Two Spirometer Tests Two Different Readings Which Is Correct

Spirometer

It too is a spirometer that is attached directly to a smartphone, and information technology too generates charts to assist patients and clinicians monitor changes in peak menses rate and accept appropriate action.

From: The Transformative Power of Mobile Medicine , 2019

Lung Volumes and Airway Resistance

Joseph Feher , in Quantitative Homo Physiology (Second Edition), 2017

Abstruse

Spirometers can measure out three of four lung volumes, inspiratory reserve volume, tidal volume, expiratory reserve book, but cannot measure residual book. 4 lung capacities are also defined: inspiratory capacity, vital capacity, functional residual capacity, and the total lung capacity. Pulmonary ventilation is the product of tidal book and respiratory frequency. The maximum voluntary ventilation is the maximum air that tin can be moved per minute. Spirometry also provides a measure of airway resistance by apply of the forced expiratory volume test. The clinical spirogram presents the forced vital capacity differently. In laminar flow, pressure necessary to drive menses increases linearly with the flow. In turbulent flow, pressure increases with the square of the period. The Reynolds number is used to estimate whether flow is laminar or turbulent. Airway resistance also increases inversely with lung book because stretch of the lungs opens airways. Dynamic pinch limits period at high expiratory effort.

Read full affiliate

URL:

https://www.sciencedirect.com/science/commodity/pii/B9780128008836000616

Pulmonary Office Testing

Bruce H. Culver , in Clinical Respiratory Medicine (Fourth Edition), 2012

Measurement by Helium Dilution

A spirometer is prepared that contains a known volume and concentration of an inert gas, typically 10% helium ( Figure 9-three ). While the subject field breathes through a mouthpiece with nose clipped, a valve is turned at stop-tidal exhalation to connect the airway to this airtight system. As normal tidal breathing continues over the class of a few minutes, the gas in the subject'southward lung equilibrates with gas in the spirometer, and the helium concentration, which is continuously monitored, falls to a new, lower, steady-state level. Carbon dioxide is removed from the closed organisation past soda lime absorption, and a low flow of oxygen is added to compensate for the field of study's ongoing oxygen consumption by keeping the mixing bedroom or spirometer volume constant. The ratio of the initial to the final concentration of helium allows calculation of the unknown volume (FRC) added to the system. A continuous tracing of the spirogram, including a maximum inspiratory and expiratory effort, allows calculation of the subdivisions of lung volume, and correction for any get-go from the relaxed FRC at the moment the valve was opened to kickoff the examination.

Read full affiliate

URL:

https://www.sciencedirect.com/scientific discipline/article/pii/B978145570792800009X

Lung function testing

Roger Hainsworth , in Foundations of Anesthesia (Second Edition), 2006

Spirometer types

A spirometer is a device for measuring the volumes of air that can be breathed. If the book signal is differentiated, either electronically or by manual measurements from the book–fourth dimension traces, spirometers can besides be used to derive the gas flow rates. The most accurate type of spirometer is the h2o-sealed bell spirometer. This is an inverted bell, sealed under water and counterbalanced (Fig. l.ane). Assuming the bong is a perfect cylinder, the displacement of the counterweight and the attached pen is directly related to the alter in volume. If the recording kymograph is set to movement chop-chop, it is possible to determine the rate of change of volume and hence the expiratory and inspiratory flow rates.

Although this type of spirometer is inherently very simple, at that place are a number of precautions relating to its apply. Mostly, the bong will have a diameter to match the calibration on the recording device or the supplied paper. However, a check should exist made by injecting known volumes of gas. The readout gives volumes at ambience pressure and temperature, although the volumes actually within the lung are at trunk temperature and atmospheric pressure level saturated with water vapor (BTPS). This is usually about 10% greater than the measured volume, and should be corrected appropriately by applying the gas laws or past the apply of appropriate tables.

For accurate measurements of high menstruation rates the spirometer bell and counterweight should have minimum inertia, and bells constructed of lightweight plastic materials are preferred. Another problem may be leaks in the organisation; these can easily be checked by occluding the connecting tubing and applying a weight on the top of the bong. The bell should not go on to movement.

Water-filled spirometers have the disadvantages that they are heavy, subject to spillage, and that electronic outputs are non straight obtained. In attempts to solve these problems, various other devices have been introduced. 1 widely used device that is user-friendly and readily transported is the bellows or wedge spirometer. As gas moves into the bellows, the bellows move about the hinge and a arrow tracks over moving paper to define the expiratory book–time trace. It does not, however, record tidal volume or inspiratory volumes. Bellows spirometers need to be carefully calibrated, with particular attention paid to the linearity of the readings.

