Aspiration of dead space in the management of chronic obstructive pulmonary disease patients with respiratory failure.
BACKGROUND
Carbon 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.


METHODS
With 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.


CONCLUSIONS
ASPIDS is a simple adjunct to mechanical ventilation that can decrease P(aCO(2)) during conventional mechanical ventilation and permissive hypercapnia.
Liu
You-Ning
YN
Department of Respiratory Medicine, General Hospital of the Chinese People's Liberation Army, 28 Fuxing Road, Beijing 100853, China. liuyn@301hospital.com.cn.
Zhao
Wei-Guo
WG
Xie
Li-Xin
LX
Cao
De-Sen
DS
Chen
Liang-An
LA
Zhang
Jian-Peng
JP
Zhang
Bo
B
Ma
Ying-Min
YM
Li
Yu-Zhu
YZ
Zhang
Xin-Gang
XG
Jia
Yan-Hong
YH
D000368:Aged; D002245:Carbon Dioxide / Q000378:metabolism; D002681:China; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000009:adverse effects; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000628:therapy*; D012121:Respiration, Artificial / Q000009:adverse effects*; D012126:Respiratory Dead Space / Q000502:physiology*; D012131:Respiratory Insufficiency; D013396:Suction / Q000379:methods*
D002245:Carbon Dioxide