Inhalation
Inhalation (also known as inspiration) is the drawing in of a substance into the lungs.
Inhalation of air
Inhalation of air, as part of the cycle of breathing, is a vital process for all human life. As such, it happens automatically (though there are exceptions in some disease states) and does not need conscious control or effort.[1] However, breathing can be consciously controlled or interrupted (within limits).
Breathing allows oxygen (which humans and many 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 (eg. in drowning), smoke, food, vomitus and less common foreign bodies[2] (eg. condoms,[3] tooth fragments, coins, batteries, small toy parts, needles).
Other substances - deliberate
Recreational use
Legal - helium, nitrous oxide ("laughing gas")
Illegal - various gaseous, vaporised or aerosolised recreational drugs
Medical use
Diagnostic
Various specialised investigations use the inhalation of known substances for diagnostic purposes. Examples include pulmonary function testing (eg. nitrogen washout test, diffusion capacity testing (carbon monoxide, helium, methane)) and diagnostic radiology (eg.radioactive xenon isotopes).
Therapeutic
Gases and other drugs used in anaesthesia include oxygen, nitrous oxide, helium, xenon, volatile anaesthetic agents. Medication for asthma, croup, cystic fibrosis and some other conditions.
Suicide
Carbon monoxide from vehicle exhaust emissions.
Mechanism of inhalation
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 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. Air enters, inflating the lung through either the nose or the mouth into the pharynx (throat) and trachea before entering the alveoli.[citation needed]
Other muscles that can be involved in inhalation include:[4]
Hyperaeration
Hyperaeration or hyperinflation is where the lung volume is abnormally increased, with increased filling of the alveoli. This results in an increased 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 mucous plugs in asthma.[5]
It causes one form of overexpansion of the lung. Overexpansion, however, can also be caused by increase in lung mass itself.[citation needed]
See also
- Exhalation
- Inhalant – psychoactive drugs consumed through inhalation
- List of terms of lung size and activity
- Respiratory system
- Smoking - a specific inhalation route
- Ventilation (physiology)
- Work of breathing
References
- ^ "Control of ventilation". Wikipedia, the free encyclopedia.
- ^ Passàli, D; Lauriello, M; Bellussi, L; Passali, GC; Passali, FM; Gregori, D (2010). "Foreign body inhalation in children: an update". Acta Otorhinolaryngol Ital. PMID 2881610.
- ^ Arya, CL; Gupta, R; Arora, VK (2004). "Accidental condom inhalation". Indian J Chest Dis Allied Sci. PMID 14870871.
- ^ Template:GeorgiaPhysiology[dead link]
- ^ "Hyperinflation". Medcyclopaedia. GE. Archived from the original on 2012-02-05.
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