Pulmonary Function Tests Scribd

7/31/2019 Pulmonary Function Tests Scribd

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Ms. Namita Jadhao.

M.Sc Nursing final year.


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Classification of PFTs

I. Tests to assess Ventilator function:

1. Elastic Properties

a) Lung volume

I) Spirometryii) Body Plethysmography

iii) Gas Dilution

b) Elastic Resistance of Lungsc) Elastic Resistance of Chest Wall

d) Elastic Resistance of Lung + Chest Wall


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2. Airway Function

a) Airway Resistance

b) Forced Vital Capacity

c) Maximum Voluntary Ventilation

d) Post bronchodilator Studies

e) Airway Provocation

3. Respiratory Muscle Function


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II. Tests to assess blood & gasdistribution and of gas exchange:

1. Intrapulmonary Gas Distributiona) Multiple-Breath Dilution Techniques

b) Single-Breath Dilution Techniques

c) Frequency Dependence of Compliance2. Pulmonary Blood Flow Distribution

3. Diffusion

a) Steady-State CO Diffusing Capacityb) Single-Breath CO Diffusing Capacity

c) Pulmonary Capillary Blood


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4. Assessment of Gas Exchange

a) Blood & Gas Sampling & Analysis

b) Calculation of Parameters of GasExchange

i) O2 Consumption

ii) CO2 Production

iii) Respiratory Quotient

iv) Physiologic Dead Space

5. Acid-Base Status6. Response to Exercise

7. Chemical Regulation of Respiration


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Assessment of ventilation

1. ELASTIC PROPERTIES OF LUNG:

a) Lung volumes & capacities-

Measured using (i) Spirometer,(ii) Plethysmograph, (iii) Gas dilution

techniques


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Spirogram


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Lung Volumes:

1. Tidal Volume

2. Inspiratory Reserve Volume

3. Expiratory Reserve Volume

4. Residual VolumeLung Capacities:

1. Inspiratory Capacity

2. Functional Residual Capacity3. Vital Capacity

4. Total Lung Capacity


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Body Plethysmography:

Based on Boyles Law

P1 x TGV = (P1 +Pm) (TGV +Vp) where

P1- initial pressure

Pm-mouth or airway pressure

Vp- volume in box

TGV- Thoracic Gas Volume


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Gas Dilution:

Insoluble gases like helium, hydrogen or nitrogen

is used.FRC, RV and TLC can be measured.

i) Multiple breath Helium Technique

FRC = (VS + VDS) (FIHE FEHE)FEHE

Where VS- initial vol of gas in spirometer

VDS

- dead space of the system

FIHE- initial He concentration

FEHE- He conc at equilibrium


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ii)Single-Breath Helium Technique

TLC x FEHE

= (VC x FIHE

) + (RV x FOHE

)

Where TLC- total lung capacity

VC- vital capacity

RV- residual volumeFEHE- He conc at equilibrium

FIHE- initial He concentration

FOHE- He conc in lungs at onset ofinspiration


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iii) Multiple-Breath N2 washout

Closed circuit 100% O2 breathing for 7mins

iv) Single-Breath N2 Clearance

01 2 3 4 5 6

10

20

30

80

TLCRVCV30%VC

Vital CapacityRV

N2conc(%)

Volume (L)


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b) Elastic Resistance of lung

i) Transpulmonary Pressure

ii) Airflow & Volume- usingpneumotachogram and spirometer

iii) Compliance of lung- Static & Dynamic

c) Elastic Resistance of total pulm system

Relaxation Pressure-Volume Curve

d) Elastic Resistance of Chest Wall

1/CT = 1/CL + 1/CCW


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2. AIRWAY FUNCTION:

a) Airway Resistance

Measured using plethysmograph

Raw =Pm/V

b)Forced Vital CapacitySlow inhalation to TLC and fast & hard

exhalation to RV (6 sec)

FEV1- 85%; FEV2- 93%; FEV3- 98 to 100%


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c) Maximum Voluntary Ventilation

