(3)lung_volumes.pptx and respiratory physiology

Respiratory physiology

1. Lung volumes and capacities By: Dr.Abdalla M.Osman

2. Tidal volume The volume of gas inspired or expired in an unforced respiratory cycle At rest is about 500ml in a normal adult male Its volume varies with body size, sex, age and activity Measured by a spirometer

3. Anatomic dead space. 150 ml of atmospheric air entering the respiratory system during each inspiration never reaches the alveoli but is moved in and out of the airways.

4. Respiratory minute volume Also called pulmonary ventilation Volume of air breathed in and out of the lungs each minute Tidal volume x respiratory rate 500 x 12= 6000 ml

5. Inspiratory reserve volume The maximum volume of gas that can be inspired during forced breathing in addition to tidal volume About 3000 ml—that is, six fold greater than resting tidal volume.

6. Expiratory reserve volume The maximum volume of gas that can be expired during forced breathing in addition to tidal volume about 1500 ml.

7. Residual volume The volume of gas remaining in the lungs after a maximum expiration approximately 1000 ml of air

8. Lung Capacities Measurements that are the sum of two or more lung volumes

9. Functional residual capacity The amount of gas remaining in the lungs after a normal tidal expiration and averages about 2500 ml.

10. Total lung capacity The total amount of gas in the lungs after a maximum inspiration

11. Vital capacity The maximum amount of gas that can be expired after a maximum inspiration

12. Inspiratory capacity The maximum amount of gas that can be inspired after a normal tidal expiration

13. Pulmonary function tests Spirometry

14. Spirometry is useful in the diagnosis of lung diseases. On the basis of pulmonary function tests lung disorders can be classified as restrictive or obstructive.

15. Forced expiratory volume (FEV1) and FEV1/FVC ratio . FEV1 is the maximum amount of air that can be exhaled in 1 second after a maximal inspiration . . In healthy individuals, the FEV1 typically constitutes about 80% of FVC; this relationship is usually expressed as a ratio: FEV1 = FVC = : 8

16. The FEV 1 /FVC ratio is clinically useful in helping to distinguish between restrictive and obstructive lung disease. The FEV 1 /FVC ratio decreases in obstructive lung disease and increases in restrictive lung disease.

17. In a healthy normal adult male, FVC is approximately 5.0 L FEV 1 is approximately 4.0 L The calculated FEV 1 /FVC is 80% Patients with obstructive or restrictive diseases display reduced FVC, on the order of 3.0 L, and this measurement alone does not differentiate between the two

18. In obstructive disorders, patients tend to show a slow, steady slope to the FVC, resulting in a small FEV 1 , on the order of 1.3 L In the restrictive disorder patients, air flow tends to be fast at first, and then due to the loss of elasticity, quickly levels out to approach FVC. The resultant FEV 1 is much greater, on the order of 2.8 L

19. Calculation of FEV 1 /FVC: For obstructive (42%) For restrictive (90%) Obstructive disorders result in a marked decrease in both FVC and FEV 1 /FVC Whereas restrictive disorders result in a loss of FVC without loss in FEV 1 /FVC.