Author:
Tusman G.,Areta M.,Climente C.,Plit R.,Suarez-Sipmann F.,Rodríguez-Nieto M. J.,Peces-Barba G.,Turchetto E.,Böhm S. H.
Abstract
The objective of this study was to evaluate the effects of lung perfusion on the slopes of phases II ( SII) and III ( SIII) of a single-breath test of CO2 (SBT-CO2). 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-CO2, respiratory, and hemodynamic variables remained unchanged before and after CPB, reflecting a constant condition at those stages. SIII was similar before and after CPB (19.6 ± 2.8 and 18.7 ± 2.1 mmHg/l, respectively). SIII 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, SII and the CO2 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 SII and SIII were normalized by the mean percent expired CO2, they remained unchanged during the protocol. In summary, the changes in PBF affect the slopes of the SBT-CO2. Normalizing SII and SIII eliminated the effect of changes in the magnitude of PBF on the shape of the SBT-CO2 curve.
Publisher
American Physiological Society
Subject
Physiology (medical),Physiology
Cited by
37 articles.
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