Editing Spirometry (section)

==Parameters==
The most common parameters measured in spirometry are vital capacity (VC), forced vital capacity (FVC), forced expiratory volume (FEV) at timed intervals of 0.5, 1.0 (FEV1), 2.0, and 3.0 seconds, forced expiratory flow 25–75% (FEF 25–75) and maximal voluntary ventilation (MVV),<ref>[http://www.surgeryencyclopedia.com/Pa-St/Spirometry-Tests.html surgeryencyclopedia.com > Spirometry tests]. Retrieved 14 March 2010.</ref> also known as Maximum breathing capacity.<ref>[http://www.biology-online.org/dictionary/Maximum_breathing_capacity MVV and MBC]</ref> Other tests may be performed in certain situations.

Results are usually given in both raw data (litres, litres per second) and percent predicted—the test result as a percent of the "predicted values" for the patients of similar characteristics (height, age, sex, and sometimes race and weight). The interpretation of the results can vary depending on the physician and the source of the predicted values. Generally speaking, results nearest to 100% predicted are the most normal, and results over 80% are often considered normal. Multiple publications of predicted values have been published and may be calculated based on age, sex, weight and ethnicity.  However, review by a doctor is necessary for accurate diagnosis of any individual situation.

A bronchodilator is also given in certain circumstances and a pre/post graph comparison is done to assess the effectiveness of the bronchodilator. See the example printout.

[[Functional residual capacity]] (FRC) cannot be measured via spirometry, but it can be measured with a [[plethysmograph]] or dilution tests (for example, helium dilution test).

[[File:Normal values for FVC, FEV1 and FEF 25-75.png|thumb|220px|left|Average values for forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1) and forced expiratory flow 25–75% (FEF25–75%), according to a study in the United States 2007 of 3,600 subjects aged 4–80 years.<ref>{{cite journal  |vauthors=Stanojevic S, Wade A, Stocks J, etal |title=Reference Ranges for Spirometry Across All Ages: A New Approach |journal=Am. J. Respir. Crit. Care Med. |volume=177 |issue=3 |pages=253–60 |date=February 2008 |pmid=18006882 |pmc=2643211 |doi=10.1164/rccm.200708-1248OC }}</ref> Y-axis is expressed in litres for FVC and FEV1, and in litres/second for FEF25–75%.]]

[[Image:LungVolume.jpg|frameless|600px|Output of a 'spirometer']]

===Forced vital capacity (FVC)===
Forced [[vital capacity]] (FVC) is the volume of air that can forcibly be blown out after full inspiration,<ref name="Office">{{Cite journal|last1=Perez|first1=LL|title=Office spirometry|journal= Osteopathic Family Physician  |volume=5 |issue=2 |pages=65–69 |date=March–April 2013|doi =10.1016/j.osfp.2012.09.003}}</ref> measured in liters. FVC is the most basic maneuver in spirometry tests.

===Forced expiratory volume in 1 second (FEV1)===
FEV1 is the volume of air that can forcibly be blown out in first 1-second, after full inspiration.<ref name="Office"/> Average values for FEV1 in healthy people depend mainly on sex and age, according to the diagram.
Values of between 80% and 120% of the average value are considered normal.<ref name=uppsala>LUNGFUNKTION — Practice compendium for semester 6. Department of Medical Sciences, Clinical Physiology, Academic Hospital, Uppsala, Sweden. Retrieved 2010.</ref> Predicted normal values for FEV1 can be calculated and depend on age, sex, height, mass and ethnicity as well as the research study that they are based on.

===FEV1/FVC ratio===
[[FEV1/FVC ratio|FEV1/FVC]] is the ratio of FEV1 to FVC. In healthy adults this should be approximately 70–80% (declining with age).<ref>{{cite book|last1=Clinic|first1=the Cleveland|title=Current clinical medicine 2010|date=2010|publisher=Saunders|location=Philadelphia, Pa.|isbn=978-1416066439|page=8|edition=2nd}}</ref> In obstructive diseases (asthma, COPD, chronic bronchitis, emphysema) FEV1 is diminished because of increased airway resistance to expiratory flow; the FVC may be decreased as well, due to the premature closure of airway in expiration, just not in the same proportion as FEV1 (for instance, both FEV1 and FVC are reduced, but the former is more affected because of the increased airway resistance). This generates a reduced value (<70%, often ~45%). In restrictive diseases (such as [[pulmonary fibrosis]]) the FEV1 and FVC are both reduced proportionally and the value may be normal or even increased as a result of decreased lung compliance.

