Spirometry
Spirometry | |
---|---|
MeSH | D013147 |
OPS-301 code | 1-712 |
Spirometry (meaning the measuring of breath) is the most common of the
Spirometry generates pneumotachographs, which are charts that plot the volume and flow of air coming in and out of the lungs from one inhalation and one exhalation.
Testing
Spirometer
The spirometry test is performed using a device called a spirometer,[2] which comes in several different varieties. Most spirometers display the following graphs, called spirograms:
- a volume-time curve, showing volume (litres) along the Y-axis and time (seconds) along the X-axis
- a flow-volume loop, which graphically depicts the rate of airflow on the Y-axis and the total volume inspired or expired on the X-axis
Procedure
The basic forced volume vital capacity (FVC) test varies slightly depending on the equipment used. It can be in the form of either closed or open circuit. Regardless of differences in testing procedure providers are recommended to follow the ATS/ERS Standardisation of Spirometry. The standard procedure ensures an accurate and objectively collected data, based on a common reference, to reduce compatibility of the results when shared across differing medical groups.
The patient is asked to put on soft nose clips to prevent air escape and a breathing sensor in their mouth forming an air tight seal. Guided by a technician, the patient is given step by step instructions to take an abrupt maximum effort inhale, followed by a maximum effort exhale lasting for a target of at least 6 seconds. When assessing possible
Limitations
Clinically useful results are highly dependent on patient cooperation and effort and must be repeated for a minimum of three times to ensure reproducibility with a general limit of ten attempts. Given variable rates of effort, the results can only be underestimated given an effort output greater than 100% is not possible.[citation needed]
Due to the need for patient cooperation and an ability to understand and follow instructions, spirometry can typically only be done in cooperative children when they at least 5 years old
Another limitation is that persons with intermittent or mild asthma can present normal spirometry values between acute exacerbation, reducing spirometry's effectiveness as a diagnostic tool in these circumstances.[citation needed]
Supplemental diagnostics
Spirometry can also be part of a
To assess the reversibility of a particular condition, a bronchodilator can be administered before performing another round of tests for comparison. This is commonly referred to as a reversibility test, or a post bronchodilator test (Post BD), and is an important part in diagnosing asthma versus COPD.
Other complementary lung functions tests include
Indications
Spirometry is indicated for the following reasons:
- to diagnose or manage asthma[5][6][7]
- to detect respiratory disease in patients presenting with symptoms of breathlessness, and to distinguish respiratory from cardiac disease as the cause[8]
- to measure bronchial responsiveness in patients suspected of having asthma[8]
- to diagnose and differentiate between obstructive lung disease and restrictive lung disease[8]
- to follow the natural history of disease in respiratory conditions[8]
- to assess of impairment from occupational asthma[8]
- to identify those at risk from pulmonary barotrauma while scuba diving[8]
- to conduct pre-operative risk assessment before anaesthesia or cardiothoracic surgery[8]
- to measure response to treatment of conditions which spirometry detects[8]
- to diagnose the vocal cord dysfunction.
Contraindications
Forced expiratory maneuvers may aggravate some medical conditions.[9] Spirometry should not be performed when the individual presents with:
- Hemoptysis of unknown origin
- Pneumothorax
- Unstable cardiovascular status (angina, recent myocardial infarction, etc.)
- Thoracic, abdominal, or cerebral aneurysms
- Cataractsor recent eye surgery
- Recent thoracic or abdominal surgery
- Nausea, vomiting, or acute illness
- Recent or current viral infection
- Undiagnosed hypertension
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),[10] also known as Maximum breathing capacity.[11] 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).
Forced vital capacity (FVC)
Forced vital capacity (FVC) is the volume of air that can forcibly be blown out after full inspiration,[13] 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.[13] 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.[14] 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 is the ratio of FEV1 to FVC. In healthy adults this should be approximately 70–80% (declining with age).[15] 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.[medical citation needed]
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
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.[16]
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.[17][18] 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.[19][20]
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.[16]
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.[medical citation needed]
Peak expiratory flow (PEF)
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.[medical citation needed]
Total lung capacity (TLC)
Diffusing capacity (DLCO)
Maximum voluntary ventilation (MVV)
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.[medical citation needed]
Static lung compliance (Cst)
When estimating static lung compliance, volume measurements by the spirometer needs to be complemented by
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".[25]
Measurement | 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)
Forced Expiratory Time (FET) measures the length of the expiration in seconds.
Slow vital capacity (SVC)
Slow vital capacity (SVC) is the maximum volume of air that can be exhaled slowly after slow maximum inhalation.
Maximal pressure (Pmax and Pi)
Spirometer - ERV in cc (cm3) average Age 20 | |
Male | Female |
4320 | 3387 |
Pmax is the asymptotically maximal pressure that can be developed by the respiratory muscles at any lung volume and Pi is the maximum inspiratory pressure that can be developed at specific lung volumes.[26] 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.[14] A derived parameter is the coefficient of retraction (CR) which is Pmax/TLC .[16]
Mean transit time (MTT)
Mean transit time is the area under the flow-volume curve divided by the forced vital capacity.[27]
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.
Technologies used in spirometers
- Volumetric Spirometers
- Water bell
- Bellows wedge
- Flow measuring Spirometers
- Fleisch-pneumotach
- Lilly (screen) pneumotach
- Turbine/Stator Rotor (normally incorrectly referred to as a turbine. Actually a rotating vane which spins because of the air flow generated by the subject. The revolutions of the vane are counted as they break a light beam)
- Pitot tube
- Hot-wire anemometer
- Ultrasound
See also
- Anaesthesiology
- Peak flow meter
- Nitrogen washout
References
- ^ "Spirometry". National Institute for Occupational Safety and Health (NIOSH). Retrieved 31 January 2017.
- ^ "Spirometry". Cleveland Clinic. Retrieved 13 September 2020.
- ^ Montes, Jacqueline; Kaufmann, Petra (2015). "Outcome Measures in Neuromuscular Diseases". ScienceDirect. Neuromuscular Disorders of Infancy, Childhood, and Adolescence (Second Edition). Retrieved 14 July 2023.
- ^ Pruthi, M.D., Sandhya (6 January 2022). "Asthma: Steps in testing and diagnosis". Mayo Clinic. Retrieved 14 July 2023.
- ABIM Foundation. American Academy of Allergy, Asthma, and Immunology. Retrieved 14 August 2012.)
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- ^ surgeryencyclopedia.com > Spirometry tests. Retrieved 14 March 2010.
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- ^ a b c d LUNGFUNKTION — Practice compendium for semester 6. Department of Medical Sciences, Clinical Physiology, Academic Hospital, Uppsala, Sweden. Retrieved 2010.
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- ^ Kreider, Maryl. "Chapter 14.1 Pulmonary Function Testing". ACP Medicine. Decker Intellectual Properties. Retrieved 29 April 2011.
- PMID 2497892. Adapted by Clement Clarke for use in EU scale — see Peakflow.com ⇒ Predictive Normal Values (Nomogram, EU scale)
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Further reading
- Miller MR, Crapo R, Hankinson J, Brusasco V, Burgos F, Casaburi R, Coates A, Enright P, van der Grinten CP, Gustafsson P, Jensen R, Johnson DC, MacIntyre N, McKay R, Navajas D, Pedersen OF, Pellegrino R, Viegi G, Wanger J (July 2005). "General considerations for lung function testing". European Respiratory Journal. 26 (1): 153–161. S2CID 5626417.