بسم الله الرحمن الرحیم Fariba Rezaeetalab Assistant professor,pulmonologist.

الرحیم الرحمن الله بسم

Fariba RezaeetalabAssistant professor ,pulmonologist

Lung Volumes4 Lung Volumes, 3 of which can be measured with simple spirometry.

Tidal Volume (Vt): The volume of air that normally moves into and out of the lungs in one “quiet” breath.

Normal: 5-8 ml/kg (70 kg * 7 ml/kg = 500 ml).

Inspiratory Reserve Volume (IRV): The maximum volume of air that can be inhaled after a normal tidal volume.

Normal: 3,100 mL

Expiratory Reserve Volume (ERV): The volume of air that can be exhaled after a normal tidal volume.

Normal: 1,200 mLResidual Volume (RV): The amount of air remaining in the lung after a maximal exhalation.

Normal: 1,200 mL Cannot be measured with simple spirometery

Lung Volume

Directions for Lung Volume/Capacity Measurements

Tidal Volume (Vt): Breathe normally in and out.

Inspiratory Reserve Volume (IRV): Inhale as much as you can from a normal inhalation.

Expiratory Reserve Volume (ERV): Exhale as much as you can from a normal exhalation..

Residual Volume (RV): This volume cannot be measured directly with simple spirometry.

Slow Vital Capacity (SVC): Take a deep breath in, as deep as you can, and then blow it out slowly until you can’t blow out any more.

Indirect Measurements of RV

The residual volume (and the capacities which have it as a part – FRC & TLC) must be measured indirectly by one of three methods: Helium Dilution – Closed Circuit Method Nitrogen Washout – Open Circuit

Method Body Plethysmography

Lung Volumes / Gas Distribution

Indirect Spirometry

Two basic approaches

Gas dilution

Body plethysmography

Measurements are in Liter or Milliliters Reported at BTPS


Indirect Spirometry

Required for the determination of RV, FRC and TLC

Most often, indirect spirometry is performed to measure FRC volume

FRC is the most reproducible lung volume and it provides a consistent baseline for measurement


Gas dilution techniques

All operate on a principle SIMILAR to Boyle’s Law (P1 V1 = P2 V2), which states,

In isothermic conditions, the volume of a gas varies inversely with its pressure

Fractional concentration of a known gas is used instead of its partial pressure

C1 V1 = C2 V2



By having a known (or measured) gas concentration at the start and end of the study and a single known volume, the unknown volume can be determined. For example:

V1 = C2 V2

C1

TOTAL LUNG CAPACITY

By applying Boyle’s law (P · V = constant) TLC

• Measured by – body plethysmography– helium dilution– Nitrogen washout – Body plethysmography– mouthpiece obstructed with

shutter– rapid panting chest volume expand and

decompress the air in the lungs

changes in pressure inside the box allow determination of the lungof the lung volume

HELIUM DILUTION

TOTAL LUNG CAPACITY

• Helium dilution- Spirometer of known volume and helium concentration connected to the patient- Closed circuit - Law of conservation of mass

• [He]initial.Vs=[He]final.(Vs+VL)

• Unknown lung volume canbe calculated

[He] [He] initial · Vs =

{H.,.,.H{[[) initial · Vs = [He] final · (Vs + )

RV=TLC-VCFRC=TLC- IC

NITROGEN WASHOUT


Objectives

Describe the measurement of lung volume using direct and indirect spirometry

Explain two advantages of measuring lung volumes using the body plethysmograph


Objectives

Calculate residual volume and total lung capacity from FRC and the subdivisions of VC

Identify restriction from measuring lung volumes


Direct Spirometry

Used to measure all volumes and capacities EXCEPT for RV, FRC and TLC



Can only measure lung volumes in communication with conducting airways !!!



Obstruction or bullous disease can have trapped, noncommunicating air within the lungs

FRC may be measured as being less than its actual volume


Open-Circuit Nitrogen Washout

The natural volume of nitrogen in the subject’s lungs at FRC is washed out and diluted with 100% oxygen

Test must be carefully initiated from the FRC baseline level



All exhaled gas is collected in a Tissot (large volume) spirometer for measurement of its volume

Analyzer in the breathing circuit monitors nitrogen concentrations







Approximately 3-7 minutes of breathing 100% O2 to wash out N2 from the lungs

If oxygen-induced hypoventilation is a documented problem (as in COPD), a different method of FRC determination is needed



Test is successfully completed when the N2 levels decrease to become less than 1.5% for at least 3 successive breaths (subjects without obstructive disorders)

Premature discontinuation may occur due to:

System leak Patient unable to continue Tissot spirometer is full



The FRC has a N2 concentration of approximately 0.75, based on the atmospheric nitrogen minus CO2 and water vapor at BTPS:

(CAlvN2) = 0.75



The final collected volume of exhaled gas in the Tissot spirometer

(VExh)

Has a measurable concentration of N2

(CExhN2)



FRC determination is based on the following equation:

VFRC = (CExhN2)(VExh) CAlvN2



In the actual FRC determination by this method, the calculation is more complex

Do not get scared !You will not be asked to do

the calculation!



