Study Of Clinical Application Value Of Volumetric Capnography In Chronic Obstructive Pulmonary Disease

[Objective] To investigate the diagnostic value of volumetric capnography (VCap) in chronic obstructive pulmonary disease(COPD) staging.[Method] Sixty-six stable COPD patients and twenty healthy controls performed spirometry and volumetric capnography recoding. All of the subjects undertook spirometry followed by volumetric capnography. And they were neither treated by short-acting bronchodilators for 6 hours nor by long-acting bronchodilators for 12 hours before the test.[Results] Compared with control group[(101±9)%,( 80±6)%,( 96.6±12.4)%], all of COPD groups showed a significant decrease in FEV1/pre[Ⅰ:(88±4)%,Ⅱ:(63±8)%,Ⅲ:(38±7)%,Ⅳ:(22±4)%] and FEV1/FVC [Ⅰ:( 67±3)%,Ⅱ:( 59±7)%,Ⅲ:( 47±8)%,Ⅳ:( 36±8)%]and MMEF/pre[Ⅰ:( 67.9±26.7)%,Ⅱ:( 21.1±5.9)%,Ⅲ:( 12.0±4.2)%,Ⅳ:( 6.7±1.8)%], and RV/TLC showed a significant increase in COPDⅡ-Ⅳstage groups[Ⅱ:( 52±8)%,Ⅲ:( 67±9)%,Ⅳ:( 74±4)%] compared with that of control group[(39±6)%]; the difference was significant (P<0.05). On the other hand, VCap of COPD group is different from that of control group in PartⅡandⅢ. In its parameters, compared with that of control group[(30±8)/L], dC2/DV showed a decrease in COPDⅡ-Ⅳstage groups[Ⅱ:( 22±3)/L,Ⅲ: 19±3)/L,Ⅳ:( 14±3)/L, P<0.05]. And dC3/DV showed a increase in COPDⅡ-Ⅳstage groups[Ⅱ:( 2.2±0.4)/L,Ⅲ:( 3.1±0.8)/L,Ⅳ:( 4.1±1.9)/L] compared with that of control group[(1.1±0.4)/L]. And SR23 showed a increase in COPDⅡ-Ⅳstage groups[Ⅱ:( 10.0±2.7)%,( 16.5±3.4)%,( 29.1±6.9)%] compared with that of control group[(3.7±1.4)%]; the difference was significant (P<0.05). For dC3/DV and SR23, the difference was significant between COPD groups(P<0.05). In Pearson correlation analysis, dC2/DV with FEV1/pre, dC2/DV with FEV1/FVC, dC2/DV with MMEF/pre were positively correlated ( r = 0.769 and 0.715 and 0.669, P<0.01 ), dC3/DV with FEV1/pre, dC3/DV with FEV1/FVC, dC3/DV with MMEF/pre were negatively correlated significantly ( r = -0.803 and -0.687 and -0.740, P<0.01 ), SR23 with FEV1/pre, SR23 with FEV1/FVC, SR23 with MMEF/pre were negatively correlated significantly ( r = -0.840 and -0.755 and -0.700, P<0.01 ).[Conclusions] Volumetric capnography is a quantitative method for evaluating the severity of airflow obstruction. It can be performed easily during tidal breathing. Thus, it can be used in COPD diagnosis and staging.