pulmonary function testing (spirometry )

Pulmonary Function testing(Spirometry )

Dr. Emad EfatShebin El kom Chest hospital

July 2016

PFTs - Significance

1. Pulmonary Function tests (PFTs) Help in diagnosis and differentiation of many respiratory diseases (restrictive and obstructive lung disorders, diagnose exercise induced asthma, differentiate chronic bronchitis from Bronchial asthma (BA) )

2. Explain the cause of symptoms in patients who are diseased and clinically normal (as early detection of small air way disease)

3. Assessing the course of the disease and effect of therapy (as steroids with Bronchial asthma and radiotherapy with cancer)

4. Objective quantitative measurements of lung damage due to occupational injury

5. Pre-operative assessment

PFTs - Classification

1. Tests of ventilatory function:

Evaluate lung volumes and capacities:

• Spirometry (FVC, FEV1, FEF25-75, MVV)

• Body plethysmography

• Gas dilution method (functional residual capacity (FRC) and residual volume (RV) detection)

Evaluate hypersensitivity: broncho-provocative test

2. Tests for gas exchange: tests of diffusion (DLCo, ABGs) Oximetry for O2 saturation and Capnographyfor trans-cutaneous CO2

PFTs - Classification

3. Other Tests:

Tests for lung compliance

Tests for resistance and impedance: impulse oscillometry

Assessment of regional lung functions

Cardio-pulmonary stress tests (CPX) and assessment of respiratory muscle strength

Breath condensate

Spirometry

• Spirometry with flow volume loops assesses the mechanical properties of the respiratory system by measuring expiratory volumes and flow rates.

• Maximal inspiratory and expiratory effort.

• At least 3 tests of acceptable effort are performed to ensure reproducibility.

ways of representing the spirometry test

Spirometry

Acceptability and Reproducibility Criteria:

1. Acceptability criteria (within maneuver criteria):

Individual spirograms are "acceptable" if:

Lack of artifact induced by coughing, glotticclosure, or equipment problems (primarily leak).

Satisfactory start to the test without hesitation or coughing for the 1st second.

Satisfactory exhalation with 6 seconds of smooth continuous exhalation, or a reasonable duration of exhalation with a plateau of at least 1 second.

Spirometry - Acceptability criteria

Cough Variable Effort

Spirometry - Acceptability criteria

Sub maximal effort

Trace does not curve upwards smoothly

Abnormal Forced vital capacity (FVC):

Early stoppage

• Trace does not curve smoothly up to a plateau

• Affects the volume of the Forced vital capacity

Abnormal Forced vital capacity

Coughing Trace is irregular

Extra inhalation during coughing will affect volume of FVC

Coughing is a common problem with bronchial

hyper reactivity.


Extra breath• Trace is not smooth and upward

• Extra breath has affected the volume of the FVC

• Affect FEV1 \ FVC giving a falsely low ratio.


Slow start

Patient has not

made a maximum

effort from the start

of the blow

Affects the volume

FEV1 and FEV1 to

FVC


acceptable & unacceptable spirometric curves

Again, acceptable & unacceptable spirometric curves

2. Reproducibility criteria (Between maneuver criteria)

After 3 acceptable spirograms have been obtained, apply the following tests:

Are the two largest FVC within 0.2 L of each other?

Are the two largest FEV1 within 0.2 L of each other?

PEF values may be variable (within 15%).

If these criteria are met, the test session may be concluded.

Best two blows within 5% or 200ml of each other.

Spirometry - Reproducibility criteria

If these criteria are not met, continue testing until:

The criteria are met with analysis of additional acceptable spirograms; OR

A total of 8 tests have been performed; OR

The patient cannot or should not continue

Save at a minimum the three best maneuvers


Spirometry - Indications

• Indications:

1. Diagnostic

A. To evaluate symptoms, signs or abnormal laboratory tests Symptoms: dyspnea, wheezing, orthopnea, cough, phlegm

production, chest pain

Signs: diminished breath sounds, overinflation, expiratory slowing, cyanosis, chest deformity, unexplained crackles

Abnormal laboratory tests: hypoxemia, hypercapnia, polycythemia, abnormal chest radiographs

B. To measure the effect of disease on pulmonary function


C. To screen individuals at risk of having pulmonary disease:

Smokers

Individuals in occupations with exposures to injurious substances

Some routine physical examinations

D. To assess pre-operative risk

E. To assess prognosis (lung transplant ...etc.)

F. To assess health status before beginning strenuous physical activity programs


2. Monitoring

To assess therapeutic intervention

Bronchodilator therapy

Steroid treatment for asthma, interstitial lung disease (ILD), etc.

