sema umut. lung factors affecting function mechanical properties resistive elements

Sema Umut

Lung Factors Affecting FunctionMechanical properties Resistive elements

Mechanical PropertiesCompliance

Describes the stiffness of the lungsChange in volume over the change in pressure

Elastic recoilThe tendency of the lung to return to it’s

resting state

Resistive PropertiesDetermined by airway caliberAffected by

Lung volumeBronchial smooth musclesAirway collapsibility

A TEST SHOULD BEAcceptabile,easyNoninvasiveCost effectiveInformativeReproducible

Acceptabile,easyAcceptabile,easyNoninvasiveCost effectiveCost effectiveInexpensiveInexpensiveInformativeInformativeReproducibleReproducible

SpirometryIt is the most

commonly used lung function screening study

It should be the clinician's first option

When can spirometry help us?

- Diagnosing disease

- Monitoring disease

- Prognosis

- Directing therapy

Indications for Spirometry DiagnosticTo evaluate symptoms, signs, or

abnormal laboratory tests Dyspnea Wheezing CoughAbnormal breath soundsOverinflation Expiratory slowing Cyanosis

Abnormal laboratory tests

Hypoxemia Hypercapnia PolycythemiaAbnormal chest radiographs

To screen individuals at risk of having pulmonary diseases Smokers Individuals in occupations with exposures to injurious substances

Indications for Spirometry

To assess preoperative risk

To assess health status before physical activity programs

To evaluate therapy

Disability/Impairment Evaluations

To assess individuals for legal reasons

Prognosis

Survival predictor ofgeneral population

Copenhagen City Heart Study13,900 subjects for 25 yrs

Lange P. J Clin Epidemiol 1990; 43: 867-873.

Cox proportional hazards

FEV1/ht2 best indexFramingham study

Spirometry Requirements

2. Good technicians (efor dependent) 3. Good clinicians

- correct indication- correct use / presentation of the data- correct decision making

1. Good equipment

Pulmonary Function Testing relates

Age : Smaller lung volumes as we age Gender : The lung volumes of males are

larger than femalesHeightRace

Perform manoeuvre Attach nose clip, place

mouthpiece in mouth Inhale completely and

rapidlyExhale maximally until

no more air can be expelled

Repeat for a minimum of 3 manoeuvres

Forced Vital Capacity FVC

Total volume of air expired forcefully after a full inspiration

Patients with restrictive lung disease have a decreased vital capacity

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

FEV1 Volume of air

expired in the first second during maximal expiratory effort

Forced Expiratory Volume in 1 Second

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

Tidal volume TV

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

RESIDUEL VOLUME (RV)

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

FUNCTIONAL RESIDUEL CAPACITY(FRC)

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

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 Can not be measured by spirometryHelium dilutionNitrogenmetryBody plethysmography

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

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

INTERPRETATION OF SPIROMETRY

Categories of DiseaseObstructiveRestrictiveMixed

Spirogram measures two components - air flow and volume

If flow is reduced, the defect is obstructive

If volume is reduced the defect is restrictive

Interpretation

FVC and FEV1 are normal – NORMAL

FVC is low but FEV1/FVC is >80 RESTRICTIVE

FEV1/FVC < 70% OBSTRUCTIVE

Spirometry

Obstruction (FEVı /FVC) < %70

Obstructive Lung DiseasesAsthma Chronic obstructive pulmonary disease

COPD-COPD is 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

SYMPTOMScoughcough

sputumsputumshortness of breathshortness of breath

EXPOSURE TO RISKFACTORS

tobaccotobaccooccupationoccupation

indoor/outdoor pollutionindoor/outdoor pollution

SPIROMETRYSPIROMETRY

Diagnosis of COPDDiagnosis of COPD

AsthmaAsthma is a chronic inflammatory disease of the airways

Inflammation causes the airways to narrow periodically

This produces wheezing and breathlessness

Obstruction to air flow is reversible

Evaluates how responsive the patient is to a bronchodilator medication

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

Bronchodilator Test

WHY TEST FOR REVERSIBILITY?

To determine best functionTo follow rate of change in PFTs over time

To exclude asthmaTo determine response to therapy

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

0 2 4 6 8

40

30

20

10

0

Both drugs combined

REVERSIBILITY

RestrictionRestriction means a decrease in lung volumes

Extrinsic Restrictive Lung Disorders. Neuromuscular Disorders . Scoliosis, Kyphosis . Rib fractures. Pleural Effusion . Pregnancy. Gross Obesity. Tumors. Ascites

Intrinsic Restrictive Lung Disorders Pnuemonectomy PneumoniaLung tumorsInterstitial lung diseases SarcoidosisLung oedema

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

Characterized by diminished lung volume

Decreased TLC, FVC

Normal FEV1/FVC ratio

Large Airway Obstruction can be detected by Flow – Volume Loop

Characterized by a truncated inspiratory or expiratory loop

Extra-thoracic Upper Airway Obstruction

0 1 2 3 4 5 6

-8

-6

-4

-2

0

2

4

6

8

10

12F

low

in

L/s

Liters

Peak Expiratory Flow Rate PEFR

The maximum flow rate during the forced vital capacity maneuver

Useful to monitor asthma

Measuring PEFPEF 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?

PEF can be very useful

in diagnosing occupationa

l asthma

ARTERIAL BLOOD GASES ARTERIAL BLOOD GASES INDICATIONINDICATIONOxygenationVentilationAcid-Base Status

ARTERIAL BLOOD GASESARTERIAL BLOOD GASESBlood gases is a measurement of how much oxygen and carbon dioxide is in the blood

Determines the acidity (pH) of the blood

ARTERIAL BLOOD GASESARTERIAL BLOOD GASESBlood is taken from an artery The blood may be collected from the radial artery, the femoral artery , or the brachial artery

ARTERIAL BLOOD GASESARTERIAL BLOOD GASESAfter 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 ReportBlood Gas Report

pH 7.4 PaCO2 (mm Hg) 40

PaO2 (mm Hg) 110 - 0.5(age)

HCO3- (mmol/L) 24

B.E. (mmol/L) 0O2 saturation >90%

Causes of a low PaOCauses of a low PaO22

V/Q mismatchDead space ventilationShuntDiffusion ImpairmentAlveolar HypoventilationAltitude

Alveolar HypoventilationAlveolar Hypoventilation

Reduced Respiratory Drive Pump failure

ANALYSIS OF VENTILATONANALYSIS OF VENTILATON

Hypercapnea > 45 mm Hg Hypoventilation

Respiratory Acidosis

Hypocapnea < 35 mm Hg Hyperventilation

Respiratory Alkalosis

Respiratory alkalosis

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

Respiratory acidosisThe 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)

PitfallsVenous Sample _PaO2 = 40, PaCO2 = 45

Free flow into syringeAir-bubble in syringe

Falsely elevated PaO2 Arterial blood sample should be

transported on ice under anaerobic conditions

Spirometry is essential in respiratory evaluation

as tension arterial measurement is essential

in cardiovascular evaluation