Editing Inhalation

{{short description|Flow of the respiratory current into an organism}}
{{More citations needed|date=March 2020}}
{{redirect|Inhale|the 2013 Marsheaux album|Inhale (album)}}
[[File:Inhalation diagram.svg|thumb|Diagram showing inhalation]]
'''Inhalation''' (or '''inspiration''') happens when air or other gases enter the lungs.

== Inhalation of air ==
Inhalation of air, as part of the cycle of [[breathing]], is a vital process for all human life. The process is autonomic (though there are exceptions in some disease states) and does not need conscious [[Control of ventilation|control]] or effort. However, breathing can be consciously controlled or interrupted (within limits).

Breathing allows oxygen (which humans and a lot of other species need for survival) to enter the lungs, from where it can be absorbed into the bloodstream.

== Other substances – accidental ==
Examples of accidental inhalation includes inhalation of water (e.g. in drowning), smoke, food, vomitus and less common foreign substances<ref>{{Cite journal|last2=Lauriello|first2=M|last3=Bellussi|first3=L|last4=Passali|first4=GC|last5=Passali|first5=FM|last6=Gregori|first6=D|date=2010|title=Foreign body inhalation in children: an update|pmc=2881610|journal=Acta Otorhinolaryngol Ital|pmid=20559470|last1=Passàli|first1=D|volume=30|issue=1|pages=27–32}}</ref> (e.g. tooth fragments, coins, batteries, small toy parts, needles).

== Other substances – deliberate ==

=== Recreational use ===
[[Nitrous oxide]] ("laughing gas") has been [[Recreational use of nitrous oxide| used recreationally since 1899]] for its ability to induce [[euphoria]], [[hallucinogenic]] states and [[Relaxation (psychology)|relaxation]], and is legal in some countries.

[[Helium]] can be inhaled to give the voice a reedy, duck-like quality, but this can be dangerous as the gas is an [[asphyxiant gas|asphyxiant]] and displaces the oxygen needed for normal respiration.<ref name="Grass">{{Cite journal| title = Suicidal asphyxiation with helium: Report of three cases Suizid mit Helium Gas: Bericht über drei Fälle| journal = Wiener Klinische Wochenschrift| volume = 119|issue =9–10|date = 2007|doi = 10.1007/s00508-007-0785-4|author = Grassberger, Martin|author2 = Krauskopf, Astrid |pages = 323–325 |language=de, en| pmid = 17571238|s2cid = 22894287}}</ref> 

Various illegal gaseous, vapourised  or aerosolized [[recreational drugs]] exist, and are classed as [[inhalant]]s.

=== Medical use ===

==== Diagnostic ====

Various specialized investigations use the inhalation of known substances for diagnostic purposes. Examples include [[pulmonary function testing]] (e.g. [[nitrogen washout]] test, [[Diffusing capacity|diffusion capacity]] testing ([[carbon monoxide]], [[helium]], [[methane]])) and [[diagnostic radiology]] (e.g. [[Isotopes of xenon|radioactive xenon isotopes]]).

==== Therapeutic ====

Gases and other drugs used in anaesthesia include oxygen, nitrous oxide, helium, xenon, [[Inhalational anaesthetic|volatile anaesthetic agents]]. Medication for [[asthma]], croup, cystic fibrosis and some other conditions.


== Mechanism ==
Inhalation begins with the contraction of the muscles attached to the rib cage; this causes an expansion in the chest cavity.  Then takes place the onset of contraction of the [[thoracic diaphragm]], which results in expansion of the [[intrapleural space]] and an increase in negative pressure according to [[Boyle's law]].  This negative pressure generates airflow because of the pressure difference between the atmosphere and alveolus. 