Considering spirometry is used to assess the volumes of the gas breathed and catamenia is derived from the rate of change of volume, an alternative approach is really to determine flow and so derive volume by integration. Some circumspection, withal, is required with this approach, as integration over relatively long fourth dimension periods, such equally may occur in patients with astringent obstructive lung disease, tends to be unstable. Authentic flow-measuring devices and high-quality electronic circuits are therefore required. I widely used and accurate menses-measuring device is the Fleisch pneumotachograph, in which menstruation is determined from the pressure level deviation across a small resistance. It is based on Poiseuille's equation, which states that the flow through a tube is directly proportional to the pressure difference across it. This human relationship applies but to laminar period, which depends on the critical value of Reynold's number not being exceeded (run across Chapter 11). Because Reynold's number is directly related to the diameters of the tubes through which the gas flows, the Fleisch pneumotachograph uses a bundle of tubes of minor diameter instead of one large tube to provide the resistance. Condensation in the device is prevented by a heating element.

A very uncomplicated lightweight device that determines the summit flow rate is the Wright pinnacle flowmeter. The expired gas passes through an orifice and moves a lever against a spring by an corporeality calibrated to read the peak flow. This device is not as accurate as most other spirometers, but it is unproblematic, cheap, and user-friendly, and may be used by patients at home.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780323037075500565

Lung Volumes and Airway Resistance

Joseph Feher , in Quantitative Human Physiology, 2012

Spirometers Measure out Lung Volumes and Let Identification of Several Lung Volumes and Lung Capacities

The volume of air that can be inhaled or exhaled can exist estimated using spirometry . Several unlike kinds of spirometers exist. Here we depict a volume deportation Collins respirometer in which a person breathes through a small tube that is connected to an air space located within a lightweight bell jar that is isolated from the ambient air by a layer of water. When air enters the lungs, it leaves the bong jar and reduces the book of air in the jar by the aforementioned volume of air that is inhaled, and this can exist measured continuously by linking movement of the bell jar to a recording pen. The setup is illustrated in Figure 6.2.ane.

Effigy 6.2.1. Typical setup for a book–deportation spirometer. The person places a prune on the nose and so that all air passes through the oral fissure. The person then breathes in air that is continued to a closed infinite in a light cylindrical bell jar that is sealed from the outside by a layer of water retained between ii concentric cylinders. The movement of the bong jar is converted to the motion of a pen that writes on moving paper. The pen movement is inverted from the original bell jar. Inspiration results in down motion of the bell jar and upward move of the pen. The person is instructed to breathe commonly for a few breaths, and then to inspire equally securely every bit possible and and then expire as deeply equally possible. The trace allows identification and measurement of several lung volumes and capacities, as described in the text.

The spirometer aids in identifying several useful lung volumes and capacities. These are:

A.

The tidal volume, TV, is the amount of air breathed in and out during normal, restful animate. Its typical value, every bit shown in Effigy 6.2.one, is about 500   mL=0.5   L. The magnitude of the Telly depends on the size of the individual and their metabolic land. The spirometer recording shown in Figure six.2.1 is idealized: the TV commonly varies from breath to breath.

B.

The inspiratory reserve volume, IRV, is the additional volume of air that can be inspired at the stop of a normal or tidal inspiration. The typical value for a immature adult male of normal size is virtually 3000   mL.

C.

The expiratory reserve book, ERV, is the additional volume of air that can be expired after a normal or tidal expiration. A typical value is near 1100   mL for a young adult male.

D.

The remainder volume, RV, is the volume remaining in the lung after a maximum expiration. Even a maximum try cannot void the lungs of all air. This volume of air cannot be measured by spirometry merely it can be calculated by measuring the functional remainder capacity by ii other techniques: gas dilution and body plethysmography. The value of the RV is typically most 1200   mL.

Read full affiliate

URL:

https://www.sciencedirect.com/science/commodity/pii/B978012382163800061X

Atemwege und Lunge

Stephan Illing , in Klinikleitfaden Pädiatrie (7), 2006

Verschiedene Geräte bzw. Techniken

•

Spirometer: Forcierte Ausatmung in Gerät, Aufzeichnung eines einzelnen Atemzuges, zur Erfassung von FVC und FEVj (

Tab. 14.ane). Meist ab 4./5. Lj. möglich, kooperationsabhängig (

Abb. 14.three)!

