Is the Effect on Elimination of Apparatus Dead Space Different according to Ventilation Modes?

Abstract

Background: The objective of this study was to observe that the effect on the elimination of apparatus dead space was different according to modes of ventilation. Methods: In 30 patients undergoing esophageal surgery, we placed a double-lumen endobronchial tube in the midtrachea and used the bronchial lumen with a conventional Y connector while the tracheal lumen was clamped for conventional ventilation (CV) or used both lumens with special connectors that separated the inspiratory limb and the expiratory limb for separated ventilation (SV). Four ventilation modes were used in each patient. Type CV10 is a mode with 10 ml/kg of tidal volume, and a frequency of 10/min, and type CV5 is a mode with 5 ml/kg of tidal volume, and a frequency of 20/min. Except for the special connectors, type SV10 and SV5 are the same as CV10 and CV5, respectively. Results: The means ﾅ standard deviations of PaCO2 in CV10, SV10, CV5, and SV5 were 34.8 K 5.7 mmHg, 32.3 5.1 mmHg, 39.2 6.6 mmHg, and 34.9 5.9 mmHg, respectively. The PaCO2 in SV10 and SV5 decreased significantly when compared with that seen in CV10 and CV5, respectively (P 0.001), showing the effect of the elimination of apparatus dead space. Moreover, the PaCO2 difference observed between CV5 and SV5 (4.4 4.1 mmHg) was significantly greater than that observed between CV10 and SV10 (2.5 2.4 mmHg) (P = 0.014). Conclusions: The elimination of apparatus dead space to improve CO2 removal can be more beneficial in a ventilation mode with 5 ml/kg of tidal volume, and a frequency of 20/min rather than in 10 ml/kg of tidal volume, and a frequency of 10/min.