Lung function tests
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Lung Function Tests. Sema Umut. Lung Factors Affecting Function. Mechanical properties Resistive elements. Mechanical Properties. Compliance Describes the stiffness of the lungs Change in volume over the change in pressure Elastic recoil

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Lung function tests

LungFunctionTests

Sema Umut


Lung factors affecting function

Lung Factors AffectingFunction

  • Mechanical properties

  • Resistive elements


Mechanical properties

Mechanical Properties

Compliance

  • Describes the stiffness of the lungs

  • Change in volume over the change in pressure

    Elastic recoil

  • The tendency of the lung to return to it’s resting state


Resistive properties

Resistive Properties

  • Determined by airway caliber

  • Affected by

    • Lung volume

    • Bronchial smooth muscles

    • Airway collapsibility


A test should be

A TEST SHOULD BE

  • Acceptabile,easy

  • Noninvasive

  • Cost effective

  • Informative

  • Reproducible


Spirometry

Spirometry

Acceptabile,easy

Noninvasive

Costeffective

Inexpensive

Informative

Reproducible


Spirometry1

Spirometry

  • It is the most commonly used lung function screening study

  • It should be the clinician's first option


Lung function tests

When can spirometry help us?

  • - Diagnosing disease

  • - Monitoring disease

  • - Prognosis

  • Directing therapy


Indications for spirometry

Indications for Spirometry

Diagnostic

  • To evaluate symptoms, signs, or abnormal laboratory tests

    • Dyspnea

    • Wheezing

    • Cough

    • Abnormal breath sounds

    • Overinflation

    • Expiratory slowing

    • Cyanosis


Abnormal laboratory tests

Abnormallaboratorytests

  • Hypoxemia

  • Hypercapnia

  • Polycythemia

  • Abnormal chest radiographs


Lung function tests

To screen individuals at risk of having pulmonary diseases

  • Smokers

  • Individuals in

    occupations with

    exposures to

    injurious substances


Indications for spirometry1

Indications for Spirometry

  • To assess preoperative risk

  • To assess health status before physical activity programs

  • To evaluate therapy


Disability impairment evaluations

Disability/ImpairmentEvaluations

  • To assess individuals for legal reasons


Lung function tests

Prognosis

Survival predictor of

general population

Copenhagen City Heart Study

13,900 subjects for 25 yrs

Lange P. J Clin Epidemiol

1990; 43: 867-873.

Cox proportional hazards

FEV1/ht2 best index

Framingham study


Lung function tests

Spirometry Requirements

1. Good equipment

2. Good technicians (efor dependent)

3. Good clinicians

- correct indication

- correct use / presentation of the data

- correct decision making


Pulmonary function testing relates

Pulmonary Function Testing relates

  • Age : Smaller lung volumes as we age

  • Gender : The lung volumes of males are larger than females

  • Height

  • Race


Perform manoeuvre

Perform manoeuvre

  • Attach nose clip, place mouthpiece in mouth

  • Inhale completely and rapidly

  • Exhale maximally until no more air can be expelled

  • Repeat for a minimum of 3 manoeuvres


Lung function tests

ForcedVitalCapacity FVC

  • Total volume of airexpiredforcefullyafter a fullinspiration

  • Patientswithrestrictivelungdiseasehave a decreasedvitalcapacity


Slow vital capacity svc

Slow Vital Capacity (SVC)

  • This is the total volume of air expired slowly after a full inspiration

  • If the SVC is greater than FVC,it indicates the presence of obstructive disease


Lung function tests

Forced Expiratory Volume in 1 Second

FEV1

Volume of air expired in the first second during maximal expiratory effort


Fev1 fvc

FEV1/FVC

  • Percentage of the forced vital capacity which is expired in the first second of maximal expiration to forced vital capacity

  • In health the FEV1/FVC is usually around 80%

  • Decrease in FEV1/FVC means obstruction


Lung function tests

Tidal volume TV

The volume of air moved during normal quiet breathing (about 0.5 L)


Residuel volume rv

RESIDUEL VOLUME (RV)

The volume of air remaining in the lungs after a forceful expiration (about 1.0 L).


Functional residuel capacity frc

FUNCTIONAL RESIDUEL CAPACITY(FRC)

The amount of air remaining in the lungs after a normal quiet expiration


Total lung capacity tlc

TOTAL LUNG CAPACITY (TLC)

It is the volume of air in the lungs when the person has taken a full inspiration

TLC = RV + VC


Tlc rv frc

TLC,RV,FRC

Can not be measured by spirometry

  • Helium dilution

  • Nitrogenmetry

  • Body plethysmography


Lung function tests

INTERPRETATION OF SPIROMETRY

  • Compare the measured values of the patient with normal values derived from population studies

  • The percent predicted normalis used to define normal and abnormal and to grade the severity of the abnormality


Categories of disease

Categories of Disease

  • Obstructive

  • Restrictive

  • Mixed


Lung function tests

Spirogrammeasurestwocomponents - airflowandvolume

Ifflow is reduced, thedefect is obstructive

Ifvolume is reducedthedefect is restrictive


Interpretation

Interpretation

FVC and FEV1 are normal – NORMAL

FVC is low but FEV1/FVC is >80 RESTRICTIVE

FEV1/FVC < 70% OBSTRUCTIVE


Spirometry2

Spirometry

  • Obstruction (FEVı /FVC) < %70


Obstructive lung diseases

Obstructive Lung Diseases

  • Asthma

  • Chronicobstructivepulmonarydisease


Lung function tests

COPD

-COPDis characterized by airflow limitation that is not fully reversible

-The airflow limitation is usually progressive and associated with an abnormal inflammatory response of the lung to noxious particles or gases


