Measuring Lung Volumes

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What is the recommended range of breathing frequency when measuring VTG?

0.5 to 1 Hz

What is the purpose of the piston in the calibration process of the transducer?

To relate the pressure change to the known volume and obtain the calibration factor

What is the graph of Pmouth and Pbox representative of?

A sloping line equal to ΔP/ΔV, where ΔP equals the change in alveolar pressure, and ΔV equals the change in alveolar volume (VA)

How is the change in VA measured indirectly?

By noting the reciprocal change in plethysmograph volume Signup and view all the answers

What is the minimum number of technically satisfactory FRCpleth values that should be obtained?

At least three Signup and view all the answers

Why should breathing too quickly be avoided during the measurement?

It may result in an overestimation of lung volume Signup and view all the answers

What is the purpose of the technologist's comments on the acceptability of the maneuvers?

To note the acceptability of the maneuvers Signup and view all the answers

What is the equation used to obtain VTG from the slope of the tracing?

VTG = (PB /lambdaVTG) x (PBoxcal/Pmouthcal) x K Signup and view all the answers

What is the criterion for acceptability of FRCpleth in terms of breathing frequency?

Breathing frequency should be between 0.5 and 1.0 Hz Signup and view all the answers

Why is FRC considered an effort-independent maneuver?

It is determined by the balance of lung and chest wall recoil at relaxed end expiration Signup and view all the answers

What is the term for the volume of gas remaining in the lungs after vital capacity has been exhaled?

Residual volume (RV) Signup and view all the answers

What is the term for the volume of gas in the lungs at the end of a normal expiration?

Functional residual capacity (FRC) measured with the body plethysmograph (FRCpleth) Signup and view all the answers

What is the equation used to calculate total lung capacity (TLC)?

TLC = RV + IVC (inspiratory vital capacity) Signup and view all the answers

What is the method of measuring lung volumes that involves washing out nitrogen from the lungs using a single breath of oxygen?

Single-breath N2 washout Signup and view all the answers

When there is no airflow, mouth pressure equals alveolar pressure. T or F?

True Signup and view all the answers

What is the term for the volume of gas that can be exhaled from the lungs after a normal tidal inspiration?

Expiratory reserve volume (ERV) Signup and view all the answers

What is the unit of measurement for reporting lung volumes, such as residual volume (RV) and total lung capacity (TLC)?

Liters (L) or milliliters (mL) corrected to body temperature, pressure, and saturation (BTPS) Signup and view all the answers

What is the purpose of momentarily occluding the airway during pneumography?

To allow the air pressure in the mouth to equalize with the alveolar pressure Signup and view all the answers

How must the gas volume remaining in the lungs after the vital capacity (VC) has been exhaled be measured ?

Indirectly Signup and view all the answers

6 methods for Measurement of Lung Volumes ?

<ul> <li>Multiple-breath He dilution</li> <li>Multiple-breath N2 washout</li> <li>Single-breath N2 washout</li> <li>Single-breath He (or other inert gas; e.g., neon) dilution (Calculated as part of Dlco (VA))</li> <li>Plethysmography</li> <li>Chest radiograph, Chest computerized tomography (CT), Magnetic resonance imaging (MRI)</li> </ul> Signup and view all the answers

What is VTG ?

The lung volume where closed-shutter breathing is performed to calculate FRC. Signup and view all the answers

How is obtained RV?

The expiratory reserve volume (ERV) measured immediately after the acquisition of FRC is subtracted from the FRC. Signup and view all the answers

How is obtained TLC?

The calculated value for RV is added to the “linked” inspiratory vital capacity (IVC). Signup and view all the answers

FRC measured with the body plethysmograph (FRCpleth) refers to the volume of intrathoracic gas measured when airflow occlusion occurs at end expiration (FRC) during shutter closure. T or F?

True Signup and view all the answers

WHat mouth pressure theoretically equals when there is no airflow?

alveolar pressure Signup and view all the answers

How are changes in pulmonary gas volume estimated?

By measuring pressure changes in the plethysmograph. Signup and view all the answers

Describe and explain the procedure to measure the FRC inside the pletismograph.

