body plethysmography · 2020. 9. 21. · body plethysmography • body plethysmography is used to...

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Body Plethysmography Prof. Ellie Oostveen, lung physiologist Antwerp University Hospital BVP 2020 [email protected]

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Page 1: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Body Plethysmography

Prof. Ellie Oostveen, lung physiologist

Antwerp University Hospital

BVP 2020

[email protected]

Page 2: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

The origins."I do not have photographs of my lab because it was the broom closet of the basement of the medical school, and hard to take pictures there until Dr. Comroe, an excellent chief, moved me upstairs to the 8th floor of the Gates Pavilion in the hospital. He wanted me to make his body box work. Then, I could have my picture taken.

Now that I am emeritus I am back down in a basement again and underneath the parking lot.“

Courtesy by Arthur B. DuBois

A. B. DuBois, April 2007

Page 3: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Body plethysmography

• Body plethysmography is used to determine:

– Lung volumes

– Airway resistance (or conductance, the inverse of resistance)

• A body plethysmohraph is (usually) an airtightcabin with the size of an telephone booth(~900 Liter)

Page 4: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Body plethysmography

• Body plethysmography is used to determine:

– Lung volumes

– Airway resistance (or conductance, the inverse of resistance)

• A body plethysmohraph is (usually) an airtightcabin with the size of an telephone booth(~900 Liter)

Page 5: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Measurements are difficult/impossible in patients:

• With claustrophobia

• Who are immobile

A closed “telephone booth”…

Page 6: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Body plethysmography

• Body plethysmography is used to determinelongvolumes (L):

– RV: residual volume (amount of air in the lungsafter full deflation)

– FRC: functional residual capacity ((I)TGV, EELV, amount of air in the lungs at the end of a normalexpiration)

– TLC: total lung capacity (amount of air in the lungsafter full inflation)

Page 7: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Interpretation scheme ATS-ERS 2005

Page 8: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Measurement´s principle

Plethysmographic measurements are based on Boyle’s Law, which states that,

under isothermal conditions,

when a constant mass of gas is compressed or decompressed, the gas volume decreases or increases and gas pressure changes such that the product of volume and pressure at any given moment is constant.

P × V = constant

A constant mass of gas, i.e. a “closed” lung

Page 9: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Boyle’s Law: P×V = constant

• Shutter closes at FRC:

1) V= VL= FRC 2) P= (PB-PH2O)

• An inspiratory effort will lead to:

increase in VL, decrease in P

P×V = (P - DP) × (V + DV)

P×V = P×V+ P×DV - DP×V - DP×DV

P×V = P×V+ P×DV - DP×V - DP×DV

DP×V = P×DV

V = DV/ DP × P

Page 10: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Boyle’s Law: P×V = constant

V = DV/ DP × PThis equation states that:• If we know the initial pressure in the lung, and we

can measure the pressure swing in the lung inducedby the inspiratory and expiratory “breathing” manoeuvre and the corresponding volume change, we can calculate VL.

• Initial pressure: PB

• Pressure swing: DP measured at the mouth

• Volume change: DV is measured through the change in box pressure

Page 11: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Boyle’s Law: P×V = constant

Pm

Pb

FRCpleth= (DPb/DPm) × PB

FRCpleth= (DVL/DPA) × PB

Page 12: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Lung volume: P V = constant

DP=1kPa DV= 10 ml

Pm

Pb

1 L

DP=1kPa DV= 30 ml

Pb

Pm

3 L

VL = (DVL/DPA) PB

Page 13: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Body plethysmography

The bodybox is equiped with:

• Pneumotachograph to

measure airflow (V´)

• Shutter

• Pressure tranducer to record

Pmouth

• Pressure transducer to

record changes in box

pressure (Pbox)

V´ Pm

Pbox

Page 14: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Calibration

1) Leakage

control

2) Pbox

3) Pneumo…

Page 15: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

ATS-ERS 2005

Page 16: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

In Belgium practice:

• When performing bodybox: voluntary increasein breathing frequency to reliably measuresRaw (thus no “quiet” breathing!)

• Increase in frequency often changes “FRC”

• RV and TLC are not influenced (except whenVC- manoeuvre is submaximal)!