The inflow of air into the lungs occurs via the [[respiratory airways]]. In health, these airways [[Obligate nasal breathing|begin with the nose]].<ref name=cc>{{cite web
|url=https://health.clevelandclinic.org/breathe-mouth-nose/
|title=Should You Breathe Through Your Mouth or Your Nose?
|access-date=2020-06-28
|last=Turowski
|first=Jason
|date=2016-04-29
|publisher=[[Cleveland Clinic]]
}}</ref><ref name="guardian">{{cite web|title=Your Nose, the Guardian of Your Lungs|url=https://www.bmc.org/otolaryngology-head-neck-surgery/resources/your-nose-guardian-your-lungs|access-date=2020-06-29|publisher=[[Boston Medical Center]]}}</ref> It is possible to begin with the mouth, which is the backup breathing system. However, chronic [[mouth breathing]] leads to, or is a sign of, illness, and it does not have mucus in the mouth to trap the unwanted substance unlike the nostrils<ref name=harmful>{{cite web
|url=https://www.nbcnews.com/healthmain/mouth-breathing-gross-harmful-your-health-1C6437430
|title='Mouth-breathing' gross, harmful to your health
|access-date=2020-06-28
|last=Dahl
|first=Melissa
|date=2011-01-11
|publisher=NBC News
}}</ref><ref name="role">{{cite web
|url=https://www.journal-imab-bg.org/issues-2018/issue1/JofIMAB-2018-24-1p1878-1882.pdf
|title=THE ROLE OF MOUTH BREATHING ON DENTITION DEVELOPMENT AND FORMATION
|access-date=2020-05-31
|last=Valcheva
|first=Zornitsa
|date=January 2018
|publisher=Journal of IMAB
}}</ref><ref name="nesnpr">{{cite web
|url=https://www.npr.org/transcripts/862963172
|title=How The 'Lost Art' Of Breathing Can Impact Sleep And Resilience
|access-date=2020-06-23
|last=Gross
|first=Terry
|date=2020-05-27
|publisher=[[NPR|National Public Radio (NPR)]]/[[Fresh Air]]
}}</ref> They end in the microscopic dead-end sacs([[Pulmonary alveolus|alveoli]]) always opened, though the diameters of the various sections can be changed by the [[Sympathetic nervous system|sympathetic]] and [[parasympathetic nervous system]]s. The alveolar air pressure is therefore always close to atmospheric air pressure (about 100&nbsp;[[Pascal (unit)|kPa]] at sea level) at rest, with the pressure gradients that cause air to move in and out of the lungs during breathing rarely exceeding 2–3&nbsp;kPa.<ref name="Chrisvan L 1995">{{cite journal |last1=Koen |first1=Chrisvan L. |last2=Koeslag |first2=Johan H. | title=On the stability of subatmospheric intrapleural and intracranial pressures |journal= News in Physiological Sciences | date=1995 |volume=10 |issue=4 |pages=176–178 |doi=10.1152/physiologyonline.1995.10.4.176}}</ref><ref name="Williams & Wilkins">{{cite book |last1=West |first1=J.B. |title=Respiratory physiology: the essentials. |location=Baltimore |publisher=Williams & Wilkins |date=1985| pages= 21–30, 84–84, 98–101 }}</ref>

Other muscles that can be involved in inhalation include:<ref>{{cite book| title= Essentials of Human Physiology| first= Thomas M. |last= Nosek| chapter=Section 4/4ch2/s4ch2_10 |chapter-url=http://humanphysiology.tuars.com/program/section4/4ch2/s4ch2_10.htm |archive-url=https://web.archive.org/web/20160324124828/http://humanphysiology.tuars.com/program/section4/4ch2/s4ch2_10.htm|archive-date=2016-03-24}}</ref>
* [[External intercostal muscles]]
* [[Scalene muscles]]
* [[Sternocleidomastoid muscle]]
* [[Trapezius muscle]]

==Hyperinflation==
{{For-multi|another similar term|Dynamic hyperinflation|the Economics term|Hyperinflation}}

