Diagnosis and evaluation of volumetric capnography for pulmonary gas exchange dysfunction in patients with pulmonary disease

Abstract

Objective To evaluate the diagnostic and clinical value of volumetric capnography（VCap） for pulmonary gas exchange dysfunction in patients with pulmonary disease. Methods VCap was performed on all patients with pulmonary disease, including 287 chronic obstructive pulmonary disease （COPD） patients,251 asthma patients, 45 interstitial lung diseases （ILD） patients and 94 control subjects. Main variables., maximum CO2 concentration（CO2 max）, the slope of phase3 （dC/dV3）, volume between 25% and 50V0 of CO2 max （Vm25-50）,volume between 50% and 75% of CO2 max （Vm50-75）,Vm25-50/VT,Vn50-75/VT. Results ① Four variatblos of Vcap exhibited statistical differences （ P〈0.01） between three disease groups （ILD,asthma,COPD） and control group; ②Vm50-75/VT and dC/dV; had no statistical differences between light asthma and light COPD, but showed statistical differences （P〈0.01） between moderate, severe asthma and COPD, and had no statistical d iiJerences between COPD（emphysema） and asthma combining with emphysema;③Vm50-75/VT and dC/dV3 had high sensitivity（98.3%,96.5%） and specificity（91.4%, 86.1%） in estimating COPD（emphysema）. Conclusions ①The values and pattern of VCap are obviously abnormal,which can be used for diagnosing pulmonary gas exchange dysfunction of patients with COPD. dC/dV3 （91.3G） has a prominent rise in COPD patients and relates to the severity of COPD, showing an unequal pulmonary gas distributing; ②Vm50-75/VT and Vm255o/VT are less affected by physiological factors and expired volume, Vm25-50/VT （ ≥7% ）, Vm50-75/VT （ ≥10%） indirectly reflects alveolar dead space increasing and unequal ventilation-perfusion ratio commendably; ③VCap is simple, rapid, non-invasive, and secure and can be repeated well. Key words: Volumetric capnoraphy; Alveolar dead space; Ventilation-perfusion tatio; Gas distribution; Pulmonary disease