بسم الله الرحمن الرحیم

1. بسم الله الرحمن الرحیم Fariba Rezaeetalab Assistant professor ,pulmonologist

2. Lung Volumes 4 Lung Volumes, 3 of which can be measured with simple spirometry. • Tidal Volume (Vt): The volume of air that normally moves into and out of the lungs in one “quiet” breath. • Normal: 5-8 ml/kg (70 kg * 7 ml/kg = » 500 ml). • Inspiratory Reserve Volume (IRV): The maximum volume of air that can be inhaled after a normal tidal volume. • Normal: 3,100 mL

3. Expiratory Reserve Volume (ERV): The volume of air that can be exhaled after a normal tidal volume. • Normal: 1,200 mL • Residual Volume (RV): The amount of air remaining in the lung after a maximal exhalation. • Normal: 1,200 mL • Cannot be measured with simple spirometery

6. Lung Volume

7. Directions for Lung Volume/Capacity Measurements • Tidal Volume (Vt): Breathe normally in and out. • Inspiratory Reserve Volume (IRV): Inhale as much as you can from a normal inhalation. • Expiratory Reserve Volume (ERV): Exhale as much as you can from a normal exhalation..

8. Residual Volume (RV): This volume cannot be measured directly with simple spirometry. • Slow Vital Capacity (SVC): Take a deep breath in, as deep as you can, and then blow it out slowly until you can’t blow out any more.

9. Indirect Measurements of RV • The residual volume (and the capacities which have it as a part – FRC & TLC) must be measured indirectly by one of three methods: • Helium Dilution – Closed Circuit Method • Nitrogen Washout – Open Circuit Method • Body Plethysmography

10. Lung Volumes / Gas Distribution • Indirect Spirometry • Two basic approaches • Gas dilution • Body plethysmography • Measurements are in Liter or Milliliters • Reported at BTPS

11. Lung Volumes / Gas Distribution • Indirect Spirometry • Required for the determination of RV, FRC and TLC • Most often, indirect spirometry is performed to measure FRC volume • FRC is the most reproducible lung volume and it provides a consistent baseline for measurement

12. Lung Volumes / Gas Distribution • Gas dilution techniques • All operate on a principle SIMILAR to Boyle’s Law (P1 V1 = P2 V2), which states, In isothermic conditions, the volume of a gas varies inversely with its pressure Fractional concentration of a known gas is used instead of its partial pressure C1 V1 = C2 V2

13. Lung Volumes / Gas Distribution • Gas dilution techniques • By having a known (or measured) gas concentration at the start and end of the study and a single known volume, the unknown volume can be determined. For example: V1 = C2 V2 C1

14. TOTAL LUNG CAPACITY  By applying Boyle’s law (P · V = constant)  TLC • Measured by • body plethysmography • helium dilution • Nitrogen washout • Body plethysmography • mouthpiece obstructed with shutter • rapid panting • chest volume expand and decompress the air in the lungs • changes in pressure inside the box allow determination of the lungof the lung volume

16. HELIUM DILUTION

17. TOTAL LUNG CAPACITY • Helium dilution- Spirometer of known volume and helium concentration connected to the patient- Closed circuit - Law of conservation of mass • [He]initial.Vs=[He]final.(Vs+VL) • Unknown lung volume canbe calculated [He] [He] initial · Vs = {H.,.,.H{[[) initial · Vs = [He] final· (Vs + )

18. RV=TLC-VCFRC=TLC- IC

19. NITROGEN WASHOUT

20. Lung Volumes / Gas Distribution • Objectives • Describe the measurement of lung volume using direct and indirect spirometry • Explain two advantages of measuring lung volumes using the body plethysmograph

21. Lung Volumes / Gas Distribution • Objectives • Calculate residual volume and total lung capacity from FRC and the subdivisions of VC • Identify restriction from measuring lung volumes

22. Lung Volumes / Gas Distribution • Direct Spirometry • Used to measure all volumes and capacities EXCEPT for RV, FRC and TLC

23. Lung Volumes / Gas Distribution • Gas dilution techniques • Can only measure lung volumes in communication with conducting airways !!!