''Hyperinflation'' or ''hyperaeration'' is where the lung volume is abnormally increased, with increased filling of the alveoli. This results in an increased [[radiodensity|radiolucency]] on X-ray, a reduction in lung markings and depression of the diaphragm. It may occur in partial obstruction of a large airway, as in e.g. [[congenital lobar emphysema]], bronchial [[atresia]] and mucus plugs in [[asthma]].<ref>{{cite web|url=http://www.medcyclopaedia.com/library/topics/volume_vii/h/hyperinflation.aspx|archive-url=https://archive.today/20111208222639/http://www.medcyclopaedia.com/library/topics/volume_vii/h/hyperinflation.aspx|url-status=dead|archive-date=2011-12-08|title=Hyperinflation|publisher=[[General Electric|GE]]|work=Medcyclopaedia}}</ref>

==Yoga==
Yogis such as [[B. K. S. Iyengar]] advocate both [[Obligate nasal breathing|inhaling and exhaling through the nose]] in the practice of [[yoga]], rather than inhaling through the nose and [[Mouth breathing|exhaling through the mouth]].<ref name=yj>{{cite web
|url=https://www.yogajournal.com/practice/take-a-breath
|title=Q&A: Is Mouth Breathing OK in Yoga?
|access-date=2020-06-26
|date=2017-04-12
|publisher=[[Yoga Journal]]
}}</ref><ref name=dummies>{{cite web
|url=https://www.dummies.com/health/exercise/yoga/yogic-breathing-tips-for-breathing-through-your-nose-most-of-the-time/
|title=Yogic Breathing: Tips for Breathing through Your Nose (Most of the Time)
|access-date=2020-06-26
|last=Payne
|first=Larry
|publisher=[[For Dummies|Yoga For Dummies, 3rd Edition]]
}}</ref><ref name=guide>{{cite web
|url=https://www.himalayaninstitute.org/wisdom-library/yogic-breathing-study-guide/
|title=Yogic Breathing: A Study Guide
|access-date=2020-06-26
|last=Himalayan Institute Core Faculty
|first=Himalayan Institute Core Faculty
|date=2017-07-13
|publisher=[[Himalayan Institute of Yoga Science and Philosophy]]
}}</ref> They tell their students that the "nose is for breathing, the mouth is for eating."<ref name=dummies/><ref name=sparks>{{cite book
|url=https://books.google.com/books?id=QPk_nshsngoC&q=%22the+nose+is+for+breathing%2C+the+mouth+is+for+eating%22+yoga&pg=RA1-PA11
|title=Yoga Sparks
|access-date=2020-05-31
|last=Krucoff
|first=Carol
|date=2013
|publisher=New Harbinger Publications
|isbn=9781608827022
}}</ref><ref name=run>{{cite book
|url=https://books.google.com/books?id=fEm6XnTajm0C&q=%22the+nose+is+for+breathing%2C+the+mouth+is+for+eating%22+yoga&pg=PA108
|title=Eat and Run
|access-date=2020-05-31
|last=Jurek
|first=Scott
|date=2012
|publisher=Houghton Mifflin
|isbn=978-0547569659
}}</ref><ref name=yj/>

==See also==
{{Wiktionary|inhalation|sniffing}}
* [[Exhalation]]
* [[Inhalant]] – psychoactive drugs consumed through inhalation
* [[List of terms of lung size and activity]]
* [[Mouth breathing]]
* [[Obligate nasal breathing]]
* [[Respiratory system]]
* [[Smoking]] - a specific inhalation route
* [[Breathing]]
* [[Work of breathing]]

==Further reading==
* {{Cite book|title=[[Breath: The New Science of a Lost Art]]
|last=Nestor|first=James|publisher=Riverhead Books |year=2020|isbn= 978-0735213616 }}

==References==
{{reflist}}

{{Dosage forms}}
{{Respiratory physiology}}

[[Category:Respiration]]
[[Category:Respiratory physiology]]