Tab. fourteen.1. Wichtige Parameter der Lungenfunktion

Abk.	Bezeichnung	Maßeinheit	Kommentar
FVC	Forcierte Vitalkapazität	Liter (l)	–
FEV one	Forciertes exsp. Vol. n. ane s	Liter (fifty)	Normalwert > 80% FVC
PEF	Acme exspiratory Flow = max. Stromgeschwindigkeit	l/s oder fifty/Min.	Auch Selbstkontrolle mit Mini-Top-Flow-Meter
MEF 75 MEF 50 MEF 25	Max. exsp. Flow bei 75/50/25% gefüllter Lunge	l/s oder l/Min.	Beschreibung der Fluss-Volumen-Kurve
TLC	Totale Lungenkapazität	l	Unwichtig
ERV	Exsp. Reservevolumen	l	Wichtig f. d. Berechnung des RV
ITGV	Intrathorakales Gasvolumen	fifty	Enthält ERV+RV
RV	Residualvolumen	l	Sehr wichtig, Maß für Gefährdung bei Asthma
R, RAW	Resistance of Airways = Atemwegswiderstand	mbar/l/s kPa/fifty/due south	Oszillationsmethode, Bodyplethysmographie
DLCO	Diffusionskap. der Lunge für CO	ml/Min. × Torr	Bei interstitiellen Lungenerkrankungen

Abb. 14.three. Spirometrie/Atemvolumina [L 190]

•

Fluss-Volumen-Kurve (

Abb. 14.4): Forcierte Ausatmung, Aufzeichnung von Ein-Aus-atemkurve, nur letztere relevant. Angabe von FVC, PEF, MEF_75/50/25, FEVj. Wichtigste Lufu-Untersuchung, kooperationsabhängig!

Abb. 14.4. Fluss-Volumen-Kurven [A300–157]

•

Atemwiderstand (Oszillationsmethode): Dem Atemstrom wird eine niederfrequente Luftströmung überlagert, aus Phasenverschiebung und Reflexion dieser stehenden Welle wird der Atemwiderstand berechnet. Aussagekraft limitiert, fehleranfällig, aber einfach vorzunehmen, unabhängig von Kooperation.

•

Bodyplethysmographie: Messung in geschlossener Kammer, Druck- und Volumenaufnehmer am Pat. und in der Kammer. Messung bzw. Berechnung sämtlicher Volumina, vor allem auch RV sowie genauere Messung des Atemwiderstandes. Kooperationsabhängig.

•

Sauerstoffsättigung: Einzelmessung bei allen Erkrankungen mit potenzieller Hypoxämie.

Lungenfunktionsuntersuchungen aus Kooperationsgründen erst ab 5./6. Lj. gut möglich.

Normwerte sind abhängig von Körpergröße, Geschlecht, Gewicht und Alter, daher diese Angaben bei Anforderung der Lufu angeben!

Read full chapter

URL:

https://world wide web.sciencedirect.com/science/article/pii/B9783437222528500203

LUNG FUNCTION TESTS

Andrew Davies MA PhD DSc , Carl Moores BA BSc MB ChB FRCA , in The Respiratory Organisation (Second Edition), 2010

Spirometry

A simple spirometer ( Fig. v.2, p. 63) will provide much useful information virtually a patient's lungs. Large people take larger lungs than small people and historic period exerts its malign effect. Extensive report of these relationships has provided us with tables which, for example, relate vital chapters to height (run across Appendix).

Measurements made on a spirometer may be classified as:

•

static, where the only consideration is the volume exhaled, or

•

dynamic, where the time taken to exhale a certain book is what is being measured.

Although such measurements as inspiratory reserve book (IRV) and expiratory reserve volume (ERV) can be informative, the most usual and useful static spirometric test is the forced vital capacity (FVC). This is 'forced' because the subject field is enthusiastically urged to exhale in as far every bit he tin can and out as far as he tin can (Fig. xi.1). This test, which can exist classed as static because information technology does not involve an element of time, is often combined with a dynamic test, the FEV_ane:

•

Forced expired volume in ane 2nd (FEV_one). The field of study is urged to exhale in as far as he can and breathe out as fast and far every bit he tin. The volume he breathes out in 1 second is the FEV₁.

