Which of the following has the better correlation with dyspnea and quality of life in COPD? -
1. FEV1
2. RV/TLC
3. FVC
4. IC
Answer with reason and proper references.
Arnab- I think among the ones you have listed - it will be FEV1. References - the ones I can provide you would be
1) http://www.pulmonaryrehab.com.au/pdfs/BodeIndexForCOPD.pdf
2) http://crd.sagepub.com/content/5/1/7.abstract
3) http://www.thoracic.org/statements/resources/copd/copdexecsum.pdf
4) http://www.advanceweb.com/web/AstraZeneca/focus_on_asthma_copd_issue4_ToolsForDiagnosis/issue4.html
I think FEV1 forms the single most important value in COPD prognostication.
FEVI is the one but now more sophisticated and comprehensive BODE index reveals best in predicting COPD related outcomes (Celli BR, 2004, NEJM)
All of them have a certain value. Dyspnea in COPD has many dimensions (respiratory, cardiovascular, muscular, mental etc.). Among the respiratory you listed, the most valuable is the IC since it reflects hyperinflation. However, in static and not dynamic (exercise) conditions, hyperinflation is better represented by FRC or TGV if you prefer (in body plethysmograph). RV/TLC reflects gas trapping which is also assumed by FVC (since RV+VC=TLC). Gas trapping is a paragog of hyperinflation. FEV1, although the most widely used spirometric index, supports COPD diagnosis and classification, however it does not correlate with dyspnea.
Dyspnea in COPD can be due to multiple factors , such as
1) Obstructive airway disease due to severe COPD ( FEV1 < 50 ) or very severe COPD ( FEV1
none of these correlate consistently with dyspnoea in COPD. To me, this is one of the difficulties in this illness. Another factor you might think correlates is DLCO or KCO, but it also doesn't correlate. I suspect its because dyspnoea, like pain, is a complex experience which occurs in a particular person, in a particular psychosocial and cultural context that gives meaning to the experience. I think there was an article a couple of years ago comparing GOLD class to mMRC dyspnoea score, but the correlation was weak and inconsistent as i recall.
IC correlates best with dyspnea, exercise intolerance and quality of life in COPD as there is documented reversal of IC in COPD to a significant amount after bronchodialation as there is improvement in hyperinflation and IC is a marker of hyperinflation. The following is the reference of my answer
http://erj.ersjournals.com/content/21/1/86.full.pdf
1.With increasing exercise a close correlation have been shown between the reduction of IC and the intensity of exertional dyspnea (O'Donnell et al 1997 "Qualitative aspects of exertional breathlessness in chronic airflow limitation..." O'Donnell et al, 1993 "exertional breathlessness in patients with chronic airflow limitation..."
2. among patients with an identical FEV1, those with lower DLCO had a more rapid rate of rise of FH and greater exertional dyspnea compared with the preserved DLCO group (O'Donnell et al, Am J Resp Crit Care Med 2001; 164)
Dypnea has a multicultural mechanism se we cannot assume that one is high correlate over the other . Reference (GOLD)
https://www.researchgate.net/publication/305914621_When_Pulmonary_Function_Test_is_available_should_we_wait_for_the_COPD_symptoms_to_develop
Article When Pulmonary Function Test is Available, Should we Wait fo...