This study analyzes lung volume measurements in COPD patients using whole body plethysmography (WBP) and multi-breath helium dilution (MBHD) methods. The results demonstrate that differences in lung volumes between WBP and MBHD correlate with COPD severity, with WBP showing significantly higher values than MBHD. The findings suggest that these measurement techniques can effectively differentiate the levels of airflow obstruction and gas trapping in COPD patients.

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.
• Check for blood clots in the arms and legs.
• Air 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 (PB) = P mouth = Equilibrium alveolar pressure
V lung (VL) = FRC
 The shutter closes, the lung is a closed compartment with a fixed amount of
gas and object starts inspiration:
PB.VL= (PB- ∆P) . (VL+ ∆V)
PB.VL= PB.VL + PB. ∆V - ∆P. VL - ∆P.∆V
∆P. VL= PB . ∆V

5. Body/lung Plethysmography
∆V lung = - ∆V pleth (shift volume)
Boyle – Mariotte law:
∆ 𝑽 𝒍𝒖𝒏𝒈
𝑭𝑹𝑪
=
𝑨𝒗𝒆𝒐𝒍𝒂𝒓 𝒑𝒓𝒆𝒔𝒔𝒖𝒓𝒆 𝒄𝒉𝒂𝒏𝒈𝒆
𝑬𝒒𝒖𝒊𝒍𝒊𝒃𝒊𝒓𝒊𝒖𝒎 𝒂𝒗𝒆𝒐𝒍𝒂𝒓 𝒑𝒓𝒆𝒔𝒔𝒖𝒓𝒆
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 spirometer  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
• Patient: COPD patients
• Intervention: Whole Body Plethysmography(WBP) and Multi Breath
Helium Dilution method (MBHD)
• Comparison: lung volumes with COPD severities
• Outcome: 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
• Lung volume measurement of the differences between WBP and MBHD may be an
alternative marker to reflect the degree of airflow obstruction and gas trapping

22. THANK YOU FOR YOUR ATTENTION!