The small final concentration of alveolar N2 remaining in the lung needs to be subtracted from the original CalvN2

Deep breath of O2 at the end of the test and slowly exhaled. The end-expiratory CN2 is used as the CFN2 (This volume should not be exhaled into the spirometer)



The second correction is the volume of nitrogen released from the body tissues during the washout procedure (body tissue N2 factor or BTN2)

Rages from 30 – 50 ml/minute of the washout procedure (TTest)



Final Calculation

VFRC = (CExhN2 X (VExh +VD) ) - BTN2 Factor X TTest

CAlvN2 – CFN2

Must be BTPS converted Test can be repeated after 15 minutes (longer if COPD)



Modern computer-operated pneumotachometer systems do not require collection of total VExh or measurement of the CExhN2

Breath-by-breath CExhN2 and VExh measurements are made






Open-Circuit Nitrogen Washout Leak



Criteria for Acceptability

The washout tracing/display should indicate a continually falling concentration of alveolar N2

The test should be continued until the N2 concentration falls to <1.5% for 3 consecutive breaths




Washout times should be appropriate for the subject tested. Healthy subjects should washout N2 completely in 3-4 minutes

The washout time should be reported. Failure to wash out N2 within 7 minutes should be noted




Multiple measurements should agree within 10%

Average FRC from acceptable trials should

be used to calculate lung volumes

At least 15 minutes of room-air breathing should elapse between repeated trials, >1 hour for patients with severe obstructive or bullous disease


Closed-Circuit Helium Dilution

FRC is calculated indirectly by diluting the gas in the lungs at the end-expiration level with a known concentration of helium (an inert gas)



FRC



Procedure

•Spirometer is filled with a known volume of air with added oxygen of 25 – 30%

•A volume of He is added so that a concentration of approximately 10% is achieved

•System volume (spirometer, tubing) and He concentration are measured


C1 V1 = C2 V2

(C1 initial He concentration)(V1 system volume)




Procedure

•The patient breathes through a free-breathing valve that allows either connection to both room air or the rebreathing system

•The patient is switched into the rebreathing system at end-expiration level (FRC)

•The patient rebreathes the gas in the spirometer, until the He concentration falls to a stable level



CO2 Absorbed

O2 Added

H2O Absorbed



He Concentration

System Volume





Procedure

•Once the He reaches equilibrium between the spirometer and the patient, the final concentration of He is recorded

•The FRC can then be calculated

FRC


C1 V1 = C2 V2


(CIHe)(SV) = (CFHe)(FRC)

FRC = (%HeInitial - %HeFinal) x System volume

%HeFinal


Volume Corrections

A volume of 100 ml is sometimes subtracted from the FRC to correct loss of He to the blood

The dead space volume of the breathing valve and filter should be subtracted from the FRC




Spirometer tracing should indicate no leaks (detected by a sudden decrease in He), which would cause an overestimation of FRC

Test is successfully completed when He readings change by less than 0.02% in 30 seconds or until 10 minutes has elapsed




Multiple measurements of FRC should agree within 10%

The average of acceptable multiple measurements should be reported


Body Plethysmography (BP)

Measurement of FRC by body plethysmograph is based on an application of Boyle’s law

P1V1 = P2V2

or

V1 = P2V2

P1



Unlike gas dilution tests, BP includes both air in communication with open airways as well as air trapped within noncommunicating thoracic compartments

In patients with air trapping, plethysmography lung volumes are usually larger those measured with gas dilution methods

Volume measured is referred to as thoracic gas volume (TGV or VTG)

ATS is recommending term be dropped and changed to “plethysmographic lung volume” (VL, pleth), and “FRC by body plethysmography” or TGV at FRC (FRCpleth)




Procedure

•Patient is required to support cheeks with both hands and pant with an open glottis at a rate of 0.5 - 1 Hz (30 – 60 breaths/min)