• Thus: determine RV and TLC reliably!

Page 17: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)
Page 18: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

FRCplethdetermination

Page 19: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)
Page 20: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)
Page 21: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)
Page 22: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

TLC = RV + VC

FRC (ITGV)

RV = FRC - ERV

1

2

3

FRC (ITGV)

TLC = FRC + IC

RV = TLC - VC

1

2

1

3

2

How are FRC, TLC and RV determined?

Page 23: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

TLC = FRC + IC

FRC1

2

Or, in very dyspneuic patients: FRCpleth + IC TLC

TLC – VC RV

IC IVC

Page 24: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Body plethysmography

• The absolute gas volume in de lung is determined at the moment the shutter is closed (FRCpleth), this includes closed bullea.

• By subsequently exhaling completely (ERV-manoeuvre) and then inhaling maximally (IVC-manoeuvre) RV and TLC are determined.

Page 25: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

ATS/ERS guidelines 2005

• How many measurements per patient?

At least 3 fully and technically acceptablemeasurements , i.e 3 times (TGV + VC).

• Calculation of the end-result?

FRC= average FRC

RV= average FRC – average ERV

TLC= RV + largest IVC

Page 26: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

ATS/ERS guidelines 2005

An acceptable difference between 3 measurements?

1) (largest FRC - lowest FRC )

mean

2) VC: largest and second largest ≤ 150 mL

≤ 10%

Page 27: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Airway resistance: Raw

Vm

Pb

Raw-measurement: to inhale, alveolar pressure

needs to decrease below atmospheric pressure.

This will lead to a proportional increase in Pbox

.

Raw = PA/V’

Page 28: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Raw-measurement: Raw= DP/DV’

V’m

Pb

sRaw = DPb / DV’m

Page 29: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Body plethysmography is beingused to determine:

– Lung volumes

– sRaw-loops

sRaw-loops

(I)TGV-measur.

Page 30: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Raw-measurements

Advantages:

• Airway resistance is a measure of airwayobstruction which is independent of a special breathing maneuvre.

• Airway resistance is measured at FRC, the normal lung volume at which the patientbreathes

Page 31: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

+0.5 L/s

-0.5 L/s

sReff sR0.5 sRmid sRtot

Different sRaw-calculations…

Page 32: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Reproducibility of bodybox measurements?

2,5

3,0

3,5

4,0

4,5

5,0

5,5

6,0

6,5

7,0

0 10 20 30 40 50 60 70

FRC

(L)

TLC

(L)

weeknummer

FRC - TLC: Bio-ijk #1

Lab 1

Lab 2

Lab 3

Lab 4

Page 33: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

2,5

3,0

3,5

4,0

4,5

5,0

5,5

6,0

6,5

7,0

0 10 20 30 40 50 60 70

FRC

(L)

TLC

(L)

weeknummer

FRC - TLC: Bio-ijk #2

Lab 1

Lab 2

Lab 3

Lab 4

Reproducibility of bodybox measurements?

Page 34: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)
Page 35: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Casus:

Page 36: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Mr KGD, 63 yrs, 1.67m, 101 kg

Page 37: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

P mond (kPa)

Volume shift (ml)

ITGV (L): 3.87 2.77 2.96 3.76 3.15

Page 38: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

ITGV & sRaw (breathing loop)

Page 39: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Comparisongas dilution vs. body plethysmography

• In healthy subjects: comparable results

• Severe airways obstruction: gas dilution techniques underestimates FRC in case of poorly or non-ventilated lung regions (or a too short wash-in or wash-out measurement)

• Body plethysmography: over-estimation of FRC attoo high panting frequencies (> 1 Hz)

• D (gasdilution and box): estimation of trapped air

Page 40: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

TLCbodybox= 0.02+1.03×TLCHe

TLCHe verdunning (L)

3

4

5

6

7

8

9

3 4 5 6 7 8 9 10

Labadie & Van EenigeNTvG 1971; 115:938-940

Page 41: Body Plethysmography · 2020. 9. 21. · Body plethysmography • Body plethysmography is used to determine: –Lung volumes –Airway resistance (or conductance, the inverse of resistance)

Thank you!