Spirometry A H Mehrparvar MD Occupational Medicine department

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

Lung volumes

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

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

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

Spirometry Parameters p Forced Vital Capacity n p Forced Expiratory Volume in One Second n p FEV 1 Forced Expiratory Volume in One Second Expressed as a Percentage of the Forced Vital Capacity n p FVC FEV 1/FVC % Mean Forced Expiratory Flow during the Middle Half of the Forced Vital Capacity n FEF 25 -75%

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

FEV 1 p Definition: n n n The volume of air exhaled during the first second of a forced expiratory maneuver normal FEV 1 about 3 liters FEV 1 needs to be normalized to individual’s vital capacity (FVC)

FEV 1/FVC% p Definition: n 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.

FEF 25 -75% p Definition: n The mean expiratory flow during the middle half of the FVC More sensitive than FEV 1 p Considerably more variability than FVC and FEV 1 p ATS recommends only be considered after determining presence and clinical severity of impairment and should not be used to diagnosis disease in individual patients p

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

Most important parameters p p p FEV 1 FVC FEV 1/FVC p p PEF FEF 25 -75% V-T Curve F-V loop

Spirometry Performance Steps p p p p p 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 p p p p p Flow-type spirometer Calibration Has a monitor showing flow-volume and volumetime 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 position 1. 2. 3. 4. 5. 6. Sitting or standing? Chair with arms & without wheels Clothing Chin & neck position Nose clip Denture

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