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Illustration of human body changes by breathing

Breathing is the process that takes oxygen in and carbon dioxide in and then out of the body. Aerobic organisms require oxygen to release energy via respiration, in the form of the metabolism of energy-rich molecules such as glucose. The medical term for normal relaxed breathing is eupnea.

Breathing is only part of the processes that deliver oxygen to where it is needed in the body and remove carbon dioxide. The process of gas exchange occurs in the alveoli by passive diffusion of gases between the alveolar gas and the blood passing by in the lung capillaries. Once these dissolved gases are in the blood, the heart powers their flow around the body (via the circulatory system).

In addition to removing carbon dioxide, breathing results in loss of water from the body. Exhaled air has a relative humidity of 100% because of water diffusing across the moist surface of breathing passages and alveoli.

Contents

Mechanics

In mammals, breathing in, or inhaling, is usually an active movement, with the contraction of the diaphragm muscle. This is known as negative pressure breathing. Normally, the diaphragm's relaxed position recoils (decreasing the thoracic volume) whereas in the contracted position it is pulled downwards (increasing the thoracic volume). This process works in conjunction with the intercostal muscles connected to the rib cage. Contraction of these muscles lifts the rib cage, thus aiding in increasing the thoracic volume. Relaxation of the diaphragm compresses the lungs, effectively decreasing their volume while increasing the pressure inside them. The intercostal muscles simultaneously relax, further decreasing the volume of the lungs. With a pathway to the mouth or nose clear, this increased pressure forces air out of the lungs. Conversely, contraction of the diaphragm increases the volume of the (partially empty) lungs, decreasing the pressure inside, which creates a partial vacuum. Environmental air then follows its pressure gradient down to fill the lungs.

In amphibians, the process used is positive pressure breathing. Muscles lower the floor of the oral cavity, enlarging it and drawing in air through the nostrils (which uses the same mechanics - pressure, volume, and diffusion - as a mammalian lung). With the nostrils and mouth closed, the floor of the oral cavity is forced up, which forces air down the trachea into the lungs.

At rest, breathing out, or exhaling, is a combination of passive and active processes powered by the elastic recoil of the alveoli, similar to a deflating balloon, and the contraction of the muscular body wall. The following organs are used in respiration: the mouth; the nose and nostrils; the pharynx; the larynx; the trachea; the bronchi and bronchioles; the lungs; the diaphragm; and the terminal branches of the respiratory tree, such as the alveoli.

Control of breathing

Breathing is one of the few bodily functions which, within limits, can be controlled both consciously and unconsciously.

Conscious control

Conscious control of breathing is common in many forms of meditation, specifically forms of yoga for example pranayama unlike anapana which is only awareness of breath. In swimming, cardio fitness, speech or vocal training, one learns to discipline one's breathing, initially consciously but later sub-consciously, for purposes other than life support. Human speech is also dependent on conscious breath control. Also breathing control is used in Buteyko method.

Unconscious control

Unconsciously, breathing is controlled by specialized centers in the brainstem, which automatically regulate the rate and depth of breathing depending on the body’s needs at any time. When carbon dioxide levels increase in the blood, it reacts with the water in blood, producing carbonic acid. Lactic acid produced by anaerobic exercise also lowers pH. The drop in the blood's pH stimulates chemoreceptors in the carotid and aortic bodies in the blood system to send nerve impulses to the respiration centre in the medulla oblongata and pons in the brain. These, in turn send nerve impulses through the phrenic and thoracic nerves to the diaphragm and the intercostal muscles, increasing the rate of breathing. Even a slight difference in the blood's normal pH, 7.4, could cause death, so this is an important process.[citation needed]

This automatic control of respiration can be impaired in premature babies, or by drugs or disease.

Examples

For instance, while exercising, the level of carbon dioxide in the blood increases due to increased cellular respiration by the muscles, which activates carotid and aortic bodies and the respiration center, which ultimately cause a higher rate of respiration.

During rest, the level of carbon dioxide is lower, so breathing rate is lower. This ensures an appropriate amount of oxygen is delivered to the muscles and other organs. It is important to reiterate that it is the buildup of carbon dioxide making the blood acidic that elicits the desperation for a breath much more than lack of oxygen.

Interaction

It is not possible for a healthy person to voluntarily stop breathing indefinitely. If we do not inhale, the level of carbon dioxide builds up in our blood, and we experience overwhelming air hunger. This irrepressible reflex is not surprising given that without breathing, the body's internal oxygen levels drop dangerously low within minutes, leading to permanent brain damage followed eventually by death. However, there have been instances where people have survived for as long as two hours without air; this is only possible when submerged in cold water, as this triggers the mammalian diving reflex [1] as well as putting the subject into a state of suspended animation.

