Respiratory Function Tests RFTs
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Respiratory Function Respiratory Function Tests RFTsTests RFTs
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Review Of Anatomy & Review Of Anatomy & physiologyphysiology
Lungs comprised of AirwaysAlveoli
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Mechanics of BreathingMechanics of BreathingInspiration
◦Active process caused mainly by contraction of diaphragm . Accessory muscles may used during exercise and distress
Expiration◦Quiet breathing is a passive process
but can become active , with forced expiration
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Lung Volumes
IRV
TV
ERV
RV
IC
FRC
VC
TLCTLC
RV
4 Volumes4 Capacities
◦Sum of 2 or more lung volumes
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Tidal Volume (TV)Tidal Volume (TV)
IRV
TV
ERV
RV
IC
FRC
VC
TLC
RV
Volume of air inspired or expired during normal quiet breathing
TV = 500 ml
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The Inspiratory Reserve Volume IRVThe Inspiratory Reserve Volume IRV
The extra volume of air that can be inspired over and above the normal tidal volume , when person inspires with full force
IRV= 3000 ml
IRV
TV
ERV
RV
IC
FRC
VC
TLC
RV
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The extra volume of air that can be exhaled over normal tidal volume when person expires forcefully
ERV= 1100ml
Expiratory Reserve Volume Expiratory Reserve Volume (ERV)(ERV)
IRV
TV
ERV
RV
IC
FRC
VC
TLC
RV
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Residual Volume (RV)Residual Volume (RV)
IRV
TV
ERV
Volume of air remaining in the lungs at the end of maximum expiration.
RV =1200 ml
RV
IC
FRC
VC
TLC
RV
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Vital Capacity (VC)Vital Capacity (VC)
IRV
TV
ERV
The maximum amount of air a person can expel from the lungs after filling the lungs to their maximum extent and then expires to the maximum extent. Also called Forced vital capacity FVC
VC=4600ml VC=IRV+TV+ERV
RV
IC
FRC
VC
TLC
RV
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Inspiratory Capacity (IC)Inspiratory Capacity (IC)
IRV
TV
ERV
The amount of air a person can breathe in beginning at the normal expiratory level and distending the lung to the maximum amount.
IC = IRV + TV IC= 3500ml
RV
IC
FRC
VC
TLC
RV
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Functional Residual Capacity Functional Residual Capacity (FRC)(FRC)
IRV
TV
ERV
Volume of air remaining in the lungs at the end of a normal expiration
FRC = ERV + RV FRC= 2300 ml
RV
IC
FRC
VC
TLC
RV
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Total Lung Capacity (TLC)Total Lung Capacity (TLC)
IRV
TV
ERV
Volume of air in the lungs after a maximum inspiration
TLC = IRV + TV + ERV + RV
=5800ml
RV
IC
FRC
VC
TLC
RV
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Factors affecting lung Factors affecting lung volumevolumeAgeSexHeightWeightRaceDisease
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CLINICAL SIGNIFICANCE CLINICAL SIGNIFICANCE VC% < 80% is abnormalRV/TLC% (residual air rate) normal : < 35% emphysema: > 40 % old person can be 50%.FRC ↑ : emphysema
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Value of Respiratory function Value of Respiratory function teststests
Evaluates 1 or more major aspects of the respiratory system◦Lung volumes◦Airway function◦Gas exchange
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IndicationsIndications
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PFTsPFTs
1. Arterial blood gases2. Blood PH3. Pulse oximeter 4. Peak flow meter measuring
peaked expiratory flow rate.5. Spirometry
1. Arterial blood gases2. Blood PH3. Pulse oximeter 4. Peak flow meter measuring
peaked expiratory flow rate.5. Spirometry
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Peak flow meter measuring Peak flow meter measuring peaked expiratory flow rate peaked expiratory flow rate PEFRPEFR
This is extremely simple and cheap test
It describes maximal airflow rate in a given time.
It measures the airflow through the bronchi and thus the degree of obstruction in the airways.
Is best for monitoring the progression of disease
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ContCont..…..…it can detect airway narrowing,
commonly used in asthma, Even by the patient himself to know when he need an emergency interference.
the effectiveness of a person's asthma management and treatment plan.
when to stop or add medication, as directed by physician.
what triggers the asthma attack (such as exercise-induced asthma )
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To perform this testTo perform this test
Loosen any tight clothing that might restrict your breathing.
