Effect of pulmonary perfusion on the slopes of single-breath test of CO2.
The objective of this study was to evaluate the effects of lung perfusion on the slopes of phases II (S(II)) and III (S(III)) of a single-breath test of CO(2) (SBT-CO(2)). Fourteen patients submitted to cardiac surgery were studied during weaning from cardiopulmonary bypass (CPB). Pump flow was decreased in 20% steps, from 100% (total CPB = 2.5 l.min(-1).m(-2)) to 0%. This maneuver resulted in a progressive and opposite increase in pulmonary blood flow (PBF) while maintaining ventilator settings constant. SBT-CO(2), respiratory, and hemodynamic variables remained unchanged before and after CPB, reflecting a constant condition at those stages. S(III) was similar before and after CPB (19.6 +/- 2.8 and 18.7 +/- 2.1 mmHg/l, respectively). S(III) was lowest during 20% PBF (8.6 +/- 1.9 mmHg/l) and increased in proportion to PBF until exit from CPB (15.6 +/- 2.2 mmHg/l; P < 0.05). Similarly, S(II) and the CO(2) area under the curve increased from 163 +/- 41 mmHg/l and 4.7 +/- 0.6 ml, respectively, at 20% PBF to 313 +/- 32 mmHg/l and 7.9 +/- 0.6 ml (P < 0.05) at CPB end. When S(II) and S(III) were normalized by the mean percent expired CO(2), they remained unchanged during the protocol. In summary, the changes in PBF affect the slopes of the SBT-CO(2). Normalizing S(II) and S(III) eliminated the effect of changes in the magnitude of PBF on the shape of the SBT-CO(2) curve.
Tusman
G
G
Department of Anesthesiology, Hospital Privado de Comunidad, Cordoba 4545, 7600 Mar del Plata, Argentina. gtusman@hotmail.com
Areta
M
M
Climente
C
C
Plit
R
R
Suarez-Sipmann
F
F
Rodríguez-Nieto
M J
MJ
Peces-Barba
G
G
Turchetto
E
E
Böhm
S H
SH
D000368:Aged; D001944:Breath Tests / Q000379:methods*; D002245:Carbon Dioxide / Q000032:analysis / Q000378:metabolism*; D002315:Cardiopulmonary Bypass; D003198:Computer Simulation; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011652:Pulmonary Circulation; D012123:Pulmonary Ventilation; D015203:Reproducibility of Results; D012119:Respiration; D012680:Sensitivity and Specificity; D013223:Statistics as Topic
D002245:Carbon Dioxide