Management of congestive heart failure

Other (antibiotics in cystic fibrosis, etc.)

To describe the course of diseases that affect lung function

• Pulmonary diseases (Obstructive airway diseases, ILD)

• Cardiac diseases (Congestive heart failure)

• Neuromuscular diseases (Guillian-Barre Syndrome)


To monitor people exposed to injurious agents

To monitor for adverse reactions to drugs with known pulmonary toxicity

3. To identify flow-volume loop patterns

4. Disability/impairment evaluations To assess patients as part of a rehabilitation program (medical,

industrial, vocational)

To assess risks as part of an insurance evaluation

To assess individuals for legal reasons

5. Public healthEpidemiological surveys and Derivation of reference equations

Clinical research

Spirometry

• Contraindications to Use of SpirometryUncooperative patient and Severe dyspnoea

Infectious diseases (TB) and Hemoptysis of unknown origin

Pneumothorax

Recent myocardial infarction or unstable angina

Acute disorders (e.g., vomiting, nausea, vertigo) .

Recent abdominal or thoracic surgery

Recent eye surgery (increases in intraocular pressure during spirometry)

Thoracic aneurysms (risk of rupture because of increased thoracic pressure)

N.B Spirometry should be avoided after recent heart attack or stroke

Spirometry

• Performing Spirometry

How to do it ?? 1. Withholding Medications Before performing

spirometry, withhold:

Short acting β2-agonists for 6 hours

Ipratropium for 6 hours

Long acting β2-agonists for 12 hours

Tiotropium for 24 hours

Spirometry - Preparation

2. Preparation

Explain the purpose of the test and demonstrate the procedure

Record the patient’s age, height and gender

Note when bronchodilator was last used

The patient sits comfortably

Loosen any tight clothing

Empty the bladder

Breath in until the lungs are full

Spirometry - Preparation

Hold the breath and seal the lips tightly around a clean mouthpiece

Blast the air out as forcibly and fast as possible. Provide lots of encouragement!

Continue blowing until the lungs feel empty

Watch the patient during the blow to assure the lips are sealed around the mouthpiece

Check to determine if an adequate trace has been achieved

Repeat the procedure at least twice more until ideally 3 readings within 5% of each other are obtained.

Spirometry - Quality Control

• Most common cause of inconsistent readings is poor patient technique

• Sub-optimal inspiration

• Sub-maximal expiratory effort

• Delay in forced expiration

• Shortened expiratory time

• Air leak around the mouthpiece

• Subjects must be observed and encouraged throughout the procedure

Inadequate or incomplete blow & Lack of blast effort during exhalation

Slow start to maximal effort

Lips not sealed around mouthpiece

Coughing during the blow & Extra breath during the blow

Glottic closure or obstruction of mouth piece by tongue or teeth

Poor posture – leaning forwards

Spirometry - Common Problems

Spirometry - Lung volumes

Lung volumes that can be measured by spirometer:

1. Static Lung Volumes: Lung volumes that are notaffected by the rate of air movement in and out of the lungs (VT, IRV, ERV, IC and VC).

CAN’T MEASURE – FRC, RV, TLC. It can be measured by:

nitrogen washout technique

Helium dilution method

Body plethysmography

2. Dynamic Lung Volumes: Lung volumes that depend upon the rate at which air flows out of the lungs (FVC, MVV, FEF 25–75, MRV and FEV1)

Lung Volumes and Capacities - Static

Respiratory Volumes - Static

• Static Lung Volumes and Capacities: 4 Volumes

4 Capacities: Sum of 2 or more lung volumes

1. Tidal volume (Vt), about 500 mL, is the amount of air inspired during normal, relaxed breathing.

2. Inspiratory reserve volume (IRV), about 3,100 mL, is the additional air that can be forcibly inhaled after the inspiration of a normal tidal volume.

3. Expiratory reserve volume (ERV), about 1,200 mL, is the additional air that can be forcibly exhaled after the expiration of a normal tidal volume.

4. Residual volume (RV), about 1,200 mL, is the volume of air still remaining in the lungs after the expiratory reserve volume is exhaled.