A derived value of FEV1 is '''FEV1% predicted''' (FEV1%), which is defined as FEV1 of the patient divided by the average FEV1 in the population for any person of the same age, height, gender, and race.{{medcn|date=November 2019}}

===Forced expiratory flow (FEF)===
Forced expiratory flow   (FEF) is the flow (or speed) of air coming out of the lung during the middle portion of a forced expiration.
It can be given at [[discrete time]]s, generally defined by what fraction of the forced vital capacity (FVC) has been exhaled.
The usual discrete intervals are 25%, 50% and 75% (FEF25, FEF50 and FEF75), or 25% and 50% of FVC that has been exhaled.
It can also be given as a mean of the flow during an interval, also generally delimited by when specific fractions remain of FVC, usually 25–75% (FEF25–75%). Average ranges in the healthy population depend mainly on sex and age, with FEF25–75% shown in diagram at left. Values ranging from 50 to 60% and up to 130% of the average are considered normal.<ref name=uppsala/> Predicted normal values for FEF can be calculated and depend on age, sex, height, mass and ethnicity as well as the research study that they are based on.

'''MMEF''' or '''MEF''' stands for maximal (mid-)expiratory flow and is the peak of expiratory flow as taken from the flow-volume curve and measured in liters per second. It should theoretically be identical to [[peak expiratory flow]] (PEF), which is, however, generally measured by a peak flow meter and given in liters per minute.<ref name=hedenstrom2009>Interpretation model — compendium at Uppsala Academic Hospital. By H. Hedenström. 2009-02-04</ref>

Recent research suggests that FEF25-75% or FEF25-50% may be a more sensitive parameter than FEV1 in the detection of obstructive small airway disease.<ref>{{cite journal|last1=Simon|first1=Michael R.|last2=Chinchilli|first2=Vernon M.|last3=Phillips|first3=Brenda R.|last4=Sorkness|first4=Christine A.|last5=Lemanske Jr.|first5=Robert F.|last6=Szefler|first6=Stanley J.|last7=Taussig|first7=Lynn|last8=Bacharier|first8=Leonard B.|last9=Morgan|first9=Wayne|title=Forced expiratory flow between 25% and 75% of vital capacity and FEV1/forced vital capacity ratio in relation to clinical and physiological parameters in asthmatic children with normal FEV1 values|journal=Journal of Allergy and Clinical Immunology|date=1 September 2010|volume=126|issue=3|pages=527–534.e8|doi=10.1016/j.jaci.2010.05.016|pmid=20638110|pmc=2933964}}</ref><ref>{{cite journal|last=Ciprandi|first=Giorgio|author2=Cirillo, Ignazio |title=Forced expiratory flow between 25% and 75% of vital capacity may be a marker of bronchial impairment in allergic rhinitis|journal=Journal of Allergy and Clinical Immunology|date=1 February 2011|volume=127|issue=2|pages=549; discussion 550–1|doi=10.1016/j.jaci.2010.10.053|pmid=21281879}}</ref>  However, in the absence of concomitant changes in the standard markers, discrepancies in mid-range expiratory flow may not be specific enough to be useful, and current practice guidelines recommend continuing to use FEV1, VC, and FEV1/VC as indicators of obstructive disease.<ref>{{cite journal |vauthors=Pellegrino R, Viegi G, Brusasco V, Crapo RO, Burgos F, Casaburi R, Coates A, van der Grinten CP, Gustafsson P, Hankinson J, Jensen R, Johnson DC, MacIntyre N, McKay R, Miller MR, Navajas D, Pedersen OF, Wanger J | title = Interpretative strategies for lung function tests | journal = The European Respiratory Journal | volume = 26 | issue = 5 | pages = 948–68 | date = November 2005 | pmid = 16264058 | doi = 10.1183/09031936.05.00035205 | s2cid = 2741306 | doi-access = free }}</ref><ref name="ACP Medicine">{{cite web|last=Kreider|first=Maryl|title=Chapter 14.1 Pulmonary Function Testing|url=http://online.statref.com/Notes/ResolveNote.aspx?NoteID=48177&grpalias=TEX|website=ACP Medicine|publisher=Decker Intellectual Properties|access-date=29 April 2011}}</ref>

More rarely, forced expiratory flow may be given at intervals defined by how much remains of total lung capacity. In such cases, it is usually designated as e.g. FEF70%TLC, FEF60%TLC and FEF50%TLC.<ref name=hedenstrom2009/>

===Forced inspiratory flow 25–75% or 25–50%===
Forced inspiratory flow 25–75% or 25–50% (FIF 25–75% or 25–50%) is similar to FEF 25–75% or 25–50% except the measurement is taken during inspiration.{{medcn|date=November 2019}}

===Peak expiratory flow (PEF)===
[[File:Normal values for peak expiratory flow - EU scale.svg|thumb|right|250px|Normal values for peak expiratory flow (PEF), shown on EU scale.<ref>{{cite journal |vauthors=Nunn AJ, Gregg I |title=New regression equations for predicting peak expiratory flow in adults |journal=BMJ |volume=298 |issue=6680 |pages=1068–70 |date=April 1989 |pmid=2497892 |pmc=1836460 |doi=10.1136/bmj.298.6680.1068}} Adapted by Clement Clarke for use in EU scale — see [http://www.peakflow.com/top_nav/normal_values/index.html Peakflow.com ⇒ Predictive Normal Values (Nomogram, EU scale)]</ref>]]
[[Peak expiratory flow]] (PEF) is the maximal flow (or speed) achieved during the maximally forced expiration initiated at full inspiration, measured in liters per minute or in liters per second.

