Plethysmography vs Helium dilution in COPD.pptx

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1. Journal Club The measurement of lung volumes using body plethysmography and helium dilution methods in COPD patients: a correlation and diagnosis analysis Sci Rep. 2016 Nov 23;6:37550. doi : 10.1038/srep37550 Tien Thanh, MD

2. BACKGROUND “ Plethysmo -”: full Plethysmography: measures changes in volume in different parts of the body . C heck for blood clots in the arms and legs. A ir in lungs Type: Limb plethysmography Body/lung plethysmography https://www.uptodate.com/contents/epidemiology-clinical-presentation-and-diagnostic-evaluation-of-parapneumonic-effusion-and-empyema-in-adults

3. Body/lung Plethysmography Body/lung Plethysmography

4. Body/lung Plethysmography Boyle – Marriote law: at constant temperature, the volume V of a gas mass is inversely proportional to its pressure P P. V = const At the end of normal expiration: P box (P B ) = P mouth = Equilibrium alveolar pressure V lung (V L ) = FRC The shutter closes, the lung is a closed compartment with a fixed amount of gas and object starts inspiration: P B .V L = (P B - P) . (V L + V ) P B .V L = P B .V L + P B V - P. V L - P. V P. V L = P B V  

5. Body/lung Plethysmography V lung = - V pleth (shift volume) Boyle – Mariotte law: = RV = FRC - ERV TLC = FRC + IC = RV +IVC   Body/lung Plethysmography

6. https://www.uptodate.com/contents/management-and-prognosis-of-parapneumonic-pleural-effusion-and-empyema-in-adults Helium Dilution Spirometer with a defined volume and concentration of air mixed with helium At the end of tidal expiration (FRC), breathing from sp irometer  gas in spirometer mix with gases of the lungs  helium is diluted by FRC gases

7. The measurement of lung volumes using body plethysmography and helium dilution methods in COPD patients: a correlation and diagnosis analysis Tang Y, Zhang M, Feng Y, Liang B Sci Rep. 2016 Nov 23;6:37550. doi : 10.1038/srep37550. PMID: 27876834; PMCID: PMC5120321.

8. PICO P atient: COPD patients I ntervention: Whole Body Plethysmography(WBP) and Multi Breath Helium Dilution method (MBHD) C omparison: lung volumes with COPD severities O utcome: correlation between lung volumes and differences between WBP and MBHD with level of airway limitation, DLCO

9. METHODS Study design: Prospective, descriptive study Site: West China Hospital of Sichuan University Time: January 2014 to March 2015

10. METHODS Population Inclusion criteria: > 18 years of age Being diagnosed COPD with FEV1/FVC < 0,7 after bronchodilation No exacerbation during previous 4 weeks Stop medication at least 3 days Exclusion criteria Age < 18 years Co-existing medical condition interfering PFT

11. Intervention Perform WBP and MBHD for all enrolled patients WBP: went through 3 phases (maximal inhalation, forced exhalation, prolonged exhalation to volume constant and more than 6 seconds) Airflow: FEV1, PEF Volume: TLC, RV MBHD: achieve stable end-tidal expiratory level  switch to helium gas  noted helium concentration every 15 seconds  helium equilibration Volume: RV and TLC

12. OUTCOME MEASURE TLC%pred , RV%pred , RV/TLC in correlation with COPD classifications, Correlation of TLC%pred , RV%pred , RV/TLC with COPD severities Accuracy of TLC%pred , RV%pred , RV/TLC in discriminating different COPD severities Correlation of TLC%pred , RV%pred , RV/TLC with DLCO  

13. STUDY RESULT

14. Result Study Sample: 170 patient diagnosed COPD - No acute exacerbation during the last 4 weeks - Stop medication at least 72h

15. Lung volumes and COPD severities

16. Differences of lung volumes between WBP and MBHD correlated with COPD severities

17. Differences of lung volumes between WBP and MBHD correlated with COPD severities

18. Accuracy of differences of lung volumes between WBP and MBHD in discriminating COPD severities AUC of TLC%pred : 0.886 (95%CI 0.834 – 0.939)  

19. Differences of lung volumes and DLCO

20. Conclusion TLC%pred , RV%pred and RV/TLC as measured by WBP were significantly increased as COPD exacerbated TLC%pred , RV%pred and RV/TLC measured by WBP were significantly higher than those measured by MBHD method TLC%pred , RV%pred , RV/TLC by these two methods were negatively correlated with FEV1%pred and effectively differentiated COPD severity .  

21. REVIEW Limitation: The sample size is small (32 participants) Lack of assessment of related factors: history of exacerbation, comorbidities, demographic (age, educational level), Any connection with clinical symptom control Application L ung volume measurement of the differences between WBP and MBHD may be an alternative marker to reflect the degree of airflow obstruction and gas trapping

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