24. Lung Volumes / Gas Distribution • Gas dilution techniques • Obstruction or bullous disease can have trapped, noncommunicating air within the lungs • FRC may be measured as being less than its actual volume

25. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout • The natural volume of nitrogen in the subject’s lungs at FRC is washed out and diluted with 100% oxygen • Test must be carefully initiated from the FRC baseline level

26. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout • All exhaled gas is collected in a Tissot (large volume) spirometer for measurement of its volume • Analyzer in the breathing circuit monitors nitrogen concentrations

27. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout

28. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout

29. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout • Approximately 3-7 minutes of breathing 100% O2 to wash out N2 from the lungs • If oxygen-induced hypoventilation is a documented problem (as in COPD), a different method of FRC determination is needed

30. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout • Test is successfully completed when the N2 levels decrease to become less than 1.5% for at least 3 successive breaths(subjects without obstructive disorders) • Premature discontinuation may occur due to: • System leak • Patient unable to continue • Tissot spirometer is full

31. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout • The FRC has a N2 concentration of approximately 0.75, based on the atmospheric nitrogen minus CO2 and water vapor at BTPS: (CAlvN2) = 0.75

32. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout • The final collected volume of exhaled gas in the Tissot spirometer (VExh) • Has a measurable concentration of N2 (CExhN2)

33. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout • FRC determination is based on the following equation: VFRC = (CExhN2)(VExh) CAlvN2

34. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout • In the actual FRC determination by this method, the calculation is more complex Do not get scared ! You will not be asked to do the calculation!

35. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout • The small final concentration of alveolar N2 remaining in the lung needs to be subtracted from the original CalvN2 • Deep breath of O2 at the end of the test and slowly exhaled. The end-expiratory CN2 is used as the CFN2 (This volume should not be exhaled into the spirometer)

36. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout • The second correction is the volume of nitrogen released from the body tissues during the washout procedure (body tissue N2 factor or BTN2) • Rages from 30 – 50 ml/minute of the washout procedure (TTest)

37. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout • Final Calculation VFRC = (CExhN2 X (VExh +VD) ) - BTN2 Factor X TTest CAlvN2 – CFN2 • Must be BTPS converted • Test can be repeated after 15 minutes (longer if COPD)

38. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout • Modern computer-operated pneumotachometer systems do not require collection of total VExh or measurement of the CExhN2 • Breath-by-breath CExhN2 and VExh measurements are made

39. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout

40. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout

41. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout • Leak

42. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout Criteria for Acceptability • The washout tracing/display should indicate a continually falling concentration of alveolar N2 • The test should be continued until the N2 concentration falls to <1.5% for 3 consecutive breaths

43. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout Criteria for Acceptability • Washout times should be appropriate for the subject tested. Healthy subjects should washout N2 completely in 3-4 minutes • The washout time should be reported. Failure to wash out N2 within 7 minutes should be noted

44. Lung Volumes / Gas Distribution • Open-Circuit Nitrogen Washout Criteria for Acceptability • Multiple measurements should agree within 10% • Average FRC from acceptable trials should be used to calculate lung volumes • At least 15 minutes of room-air breathing should elapse between repeated trials, >1 hour for patients with severe obstructive or bullous disease

45. Lung Volumes / Gas Distribution • Closed-Circuit Helium Dilution • FRC is calculated indirectly by diluting the gas in the lungs at the end-expiration level with a known concentration of helium (an inert gas)

46. Lung Volumes / Gas Distribution • Closed-Circuit Helium Dilution FRC

47. Lung Volumes / Gas Distribution • Closed-Circuit Helium Dilution • Procedure • Spirometer is filled with a known volume of air with added oxygen of 25 – 30% • A volume of He is added so that a concentration of approximately 10% is achieved • System volume (spirometer, tubing) and He concentration are measured

48. Lung Volumes / Gas Distribution • Closed-Circuit Helium Dilution C1 V1 = C2 V2 (C1 initial He concentration)(V1 system volume)

49. Lung Volumes / Gas Distribution • Closed-Circuit Helium Dilution • Procedure • The patient breathes through a free-breathing valve that allows either connection to both room air or the rebreathing system • The patient is switched into the rebreathing system at end-expiration level (FRC) • The patient rebreathes the gas in the spirometer, until the He concentration falls to a stable level

50. Lung Volumes / Gas Distribution • Closed-Circuit Helium Dilution O2 Added CO2 Absorbed H2O Absorbed