===Tidal volume (TV)===
[[Tidal volume]] is the amount of air inhaled or exhaled normally at rest.{{medcn|date=November 2019}}

===Total lung capacity (TLC)===
[[Total lung capacity]] (TLC) is the maximum volume of air present in the lungs.{{medcn|date=November 2019}}

===Diffusing capacity (DLCO)===
[[Diffusion capacity|Diffusing capacity]] (or [[DLCO]]) is the carbon monoxide uptake from a single inspiration in a standard time (usually 10 seconds). During the test the person inhales a test gas mixture that consisting of regular air that includes an inert [[tracer gas]] and CO, less than one percent. Since hemoglobin has a greater affinity to CO than oxygen the breath-hold time can be only 10 seconds, which is a sufficient amount of time for this transfer of CO to occur. Since the inhaled amount of CO is known, the exhaled CO is subtracted to determine the amount transferred during the breath-hold time. The tracer gas is analyzed simultaneously with CO to determine the distribution of the test gas mixture. This test will pick up diffusion impairments, for instance in pulmonary fibrosis.<ref>{{MedlinePlusEncyclopedia|003854|Lung diffusion testing}}</ref> This must be corrected for anemia (a low hemoglobin concentration will reduce DLCO) and pulmonary hemorrhage (excess RBC's in the interstitium or alveoli can absorb CO and artificially increase the DLCO capacity). Atmospheric pressure and/or altitude will also affect measured DLCO, and so a correction factor is needed to adjust for standard pressure.

===Maximum voluntary ventilation (MVV)===
<!--target for redirect [[Maximum voluntart ventilation]] -->
Maximum voluntary ventilation (MVV) is a measure of the maximum amount of air that can be inhaled and exhaled within one minute. For the comfort of the patient this is done over a 15-second time period before being extrapolated to a value for one minute expressed as liters/minute. Average values for males and females are 140–180 and 80–120 liters per minute respectively.{{medcn|date=November 2019}}

===Static lung compliance (C<sub>st</sub>)===
When estimating static lung compliance, volume measurements by the spirometer needs to be complemented by [[pressure transducer]]s in order to simultaneously measure the [[transpulmonary pressure]]. When having drawn a curve with the relations between changes in volume to changes in transpulmonary pressure, C<sub>st</sub> is the slope of the curve during any given volume, or, mathematically, ΔV/ΔP.<ref name=Ronald>{{cite book |first=Ronald B. |last=George |title=Chest medicine: essentials of pulmonary and critical care medicine |year=2005 |publisher=Lippincott Williams & Wilkins |isbn=978-0-7817-5273-2 |page=96 }}</ref> Static lung compliance is perhaps the most sensitive parameter for the detection of abnormal pulmonary mechanics.<ref>{{cite journal | last1 = Sud | first1 = A. | last2 = Gupta | first2 = D. | last3 = Wanchu | first3 = A. | last4 = Jindal | first4 = S. K. | last5 = Bambery | first5 = P. | title = Static lung compliance as an index of early pulmonary disease in systemic sclerosis | journal = Clinical Rheumatology | volume = 20 | issue = 3 | pages = 177–180 | year = 2001 | pmid = 11434468 | doi = 10.1007/s100670170060 | s2cid = 19170708 }}</ref> It is considered normal if it is 60% to 140% of the average value in the population for any person of similar age, sex and body composition.<ref name=uppsala/>

In those with acute respiratory failure on mechanical ventilation, "the static compliance of the total respiratory system is conventionally obtained by dividing the tidal volume by the difference between the 'plateau' pressure measured at the airway opening (PaO) during an occlusion at end-inspiration and positive end-expiratory pressure (PEEP) set by the ventilator".<ref>{{cite journal |last1=Rossi |first1=A. |last2=Gottfried |first2=S. B. |last3=Zocchi |first3=L. |last4=Higgs |first4=B. D. |last5=Lennox |first5=S. |last6=Calverley |first6=P. M. |last7=Begin |first7=P. |last8=Grassino |first8=A. |last9=Milic-Emili |first9=J. |title=Measurement of static compliance of the total respiratory system in patients with acute respiratory failure during mechanical ventilation. The effect of intrinsic positive end-expiratory pressure |journal=The American Review of Respiratory Disease |date=May 1985 |volume=131 |issue=5 |pages=672–677 |doi=10.1164/arrd.1985.131.5.672 |doi-broken-date=1 November 2024 |pmid=4003913 }}</ref>

