Physiology

1. SPIROMETRY
DR. TEODORA TIMIS

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