Editing Exhalation (section)

==Spirometry==

[[Spirometry]] is the measure of lung function.  The [[total lung capacity]] (TLC), [[functional residual capacity]] (FRC), [[Lung volumes|residual volume]] (RV), and [[vital capacity]] (VC) are all values that can be tested using this method.  Spirometry is used to help detect, but not diagnose, respiratory issues like [[COPD]], and asthma.  It is a simple and cost effective screening method.<ref name=Kivastik>{{cite journal |doi=10.1046/j.1365-2281.2001.00352.x |pmid=11442581 |title=Spirometric reference values in Estonian schoolchildren |journal=Clinical Physiology |volume=21 |issue=4 |pages=490–7 |year=2001 |last1=Kivastik |first1=Jana |last2=Kingisepp |first2=Peet-Henn |doi-access=free }}</ref> Further evaluation of a person's respiratory function can be done by assessing the [[minute ventilation]], [[forced vital capacity]] (FVC), and [[forced expiratory volume]] (FEV). These values differ in men and women because men tend to be larger than women.

TLC is the maximum amount of air in the lungs after maximum inhalation. In men the average TLC is 6000 ml, and in women it is 4200 ml. FRC is the amount of air left in the lungs after normal exhalation. Men leave about 2400 ml on average while women retain around 1800 ml.  RV is the amount of air left in the lungs after a [[forced exhalation]].  The average RV in men is 1200 ml and women 1100 ml.  VC is the maximum amount of air that can be exhaled after a maximum inhalation.  Men tend to average 4800 ml and women 3100 ml.{{citation needed|date=May 2015}}

Smokers, and those with Asthma and COPD, have reduced airflow ability. People with asthma and COPD show decreases in exhaled air due to inflammation of the airways.  This inflammation causes narrowing of the airways which allows less air to be exhaled.  Numerous things cause inflammation; some examples are cigarette smoke and environmental interactions such as allergies, weather, and exercise.  In smokers the inability to exhale fully is due to the loss of elasticity in the lungs.  Smoke in the lungs causes them to harden and become less elastic, which prevents the lungs from expanding or shrinking as they normally would.{{citation needed|date=May 2015}}

[[Dead space (physiology)|Dead space]] can be determined by two types of factors which are anatomical and physiological.  Some physiological factors are having non-perfuse but ventilated alveoli, such as a pulmonary embolism or smoking, excessive ventilation of the alveoli, brought on in relation to perfusion, in people with chronic obstructive lung disease, and "[[Pulmonary shunt|shunt]] dead space," which is a mistake between the left to right lung that moves the higher {{CO2}} concentrations in the venous blood into the arterial side.<ref name="Assessing dead space">{{cite journal |pmid=16682925 |url=http://www.minervamedica.it/index2.t?show=R02Y2006N06A0521 |year=2006 |last1=Hedenstierna |first1=G |title=Assessing dead space. A meaningful variable? |journal=Minerva Anestesiologica |volume=72 |issue=6 |pages=521–8 |last2=Sandhagen |first2=B }}</ref>  The anatomical factors are the size of the airway, the valves, and tubing of the respiratory system.<ref name="Assessing dead space" />  Physiological dead space of the lungs can affect the amount of dead space as well with factors including smoking, and diseases. Dead space is a key factor for the lungs to work because of the differences in pressures, but it can also hinder the person.{{citation needed|date=May 2015}}

One of the reasons we can breathe is because of the [[Lung compliance|elasticity of the lungs]].  The internal surface of the lungs on average in a non-emphysemic person is normally 63m2 and can hold about 5lts of air volume.<ref name="surface area">{{cite journal |doi=10.1136/thx.22.6.483 |pmid=5624577 |pmc=471691 |title=Internal surface area and other measurements in emphysema |journal=Thorax |volume=22 |issue=6 |pages=483–96 |year=1967 |last1=Thurlbeck |first1=W. M. }}</ref>  Both lungs together have the same amount of surface area as half of a tennis court.  Disease such as, emphysema, tuberculosis, can reduce the amount of surface area and elasticity of the lungs. Another big factor in the elasticity of the lungs is smoking because of the residue left behind in the lungs from the smoking.  The elasticity of the lungs can be trained to expand further.{{citation needed|date=May 2015}}