LUNG VOLUMES What Are They Good For? - CACPT · 2019-09-10 · ATS/ERS Lung Volumes • No one...
Transcript of LUNG VOLUMES What Are They Good For? - CACPT · 2019-09-10 · ATS/ERS Lung Volumes • No one...
LUNG VOLUMESWhat Are They
Good For?
Gregg L. Ruppel, MEd, RRT, RPFT, FAARCAdjunct Professor, Pulmonary, Critical Care & Sleep Medicine
Saint Louis University Hospital
4 Questions
1. Do lung volumes add to clinical decision making?
2. Is a low TLC (i.e. restriction) a useful measurement?
3. Do lung volumes tell us anything meaningful about obstruction?
4. Does it make any difference how you measure lung volumes?
Physiology, physiology, physiology• Evidence-based grade for CPET in patients
with unexplained dyspnea = D*
• Evidence-based grade for TLC in patients with unexplained dyspnea = D**– non-specific but quantitative
– describes physiology, not disease
• FVC (or VC) commonly used to define ‘restriction’ (esp. chest wall abnormality)
* Palange et al: Recommendations on the use of exercise testing in
clinical practice. Eur Resp J 2007; 29:185-209.
** CUSLR (completely un-scientific literature review)
Low FVC = Restriction
Aaron SD et al., Chest 1999; 115:869-873
Glady et al, 2003
PFT Lab - SLUH
Spirometry
N=1678
FVC<85%
N=1015
FVC> 85%
N=663
FEV1/FVC <55%
N=131FEV1/FVC > 55%
N=884
Restriction?
884/1678 (53%)
Proceed to lung volumes
NHANES III
“Who Needs Lung Volumes” Algorithm
FVC, FEV6 and Restriction
Non-obstructedmales
females
Obstructedmales
females
Vandevoorde et al. Eur Resp J 2008
Lung Volumes (TLC)
may be indicated in:Asthma – restriction (Miller 2007)ILD (Boros 2004)Radiation/chemotherapy (Gopal 2003)Combined obstruction/restriction (Balfe 2002)Obesity (Watson 2010, Babb 2008)
not indicated in:Sarcoidosis (Boros 2010)
How Important Is A Low TLC?
• FVC - TLC relationship
• “Non-specific” ventilatory impairment
• Mixed obstructive/restrictive disease
• FRC in obesity
FVC → TLC Relationship • Normal FVC (VC) almost always excludes restriction
• TLC = FVC + RV
• TLC = FVC / (1 – RV/TLC)
y = 0.0028x + 0.1704
15%
20%
25%
30%
35%
40%
45%
50%
10 20 30 40 50 60 70 80 90
Neder (Brazil)
Roca (Spain)
Roberts (UK)
Goldman (S Africa)
ECCS (Europe)
Garcia-Rio (Spain)
Quanjer (NL)
Miller (US)
Mean
Linear (Mean)
RV/TLC in healthy Caucasians
(Predicting TLC from FVC?)
Non-specific PFT pattern(Low FVC and FEV1, normal FEV1/FVC and TLC,
prevalence 4-10%)
Iyer et al, 2010
Hyatt et al, 2009
Follow up of
1284 NS patients
Mixed Obstruction-Restriction
Very few obstructedsubjects have restriction
Dykstra et al, 1999
Adjusting Severity in Mixed Obstruction-Restriction
FEV1 %PREDadj = FEV1 %PRED / TLC %PRED
Gardner et al, Chest, 2011
Obesity, TLC and FRC
Jones et al,
2006
Exponential
decrease
Obesity (waist size) and FVC
Leone et al, 2009
40 inches 35 inches
Do lung volumes tell us anything meaningful about obstruction?
• RV (air-trapping) varies a lot in healthy subjects
• Air trapping in COPD and asthma
• IC – poor man’s FRC & beggar’s RV
RV in Healthy Subjects- NHANES III Caucasian subjects- ECCS lung volume equations
Quanjer et al, unpublished data
TLC in COPD & Asthma
Dykstra et al, 1999
Gray Zone
RV and RV/TLC in Obstruction
Dykstra et al, 1999
Gray Zone
Is IC all that is needed?
Casanova et al, 2005
IC/TLC Ratio
Is IC all that is needed?
Peak change552 ml Average change
IC 215 mlFEV1 198 ml
VanNoorde et al, 2006
That damned residual volume
2265 COPD patientsResponse to bronchodilator(10% or greater change) by GOLD stage
RV (pre BD)I 135±32%II 162±43%
III/IV 218±62%
Deesomchok et al, 2010
965 COPD patients
McCartney et al, Resp Care, 2016
Does it make any difference how you measure lung volumes?
• ATS/ERS guidelines
• Body plethysmography vs. gas dilution– Body box = gold standard?
– Body box overestimates lung volume in severe obstruction?
• Single vs. multiple breath dilution– Trapped gas?
• Imaging (CT) vs. traditional methods
ATS/ERS Lung Volumes
• No one method recommended– Pleth produces larger volumes in obstructed
patients (panting at < 1 Hz advised)– Dilutional techniques may underestimate volumes in
obstructed patients
• VC, IC and ERV should be obtained by ‘linked’ maneuvers if possible
• CT compares favorably– May expose patient to high radiation dose– Breath holding at TLC may be a problem– Cost$
Why pant at < 1.0 Hz?
Stanescu and Rodenstein, 1982
In the presence of obstruction:
1. Pm < Palv
2. Phase shift between Pm and Pbox
3. VTG is overestimated
4. 1 and 2 are frequency dependent
5. panting < 1 Hz minimizes effect
Gas Dilution vs. Plethysmography
O’Donnell et al, 2010
Obstructed patients
Milite et al, 2009
Gas Dilution vs. Plethysmography
Bias of 0.5 L,
but with little difference
due to severity of obstruction
(p for interaction = 0.25)
55 emphysema patients
Single vs. multiple breath dilution
Milite et al, 2009
Imaging for lung volumes
• Accurate? Yes, but poorly standardized
• Cost? $$$
• Risks? Low dose ionizing radiation
Eisenberg et al, 2011
Fazel et al, 2009
Conclusions1. Do lung volumes add to clinical decision
making? – Not much for making specific diagnoses
– May be needed to resolve a low (properly performed) FVC
– TLC indicated only if it will help confirm/reject a diagnosis, or assist in planning therapy
Conclusions
2. Is a low TLC (i.e. restriction) a useful measurement?
- If you know FVC, you know a lot about TLC
- Non-specific ventilatory pattern defined by a normal TLC
- TLC %Predicted may be helpful for adjusting severity in mixed disease
- FRC (but not TLC) is significant but variable in obesity
Conclusions3. Do lung volumes tell us anything meaningful
about obstruction?- RV (upper limit of normal) is quite variable in
healthy subjects
- TLC, RV, and RV/TLC vary significantly in asthma and COPD when FEV1 is near LLN
- IC tells us a lot about hyperinflation but needs to be related to TLC (and RV)
- RV may be a useful index of response to bronchodilators in moderate/severe obstruction
Conclusions4. Does it make any difference how you
measure lung volumes?- Maybe not as much as previously thought- Plethysmography probably overestimates lung
volumes in obstruction- Unclear how much dilutional methods
underestimate lung volumes in obstruction- Single breath dilutional volumes reflect severity
of obstruction- CT is expensive and increases radiation exposure,
but has become commonplace
Questions ?
Jupiter 7/9/2019