Sit up straight or stand while performing the tests
Breathe in as deeply as possible. Mouthpiece is placed in mouth with
lip sealed to prevent escape of airBlow into the instrument's
mouthpiece as hard and fast as possible.
Do this three times, and record the highest flow rate.
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Normal values vary based on a person's age, sex, and size
Normal person can empty their chest from full inspiration in 4 sec or less
Prolongation to more than 6 sec indicates airflow obstruction
A fall in peak flow can signal the onset of a lung disease flare, especially when it occurs with symptoms such as:
Shortness of breath Increased cough Wheezing
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SPIROMETRYSPIROMETRY Simple, office-based
Measures flow, volumes
Volume vs. Time
Can determine:- Forced expiratory volume in one
second (FEV1)- Forced vital capacity (FVC)- FEV1/FVC
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• Old version
– spirometer bell– kymograph pen
• New version
– portable
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Indications of Spirometry:Indications of Spirometry:diagnostic and prognosticdiagnostic and prognostic Evaluation of signs and symptoms of
pulmonary diseases like asthma and COPD
Screening at-risk populations male smokers >45 years
Preoperative assessment Assess severity of diseases Follow up response to therapy Determine further treatment goals
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A spirometer can be used to measure the following:◦ FVC and its derivatives (such as FEV1, FEF
25-75%)◦ Forced Inspiratory vital capacity (FIVC)◦ Peak expiratory flow rate◦ Maximum voluntary ventilation (MVV)◦ Slow VC◦ IC, IRV, and ERV◦ Pre and post bronchodilator studies
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TerminologyTerminology Forced vital
capacity (FVC):– Total volume of air
that can be exhaled forcefully from TLC
– The majority of FVC can be exhaled in <3 seconds in normal people, but often is much more prolonged in obstructive diseases
– Measured in liters (L)
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FVCFVCInterpretation of % predicted:
◦80-120% Normal◦70-79% Mild reduction◦50%-69% Moderate reduction◦<50% Severe reduction
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FEV1FEV1Forced expiratory
volume in 1 second: (FEV1)◦ Volume of air
forcefully expired from full inflation (TLC) in the first second
◦ Measured in liters (L)◦ Normal people can
exhale more than 75-80% of their FVC in the first second; thus the FEV1/FVC can be utilized to characterize lung disease
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FEV1FEV1Interpretation of % predicted:
◦>75% Normal◦60%-75% Mild obstruction◦50-59% Moderate obstruction◦<49% Severe obstruction
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TechniqueTechnique Have patient seated comfortablyClosed-circuit technique
◦Place nose clip on◦Have patient breathe on mouthpiece◦Have patient take a deep breath ◦Blow out the air as fast as possible
and as hard and long as possible
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Flow Volume LoopFlow Volume Loop
“Spirogram”
Measures forced Inspiratory and expiratory flow rate
Augments Spirometry results
Indications: evaluation of upper airway obstruction (stridor, unexplained dyspnea)
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Flow-Volume Loop
Illustrates maximum expiratory and Inspiratory flow-volume curves
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Obstructive Disorders◦ Characterized by a
limitation of expiratory airflow so that airways cannot empty as rapidly compared to normal (such as through narrowed airways from bronchospasm, inflammation, etc.)
Examples:◦ Asthma◦ Emphysema◦ Cystic Fibrosis
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Obstructive Disorders
Characterized by a limitation of expiratory airflow
Decreased: FEV1, FEV1/FVC ratio (<0.8)
Increased or Normal: TLC
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Spirometry in Obstructive Disease
Slow rise in upstroke May not reach plateau
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Restrictive Lung Disease
Characterized by diminished lung volume
Decreased TLC, FVC Normal FEV1 Normal or increased:
FEV1/FVC ratio
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Restrictive Disease
Rapid upstroke as in normal Spirometry
Plateau volume is low
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Bronchial Dilation TestBronchial Dilation TestMethod: to determine FEV1 and
FEV1/FVC% before and after ß2-agonist inhalation
Result: improved rate = after-before ×100%
before Positive: >15%Reversible limitation: asthma