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Spirometry in practice
1. Spirometry
in Practice
• A technique used to measure air flow in and out of the
lungs.
• A recording of lung volumes and capacities defined by
the respiratory process. These recordings may be static
(untimed) or dynamic (timed).
• Assesses the integrated mechanical functions of lungs,
chest wall and respiratory muscles.
•The gold standard for diagnosis, assessment and
monitoring of COPD.
• Better than PEFR (which is effort dependent) for
demonstrating airway obstruction in BA.
• The most commonly used PFT.
2. Indications
• Measure airflow obstruction to help make a definitive
diagnosis of COPD
• Detect airflow obstruction in smokers who may have few
or no symptoms
• Assess one aspect of response to therapy
• Perform pre-operative assessment
• Distinguish between obstruction and restriction as
causes of breathlessness
• Perform pre-employment screening in certain
professions
3. Flow
Sensitive
Spirometer
• Utilizes a sensor that measures air flow as the
primary signal and calculates volume by integration.
• Automatically calculates a wide range of ventilatory
indices and draw curves, which provide an immediate
feedback on quality.
4. How to DO?
Before the Test
1) Exclude contraindications:
• Haemoptysis of unknown origin.
• Current chest infection or within in last 6 weeks.
• Pneumothorax.
• Recent myocardial infarction or PE (< 3 m).
• Unstable angina in last 24 hours.
• Recent surgery (eye, chest, abdomen) (< 3m).
• Recent CVA (< 3m).
• Aneurysm (cerebral, thoracic, abdominal).
5. How to DO?
Before the Test
2) Stop Asthma Medications:
• SABA 6h
• LABA 12h
• Ipratropium 6h
• Tiotropium 24h
Medications may be continued if the test aims to
assess the patient condition on treatment.
6. How to DO?
Before the Test
3) Other Precautions:
• Physical and mental rest.
• No coffee or smoking for 30 mins.
• Empty the bladder in females or those with
history of urinary incontinence.
7. How to DO?
• Patient is sitting comfortably, not leaning
forwards, legs not crossed, feet firm on floor.
• No tight clothes or collars.
• Explain the procedure to the patient.
• Nasal clip is optional.
During the Test
8. How to DO?
• Ask the patient to do a
Forced Expiratory Maneuver (FEM):
- Take a maximal inspiration.
- Hold the breath and seal your lips tightly around the mouth piece.
- Blow as fast as possible (blast expiration) until the lungs feel
completely empty (at least 6 sec., up to 12 sec in obstructive disease)
During the Test
• Repeat the test 3 times and record the highest reading
• Continue watching, explanation and encouragement
throughout the procedure.
9. • Submaximal effort
o Submaximal effort
o Air leak around the mouthpiece (lips not tight enough)
o Air leak through nose
o Incomplete inspiration before the forced expiratory
maneuver (not at TLC)
o Incomplete or weak expiration (lack of blast effort)
o Slow start of expiration
o Cough (particularly within the first second of expiration)
o Glottic closure
o Obstruction of the mouthpiece by the tongue
o Vocalisation during the forced manoeuvre
o Poor posture (leaning forwards).
o Extra- breath during the blow
Causes of Poor Record
10. Spirometry includes:
• Lung volumes (most simple).
• Lung capacities (composite of > 2 volumes)
• Volume per time: as FEV1,2,3,4,5,6
• Volume / Time Curve.
• Flow / Volume Loop.
21. Bronchodilator Reversibility Testing
•FEV1 should be measured (minimum twice, within
5% or 150mls) before a bronchodilator is given
Bronchodilator* Dose FEV1 before
and after
Salbutamol 400µg 15minutes
Terbutaline 500µg 15minutes
Ipratropium 160µg 45minutes
22. Bronchodilator Reversibility Testing
• An increase in FEV1 that is both greater than 200 ml and
12% above the pre-bronchodilator FEV1 (baseline value)
is considered significant (Up to 8% increase may occur in
normal persons).