•BP shutter is suddenly closed at end-expiration prior to inspiration

•Panting is continued for several breaths against closed shutter (no air flow)



Procedure

•The thoracic-pulmonary volume changes during panting produce air volume changes within the BP cabinet

•Decreases in cabinet volume are an equal inverse response to thoracic volume increase (As thoracic volumes increase with panting inspiration, BP cabinet volume decreases and visa versa)



Criteria of Acceptability

•Panting maneuver shows a closed loop without drift

•Tracing does not go off the screen

•Panting is 0.5 – 1 Hz

•Tangents should be within 10%

•At least 3 FRCpleth values should agree within 5% and the mean reported



Airway Resistance (Raw) and Specific Airway Conductance (SGaw) can be measured simultaneously during open-shutter panting (1.5-2.5 Hz)

Most plethysmographs have built-in pneumotachometers and allow VC maneuvers to be performed during the same testing session


Single-Breath Nitrogen Washout

Measures Distribution of Ventilation

Closing Volume

Closing Capacity


SBN2 (SBO2)

Equipment


SBN2

Procedure Patient exhales to RV

Inspires a VC breath of 100% O2

Patient exhales slowly and evenly (0.3-0.5L/s)

N2 concentration is plotted against volume


SBN2

Phase I: upper airway gas from anatomical dead space (VDanat), consisting of 100% N2

Phase II: mixed airway gas in which the relative concentrations of O2 and N2 change abrubtly as VDanat volume is expired

SBN2

Phase I: upper airway gas from anatomical dead space (VDanat), consisting of 100% O2

Phase II: mixed airway gas in which the relative concentrations of O2 and N2 change abrubtly as VDanat volume is expired


SBN2

Phase III: a plateau caused by the exhalation of alveolar gas in which relative O2 and N2 concentrations change slowly and evenly

Phase IV: an abrupt increase in the concentration of N2 that continues until RV is reached


SBN2% N2 750 – 1250

Is 1.5% or less in healthy adults; up to 3% in older adults

Increased % N2 750 – 1250 is found in diseases characterized by uneven distribution of gas during inspiration or unequal emptying rates during expiration.

Patients with severe emphysema may exceed 10%


SBN2

Slope of Phase III

Is an index of gas distribution

Values in healthy adults range from 0.5% to 1.0% N2/L of lung volume


SBN2Closing Volume

The onset of Phase IV marks the lung volume at which airway closure begins

In healthy adults, airways begin closing after 80-90% of VC has been expired, which equates to 30% of TLC

Reported as a percentage of VC


SBN2Closing Capacity

If RV has been determined, CV may added to it and expressed at Closing Capacity (CC)

CC is recorded as a percentage of TLC


SBN2Normal Values for CC and CV

________________________________Male Female

CV/%VC 7.7% 8.7%

CC/%TLC 24.8% 25.1%


SBN2 CV and CC may be increased, indicating

earlier onset of airway closure in:

Elderly patients

Smokers, early obstructive disease of small airways

Restrictive disease patterns in which FRC becomes less than the CV

Congestive heart failure when the caliber of the small airways is compromised by edema


SBN2

Acceptability Criteria

Inspired and expired VC should be within 5% or 200 ml

The VC during SBN2 should be within 200 ml of a previously determined VC

Expiratory flows should be maintained between 0.3 and 0.5 L/sec.

The N2 tracing should show minimal cardiac oscillations

Lung Volumes

The most significant volumes for evaluating the effects of pulmonary disorders are VC, FRC, RV, and TLC

Lung Volume

Significance/Pathophysiology

Obstructive Pattern

Increase FRC is considered pathologic

FRC values >120% of predicted represent air trapping

Emphysematous changes Obstruction caused by asthma or

bronchitis

Lung volume

Significance/Pathophysiology

Restrictive Pattern FRC, RV and TLC typically decreased

Usually lung volumes are decreased equally

When TLC is <80% a restrictive process is present

RV/TLC is relatively normal

TLC and RV/TLC Ratio

RV/TLC% >35% + Normal TLC =

Air trapping RV/TLC% >35% + >Normal TLC =

hyperinflation

Lung Volume Changes

Patterns of Lung Volume Changes

Volume Restrictive Air Trapping Hyperinflation

TLC N VC NFRC RV RV/TLC% N

بسم الله الرحمن الرحیم Fariba Rezaeetalab Assistant professor,pulmonologist.

Documents

lung volume slide

unknown volume

reproducible lung volume

normal tidal volume

residual volume rv

helium dilution slide

maximum volume of air

pulmonologist slide