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Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a rise in arterial carbon dioxide levels is called hypercapnia. Respiratory failure is classified as either Type 1 or Type 2, based on whether there is a high carbon dioxide level, and can be acute or chronic. In clinical trials, the definition of respiratory failure usually includes increased respiratory rate, abnormal blood gases, and evidence of increased work of breathing. Respiratory failure causes an altered state of consciousness due to ischemia in the brain.
Obesity hypoventilation syndrome (OHS) is a condition in which severely overweight people fail to breathe rapidly or deeply enough, resulting in low oxygen levels and high blood carbon dioxide (CO2) levels. The syndrome is often associated with obstructive sleep apnea (OSA), which causes periods of absent or reduced breathing in sleep, resulting in many partial awakenings during the night and sleepiness during the day. The disease puts strain on the heart, which may lead to heart failure and leg swelling.
Colloquially known as "downers", depressants or CNS depressants are drugs that lower neurotransmission levels, decrease the electrical activity of brain cells, or reduce arousal or stimulation in various areas of the brain. Some specific depressants do influence mood, either positively or negatively, but depressants often have no clear impact on mood. In contrast, stimulants, or "uppers", increase mental alertness, making stimulants the opposite drug class from depressants. Antidepressants are defined by their effect on mood, not on general brain activity, so they form an orthogonal category of drugs.
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 product of the body's metabolism and is normally expelled through the lungs. Carbon dioxide may accumulate in any condition that causes hypoventilation, a reduction of alveolar ventilation (the clearance of air from the small sacs of the lung where gas exchange takes place) as well as resulting from inhalation of CO2. Inability of the lungs to clear carbon dioxide, or inhalation of elevated levels of CO2, leads to respiratory acidosis. Eventually the body compensates for the raised acidity by retaining alkali in the kidneys, a process known as "metabolic compensation".
The control of ventilation is the physiological mechanisms involved in the control of breathing, which is the movement of air into and out of the lungs. Ventilation facilitates respiration. Respiration refers to the utilization of oxygen and balancing of carbon dioxide by the body as a whole, or by individual cells in cellular respiration.
Respiratory arrest is a serious medical condition caused by apnea or respiratory dysfunction severe enough that it will not sustain the body. Prolonged apnea refers to a patient who has stopped breathing for a long period of time. If the heart muscle contraction is intact, the condition is known as respiratory arrest. An abrupt stop of pulmonary gas exchange lasting for more than five minutes may permanently damage vital organs, especially the brain. Lack of oxygen to the brain causes loss of consciousness. Brain injury is likely if respiratory arrest goes untreated for more than three minutes, and death is almost certain if more than five minutes.
Central hypoventilation syndrome (CHS) is a sleep-related breathing disorder that causes ineffective breathing, apnea, or respiratory arrest during sleep. CHS can either be congenital (CCHS) or acquired (ACHS) later in life. The condition can be fatal if untreated. CCHS was once known as Ondine's curse.
Hypocapnia, also known as hypocarbia, sometimes incorrectly called acapnia, is a state of reduced carbon dioxide in the blood. Hypocapnia usually results from deep or rapid breathing, known as hyperventilation.
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.
Non-invasive ventilation (NIV) is the use of breathing support administered through a face mask, nasal mask, or a helmet. Air, usually with added oxygen, is given through the mask under positive pressure; generally the amount of pressure is alternated depending on whether someone is breathing in or out. It is termed "non-invasive" because it is delivered with a mask that is tightly fitted to the face or around the head, but without a need for tracheal intubation. While there are similarities with regard to the interface, NIV is not the same as continuous positive airway pressure (CPAP), which applies a single level of positive airway pressure throughout the whole respiratory cycle; CPAP does not deliver ventilation but is occasionally used in conditions also treated with NIV.
Butalbital is a barbiturate with an intermediate duration of action. Butalbital is often combined with other medications, such as paracetamol (acetaminophen) or aspirin, for the treatment of pain and headache. The various formulations combined with codeine are FDA-approved for the treatment of tension headaches. Butalbital has the same chemical formula as talbutal but a different structure—one that presents as 5-allyl-5-isobutylbarbituric acid.
Central nervous system (CNS) depression is a physiological state that can result in a decreased rate of breathing, decreased heart rate, and loss of consciousness, possibly leading to coma or death.