1. Slow vital capacity (SVC): maximum amount of air that can be expired after deep inspiration by slow expiration

2. Forced (Timed) vital capacity(FVC): maximum amount of air that can be expired after deep inspiration by forced expiration

1. Vital capacity (VC), about 4,800 mL, is the total amount of air that can be expired after fully inhaling.

Vt IRV ERV VC

Respiratory Capacities - Static

Normal Slow vital capacity

• The curve is 1. Smooth

2. Has no irregularities

3. Curves upwards

4. Reaches a plateau

• FVC is read at the

top of the curve,

where it reaches a

plateau

SVC FVC

SVC FVC

SVC FVCX

2. Function residual capacity (FRC), about 2,400 mL, is the amount of air remaining in the lungs after a normal expiration.


ERV RV FRC

3. inspiratory capacity (IC), about 3,600 mL, is the maximum amount of air that can be inspired (IC = TV + IRV).

4. Total lung capacity (TLC), about 6,000 mL, is the maximum amount of air that can fill the lungs (Vt +IRV+ ERV+ RV) { VC+RV}

TLC < 80% of predicted value = restriction.

TLC > 120% of predicted value = hyperinflation.

VC RV TLC

Vt IRV ERV RV TLC


Relationship between VC, RV, and TLC

VCVC

VC

RV RV

RV

Normal RV\ TLC20-35%

Restrictive RV\ TLC≤20-35%

Obstructive RV\ TLC>35%

Dynamic Lung Volumes: Lung volumes that depend upon the rate at which air flows out of the lungs (FVC, FEV1, FEF 25–75, MVV, and MRV)

Minute Respiratory Volume (MRV) : quantity of air moved into and out of the lungs in one minute (TVx Respiratory rate).

Respiratory Volumes - dynamic

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)

Forced vital capacity (FVC)

• Interpretation of % predicted:

80-120% Normal

70-79% Mild reduction

50%-69% Moderate reduction

<50% Severe reduction

Forced 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


Normal >75%

Mild 70-75%

Moderate 50-69 %

Severe 35-49%

Very severe < 35%

Forced expiratory volume in 1 second (FEV1)

• Mean forced expiratory flow during middle half of FVC

• Measured in L/sec

• May reflect effort independent expiration and the status of the small airways

• Highly variable

• Depends heavily on FVC

Forced expiratory flow 25-75% (FEF25-75)


>60% Normal

40-60% Mild obstruction

20-40% Moderate obstruction

<20% Severe obstruction

Forced expiratory flow 25-75% (FEF25-75)

• FEV1/FVC ratio: It indicates what percentage of the total FVC was expelled from the lungs during the first second of forced exhalation

• A ratio of <70% implies obstructive disease

• If the patient has a restrictive ventilatory defect, the FEV1 and FVC are both reduced, but in proportion, so the FEV1/FVC ratio remains normal (greater than 75%).

FEV1/FVC ratio

• It is also called the maximal breathing capacity (MBC).

• It's the maximum volume of air which can be respired in 1minute by deepest and fastest breathing (test of entire respiratory system).

• Normal value: male: 80-200 L/min, female: 60-160 L/min.

• Measured by: breathing deeply and rapidly for 15 sec.

• Significance:

Index for respiratory efficiency and physical fitness

Respiratory muscle assessment.

Pre-operative assessment.

• MVV= FEV1 X35

Maximum voluntary ventilation (MVV)

Maximum voluntary ventilation (MVV)

• It's the maximum flow rate over the first 10 milliseconds of forced expiration (first part of FEV1).

• Normal value: 10 L/s (600 L/min) in healthy adult.

• Measured by peak flow meters

• Significance:

Diagnosis of Bronchial asthma ( BA ) variability >15-20 % in PEFR in a single day or from day to day is diagnostic.

Response to treatment in BA

Diagnosis of occupational asthma , and exercise induced asthma (fall of FEV1 >15%)

Peak expiratory flow (PEF)

Peak Flow Meter

Spirometry

Tests of Ventilation

Peak flow meters

1. Normal

2. Obstructive

3. Restrictive

4. Mixed Obstructive and Restrictive

Spirogram Patterns

Criteria for Normal Post-bronchodilator Spirometry

FEV1: % predicted > 80%

FVC: % predicted > 80%

FEV1/FVC: > 0.7

Spirogram Patterns

Obstruction caused by: Restrictions caused by:

COPD

BA

Bronchiolitis

Pneumonia

Bronchiectasis

Cystic fibrosis

Acute bronchitis

Alpha1 anti-trypsin

deficiency

Obesity

Pregnancy

Ascitis

Interstitial lung disease

Kyphoscoliosis

Pleural effusion

Pleural tumors

Neuromuscular disease

Diaphragmatic abnormality

Lung resection

Congestive heart failure

Inability to breathe (pain)