FEV₁ is usually expressed every bit a percentage of FVC. This takes into account the trouble that a very small person (with very small, perfectly healthy lungs) would never be able to breathe out the same amount in one 2d every bit a very large person, whose lungs may not exist and then good for you. You lot tin can look a healthy person to forcefulness out at least 70% of his vital capacity in 1 second. Using this percentage lonely can create problems in restrictive lung diseases, which restrict the expansion of the lungs: both VC and FEV_ane are reduced, therefore in those cases that pct may be normal. For this reason both absolute values and pct are measured. Many years ago a ratio of seventy% VC was considered acceptable, just that was when smoking was considered normal. A higher pct is required today.

Characteristic traces in normals and patients with chronic obstructive (emphyzematous/bronchitic) or restrictive (fibrotic) lung illness are shown in Effigy 11.i.

Although emphysema is the 'classic' obstructive lung disease it can merely exist diagnosed with certainty at post mortem (pathologists are the only people who invariably make the perfect diagnosis, only by then it'south too late). We therefore depict obstructive patterns of lung disease as asthma (reversible) or chronic obstructive pulmonary illness (COPD, irreversible).

•

Functional residual capacity (FRC) and balance volume (RV). Because a subject cannot exhale out all the air in his lungs plethysmographic (meet below) and dilution methods accept to be used to measure these two lung volumes. RV and FRC are frequently increased in diseases such every bit asthma, bronchitis and emphysema, when airways resistance is increased, and RV is peculiarly increased in air-trapping emphysema.

In the helium dilution method the principle is elementary. The patient breathes out to FRC or RV, whichever is being measured, and is connected to a spirometer of known book containing helium (He) at known concentration. The patient breathes normally for an advisable length of time and the dilution of the He by the RV or FRC in his lungs is measured. The level of the trace of his breathing is carefully watched and oxygen added at the same rate as information technology is used up to keep the overall volume in lungs + spirometer constant (Fig. 11.ii).

An interesting disparity is ofttimes seen between RV measured by plethysmography and by dilution. This arises because air trapped in the lungs, which is not in contact with the mouth, is measured by the plethysmographic method just does not accept part in the dilution of He.

Restrictive lung diseases decrease TLC, FRC, RV and VC. Frequently RV is start to be afflicted. Care should exist taken in interpreting results from obese patients, where the outward recoil of the chest wall is reduced, resulting in lower FRC.

Obstructive lung diseases show an increasing RV as gas is trapped behind the collapsed airways (run into higher up). Increased FRC and TLC in these patients is the upshot of reduced lung recoil and animate at increased lung volumes in an instinctive attempt to keep the airways open.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780702033704000116

Ventilation, Blood Flow, and Gas Commutation

Frank L. Powell PhD , ... John B. West Doc, PhD, DSc , in Murray and Nadel's Textbook of Respiratory Medicine (Sixth Edition), 2016

Functional Remainder Chapters, Residual Volume, and Total Lung Capacity

These three volumes cannot be measured with a spirometer (a device that measures the volume of air being exhaled or inhaled) considering in that location is no way of knowing the volume remaining in the lung after a maximal expiration (i.e., the RV). However, if any ane of these three volumes is measured by an contained method, the other two tin can be derived by spirometry.

The FRC can be measured conveniently by helium dilution in a closed excursion. The bailiwick is connected to a spirometer of known volume that contains a known concentration of helium (a very insoluble gas) and then rebreathes until the helium concentration in the spirometer and in the lungs is the same. The exhaled carbon dioxide is absorbed with soda lime, and oxygen is added to maintain a constant total volume. After equilibration, the full amount of helium is assumed to be unchanged considering and then little of it is removed by the blood because of its very low solubility. The FRC can then be derived from the post-obit equation that expresses this conservation of mass principle:

[1] ${\mathrm{C}}_1\times {\mathrm{V}}_{\mathrm{ane}}={\mathrm{C}}_2\times ({\mathrm{V}}_1+{\mathrm{Five}}_2)$

where C₁ and C₂ are the helium concentrations before and after equilibration, V_ane is the volume of the spirometer, and Five₂ is the volume of the lung. If the subject is switched into the equipment when at FRC, V_ii gives that volume.

