2001 OPEN FORUM Abstracts
Effect of TrachealGas Insufflation (TGI) During Dual Control (DC) Ventilation
Robert S. CampbellRRT, FAARC, Richard D. Branson, RRT FAARC, Paul N. Austin PhD CRNA (Lt ColUSAF), , Jay A. Johannigman MD, Fred A. Luchette MD, Sandra L. Miller MD, KennethDavis Jr. Md. University of Cincinnati, Cincinnati, OH 45267-0558
BACKGROUND:TGI may be useful in patients with elevated PaCO2. TGI lowers PaCO2 and reducesdeadspace ventilation by flushing CO2 from the upper and artificial airwaysduring exhalation and by augmenting Vt delivery. We designed a lung model studyto evaluate the effect of TGI on Vt and airway pressure delivery to the lungduring ventilation with four DC modes..
Methods: FourDC modes were evaluated: Adaptive Pressure Ventilatin (APV, Galileo, Hamilton),AutoFlow (AF, E4, Drager), Pressure-Regulated Volume Control (PRVC, 300, Siemens),and VolumeControl Plus (VC+, 840, Puritan-Bennett, pre-released software*).Each vent was set to ventilate on one side of a two chamber test lung (TTL,Michigan Instruments) at compliance (C-cc/cmH2O) / resistance (R-cmH2O/L/sec)combinations of: 20/5, 20/20, and 50/20. An 8 mm ET tube was inserted into anartifical trachea and TGI was provided via a 2.9 mm ID catheter positioned withthe tip 2 cm beyomd the end of the ET tube. TGI continuous flows of 0, 4, 8,and 12 LPM were used. EAch vent was set to a CMV rate of 15, target Vt of 450ml, PEEP of 10 cm H2O. Inspiratory time (T1) was set to 1.0 and 2.0 secondes.A pneumotach and pressure transducer were placed between the trachea and testlung to measure flow, volume, and pressure delivered to the lung. Inspiratoryand expiratory Vt, inspiratory and expiratorey flow; and peak and baseline pressuremeasured by each vent were also recorded. Five breaths at each condition wererecordd
Results: Table1 shows the Vt delivered to the lung and measured exhaled Vt by each vent atbaseline and with 8 lpm TGI flow at each T1 (C50, R20).
T1 = 1sec
T1 = 2sec
|Vt (vent)||Vt (lung)||Vt (vent)||Vt (lung)|
Vents (840, Evita4) that used inspiratoryVt as the target during jDC do not adjust flow output in the presence of TGIflow. THis results in an increasd Vt delivery to the lung, which is dependeantonTGI flow, T1 and C. Vents (Galileo) that use measured exhaled Vt as the targetduring DC reduced flow output and thereby Vt delivery to lung in the presenceof TGI flow. Measured Vt may exceed delivery Vt by as much as 50% in the presenceof TGI flow.
CONCLUSION: DC algorithmsvary by manufacturer and will affect the Vt delivery to the lung in the presenceof TGI flow. Practitioners should familiarize themselves with DC algorithmsprior to clinical use.