| Hypoventilation | |
|---|---|
| Other names | Respiratory depression |
Hypoventilation (also known asrespiratory depression) occurs whenventilation is inadequate (hypo meaning "below") to perform neededrespiratory gas exchange.[1] By definition it causes an increased concentration ofcarbon dioxide (hypercapnia) andrespiratory acidosis. Hypoventilation is not synonymous withrespiratory arrest, in which breathing ceases entirely and death occurs within minutes due tohypoxia and leads rapidly into completeanoxia, although both are medical emergencies. Hypoventilation can be considered a precursor to hypoxia, and its lethality is attributed to hypoxia with carbon dioxide toxicity.
Hypoventilation may be caused by:
As aside effect of medicines orrecreational drugs, hypoventilation may become potentially life-threatening. Many differentcentral nervous system (CNS)depressant drugs such asethanol,benzodiazepines,barbiturates,GHB,sedatives, andopioids produce respiratory depression when taken in large or excessive doses, or mixed with other depressants. Strong opiates (namelyfentanyl,heroin, andmorphine),barbiturates, and certain benzodiazepines (such asalprazolam) are known for depressing respiration. In an overdose, an individual may cease breathing entirely (go intorespiratory arrest) which is rapidly fatal without treatment. Opioids, in overdose or combined with other depressants, are notorious for such fatalities. Nevertheless, appropriate use of opioids in the right setting, as seen in patients with advanced cancer or severe chronic non-malignant pain, have been shown to be helpful, when used under appropriate medical care and guidance.[5]
Respiratory stimulants such asnikethamide were traditionally used to counteract respiratory depression from CNS depressant overdose, but offered limited effectiveness. A new respiratory stimulant drug calledBIMU8 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 fromopioid overdose, usually an opioid antagonist, most likelynaloxone, will be administered. This will rapidly reverse the respiratory depression unless complicated by other depressants. However an opioid antagonist may also precipitate anopioid withdrawal syndrome in chronic users.Mechanical ventilation may still be necessary during initial resuscitation.
Disorders likecongenital central hypoventilation syndrome (CCHS) andROHHAD (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 ofsudden infant death syndrome (SIDS), often termed "cot death" or "crib death".
The opposite condition ishyperventilation (too much ventilation), resulting in low carbon dioxide levels (hypocapnia), rather than hypercapnia.