Severe obstructive disorders

Cardiomegally

• Criteria: Obstructive Disease

FEV1: % predicted < 80% ( used to grade the severity )

FVC: Can be normal or reduced – usually to a lesser degree than FEV1

FEV1/FVC: < 0.7

SPIROMETRY OBSRUCTIVE DISEASE

• Criteria: Restrictive Disease

FEV1: % predicted < 80%

FVC: % predicted < 80%

FEV1/FVC: > 0.7

SPIROMETRY RESTRICTIVE DISEASE

• Criteria: Mixed Obstructive/Restrictive

FEV1: % predicted < 80%

FVC: % predicted < 80%

FEV1 /FVC: < 0.7

SPIROMETRY Mixed Obstructive/Restrictive

Measures of Assessment and Monitoring of Asthma

• Asthma diagnosis criteria:

Repeated variability in well-performed spirometic values (increase in FEV1 or FVC).

Positive bronchodilator (BD) responses (increase in FEV1 or FVC ⩾12% and 200 mL from baseline).

Positive methacholine challenge (20% fall in FEV1 at a dose ⩽8 μg/mL).

Objective lung function measurements in Asthma:

Spirometry:

Forced Expiratory Maneuvers.

Exhaled Nitric Oxide.

Peak Flows.

FEV1 Results for Asthma

Positive bronchodilator responses in asthma

GOLD 2013: Diagnosis of COPD

At Risk for COPD

Spirometric classification of airflow limitation

• Adapted from GOLD 2013

in patients with FEV1/FVC < 0.70

GOLD 1 MildFEV1 ≥80%

predicted

GOLD 2 Moderate50% ≤FEV1 <80%

predicted

GOLD 3 Severe30% ≤FEV1 <50%

predicted

GOLD 4 Very severeFEV1 <30%

predicted

Changes in Lung Volumes in Various Disease States

• Total lung capacity ( TLC ) < 80% of predicted value = restriction.

• TLC > 120% of predicted value = hyperinflation.

Volume Restrictive Air trapping Hyperinflation

TLC ↓ N ↑

VC ↓ ↓ N

FRC ↓ ↑ ↑

RV ↓ ↑ ↑

RV/TLC% N ↑ ↑

Changes in Lung Volumes in Various Disease States

Bronchodilator Reversibility Testing

Provides the best achievable FEV1 (and FVC)

Helps to differentiate COPD from asthma

Must be interpreted with clinical history - neither

asthma nor COPD are diagnosed on spirometry alone

bronchodilating agents:

Bronchodilator DoseFEV1 before and

after

Salbutamol 200 – 400 µg via large

volume spacer15 minutes

Terbutaline 500 µg via Turbohaler® 15 minutes

Ipratropium 160 µg via spacer 45 minutes


• Preparation

• Tests should be performed when patients are clinically stable and free from respiratory infection

• Patients should not have taken: Withholding Medications:

Bronchodilator Reversibility Testing - Spirometry

1. FEV1 should be measured (minimum twice, within 5%)before a bronchodilator is given.

The bronchodilator should be given by metered dose inhaler through a spacer device or by nebulizer to be certain it has been inhaled

2. FEV1 should be measured again:

10-15 minutes after a short-acting b2-agonist

30-45 minutes after the combination

The test is considered significant if there is

> 12% increase in the FEV1 and 200 ml improvement in FEV1 OR

> 12% increase in the FVC and 200 ml improvement in FVC.

• To express the degree of improvement: • Calculate the absolute changes in FEV1

• Calculate the absolute changes in FEV1 from base line

• % improvement in FEV1=

FEV1 (post BD)- FEV1 (base line) X100

FEV1 (base line)

Measuring degree of reversibility


- Spirometry

Normal flow volume loop has a rapid peak expiratory flow rate with a gradual decline in flow back to zero.

Flow Volume Loop

• As with a normal

curve, there is a

rapid peak

expiratory flow, but

the curve descends

more quickly than

normal and takes on

a concave shape

Flow Volume Loop in Obstructive lung disease

Obstruction

ObstructionNormal

Restriction

The shape of the flow volume loop:

1. Relatively unaffected in restrictive disease

2. Overall size of the curve will appear smaller when compared to normal on the same scale.

Flow Volume Loop in restrictive lung disease

Flow Volume Loop

Spirometry interpretation

1.

