toxicity.

Causes

Hypoventilation may be caused by: *A medical condition such as

stroke A stroke is a disease, medical condition in which poor cerebral circulation, blood flow to the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemorr ...

affecting the brainstem *Voluntary breath-holding or underbreathing, for example,

hypoventilation training Hypoventilation training is a physical training method in which periods of exercise with reduced breathing frequency are interspersed with periods with normal breathing. The hypoventilation technique consists of short breath holdings and can be p ...

or the

Buteyko method The Buteyko method or Buteyko Breathing Technique is a form of complementary or alternative physical therapy that proposes the use of breathing exercises primarily as a treatment for asthma and other respiratory conditions. Buteyko asserts that ...

. *

Medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy ( pharmacotherapy) is an important part of the medical field and ...

or drugs, typically when taken in accidental or intentional overdose.

Opioid Opioids are substances that act on opioid receptors to produce morphine-like effects. Medically they are primarily used for pain relief, including anesthesia. Other medical uses include suppression of diarrhea, replacement therapy for opioid use ...

s and benzodiazepines in particular are known to cause respiratory depression. Examples of opioids include pharmaceuticals such as oxycodone and hydromorphone and examples of benzodiazepines include

lorazepam Lorazepam, sold under the brand name Ativan among others, is a benzodiazepine medication. It is used to treat anxiety disorders, trouble sleeping, severe agitation, active seizures including status epilepticus, alcohol withdrawal, and che ...

and alprazolam. * Hypocapnia, which stimulates hypoventilation *

Obesity Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's ...

; see Obesity hypoventilation syndrome * Chronic mountain sickness, a mechanism to conserve energy.

Medications

As a side effect of medicines or recreational drugs, hypoventilation may become potentially life-threatening. Many different

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...

(CNS) depressant drugs such as

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

, benzodiazepines, barbiturates, GHB,

sedatives A sedative or tranquilliser is a substance that induces sedation by reducing irritability or excitement. They are CNS depressants and interact with brain activity causing its deceleration. Various kinds of sedatives can be distinguished, but ...

, and

opioid Opioids are substances that act on opioid receptors to produce morphine-like effects. Medically they are primarily used for pain relief, including anesthesia. Other medical uses include suppression of diarrhea, replacement therapy for opioid use ...

s produce respiratory depression when taken in large or excessive doses, or mixed with other depressants. Strong opiates (namely

fentanyl Fentanyl, also spelled fentanil, is a very potent synthetic opioid used as a pain medication. Together with other drugs, fentanyl is used for anesthesia. It is also used illicitly as a recreational drug, sometimes mixed with heroin, cocain ...

, heroin, and

morphine Morphine is a strong opiate that is found naturally in opium, a dark brown resin in poppies ('' Papaver somniferum''). It is mainly used as a pain medication, and is also commonly used recreationally, or to make other illicit opioids. T ...

), barbiturates, and certain benzodiazepines (such as alprazolam) are known for depressing respiration. In an overdose, an individual may cease breathing entirely (go into respiratory arrest) which is rapidly fatal without treatment. Opioids, in overdose or combined with other depressants, are notorious for such fatalities.

Treatment

Respiratory stimulants such as nikethamide were traditionally used to counteract respiratory depression from CNS depressant overdose, but offered limited effectiveness. A new respiratory stimulant drug called BIMU8 is being investigated which seems to be significantly more effective and may be useful for counteracting the respiratory depression produced by opiates and similar drugs without offsetting their therapeutic effects. If the respiratory depression occurs from opioid overdose, usually an opioid antagonist, most likely

naloxone Naloxone, sold under the brand names Narcan (4 mg) and Kloxxado (8 mg) among others, is a medication used to reverse or reduce the effects of opioids. It is commonly used to counter decreased breathing in opioid overdose. Effects begin withi ...

, will be administered. This will rapidly reverse the respiratory depression unless complicated by other depressants. However an opioid antagonist may also precipitate an opioid withdrawal syndrome in chronic users.

Mechanical ventilation Mechanical ventilation, assisted ventilation or intermittent mandatory ventilation (IMV), is the medical term for using a machine called a ventilator to fully or partially provide artificial ventilation. Mechanical ventilation helps move a ...

may still be necessary during initial resuscitation.

Associated conditions

Disorders like congenital central hypoventilation syndrome (CCHS) and ROHHAD (rapid-onset obesity, hypothalamic dysfunction, hypoventilation, with autonomic dysregulation) are recognized as conditions that are associated with hypoventilation. CCHS may be a significant factor in some cases of sudden infant death syndrome (SIDS), often termed "cot death" or "crib death". The opposite condition is hyperventilation (too much ventilation), resulting in low carbon dioxide levels ( hypocapnia), rather than hypercapnia.

References

{{Respiratory system symptoms and signs Breathing abnormalities

Causes

Medications

Treatment

Associated conditions

See also

References