If a healthy person were to voluntarily stop breathing (i.e. hold his or her breath) for a long enough amount of time, he or she would lose consciousness, and the body would resume breathing on its own. Because of this one cannot commit suicide with this method, unless one's breathing was also restricted by something else (e.g. water, see drowning)

Hyperventilating causes a drop in CO2 below normal levels, lowering blood and oxygen supply to vital organs due to CO2-induced vasoconstriction and suppressed Bohr effect. Voluntary hyperventilation can cause tissue oxygen levels to go to dangerously low levels leading to, for example, fainting due to brain hypoxia.

Breathing in the sick

Medical respiratory data (see the table below) suggest that sick people breathe about 2-3 times more air at rest than the medical norm.

Condition Minute ventilation (± standard deviation) Number of patients Reference
Normal breathing 6 l/min None Medical textbooks: [2] [3] [4] [5]
Asthma 12 l/min 101 [6]
Asthma 15 l/min 8 [7]
Asthma 14.1 (±5.7) l/min 39 [8]
Heart disease 14 (±4) l/min 88 [9]
Heart disease 12.2 (±3.3) l/min 132 [10]
Heart disease 16 (±2) l/min 11 [11]
Heart disease 15 (±4) l/min 22 [12]
Diabetes 10-20 l/min 28 [13]
Diabetes 12-17 l/min 26 [14]
Cystic fibrosis 11-14 l/min 6 [15]
Cystic fibrosis 13 (±1.8) l/min 10 [16]
COPD 12.2 (±1.9) l/min 10 [17]
Liver cirrhosis 11-18 l/min 24 [18]
Hyperthyroidism 14.9 (±0.6) l/min 42 [19]
Epilepsy 12.8 l/min 12 [20]

(Source: www.normalbreathing.com) There are many more medical studies that found 100% prevalence of chronic hyperventilation in patients with various chronic diseases.

Breathing in gas

Components

Oxygen is the essential component of all breathing gases.

The air we inhale is roughly 78% by volume nitrogen, 21% oxygen, 0.96% argon and 0.04% carbon dioxide, helium, water, and other gases. In addition to air, underwater divers often breathe oxygen-rich or helium-rich gas mixes. Oxygen and analgesic gases are sometimes given to patients under medical care. The atmosphere in space suits is pure oxygen. Also our reliance on this relatively small amount of oxygen can cause over activity or euphoria in pure or oxygen rich environments.

The permanent gases in gas we exhale are roughly 4% to 5% carbon dioxide and 4% to 5% less oxygen than was inhaled. Additionally vapors and trace gases are present: 5% water vapor, several parts per million (ppm) of hydrogen and carbon monoxide, 1 part per million (ppm) of ammonia and less than 1 ppm of acetone, methanol, ethanol (unless ethanol has been ingested, in which case much higher concentrations would occur in the breath, cf. Breathalyzer) and other volatile organic compounds. The exact amount of exhaled oxygen and carbon dioxide varies according to the fitness, energy expenditure and diet of that particular person.

Air pressure

Atmospheric air at altitude is at a lower pressure than at sea level due to the lesser weight of the air above. This lower pressure can lead to altitude sickness, or hypoxia.

Gases breathed underwater are at higher pressure than at sea level due to the added weight of water. This can lead to nitrogen narcosis, oxygen toxicity, or decompression sickness.

Cultural significance

In Tai Chi Chuan, aerobic training is combined with breathing to exercise the diaphragm muscles, and to train effective posture, which both make better use of the body's energy. In music, breath is used to play wind instruments and many aerophones. Laughter, physically, is simply repeated sharp breaths. Hiccups and yawns are other breath-related phenomena.

Ancients commonly linked the breath to a life force. The Hebrew Bible refers to God breathing the breath of life into clay to make Adam a living soul (nephesh). It also refers to the breath as returning to God when a mortal dies. The terms "spirit," "qi," and "psyche"[21] are related to the concept of breath.

