PULMONARY FUNCTIONTESTS

Dr. M HELMI AFIFI Dr. M HELMI AFIFI (MBBCh,MS,MD,MHA)(MBBCh,MS,MD,MHA)

Prof. of Anaesthesia & Intensive CareProf. of Anaesthesia & Intensive CareMenoufiya University, EgyptMenoufiya University, Egypt

Pulmonary Function Tests

• A wide variety of objective tests to assess lung function

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GOALS

To predict the presence of pulmonary dysfunction

To know the functional nature of disease (obstructive or restrictive. )

To assess the severity of diseaseTo assess the progression of diseaseTo assess the response to treatmentTo identify patients at increased risk of morbidity

and mortality, undergoing pulmonary resection.

To wean patient from ventilator in icu.Medicolegal- to assess lung impairment as a

result of occupational hazard.Epidemiological surveys- to assess the

hazards to document incidence of diseaseTo identify patients at perioperative risk of

pulmonary complications

GOALS, CONTINUED……..

INDICATIONS FOR PREOPERATIVE SPIROMETRY

• ACP GUIDELINESLung resectionH/o smoking, dyspnoeaCardiac surgeryUpper abdominal surgeryLower abdominal surgeryUncharacterized pulmonary disease(defined as

history of pulmonary Disease or symptoms and no PFT in last 60 days)

BED SIDE PFT

Single breath count: After deep breath, hold it and start counting till the

next breath. N- 30-40 COUNT Indicates vital capacity

BED SIDE PFT

SCHNEIDER’S MATCH BLOWING TEST: MEASURES Maximum Breathing Capacity.

Ask to blow a match stick from a distance of 6” (15 cms) with-

Mouth wide open Chin rested/supported No purse lipping No head movement No air movement in the room Mouth and match at the same level

• Can not blow out a match– MBC < 60 L/min– FEV1 < 1.6L

• Able to blow out a match– MBC > 60 L/min– FEV1 > 1.6L

• MODIFIED MATCH TEST: DISTANCE MBC 9” >150 L/MIN. 6” >60 L/MIN. 3” > 40 L/MIN.

BED SIDE TEST

COUGH TEST: DEEP BREATH F/BY COUGH ABILITY TO COUGH STRENGTH EFFECTIVENESSINADEQUATE COUGH IF: FVC<20 ML/KG FEV1 < 15 ML/KG PEFR < 200 L/MIN.VC ~ 3 TIMES TV FOR EFFECTIVE COUGH.

A wet productive cough / self propagated paraoxysms of coughing – patient susceptible for pulmonary Complication.

BED SIDE PFT

WRIGHT PEAK FLOW METER:

Measures PEFR

N: M- 450-700 L/min

F- 350-500 L/min

Wright respirometer measures TV, MV (15 secs times 4)

• Simple and rapid• Instrument- compact, light and portable.• Disadvantage: under- reads at low flow rates

and over- reads at high flow rates.• Can be connected to endotracheal tube or

face mask • MV- instrument record for 1 min and read

directly• TV-calculated and dividing MV by counting

Respiratory Rate.• Accurate measurement in the range of 3.7-

20l/min.(±10%)

• USES: 1)BED SIDE PFT• 2) ICU – WEANIG PTS. FROM

Ventilation.

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INTERPRETATION

General rule:

When flow is ↓→ lesion is obstructive.

When volume is↓→ lesion is restrictive.

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Flow-Volume Loops

Two ways to record results of FVC:•Flow-volume curve•Classic spirogram: volume as a function of time

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Normal vs. Obstructive vs. Restrictive

(Hyatt, 2003)

Flow Volume Loops

• Inspiratory loops can also be obtained to evaluate for the presence of large airway obstruction

• Theory changes in pressure outside and inside the thoracic cage will cause changes in airway diameter

• These airway changes can cause a limitation to airflow if large enough

Extrathoracic Obstruction

Intrathoracic Obstruction

Fixed Obstruction

Large Airway Obstruction

MEASUREMENTS OF VOLUMES

• TLC, RV, FRC – MEASURED USING Nitrogen washout methodInert gas (helium) dilution methodTotal body plethysmography

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Helium Dilution Technique

• Uses an inert gas, helium and by a closed circuit technique, allow it to come to equilibrium and FRC is measured

• May underestimate lung volumes in bullous lung disease

Nitrogen Washout

• Determine FRC by multiple breath open circuit nitrogen washout

• Involves having nitrogen in patients lung being washed out by inhaling 100% O2 for several minutes.