{| class="wikitable"
|rowspan=2| '''Measurement''' ||colspan=2| '''Approximate value'''
|-
| '''Male''' || '''Female'''
|-
|  '''Forced vital capacity''' (FVC) || 4.8 L || 3.7 L
|-
| '''Tidal volume''' (Vt) || 500 mL || 390 mL
|-
| '''Total lung capacity''' (TLC)  || 6.0 L || 4.7 L
|-
|}

===Others===
'''Forced Expiratory Time (FET)'''<br>
Forced Expiratory Time (FET) measures the length of the expiration in seconds.

'''Slow vital capacity (SVC)'''<br>
Slow [[vital capacity]] (SVC) is the maximum volume of air that can be exhaled slowly after slow maximum inhalation.

'''Maximal pressure (P<sub>max</sub>''' and '''P<sub>i</sub>''')

{| class="wikitable"
| colspan="2" |Spirometer - ERV in cc (cm<sup>3</sup>) average Age 20
|-
|Male
|Female
|-
|4320
|3387
|}
<br>
P<sub>max</sub> is the asymptotically maximal pressure that can be developed by the respiratory muscles at any lung volume and P<sub>i</sub> is the maximum inspiratory pressure that can be developed at specific lung volumes.<ref>{{cite journal |last1=Lausted |first1=Christopher G |last2=Johnson |first2=Arthur T |last3=Scott |first3=William H |last4=Johnson |first4=Monique M |last5=Coyne |first5=Karen M |last6=Coursey |first6=Derya C |title=Maximum static inspiratory and expiratory pressures with different lung volumes |journal=BioMedical Engineering OnLine |date=December 2006 |volume=5 |issue=1 |page=29 |doi=10.1186/1475-925X-5-29 |pmid=16677384 |pmc=1501025 |doi-access=free }}</ref> This measurement also requires pressure transducers in addition. It is considered normal if it is 60% to 140% of the average value in the population for any person of similar age, sex and body composition.<ref name="uppsala" /> A derived parameter is the '''coefficient of retraction (CR)''' which is P<sub>max</sub>/TLC .<ref name="hedenstrom2009" />

'''Mean transit time (MTT)'''<br>
Mean transit time is the area under the flow-volume curve divided by the forced vital capacity.<ref>{{cite journal | last1 = Borth | first1 = F. M. | title = The derivation of an index of ventilatory function from spirometric recordings using canonical analysis | journal = British Journal of Diseases of the Chest | volume = 76 | issue = 4 | pages = 400–756 | year = 1982 | doi = 10.1016/0007-0971(82)90077-8 | pmid = 7150499 | doi-access = free }}</ref>

{{anchor|Maximal inspiratory pressure}}
'''Maximal inspiratory pressure (MIP)'''
MIP, also known as '''negative inspiratory force (NIF)''', is the maximum pressure that can be generated against an occluded airway beginning at functional residual capacity (FRC). It is a marker of respiratory muscle function and strength.<ref>[https://books.google.com/books?id=JL3ZwUaO0zkC&pg=PA352 Page 352] in: {{cite book | last = Irwin | first = Richard | title = Procedures, techniques, and minimally invasive monitoring in intensive care medicine | publisher = Wolters Kluwer Health/Lippincott Williams & Wilkins | location = Philadelphia | year = 2008 | isbn = 978-0-7817-7862-6 }}</ref> Represented by centimeters of water pressure (cmH2O) and measured with a [[manometer]]. Maximum inspiratory pressure is an important and noninvasive index of [[Thoracic diaphragm|diaphragm]] strength and an independent tool for diagnosing many illnesses.<ref name="pmid19796411">{{cite journal| author=Sachs MC, Enright PL, Hinckley Stukovsky KD, Jiang R, Barr RG, Multi-Ethnic Study of Atherosclerosis Lung Study| title=Performance of maximum inspiratory pressure tests and maximum inspiratory pressure reference equations for 4 race/ethnic groups | journal=Respir Care | year= 2009 | volume= 54 | issue= 10 | pages= 1321–8 | pmid=19796411 | pmc= 3616895}}</ref> Typical maximum inspiratory pressures in adult males can be estimated from the equation, M<sub>IP</sub> = 142 - (1.03 x Age) cmH<sub>2</sub>O, where age is in years.<ref>{{cite journal |vauthors=Wilson SH, Cooke NT, Edwards RH, Spiro SG |title=Predicted normal values for maximal respiratory pressures in caucasian adults and children |journal=Thorax |volume=39 |issue=7 |pages=535–8 |date=July 1984 |pmid=6463933 |pmc=459855 |doi=10.1136/thx.39.7.535 }}</ref>