Assess validity

2.

Determine ventilatory pattern

3.

Grade severity

4.

Grade response to BD challenge

Interpreation of results

Take the best ofthe 3 consistent readings

of FEV1 and of FVC

Predicted Normals = Predicted Value

Depends on:

1. Age

2. Sex

3. Height

4. Race

Results classification

1. Normal

2. Obstructive

3. Restrictive

4. Combined

1. Obstructive

Pattern

2. Restrictive

Pattern

3.

Mixed Pattern

Abnormalities of lung function are categorized as:

Value (95 % function test confidence interval)

BMI 21- 25 kg/m2

FEV1 80-120%

FVC 80-120%

FEV1 /FVC > 80%

FEF 25-75% 65

TLC 80-120%

FRC 75-120%

RV 75- 120%

RV/TLC 20-35%

FRC/TLC 50%

Normal Values of Pulmonary Function Tests

Objective Measures: Spirometry

Is airflow obstruction present and is it at least partially reversible?

Use Spirometry to establish airflow

obstruction

1. FEV1/FVC <70%

2. FEV1 < 80%

Use Spirometry to establish reversibility

1. FEV1 increases >12% and at least 200 ml. after using inhaled SABA

2. A 2- to 3-week trial of oral corticosteroid therapy may be required to demonstrate reversibility

1. Patients data (age, sex, body weight, height)

BMI

2. Expiratory Time

3. Static lung volume

4. Dynamic lung volume (FEV1\ FVC, FEV1,

FVC, PEFR, PIFR, FEF25-75)

5. MVV

Interpretation of Spirometry

1). BMI= weight \ kg

(Height m)2


21-25

Normal

BMI

No effect

on PFT

< 21

Under

weight

Nutrition

suppleme

ntation

> 25

>25 < 30 >30 < 40 >40

Morbid

obesityObese

Over

weight

Restrictive pattern on

PFT

2). Expiratory Time


Expiratory Time

< 4 sec.

Poor initial effort

Restrictive

Pattern

Respiratory muscle

weakness

> 6 sec.Obstructive

Pattern

Normal

4-6 sec.

• imp NB: - Marked prolongation of exp.

Time denote either:-

Incorrect test …..or

Resp. center depression → drug overdose,

brain stem infarction, head trauma, bilat.

diaphragmatic paralysis→ all of these causes

mean marked noncompliance & incorrect test


3). SVC


SVC

< 80

Restrictive pattern

Severe obstructive

pattern

Combined pattern

80 - 120

Normal

• imp NB:-

– From TV we can calculate minute

ventilation

– MV= TV X RR (from Exp. T)

– FVC slightly less than SVC , but if there

is marked disparity → one of 2 tests is

incorrect


SVC FVC

SVC FVC

SVC FVCX

4). Dynamic lung volume:

• FEV1\ FVC


FEV1\ FVC 80-120 %

Nor. Or ↑

Normal

Restrictive

70 -80% Combined

< 70 % Obstructive


FVC

< 80%

Restrictive pattern

Severe obstructive

pattern

Combined pattern

80 – 120%

Normal


• FVC


• FEV1: 75 -85%


↓FEV1

Marked↓↓ Obstructive

slight↓ Restrictive

Combined


• FEF 25 -75 % : 65 % (4-5 L\ S)

• Denote small airway diseases

• The only ventilatory parameters effort

independent



• maximal voluntary ventilation (MVV)

MVV

Decrease

Obstructive Restrictive Resp. muscle

weakness

Neuro

muscular

Normal or↑↑

Restrictive Normal



All parameters of obstructive lung defects are similar to that of combined defects and differentiated only by TLC


Normal or increase TLC

Obstructive pattern

Decrease TLC

Combined

Pattern

Interpreation of results of Spirometry

• Step 1. Look at the Flow-Volume loop to determine acceptability of the test, and look for upper airway obstruction pattern.

• Step 2. Look at the FEV1 to determine if it is normal (≥ 80% predicted).

• Step 3. Look at FVC to determine if it is within normal limits (≥ 80%).

• Step 4. Look at the FEV1/FVC ratio to determine if it is within normal limits (≥ 70%).

• Step 5. Look at FEF25-75% (Normal (≥ 60%)


• If FEV1, FEV1/FVC ratio, and FEF25-75% all are normal, the patient has a normal PFT.

