1. Spirometry A. H. Mehrparvar, MD Occupational Medicine department
Yazd University of Medical Sciences

2. Lung volumes

3. FRC: the volume of gas present in the lung at endexpiration during tidal breathing
ERV: the volume of gas that can be maximally exhaled from the end-expiratory level during tidal breathing (i.e. from the FRC)
IC: The maximum volume of gas that can be inspired from FRC
IRV: the maximum volume of gas that can be inhaled from the end-inspiratory level during tidal breathing

4. RV: the volume of gas remaining in the lung after maximal exhalation (regardless of point at which exhalation was started)
TV (VT): The volume of gas inhaled or exhaled during the respiratory cycle
TGV: the absolute volume of gas in the thorax at any point in time and any level of alveolar pressure

5. TLC: the volume of gas in the lungs after maximal inspiration
VC: the volume change at the mouth between the positions of full inspiration and complete expiration
FVC: the volume of gas exhaled during a forced expiration, starting from a position of full inspiration and ending at complete expiration

6. Spirometry Parameters
Forced Vital Capacity
FVC
Forced Expiratory Volume in One Second
FEV1
Forced Expiratory Volume in One Second Expressed as a Percentage of the Forced Vital Capacity
FEV1/FVC %
Mean Forced Expiratory Flow during the Middle Half of the Forced Vital Capacity
FEF 25-75%

7. FVC
Definition:
Defined as the maximal amount of air that can be exhaled forcefully after a maximal inspiration or the most air a person can blow out after taking the deepest possible breath.

8. FVC - forced vital capacity
defines maximum volume of exchangeable air in lung (vital capacity)
forced expiratory breathing maneuver
requires muscular effort and some patient training
initial (healthy) FVC values approx 4 liters
slowly diminishes with normal aging
significantly reduced FVC suggests damage to lung parenchyma
restrictive lung disease (fibrosis)
loss of functional alveolar tissue (atelectasis)
FVC volume reduction trend over time (years) is key indicator
intra-subject variability factors
age
sex
height
ethnicity

9. FEV1
Definition:
The volume of air exhaled during the first second of a forced expiratory maneuver
normal FEV1 about 3 liters
FEV1 needs to be normalized to individual’s vital capacity (FVC)

10. FEV1/FVC%
Definition:
The value expresses the volume of air the worker exhales in one second as a percent of the total volume of air that is exhaled.

11. FEF25-75%
Definition:
The mean expiratory flow during the middle half of the FVC
More sensitive than FEV1
Considerably more variability than FVC and FEV1
ATS recommends only be considered after determining presence and clinical severity of impairment and should not be used to diagnosis disease in individual patients

12. PEF - Peak Expiratory Flow rate
measures airflow limitations in large (central) airways
large airways are rate-limiting for airflow in healthy patients
large airway flow limitations important in asthma
PEF measurements recommended for asthma management
spirometry is recommended to help make the diagnosis of asthma
PEF not recommend to evaluate patients for COPD
cannot measure small airway airflow limitations

14. Most important parameters
FEV1
FVC
FEV1/FVC
PEF
FEF25-75%
V-T Curve
F-V loop

19. Spirometry Performance Steps
Equipment performance criteria
Equipment quality control ( calibration & leak )
Contraindications & interfering condition
Age, height, race, gender
Selection of appropriate reference value
Patient maneuver
Acceptability criteria
Reproducibility criteria
Selection of best curve and best result
interpretation

20. Spirometer selection Flow-type spirometer Calibration
Has a monitor showing flow-volume and volume-time diagrams
Measures vext
Reference values (ATS, ERS)
Memory (at least 1000 tests)
Quality control messages
Measures predicted values
Post test
Measures flow at least for 14 s

22. Subject’s position Sitting or standing?
Chair with arms & without wheels
Clothing
Chin & neck position
Nose clip
Denture

23. Spirometry maneuvre Patients’ position Measuring weight and height
Birth date
Ethnicity
Training
Tidal breathing
Deep inspiration
Forced expiration