The patient has an unknown volume of gas in the lungs at the end of a normal expiration (i.e., at FRC). The airway is occluded momentarily at or near FRC; the patient is asked to gently breathe at a frequency be- tween 0.5 and 1.0 Hz (0.5–1.0 cycles per second), allowing the air in the chest to be gently compressed and decompressed. The breaths are shallow and should not create pressure changes >10cm H2O. The closed-shutter breathing causes a change in volume and pressure. The changes in pressure are easily measured at the mouth (Pmouth) with a pressure transducer. Mouth pressure theoretically equals alveolar pressure when there is no airflow. Changes in pulmonary gas volume are estimated by measuring pressure changes in the plethysmo- graph. Signup and view all the answers

The display of the shallow breathing maneuver is a graph with Pmouth and Pbox. In wich axis are each values?

Pmouth is plotted on the vertical axis, and Pbox is plotted on the horizontal axis. Signup and view all the answers

The display of the shallow breathing maneuver is a graph with Pmouth and Pbox. Pmouth is plotted on the vertical axis, and Pbox is plotted on the horizontal axis.

The resulting figure appears as a sloping line equal to ΔP/ΔV, where ΔP equals , and ΔV equals __ (VA).

The change in alveolar pressure. The change in alveolar volume. Signup and view all the answers

The VTG can then be obtained from the slope of the tracing by applying a derivation of Boyle’s law. What is the equation for the determination of the VTG ?

VTG = (PB /lambdaVTG) x (PBoxcal/Pmouthcal) x K Wherere: PB is barometric pressure minus water vapour pressure, LambdaVTG is slope of the deltaP/deltaV PBOXcal = box pressure transducer calibration factor Pmouthcal = mouth pressure transducer calibration factor K = correction factor for volume displaced by the patient Signup and view all the answers

How can the end-expiratory level be determined?

From tidal breathing Signup and view all the answers

How should Raw measurements be made ?

with the patient breathing shallow at about 1.5 to 2.5Hz (1.5–2.5 cycles per second, or 90–150 breaths/min) Signup and view all the answers

How many technically satisfactory maneuvers to determine FRC pleth should be recorded?

A minimum of three, each followed by ERV and IVC maneuvers. Signup and view all the answers

At least three FRCpleth values that agree within 5% should be obtained and the mean value re- ported. T or F?

True Signup and view all the answers

Most computerized plethysmographs automatically measure the slope of the ΔP/ΔV tracings. T or F?

True Signup and view all the answers

Criteria for acceptability FRC pleth (6)

<ol> <li>The shallow-breathing maneuver shows a closed loop without drift or another artifact.</li> <li>Pressure changes are within calibration ranges; the tracing does not go off-screen.</li> <li>Breathing frequency should be between 0.5 and 1.0 Hz.</li> <li>A minimum of three technically satisfactory shallow-breathing maneuvers should be recorded.</li> <li>At least three FRC pleth values that agree within 5% should be obtained.</li> <li>Reported FRCpleth is averaged from the three acceptable and repeatable panting maneuvers.</li> </ol> Signup and view all the answers

The FRC, RV, and TLC should be reported in liters or milliliters/second , BTPS. T or F?

False. The FRC, RV, and TLC should be reported in liters or milliliters, BTPS Signup and view all the answers

Is FRC an effort dependent or effort independent maneuver?

Unlike TLC and RV, FRC is an effort-independent maneuver determined by the balance of lung and chest wall recoil at relaxed end expiration. Signup and view all the answers

How is the change in VA measured ?

Indirectly, by noting the reciprocal change in plethysmograph volume. Signup and view all the answers

How is airway resistance calculated?

Airway resistance (Raw) is calculated as the ratio of sRaw to FRCpleth. Signup and view all the answers

What is Raw , and what does it indicate?

Raw is a measure of airway obstruction and indicates the alveolar pressure needed to establish a flow rate of 1 L s− Signup and view all the answers

How can SRaw be interpreted?

sRaw can be interpreted as the work to be performed by volume displacement to establish the flow rate of 1Litter per second Signup and view all the answers

What does pressure generation mean?

Pressure generation means that a mass of air is compressed or decompressed relative to its equilibrium volume. This difference is called “shift volume” Signup and view all the answers

Airway Resistance (Raw) what is and how is it calculated?