• If both FEV1 and FEV1/FVC are normal, but FEF25-75% is ≤ 60% ,then think about early obstruction or small airways obstruction.

• If FEV1 ≤ 80% and FEV1/FVC ≤ 70%, there is obstructive defect, if FVC is normal, it is pure obstruction. If FVC ≤ 80% , possibility of additional restriction is there.

• If FEV1 ≤ 80% , FVC ≤ 80% and FEV1/FVC ≥ 70% , there is restrictive defect, get lung volumes to confirm.


• Different patterns: Mixed

A reduced FVC together with a low FEV1/FVC%

ratio is a feature of a mixed ventilatory defect,

or air trapping.

It is necessary to measure the patient's total

lung capacity to distinguish between these two

possibilities.

FEV1\FVC

> 70%

Normal or restrictive

< 70 %

Obstructive

FVC or TLC

Decrease Normal

Normal Spirometry

Restrictive

DLCO

Normal chest wall

↓ Lung diseases

FEV1 (severity)

FVC

↓↓Normal

or ↓

TLC

↓ combined ↑↑

Pseudo- restriction

Pure

Obstruction

Again , more simple

Parameter Obstructive Combined Restrictive

Expiratory time > 6 sec. <4-4 sc. < 4 sec.

FEV1 \ FVC ↓70% 70-79% Normal or ↑

FVC Normal or ↓ ↓ ↓↓

FEV1 Marked ↓↓ ↓ Normal or

slightly ↓

PEFR ↓↓ ↓ Normal or ↑with

linear ↓in flow

vs. lung volume

PEF 25-75% ↓↓ (COPD) ↓ Normal or ↓↓

MVV ↓↓ ↓↓ ↓

TLC Normal or ↑ ↓ ↓↓

Classification of Ventilatory Abnormalities by Spirometry

• Normal• SVC=FVC ≥ 80%

• FEV1 ≥ 80%

• FEV1\FVC (IVC) ≥ 80%

• FEF 25-75 ≥ 65%

• FEF50\ FIF50≤ 1

• ET= 4-6 sec

• MVV (male 80-200 L, female 60-160 L)

• Obstruction• SVC=FVC = 80% N

• FEV1

• FEV1\FVC (IVC)

• FEF 25-75 < 65%

• FEF50\ FIF50 ≤ 0.3

• ET= ≥ 6 sec

• MVV

• Restrictive • SVC=FVC

• FEV1 N

• FEV1\FVC (IVC) N \

• FEF 25-75 ≥ 65%

• FEF50\ FIF50≤ 1

• ET= 4

• MVV (male 80-200 L, female 60-160 L)

FVC NORMALFVC < 80% Pred.

80%

Normal Lungs

FEV1÷FCV is N

Obstructive Disease

FEV1÷FCV is Low

Restrictive Disease

FEV1÷FCV is High

Combined Obs+Res

FEV1÷FCV is N or L

The Four Square GameF

EV

1 N

OR

MA

LF

EV

1<

80

% o

f P

d.

80%

In normal subject: FIF 50% or MIF50% is usually greater than FEF50%

SO, FEF50% / FIF50% → <1

Upper airway obstruction


FEF50 %

FIF50%

(MEF 50\ MIF 50%)

1 or near 1

MEF 50= MIF 50%

Fixed large airway

obstruction

High (> 1)

FIF50%

Variable extra-thoracic airway

obstruction

Very low (0.3)

FEF50%

Variable intra –thoracic air way

obstruction

1. If FEF50% / MIF50% → Less than 1→ normal2. If FEF50% = MIF50% or FEF50% / MIF50% → 1 or near 1→

fixed large airway obstructionDD:- goiters, Neoplasm, foreign body, or stricture from previous intubationNB:- Observe FEV1 & FIV1 are nearly equal.

3. If FEF50% / MIF50% → High (usually greater than 2) →variable extra thoracic airway obstruction e.g.: vocal cord paralysis, thyromegaly, tracheomalacia, or neoplasm

NB:- Observe FEV1 is greater than FIV1 .

4. If FEF50% / MIF50% → Very low (may reach 0.3) →variable intra thoracic airway obstructione.g.: tracheomalacia or neoplasmNB:- Observe FEV1 is lower than FIV1


Upper Airway Obstruction

• Truncation of flow loop:

Expiratory – Intra Thoracic

Inspiratory –Extra Thoracic

Both – Fixed Obstruction

Patterns of Abnormality

Thank you

pulmonary function testing (spirometry )

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