Another common way of measuring the FRC is with a body plethysmograph. This is a large airtight box in which the subject area sits. At the finish of a normal expiration, a shutter closes the mouthpiece, and the subject is asked to brand respiratory efforts. As the discipline tries to inhale, the gas in the lungs expands, lung book increases slightly, and the pressure in the box rises slightly because its gas volume decreases. Boyle's law (pressure times volume is constant at constant temperature) can and then exist used to calculate the alter of volume of the plethysmograph. The equation is P₁Five_ane = P₂(V₁ − ΔV), where P₁ and P_two are the box pressures before and after the inspiratory endeavor, Five₁ is the preinspiratory box book, and ΔV is the modify in the book of the box (or lung). If mouth pressure is too measured during the respiratory efforts, Boyle'south law can also be applied to the lung and FRC can be derived. The equation here is P₃V_ii = P₄(V₂ + ΔV), where P_three and P₄ are the oral cavity pressures before and after the inspiratory endeavor, and V_two is the FRC. Because this is the only unknown (ΔV was measured previously), V₂ tin be calculated.

In patients with lung affliction the FRC measured by helium dilution may be essentially less than that measured by body plethysmography. The reason is that the trunk plethysmograph measures the full book of gas in the lung, including any that is trapped behind closed airways (i.e., unventilated regions that contain gas). By contrast, the helium dilution method measures only ventilated lung regions. In immature normal subjects, these volumes are virtually identical, but they may be considerably different in patients with astringent lung affliction. Besides in these patients, regions that are poorly ventilated reduce the overall speed of equilibration of helium, which will lead to volume underestimation if rebreathing is stopped too soon.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B978145573383500004X

Pulmonary Role Testing in Children

Robert Thou. Castile Medico, MS , Stephanie D. Davis Doctor , in Kendig & Chernick's Disorders of the Respiratory Tract in Children (Eighth Edition), 2012

Equipment

Forced expiratory maneuvers in children are quantified using either a spirometer (dry out rolling seal or h2o seal) or a pneumotachometer to measure flow and then integrating the menstruum signal to obtain book. Most current devices provide immediate feedback on performance by plotting the maximal expiratory flow-volume bend. Devices that provide a continuous real-time plot of menses versus volume are the nearly useful in monitoring the efforts of children.

Equipment used for testing children should exist capable of accurately measuring small volumes and low flows. Book measurements should be authentic to within 30   mL or ± 3%. Flow measurements should be accurate to 0.ane   Fifty/sec or ± 5%. ²² Lemen and assembly ²³ assessed the frequency content of forced expiratory maneuvers in children and recommended that equipment accept a flat dynamic response through 12   Hz for flow and vi   Hz for book to record period and volume accurately during maximal expiratory maneuvers. Calibration should exist performed daily to ensure the accuracy of measurements. Equipment for testing children should permit adjustment of mouthpiece size. Guidelines for testing children were offset published past Taussig and colleagues. ²² Equipment and test operation standards for spirometry were updated by a joint American Thoracic Society/European Respiratory Society (ATS/ERS) Task Force in 2005. ²⁴

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9781437719840000127

A Mobile Approach to Diabetes and Asthma

Paul Cerrato , John Halamka , in The Transformative Power of Mobile Medicine, 2019

Peak.me, which is depicted in Fig. 5.i , is a spirometer that connects directly to a smartphone. When a patient exhales into the attachment, the device converts the exhalation air menstruum rate into an acoustic signal. A mobile app then uses an algorithm to clarify the bespeak and requite patients feedback. Accumulated spirometric values provide a detailed snapshot of the patient's respiratory status, which can be uploaded to a cloud service and electronic medical record (EMR) system and shared with clinicians for further analysis. He or she in plough can send the patient their interpretation of the data and whatever relevant communication to their mobile phone to consummate the loop. The software lets clinicians perform a trend analysis, enabling actionable early on recognition of disease flare-ups and improvements. There is too a diary to allow patients record lung office improvements, symptoms, triggers, and medications. An alert organization reminds patients to accept their medication and perform tests.

Figure five.1. Percent of apps which applied at to the lowest degree one component fully from the corresponding gamification component category.

From Tinschert P, Jakob R, Barata F, et al. The potential of mobile apps for improving asthma self-management: a review of publicly available and well-adopted asthma apps. JMIR Mhealth Uhealth 2017;v:e113. <https://www.ncbi.nlm.nih.gov/pmc/manufactures/PMC5559650/#app3>. Copyright ©Peter Tinschert, Robert Jakob, Filipe Barata, Jan-Niklas Kramer, Tobias Kowatsch.