Airway resistance is the resistance to airflow within the respiratory airways. It is calculated as the ratio of the pressure difference (alveolar pressure minus mouth pressure) to the flow rate (L/s). Signup and view all the answers

Specific Airway Resistance (sRaw):

Specific airway resistance (sRaw) is the product of airway resistance (Raw) and the lung volume (usually functional residual capacity, FRC). Mathematically, sRaw = Raw × FRC sRaw=Raw×FRC. Signup and view all the answers

the airflow into the lung does not start immediately, since building-up of a pressure gradient is required to induce mass movement. T or F?

T Signup and view all the answers

Measuring Lung Volumes

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Questions and Answers

What is the recommended range of breathing frequency when measuring VTG?

What is the purpose of the piston in the calibration process of the transducer?

What is the graph of Pmouth and Pbox representative of?

How is the change in VA measured indirectly?

What is the minimum number of technically satisfactory FRCpleth values that should be obtained?

Why should breathing too quickly be avoided during the measurement?

What is the purpose of the technologist's comments on the acceptability of the maneuvers?

What is the equation used to obtain VTG from the slope of the tracing?

What is the criterion for acceptability of FRCpleth in terms of breathing frequency?

Why is FRC considered an effort-independent maneuver?

What is the term for the volume of gas remaining in the lungs after vital capacity has been exhaled?

What is the term for the volume of gas in the lungs at the end of a normal expiration?

What is the equation used to calculate total lung capacity (TLC)?

What is the method of measuring lung volumes that involves washing out nitrogen from the lungs using a single breath of oxygen?

When there is no airflow, mouth pressure equals alveolar pressure. T or F?

What is the term for the volume of gas that can be exhaled from the lungs after a normal tidal inspiration?

What is the unit of measurement for reporting lung volumes, such as residual volume (RV) and total lung capacity (TLC)?

What is the purpose of momentarily occluding the airway during pneumography?

How must the gas volume remaining in the lungs after the vital capacity (VC) has been exhaled be measured ?

6 methods for Measurement of Lung Volumes ?

What is VTG ?

How is obtained RV?

How is obtained TLC?

FRC measured with the body plethysmograph (FRCpleth) refers to the volume of intrathoracic gas measured when airflow occlusion occurs at end expiration (FRC) during shutter closure. T or F?

WHat mouth pressure theoretically equals when there is no airflow?

How are changes in pulmonary gas volume estimated?

Describe and explain the procedure to measure the FRC inside the pletismograph.

The display of the shallow breathing maneuver is a graph with Pmouth and Pbox. In wich axis are each values?

The display of the shallow breathing maneuver is a graph with Pmouth and Pbox. Pmouth is plotted on the vertical axis, and Pbox is plotted on the horizontal axis. The resulting figure appears as a sloping line equal to ΔP/ΔV, where ΔP equals ________, and ΔV equals __________ (VA).

The VTG can then be obtained from the slope of the tracing by applying a derivation of Boyle’s law. What is the equation for the determination of the VTG ?

How can the end-expiratory level be determined?

How should Raw measurements be made ?

How many technically satisfactory maneuvers to determine FRC pleth should be recorded?

At least three FRCpleth values that agree within 5% should be obtained and the mean value re- ported. T or F?

Most computerized plethysmographs automatically measure the slope of the ΔP/ΔV tracings. T or F?

Criteria for acceptability FRC pleth (6)

The FRC, RV, and TLC should be reported in liters or milliliters/second , BTPS. T or F?

Is FRC an effort dependent or effort independent maneuver?

How is the change in VA measured ?

How is airway resistance calculated?

What is Raw , and what does it indicate?

How can SRaw be interpreted?

What does pressure generation mean?

Airway Resistance (Raw) what is and how is it calculated?

Specific Airway Resistance (sRaw):

the airflow into the lung does not start immediately, since building-up of a pressure gradient is required to induce mass movement. T or F?

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The display of the shallow breathing maneuver is a graph with Pmouth and Pbox. Pmouth is plotted on the vertical axis, and Pbox is plotted on the horizontal axis.

The resulting figure appears as a sloping line equal to ΔP/ΔV, where ΔP equals , and ΔV equals __ (VA).