• It is usually helpful to report the absolute change (in
mL) as well as the % change from baseline to set the
improvement in a clinical context .
• The absence of reversibility does not exclude asthma
because an asthmatic person’s response can vary from
time to time and at times airway calibre is clearly normal
and incapable of dramatic improvement.
24. Look at FEV1/FVC and FVC
FEV1/FVC > 0.7
FVC > 80%P
FEV1/FVC< 0.7
FVC > 80%P
FEV1/FVC > 0.7
FVC < 80%P
FEV1/FVC < 0.7
FVC < 80%P
NORMAL OBSTRUCTIVE RESTRICTIVE MIXED or
OBSTRUCTIVE + AT
Provocation
Test
BD Reversibility
Test
?Parenchymal
or ExtraParenchymal
BD Reversibility
Test
If asthma suspected
Reversible Not Reversible Reversible Not Reversible
BA COPD OBSTRUCTIVE + AT RV, TLC
Mixed
High Low
25.
26. Parenchymal RLD Extraparenchymal RLD
FVC Decreased Decreased
MVV Normal Decreased
DLCO Decreased Normal
FVC: Forced Vital Capacity
MVV: Maximum Voluntary Ventilation
DLCO: Carbon Monoxide Diffusion
28. FVC = 50%P )< 80%P(
FEV1/FVC = 0.41)< 0.7(
∴Mixed or Obstructive + AT
BD Reversibility: -6% )NO(
RV, TLC not provided
There are 2
possibilities:
1( Mixed
Ventilatory
Defect
2( Obstructive +
AT
29. Measured FEV1
Predicted FEV1
Measured FVC
Predicted FVC
FEV1/FVC
FEV1 after Bronchodilator
Is there obstructive hypoventilation?
What evidence?
Is there restrictive hypoventilation?
What evidence?
What is the degree of ventilatory impairment?
Is there significant reversibility after bronchodilator?
What evidence?
Matching condition:
BA/Interstitial Pulmonary Fibrosis/Emphysema/Acute rhinitis
How to Present Your Analysis of Spirometry Results?
Editor's Notes
Description of Volume/Time Curve:
Normal: fast rise to an early plateau at normal volume
Obstructive:slow rise to a delayed plateau at mildly reduced volume
Restrictive:fast rise to an early plateau at markedly reduced volume
Mixed:slow rise to a delayed plateau at markedly reduced volume
Description of Flow/Volume Curve:
Actually the significant abnormalities are noticed in the expiratory limb which is sensitive to obstruction. The inspiratory limb is more dependent on the active inspiratory effort and less affected by the obstruction
Normal:almost straight slope that starts high up (high PEFR) and meets X-axis late (normal FVC)
Obstructive:concave decent towards X-axis with a relatively long tail (rapid decline in flow rate but slow eventual approach of a nearly normal expiratory volume)
Restrictive:convex descent towards X-axis (normal or increased flow rates that rapidly empty a limited expiratory volume)
Mixed:in between
In obstructive pattern, FEV1/FVC &lt; 0.7 (absolute calculation, not % of predicted)
In obstructive ventilatory abnormality, low FEV1/FVC is the most important distinguishing feature. Low FEV1 is present in whatever ventilatory abnormality. FVC may be low or normal. If low, it does not distinguish between obstructive and restrictive.
In restrictive ventilatory abnormality, low FVC is the most important distinguishing feature. Low FEV1 is present in whatever ventilatory abnormality. FEV1/FVC may be normal or increased.
In mixed, the combination of both findings is characteristic but actually there remains a possibility of obstructive ventilatory defect with air trapping.
FEV1 ad FVC both decrease In obstructive, restrictive diseases, but In obstructive disease FEV1 decreases out of proportion to FVC so the most sensitive diagnostic parameter is the decrease of FEV1/FVC (measured, not % of predicted). In restrictive disease, FVC decreases in proportion to FEV1 so the ratio remains normal or may even increase