2. Introduction
It measures lung function, specifically the volume and or speed (flow) of air that
can be inhaled and exhaled by a subject
It is an objective, noninvasive, sensitive to early change and reproducible method
It is essential for the diagnosis and monitoring of many diseases of the RS
It is performed with an instrument called “spirometer” in order to:
detect the presence or absence of a lung disease (asthma, COPD, cystic fibrosis,
pulmonary fibrosis)
quantify lung impairment
monitor the effects of occupational/environmental exposures
determine the effects of medications
3. Spirometer
Spirometer is an instrument that
measures and records the volume of
inhaled and exhaled air, used to assess
pulmonary function
The computer connected to spirometer
converts the signal into numerical
values and graphical images called a
spirogram
4. Why do we do it?
To diagnose or manage asthma
To measure response to treatment of conditions which spirometry detects
To dg and differentiate between obstructive lung disease and restrictive lung
disease
To identify those at risk from pulmonary barotrauma while scuba diving
To conduct pre-op risk assessment bf anesthesia or cardiothoracic surgery
Health promotion (smoking cessation)
5. Contraindications
Hemoptysis of unknown origin
Pneumothorax
Unstable cardiovascular status (angina, recent myocardial infarction, etc.)
Thoracic, abdominal, or cerebral aneurysms
Cataracts or recent eye surgery
Recent thoracic or abdominal surgery
Nausea, vomiting, or acute illness
Undiagnosed hypertension
6. Patient positioning
Sit upright: there should be no difference in the amount of air the patient can exhale
from a sitting position compared to a standing position as long as they are sitting up
straight and there are no restrictions.
Feet flat on floor with legs uncrossed: no use of abdominal muscles for leg position.
Loosen tight-fitting clothing: if clothing is too tight, this can give restrictive pictures on
spirometry (give lower volumes than are true).
Dentures normally left in: it is best to have some structure to the mouth area unless
dentures are very loose.
Use a chair with arms: when exhaling maximally, patients can become light-headed and
possibly sway or faint.
7. Procedure
Slow maneuver (VC):
Quiet breathing
Full inspiration
Complete exhalation
Forced maneuver (FVC):
Quiet breathing
Maximal inspiration
Rapid and complete expiration
Rapid and deep inspiration
8. Static Lung Volume
tidal volume (TV): the volume of air
inhaled and exhaled during each breath =
500mL
Inspiratory reserve volume (IRV): the
maximum amount of air that can be
inspired at the end of normal inhalation =
2500 mL
Expiratory reserve volume (ERV): the
maximal volume of air that can be exhaled
from the end-expiratory position = 1500
mL
Residual volume (RV): the volume of air
remaining in the lungs after a maximal
exhalation = 1000-1500 mL
9. Lung capacities
Total lung capacity (TLC): the volume of air
contained in the lungs at the end of maximal
inspiration (TLC = TV + IRV + ERE + RV) = 5500-
6000mL air
Vital Capacity (VC): the volume of air breathed
out after the deepest inhalation (VC = TV + IRV +
ERV) = 4500mL
Inspiratory Capacity (IC): maximum amount of
air that can be breathed in (IC = TV + IRV) = 3000
Ml
Functional Residual Capacity (FRC): the volume
in the lungs at the end-expiratory position (FRC =
ERV + RV) = 3000mL
10. Dynamic lung volumes
Forced expiratory volume in one second (FEV1): the volume of air exhaled
during the first second of a forced expiration.
Percentage of predicted FEV1 value Result
80% or greater normal
70%–79% mildly abnormal
60%–69% moderately abnormal
50%–59% moderate to severely abnormal
35%–49% severely abnormal
Less than 35% very severely abnormal
11. Dynamic lung volumes
Forced vital capcity (FVC): the determination of the vital capacity from a maximally
forced expiratory effort
The Tiffneau Index (ratio of FEV1/FVC * 100); NV >= 75%
Percentage of predicted FVC value Result
80% or greater normal
less than 80% abnormal
12. Reading spirometry
ASSESSMENT OF FVC: <80% of the
theoretical value => restrictive defect
EVALUATION OF FEV: <80% of the theoretical
value => obstructive defect
EVALUATION Tiffeneau INDEX: <70 -75% of
the absolute value => obstructive deficit
13. Restrictive pulmonary disease
Restrictive disorders -> loss in lung volume:
pulmonary fibrosis, pleural disease, chest wall
disorders (kyphoscoliosis), neuromuscular
disorders, pneumonectomy, pulmonary
oedema and obesity
Restriction is characterised by:
reduced FVC
normal-to-high FEV1/FVC ratio;
normal looking shape on spirometry trace
possibly a relatively high PEF (peak expiratory
flow: the highest forced expiratory flow
measured with a peak flow meter)
14. Obstructive pulmonary disease
Obstruction -> airflow limitation => decreased airway calibre (smooth muscle
contraction, inflammation, mucus plugging or airway collapse in emphysema)
Eg: COPD, asthma, tumors of the lung/pleura, aspiration of foreign objects
Obstructive disorders are characterised by:
reduced FEV1
normal (or reduced) VC
normal or reduced FVC
reduced FEV1/FVC ratio
concave flow–volume loop
