SpirometryA. H. Mehrparvar, MD

Occupational Medicine departmentYazd University of Medical Sciences

Lung volumes

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

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

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

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%

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.

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

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)

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.

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

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

Most important parameters FEV1 FVC FEV1/FVC

PEF FEF25-75% V-T Curve F-V loop

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

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

Subject’s position1. Sitting or standing?2. Chair with arms & without wheels 3. Clothing4. Chin & neck position5. Nose clip6. Denture

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