2. An Overview of Pulmonary Function Tests Norah Khathlan M.D. Consultant Pediatric Intensivist 10/2007

3. Pulmonary function testing primarily detects two abnormal patterns: obstructive ventilatory defects (such as asthma and C.F.). restrictive ventilatory defects (such as interstitial fibrosis and chest wall deformities).

4. Lung Volumes

5. 1- Tidal Volume: The amount of air a person breathes in and out during quiet, normal breathing is called the Tidal Volume (Vt). Notice that during such breathing, a person could breathe more in or blow more out..

6. Lung Volumes

7. Inspiratory Reserve Volume (IRV) is the additional amount a person could inhale. Expiratory Reserve Volume (ERV) is the additional amount a person could exhale.

8. Lung Volumes

9. Lung volumes Residual Volume (RV). After a person blows out all the air he or she can, there is still some air in the lungs, this is called Residual volume.

10. Lung Volumes

11. The Total Lung Capacity (TLC) is exactly what you would think !!! The total amount of air the lungs can contain.

12. Lung Volumes

13. The Vital Capacity (VC) is the total amount of air the person can breathe in and out. The Functional Residual Capacity (FRC) is the total amount of air left in the lungs at the end of a normal exhalation.

14. Lung Volumes

15. Summary: TLC = RV + ERV + Vt + IRV. VC = ERV + Vt + IRV. FRC = RV + ERV.

16. Spirometry terms FVC (Forced Vital Capacity) -- This is the total volume of air expired after a full inspiration. Patients with obstructive lung disease usually have a normal or only slightly decreased vital capacity. Patients with restrictive lung disease have a decreased vital capacity

17. Spirometry Terms FEV1 (Forced Expiratory Volume in 1 Second) -- This is the volume of air expired in the first second during maximal expiratory effort. The FEV1 is reduced in both obstructive and restrictive lung disease. The FEV1 is reduced in obstructive lung disease because of increased airway resistance. It is reduced in restrictive lung disease because of the low vital capacity.

18. Spirometry Terms FEV1/FVC -- This is the percentage of the vital capacity which is expired in the first second of maximal expiration. In healthy patients the FEV1/FVC is usually around 70%. In patients with obstructive lung disease FEV1/FVC decreases and can be as low as 20-30% in severe obstructive airway disease. Restrictive disorders have a near normal FEV1/FVC.

19. Remember In Asthma( an obstructive lung disease) FEV 1 is decreased FVC is normal  Ratio of FEV 1 / FVC is Decreased

20. Remember In restrictive lung disease : Both FEV 1 AND FVC are decreased!!  Ratio is Normal