Pulmonary function testing (spirometry )

Pulmonary Function testing
(Spirometry )
Dr. Emad Efat
Shebin 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 Capnography
for 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, glottic
closure, 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 health
Epidemiological surveys and Derivation of reference equations
Clinical research

Spirometry
• Contraindications to Use of Spirometry
Uncooperative 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 not
affected 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

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
VC
VC
VC
RV RV
RV
Normal RV TLC
20-35%
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

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.

Positive bronchodilator responses in asthma

At Risk for COPD
Spirometric classification of airflow limitation
• Adapted from GOLD 2013
in patients with FEV1/FVC < 0.70
GOLD 1 Mild
FEV1 ≥80%
predicted
GOLD 2 Moderate
50% ≤FEV1 <80%
predicted
GOLD 3 Severe
30% ≤FEV1 <50%
predicted
GOLD 4 Very severe
FEV1 <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 Dose
FEV1 before and
after
Salbutamol
200 – 400 µg via large
volume spacer
15 minutes
Terbutaline 500 µg via Turbohaler® 15 minutes
Ipratropium 160 µg via spacer 45 minutes

Bronchodilator Reversibility Testing
• 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

Bronchodilator
Reversibility Testing
- 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

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

Spirometry interpretation
1.
Assess validity
2.
Determine
ventilatory pattern
3.
Grade severity
4.
Grade response
to BD challenge

Interpreation of results
Take the best of
the 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
obesity
Obese
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

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.

FEV1FVC
> 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

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%
• FEV1FVC (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
• FEV1FVC (IVC)
• FEF 25-75 < 65%
• FEF50 FIF50 ≤ 0.3
• ET= ≥ 6 sec
• MVV
• Restrictive
• SVC=FVC
• FEV1 N
• FEV1FVC (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 GameFEV1NORMALFEV1<80%ofPd.
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→ normal
2. If FEF50% = MIF50% or FEF50% / MIF50% → 1 or near 1→
fixed large airway obstruction
DD:- goiters, Neoplasm, foreign body, or stricture from
previous intubation
NB:- 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 obstruction
e.g.: tracheomalacia or neoplasm
NB:- Observe FEV1 is lower than FIV1

Upper Airway Obstruction
• Truncation of flow loop:
Expiratory – Intra Thoracic
Inspiratory –Extra Thoracic
Both – Fixed Obstruction

Pulmonary function testing (spirometry )

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