See also

References

  1. ^ Ramey CA, Ramey DN, Hayward JS. Dive response of children in relation to cold-water near drowning. J Appl Physiol 2001;62(2):665-8.Source: Diana Hacker (Boston: Bedford/St. Martin’s, 2002).Adapted from Victoria E. McMillan (Boston: Bedford/St. Martin’s, 2001). See it cited here
  2. ^ Ganong WF, Review of medical physiology, 15-th ed., 1995, Prentice Hall Int., London.
  3. ^ Guyton AC, Physiology of the human body, 6-th ed., 1984, Suanders College Publ., Philadelphia.
  4. ^ McArdle W.D., Katch F.I., Katch V.L., Essentials of exercise physiology (2-nd edition); Lippincott, Williams and Wilkins, London 2000.
  5. ^ Straub NC, Section V, The Respiratory System, in Physiology, eds. RM Berne & MN Levy, 4-th edition, Mosby, St. Louis, 1998.
  6. ^ McFadden ER & Lyons HA, Arterial-blood gases in asthma, The New Engl J of Med 1968 May 9, 278 (19): 1027-1032.
  7. ^ Johnson BD, Scanlon PD, Beck KC, Regulation of ventilatory capacity during exercise in asthmatics, J Appl Physiol. 1995 Sep; 79(3): 892-901.
  8. ^ Bowler SD, Green A, Mitchell CA, Buteyko breathing techniques in asthma: a blinded randomised controlled trial, Med J of Australia 1998; 169: 575-578.
  9. ^ Clark AL, Chua TP, Coats AJ, Anatomical dead space, ventilatory pattern, and exercise capacity in chronic heart failure, Br Heart J 1995 Oct; 74(4): 377-380.
  10. ^ Fanfulla F, Mortara , Maestri R, Pinna GD, Bruschi C, Cobelli F, Rampulla C, The development of hyperventilation in patients with chronic heart failure and Cheyne-Stokes respiration, Chest 1998; 114; p. 1083-1090.
  11. ^ Johnson BD, Beck KC, Olson LJ, O'Malley KA, Allison TG, Squires RW, Gau GT, Ventilatory constraints during exercise in patients with chronic heart failure, Chest 2000 Feb; 117(2): 321-332.
  12. ^ Dimopoulou I, Tsintzas OK, Alivizatos PA, Tzelepis GE, Pattern of breathing during progressive exercise in chronic heart failure, Int J Cardiol. 2001 Dec; 81(2-3): 117-121.
  13. ^ Tantucci C, Scionti L, Bottini P, Dottorini ML, Puxeddu E, Casucci G, Sorbini CA, Influence of autonomic neuropathy of different severities on the hypercapnic drive to breathing in diabetic patients, Chest. 1997 Jul; 112(1): 145-153.
  14. ^ Bottini P, Dottorini ML, M. Cordoni MC, Casucci G, Tantucci C, Sleep-disordered breathing in nonobese diabetic subjects with autonomic neuropathy, Eur Respir J 2003; 22: p. 654–660.
  15. ^ Tepper RS, Skatrud B, Dempsey JA, Ventilation and oxygenation changes during sleep in cystic fibrosis, Chest 1983; 84; p. 388-393.
  16. ^ Bell SC, Saunders MJ, Elborn JS, Shale DJ, Resting energy expenditure and oxygen cost of breathing in patients with cystic fibrosis, Thorax 1996 Feb; 51(2): 126-131.
  17. ^ Sinderby C, Spahija J, Beck J, Kaminski D, Yan S, Comtois N, Sliwinski P, Diaphragm activation during exercise in chronic obstructive pulmonary disease, Am J Respir Crit Care Med 2001 Jun; 163(7): 1637-1641.
  18. ^ Epstein SK, Zilberberg MD; Facoby C, Ciubotaru RL, Kaplan LM, Response to symptom-limited exercise in patients with the hepatopulmonary syndrome, Chest 1998; 114; p. 736-741.
  19. ^ Kahaly GJ, Nieswandt J, Wagner S, Schlegel J, Mohr-Kahaly S, Hommel G, Ineffective cardiorespiratory function in hyperthyroidism, J Clin Endocrinol Metab 1998 Nov; 83(11): 4075-4078.
  20. ^ Esquivel E, Chaussain M, Plouin P, Ponsot G, Arthuis M, Physical exercise and voluntary hyperventilation in childhood absence epilepsy, Electroencephalogr Clin Neurophysiol 1991 Aug; 79(2): 127-132.
  21. ^ psych-, psycho-, -psyche, -psychic, -psychical, -psychically + (Greek: mind, spirit, consciousness; mental processes; the human soul; breath of life)

Simple English

Breathing is the means by which our lungs remove carbon dioxide (CO2) take in oxygen, a gas needed along with glucose to produce energy. The air going in and out of the mouth or nose when animals breathe is called the breath. Without breathing, you will die.

CO2 must be removed because it is a waste product and is too much CO2 is poisonous.

The air humans breathe passes into the two lungs, which are protected inside the rib cage. The lungs take oxygen from the air and pass it into our bloodstream. Our blood takes oxygen all around the body. When we breathe out, the lungs get rid of used air. Adults breathe about 18 times a minute, which more than 25,000 times a day. Children breathe even faster.[[File:|thumb|alt|right|200px|An inhaler]]

People who suffer from asthma, or other breathing incidents that are dangerous, often use an inhaler to help them. The inhaler puffs a drug down into the windpipe. This makes the air passages wider and then can breathe more better than before. [1]

References

  1. Morris, Neil; Ting Morris (1998). Jim Miles, Lynne French. ed (in English). Children's First Encyclopedia. Branka Surla, Rosie Alexander. II Bardfield Centre, Great Bardfield, Essex CM7 4SL: Miles Kelly Publishing Ltd. ISBN 1-84084-332-2. 







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