Breathe hard and fast for 12secs & multiply

by 5.d) Postbronchodilator Studies

When spirometry and other tests showairflow limitation

e) Airway Provocation

To check airway hyper-responsiveness

Histamine, Methacholine, Cold air, Exercise,Occupational irritants

Aspirin, Tartrazine, Sodium salicylate, etc


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3. Respiratory Muscle Function

a) Mechanical work of breathing: pressure-

volume loopb) Metabolic work of breathing: by

measuring increment of O2 consumptionwith increment in minute ventilation

c) Efficiency of respiratory system

Mechanical work/Metabolic work

d) Respiratory muscle strength

MEP/MIP, Pdimax, Sniff test

e) Respiratory muscle endurance

f) Respiratory muscle fatigue


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ASSESSMENT OF BLOOD & GAS

DISTRIBUTION AND OF GAS EXCHANGE

1. Intrapulmonary gas distribution:

a) Multiple Breath Dilution Techniques

i) mixing efficiency for helium

ii) nitrogen washoutb) Single-Breath Dilution Techniques

i) regional distribution- xenon133- scintillationcamera

ii) single-breath nitrogen test

c) Frequency Dependence of Compliance


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2.Pulmonary Blood Flow Distribution:

Dye dilution principle

Fick Principle

Radioactive iodine labeled albumin

Radioactive Xenon

3. Diffusion:

a) Steady state CO diffusing capacity

b) Single-breath CO diffusing capacity


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4. Assessment of gas exchange:

a) Blood & gas sampling and analysis

Arterial blood sampling- Radial or brachialarteries

Gas analysis- by using electrodes-reported at body temperature

Oxygen electrode- silver anode &platinum wire cathode- oxygen isreduced when voltage is applied-

electrons pass from cathode to anode-measured by galvanometer

pH and CO2 electrodes


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5. Calculation of parameters of gas

exchange:

a) Oxygen consumptionb) CO2 production

c) Respiratory Quotient

d) Physiologic dead space

6. Acid Base Status

7. Response to exercise


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Interpretation of PFT

Interpretation of ventilatory function tests:

Lung volume compartments differ with

age, gender, race and height

Lung volume and capacity measurements

give an idea about restrictive & obstructive

disorders.

Reduced FRC, RV & TLC volume-

pressure curve shifted to right &

downwards reduced compliance of lung

and/or chest wall


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Increased FRC, RV & TLC

overdistension volume-pressure curveshifted to left and upwards obstructiveairway disease

Normal FRC + increased RV + reducedTLC mixed disorder

Vital capacity is used as surrogate to TLC


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Low FEV1 & normal FEV1/FVC ratio

suggest restrictive disorder

Low FEV1

& low FEV1

/FVC suggest

obstructive disorder


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Flow

ratel/sec

Lung volume (L)6 5 4 3 2 1 0

0123456

0

0

8

8

RESTRICTIVE PATTERN

OBSTRUCTIVE

PATTERN

IC ERV RV


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FEF25-75 and FEV1 may be normal inincreased peripheral airway resistance.

Closing volume and closing capacity arerarely used clinically

On using bronchodilator, FEV1/FEF25-75must improve by atleast 15% to tell

obstruction is reversible

Reduced PImax/Pdimax/PEmax may alsosuggest poor effort by the subject


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Interpretation of blood gases and gas

exchange: Respiratory quotient of 0.95

indicate hypo- and hyperventilation

respectively P(A-a)O2 is


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VD/VT is 30% in young and 40% in aged.

Greater than this, it indicates dead-space-

like ventilation.

Venous admixture like perfusion- low

VA/Q- physiologic shunt

True venous admixture- PaO2 fails to raiseabove 500 mm Hg on breathing 100%

oxygen

Low DLCO

is seen in diffuse pulmonary

fibrosis, pneumonectomy, end-stage

emphysema


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Acid-Base balance: blood pH of 7.35-7.45,

bicarbonate level of 20-27 mEq and PaCO2

between 40-45 mm Hg at sea level.

Respiratory alveolar ventilation COPD High PaCO2


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p yacidosis

Anaesthetics,Narcotics.

Mopathies,Neuropathies.

Kyphoscoliosis,Obesity.

g CO2.Low pH.

Normal or highHCO3

-.

Respiratoryalkalosis

alveolar ventilation Salicylates,progesterone.

Excessive mechanical

ventilation.Psychogenic, fever

Low PaCO2.High pH.

Normal or low

HCO3-

Metabolicacidosis

Gain of H+ or loss ofHCO3

- by ECFDiabetic ketoacidosis,starvation

Primary lactic acidosis

ARF, CRF, RTADiarrhoea

Low HCO3-.

Low pH.

Normal or high

PaCO2..

Metabolicalkalosis

Gain of HCO3- or loss of

H+ by ECFAntacid ingestion

Vomiting, gastricsuction

Diuretics steroid

High HCO3-.

High pH.

Normal or high

PaCO2

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