title: Noninvasive measurement of mean alveolar carbon dioxide tension and Bohr's dead space during tidal breathing.
abstract: The lack of methodology for measuring the alveolar carbon dioxide tension (PA,CO2) has forced investigators to make several assumptions, such as that PA,CO2 is equal to end-tidal (PET,CO2) and arterial CO2 tension (Pa,CO2). The present study measured the mean PA,CO2 and Bohr's dead space ratio (Bohr's dead space/tidal volume (VD,Bohr/VT)) during tidal breathing. The method used is a new, simple and noninvasive technique, based on the analysis of the expired CO2 volume per breath (VCO2) versus the exhaled VT. This curve was analysed in 21 normal, healthy subjects and 35 chronic obstructive pulmonary disease (COPD) patients breathing tidally through a mouthpiece apparatus in the sitting position. It is shown that: 1) PA,CO2 is similar to Pa,CO2 in normal subjects, whilst it is significantly lower than Pa,CO2 in COPD patients; 2) PA,CO2 is significantly higher than PET,CO2 in all subjects, especially in COPD patients; 3) VD,Bohr/VT is increased in COPD patients as compared to normal subjects; and 4) VD,Bohr/VT is lower than the "physiological" dead space ratio (VD,phys/VT) in COPD patients. It is concluded that the expired carbon dioxide versus tidal volume curve is a useful tool for research and clinical work, because it permits the noninvasive and accurate measurement of Bohr's dead space and mean alveolar carbon dioxide tension accurately during spontaneous breathing.
authors.affiliation: Dept of Respiratory Medicine, University of Athens Medical School, Sotiria Hospital for Diseases of the Chest, Greece.
authors.forename: N G
authors.initials: NG
authors.lastname: Koulouris
authors.forename: P
authors.initials: P
authors.lastname: Latsi
authors.forename: J
authors.initials: J
authors.lastname: Dimitroulis
authors.forename: B
authors.initials: B
authors.lastname: Jordanoglou
authors.forename: M
authors.initials: M
authors.lastname: Gaga
authors.forename: J
authors.initials: J
authors.lastname: Jordanoglou
mesh_terms: D000328:Adult; D000368:Aged; D002245:Carbon Dioxide / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011650:Pulmonary Alveoli / Q000503:physiopathology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000503:physiopathology*; D012016:Reference Values; D012126:Respiratory Dead Space / Q000502:physiology*; D013990:Tidal Volume / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide