sema umut. lung factors affecting function mechanical properties resistive elements
TRANSCRIPT
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