Lung function tests

Diagnosis of COPD

EXPOSURE TO RISK

FACTORS

SYMPTOMS

cough

tobacco

sputum

occupation

shortness of breath

indoor/outdoor pollution

è

è

è

SPIROMETRY


Asthma

Asthma

  • Asthma is a chronic inflammatory disease of the airways

  • Inflammation causes the airways to narrow periodically

  • Thisproduces wheezing and breathlessness

  • Obstruction to air flow is reversible


Lung function tests

Bronchodilator Test

  • Evaluates how responsive the patient is to a bronchodilator medication

  • Spirometry is repeated about 15 minutes after giving a bronchodilator (400 mg salbutamol)


Why test for reversibility

WHY TEST FOR REVERSIBILITY?

  • To determine best function

  • To follow rate of change in PFTs over time

  • To exclude asthma

  • To determine response to therapy


Reversibility

REVERSIBILITY

Increase of 200 ml or 12-15% of the baseline FEV1 shows

REVERSIBLE

OBSTRUCTION

40

Both drugs combined

30

20

10

0

0

2

4

6

8


Restriction

Restriction

  • Restriction means a decrease in lung volumes


Extrinsic restrictive lung disorders

Extrinsic Restrictive Lung Disorders

. Neuromuscular Disorders

. Scoliosis, Kyphosis

. Rib fractures

. Pleural Effusion

. Pregnancy

. Gross Obesity

. Tumors

. Ascites


Intrinsic restrictive lung disorders

Intrinsic Restrictive Lung Disorders

  • Pnuemonectomy

  • Pneumonia

  • Lung tumors

  • Interstitial lung diseases

  • Sarcoidosis

  • Lung oedema


Lung function tests

Flow – Volume Loop

is a measure of how much air can be inspired and expired from the lungs

It is a flow rate measurement


Restrictive lung disease

Restrictive Lung Disease

  • Characterized by diminished lung volume

  • Decreased TLC, FVC

  • Normal FEV1/FVC ratio


Large airway obstruction can be detected by flow volume loop

Large Airway Obstruction can be detected by Flow – Volume Loop

  • Characterized by a truncated inspiratory or expiratory loop


Extra thoracic upper airway obstruction

Extra-thoracic Upper Airway Obstruction


Lung function tests

Peak Expiratory Flow Rate PEFR

  • The maximum flow rate during the forced vital capacity maneuver

  • Useful to monitor asthma


Measuring pef

Measuring PEF

PEF must be achieved as rapidly as possible and at a high lung volume as possible

The subject must be encouraged to blow as vigorously as possible


When is pef useful

When is PEF useful?

PEF can be very useful in diagnosing occupational asthma


Arterial blood gases indication

ARTERIAL BLOOD GASES INDICATION

  • Oxygenation

  • Ventilation

  • Acid-Base Status


Arterial blood gases

ARTERIAL BLOOD GASES

  • Blood gases is a measurement of how much oxygen and carbon dioxide is in the blood

  • Determines the acidity (pH) of the blood


Arterial blood gases1

ARTERIAL BLOOD GASES

  • Blood is taken from an artery

  • The blood may be collected from the radial artery, the femoral artery , or the brachial artery


Arterial blood gases2

ARTERIAL BLOOD GASES

  • After the blood is taken, pressure is applied to the site for a few minutes to stop the bleeding

  • The sample must be quickly sent to a laboratory


Blood gas report

Blood Gas Report

  • pH 7.4

  • PaCO2 (mm Hg) 40

  • PaO2 (mm Hg) 110 - 0.5(age)

  • HCO3- (mmol/L) 24

  • B.E. (mmol/L)0

  • O2 saturation >90%


Causes of a low pao 2

Causes of a low PaO2

  • V/Q mismatch

  • Dead space ventilation

  • Shunt

  • Diffusion Impairment

  • Alveolar Hypoventilation

  • Altitude


Alveolar hypoventilation

Alveolar Hypoventilation

  • Reduced Respiratory Drive

  • Pump failure


Analysis of ventilaton

ANALYSIS OF VENTILATON

  • Hypercapnea > 45 mm Hg Hypoventilation

  • Respiratory Acidosis

  • Hypocapnea < 35 mm Hg Hyperventilation

  • Respiratory Alkalosis


Respiratory alkalosis

Respiratory alkalosis

  • Low levels of carbon dioxide in the blood due to alveolar hypervetilation (breathing excessively)


Respiratory acidosis

Respiratory acidosis

  • The kidneys and lungs maintain the body's acid/base (pH) balance

  • Respiratory acidosis develops when carbon dioxide is elevated

  • Primarily caused by alveoler hypoventilation ( decreased breathing)


Pitfalls

Pitfalls

  • Venous Sample

    _PaO2 = 40, PaCO2 = 45

    • Free flow into syringe

  • Air-bubble in syringe

    • Falsely elevated PaO2

  • Arterial blood sample should be transported on ice under anaerobic conditions


Lung function tests

Spirometry is essential in respiratory evaluation as tension arterial measurement is essential in cardiovascular evaluation


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