• Widely used, easy to perform but may underestimate bullous lung disease

Nitrogen Washout

• Performed by having the patient breath comfortably for several minutes and then turn in to 100% O2 at FRC.

• Monitor N2 concentrations and test ends when falls below 1%

• Easy to see leaks

Nitrogen Washout

• Concept is C1V1= C2V2– C1 = Nitrogen concentration at the start of the

test– V1 = FRC volume– C2 =N2 concentration in exhaled volume– V2 = Total exhaled volume during O2 breathing

period– Nitrogen is measured by photoelectric principle

Body Plethsymography

• Is a sealed box with a fixed volume• Uses Boyle’s Law that changes in pressure are

brought about by changes in volume for the person seated in the box

• P1V1= P2V2

Body Plethysmograph

Interpretation

• RLD– TLC is reduced in all – Predicted values and

interpret same as FVC and FEV1

• OLD– TLC can be increased

and is then called hyperinflation (120%)

– RV can be increased in asthma and COPD indicating air trapping

Diffusing Capacity

• Provides information about the transfer of gas between the alveoli and the pulmonary capillary bed

• It is the only noninvasive test of gas exchange• Performed by a single breath technique and

uses CO as the inert gas

Diffusing Capacity

• Diffusion of a gas is dependent of the area, the concentrations, the thickness of the membrane and the diffusing properties of the gas

• Diffusion is the rate at which a gas is transferred across the alveolar capillary membrane, the plasma, the RBC and ultimately combined with Hgb

Diffusing Capacity

• CO is typically used because it is freely diffusable

• It usually is not present in significant amounts in the blood except in some heavy smokers

• Helium or methane is also used to measure volume

• A single maximal inspiration is taken and held for 10 sec

Diffusing Capacity

• Normal result is >80%• Can be reduced in interstitial diseases such as

sarcoid or asbestosis • Can be reduced also in emphysema or

pulmonary vascular diseases• False low measurements in anemia or lung

resection

SINGLE BREATH TEST USING CO

• Pt inspires a dilute mixture of CO and hold the breath for 10 secs.

• CO taken up is determined by infrared analysis:

• DlCO = CO ml/min/mmhg• PACO – PcCO• N range 20- 30 ml/min./mmhg.• DLO2 = DLCO x 1.23

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DLCO decreases in-• Emphysema, lung resection, pul. Embolism, anaemia • Pulmonary fibrosis, sarcoidosis- increased thickness• DLCO increases in:(Cond. Which increase pulm, bld flow) Supine position Exercise Obesity L-R shunt

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Predicted Values

Measured Values

% Predicted

FVC 6.00 liters 4.00 liters 67 %

FEV1 5.00 liters 2.00 liters 40 %

FEV1/FVC 38 % 50 % 60 %

Decision : This person is obstructed

Predicted Values

Measured Values

% Predicted

FVC 5.68 liters 4.43 liters 78 %

FEV1 4.90 liters 3.52 liters 72 %

FEV1/FVC 84 % 79 % 94 %

Decision : This person is restricted

Decision: normal

Predicted Values

Measured Values

% Predicted

FVC 5.04 liters 5.98 liters 119 %

FEV1 4.11 liters 4.58 liters 111 %

FEV1/FVC 82 % 77 % 94 %

Decision: mild restrictive lung disease

Predicted Values

Measured Values

% Predicted

FVC 3.20 liters 2.48 liters 77 %

FEV1 2.51 liters 2.19 liters 87 %

FEV1/FVC 78 % 88 % 115 %

Decision: moderate obstruction

Predicted Values

Measured Values

% Predicted

FVC 3.20 liters 3.01 liters 94 %

FEV1 2.51 liters 1.19 liters 47 %

FEV1/FVC 78 % 39 % 50 %

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