• You-Ning Liu, Wei-Guo Zhao, Li-Xin Xie, De-Sen Cao, Liang-An Chen, Jian-Peng Zhang, Bo Zhang, Ying-Min Ma, Yu-Zhu Li, Xin-Gang Zhang, and Yan-Hong Jia.
• Department of Respiratory Medicine, General Hospital of the Chinese People's Liberation Army, 28 Fuxing Road, Beijing 100853, China. liuyn@301hospital.com.cn.
• Resp Care. 2004 Mar 1;49(3):257-62.

IntroductionCarbon dioxide clearance can be improved by reducing respiratory dead space or by increasing the clearance of carbon-dioxide-laden expiratory gas from the dead space. Aspiration of dead space (ASPIDS) improves carbon dioxide clearance by suctioning out (during expiration) the carbon-dioxide-rich expiratory gas while replacing the suctioned-out gas with oxygenated gas. We hypothesized that ASPIDS would allow lower tidal volume and thus reduce exposure to potentially injurious airway pressures.MethodsWith 8 hemodynamically stable, normothermic, ventilated patients suffering severe chronic obstructive pulmonary disease we tested the dead-space-clearance effects of ASPIDS. We compared ASPIDS to phasic tracheal gas insufflation (PTGI) during conventional mechanical ventilation and during permissive hypercapnia, which was induced by decreasing tidal volume by 30%. The mean P(aCO(2)) reductions with PTGI flows of 4.0 and 6.0 L/min and during ASPIDS (at 4.0 L/min) were 32.7%, 51.8%, and 53.5%, respectively. Peak, plateau, and mean airway pressure during permissive hypercapnia were significantly lower than during conventional mechanical ventilation but PTGI increased peak, plateau, and mean airway pressure. However, pressures were decreased during permissive hypercapnia while applying ASPIDS. Intrinsic positive end-expiratory pressure also increased with PTGI, but ASPIDS had no obvious influence on intrinsic positive end-expiratory pressure. ASPIDS had no effect on cardiovascular status.ConclusionsASPIDS is a simple adjunct to mechanical ventilation that can decrease P(aCO(2)) during conventional mechanical ventilation and permissive hypercapnia.

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