Freediving blackout, breath-hold blackout, or apnea blackout is a class of hypoxic blackout, a loss of consciousness caused by cerebral hypoxia towards the end of a breath-hold dive, when the swimmer does not necessarily experience an urgent need to breathe and has no other obvious medical condition that might have caused it. It can be provoked by hyperventilating just before a dive, or as a consequence of the pressure reduction on ascent, or a combination of these. Victims are often established practitioners of breath-hold diving, are fit, strong swimmers and have not experienced problems before. Blackout may also be referred to as a syncope or fainting.
Etamivan is a respiratory stimulant drug related to nikethamide. It was mainly used in the treatment of barbiturate overdose and chronic obstructive pulmonary disease, but has now largely fallen into disuse.
Amiphenazole (Daptazile) is a respiratory stimulant traditionally used as an antidote for barbiturate or opiate overdose, usually in combination with bemegride, as well as poisoning from other sedative drugs and treatment of respiratory failure from other causes. It was considered particularly useful as it could counteract the sedation and respiratory depression produced by morphine but with less effect on analgesia. It is still rarely used in medicine in some countries, although it has largely been replaced by more effective respiratory stimulants such as doxapram and specific opioid antagonists such as naloxone.
Desbutal was a brand name drug by Abbott containing 5 mg methamphetamine hydrochloride (Desoxyn) and 30 mg pentobarbital sodium (Nembutal); a substituted amphetamine and a barbiturate combined within the same pill. Desbutal was marketed as an antidepressant as well as a medication for the treatment of obesity, narcolepsy, parkinsonism, and alcoholism, although it was commonly also prescribed off-label for miscellaneous ailments. It had a high abuse potential and is no longer manufactured.
An opioid overdose is toxicity due to excessive consumption of opioids, such as morphine, codeine, heroin, fentanyl, tramadol, and methadone. This preventable pathology can be fatal if it leads to respiratory depression, a lethal condition that can cause hypoxia from slow and shallow breathing. Other symptoms include small pupils and unconsciousness; however, its onset can depend on the method of ingestion, the dosage and individual risk factors. Although there were over 110,000 deaths in 2017 due to opioids, individuals who survived also faced adverse complications, including permanent brain damage.
Benzodiazepine overdose describes the ingestion of one of the drugs in the benzodiazepine class in quantities greater than are recommended or generally practiced. The most common symptoms of overdose include central nervous system (CNS) depression, impaired balance, ataxia, and slurred speech. Severe symptoms include coma and respiratory depression. Supportive care is the mainstay of treatment of benzodiazepine overdose. There is an antidote, flumazenil, but its use is controversial.
Barbiturates are a class of depressant drugs that are chemically derived from barbituric acid. They are effective when used medically as anxiolytics, hypnotics, and anticonvulsants, but have physical and psychological addiction potential as well as overdose potential among other possible adverse effects. They have been used recreationally for their anti-anxiety and sedative effects, and are thus controlled in most countries due to the risks associated with such use.
Central sleep apnea (CSA) or central sleep apnea syndrome (CSAS) is a sleep-related disorder in which the effort to breathe is diminished or absent, typically for 10 to 30 seconds either intermittently or in cycles, and is usually associated with a reduction in blood oxygen saturation. CSA is usually due to an instability in the body's feedback mechanisms that control respiration. Central sleep apnea can also be an indicator of Arnold–Chiari malformation.
References
- ↑ "Hypoventilation" at Dorland's Medical Dictionary
- ↑ Woorons X (2014). Hypoventilation training, push your limits!. Arpeh. p. 164. ISBN 978-2-9546040-1-5.
- ↑ Zubieta-Calleja GR, Paulev PE, Zubieta-Calleja L, Zubieta-Calleja N, Zubieta-Castillo G (September 2006). "Hypoventilation in chronic mountain sickness: a mechanism to preserve energy". Journal of Physiology and Pharmacology. 57 (Suppl 4): 425–430. PMID 17072073.
- ↑ Dy, Sydney M.; Gupta, Arjun; Waldfogel, Julie M.; Sharma, Ritu; Zhang, Allen; Feliciano, Josephine L.; Sedhom, Ramy; Day, Jeff; Gersten, Rebecca A. (2020-11-19). Interventions for Breathlessness in Patients With Advanced Cancer (Report). Agency for Healthcare Research and Quality (AHRQ). doi:10.23970/ahrqepccer232.