Tracheal gas insufflation augments CO2 clearance during mechanical ventilation.
A technique that improves the efficiency of alveolar ventilation should decrease the pressure required and reduce the potential for lung injury during mechanical ventilation. Alveolar ventilation may be improved by replacing a portion of the anatomic dead space with fresh gas via an intratracheal catheter. We studied the effect of intratracheal gas insufflation as an adjunct to volume cycled ventilation in eight sedated, paralyzed patients with a variety of lung disorders. Continuous flows of 2, 4, and 6 L/min were delivered through a catheter positioned 1 or 10 cm above the carina. Carbon dioxide production, inspiratory minute ventilation, and peak and mean airway pressures did not change over the range of flows tested. PaCO2 and dead space volume/tidal volume decreased significantly as joint functions of catheter flow and position (p < 0.001). The highest catheter flow (6 L/min) and most distal catheter position (1 cm above the carina) were the most effective combination tested, averaging a 15% reduction in PaCO2 (range 9 to 23%). Certain characteristics of the expiratory capnogram were helpful in predicting the observed reduction in PaCO2. Tracheal gas insufflation may eventually prove a useful adjunct to a pressure-targeted strategy of ventilatory management (in either volume-cycled or pressure controlled modes), particularly when the total dead space is heavily influenced by its anatomic component.
Ravenscraft
S A
SA
Division of Pulmonary and Critical Care Medicine, University of Minnesota, Minneapolis/St. Paul.
Burke
W C
WC
Nahum
A
A
Adams
A B
AB
Nakos
G
G
Marcy
T W
TW
Marini
J J
JJ
D000328:Adult; D000368:Aged; D002245:Carbon Dioxide / Q000032:analysis / Q000378:metabolism*; D004526:Efficiency; D005260:Female; D005652:Functional Residual Capacity / Q000502:physiology; D006801:Humans; D007327:Insufflation; D007442:Intubation, Intratracheal / Q000295:instrumentation / Q000379:methods*; D008168:Lung / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D010100:Oxygen / Q000008:administration & dosage*; D011175:Positive-Pressure Respiration; D011312:Pressure; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology; D012119:Respiration / Q000502:physiology; D012126:Respiratory Dead Space / Q000502:physiology; D012131:Respiratory Insufficiency / Q000628:therapy*; D013990:Tidal Volume / Q000502:physiology
D002245:Carbon Dioxide; D010100:Oxygen