Read full affiliate

URL:

https://www.sciencedirect.com/scientific discipline/article/pii/B9780128149232000052

Respiratory Organization Mechanics and Energetics

William Henderson MD , ... Najib T. Ayas MD, MPH , in Murray and Nadel's Textbook of Respiratory Medicine (6th Edition), 2016

Book

Volume is divers past the infinite occupied by a gas. The volume occupied past a stock-still number of gas molecules is determined by temperature and force per unit area.

The volume of gas entering and leaving the lung tin can be adamant by a spirometer that measures book displacement or by integrating the menstruation signal measured past a pneumotachygraph. The subdivisions of lung volumes are shown in Figure five-two. Some of these subdivisions tin exist measured by spirometry lone (vital chapters, tidal volume), whereas others crave utilise of plethysmography or helium dilution. Full lung capacity (TLC) is the lung volume at the end of a maximal inspiration. Residual book is the volume at the finish of a maximal expiratory attempt. Functional balance capacity (FRC) refers to the volume in the lung at the end of a normal tidal exhalation, when at that place is commonly relaxation of both inspiratory and expiratory muscles.

Total gas book in the lung is commonly measured at FRC using plethysmographic methods or by inert gas dilution methods, and each of these techniques has advantages and disadvantages. ¹ Traditional trunk plethysmography is widely available and authentic. For the trunk plethysmography technique, subjects are completely enclosed in a gas-tight container. Lung volume can be calculated by comparison changes in alveolar pressure (measured at the oral fissure while the patient pants against an occluded mouthpiece) with changes in force per unit area in the container. ⁱⁱ Body plethysmography may overestimate lung volumes because it will include measurement of abdominal gas if that gas is compressed and decompressed during the panting maneuver. Plethysmographs that apply electrical inductance ^3,four or optical data ⁵ have been advanced as noninvasive methods for the measurement of lung volumes in those not able to tolerate traditional plethysmography. However, given the limited experience with these modalities in clinical settings, they are best considered experimental advances at this fourth dimension. ^6,7

Considering spirometry cannot judge FRC, one of several inert gas dilution techniques (usually with helium or nitrogen) or radiologic assessments is used. Historically, inert gas methods have usually used helium. For this method, subjects at FRC inhale a known concentration and volume of helium. The helium mixes with and is diluted by the gas already in the lung. A sample of exhaled gas is analyzed for helium concentration, assuasive calculation of the FRC thus:

${\mathrm{C}}_1\times {\mathrm{5}}_{\mathrm{i}}={\mathrm{C}}_2\times ({\mathrm{V}}_{\mathrm{i}}+\text{FRC})$

where C₁ is the initial (known) helium concentration in the handbag, C_two is the last (measured) helium concentration, and Five_one is the initial volume of gas in the pocketbook. Therefore

$\text{FRC}={\mathrm{V}}_{\mathrm{one}}\times ({\mathrm{C}}_1-{\mathrm{C}}_2){\text{/C}}_2$

By the same principle other nonrespiratory gases, such as sulfur hexafluoride (SF₆), may exist used to summate FRC. In full general, inert gas dilution measurements tend to underestimate total lung volume, especially in patients with substantial airway obstruction who may accept gas trapped in lung units that does not mix with inspired gas.

Another method uses the respiratory gases naturally present in a discipline's lungs (such as nitrogen) to be used for FRC determination. In the simplest class, measurement of FRC using the nitrogen dilution method requires the subject to exist ventilated with a 100% oxygen gas mixture to allow the washout of nitrogen from the respiratory system. In one case all the nitrogen has been washed out, the initial gas mixture (oxygen/air) is reinstituted, and the concentration of nitrogen is repeatedly sampled until it returns to the baseline level. The trajectory of nitrogen concentration in the exhaled gas allows the estimation of FRC. Unfortunately, the basic technique is complicated past time delays from gas analyzers. Adjustment for these delays is possible just is complex considering the delay depends on gas viscosity, which changes as the nitrogen and oxygen concentrations change. ⁸

Imaging modalities such as computed tomography (CT) and magnetic resonance imaging can provide authentic assessment of FRC. ^6,9-12 CT may overestimate the volume of alveolar gas available for gas commutation because it measures the unabridged volume of gas in the lung irrespective of whether that gas is trapped and is not partaking in gas exchange. ⁸

Read full chapter

URL:

https://www.sciencedirect.com/scientific discipline/commodity/pii/B9781455733835000051

klineskillart.blogspot.com

Source: https://www.sciencedirect.com/topics/medicine-and-dentistry/spirometer

Share this post