Tracheal Gas Insufflation
Tracheal gas insufflation (TGI): The addition of a secondary gas flow during mechanical ventilation at the level of the carina to wash CO2 from the deadspace of the large airways, endotracheal tube (ETT), and ventilator circuit (Figure 44-1).
A At end exhalation large airways, the ETT and the ventilator circuit deadspace contain a large amount of CO2.
B Washing the CO2 from these areas decreases the CO2 of the gas moving to the alveoli during the next inhalation.
C As a result, over time the arterial P2 decreases.
D Numerous case series in patients have demonstrated that TGI at flows of approximately 6 to 15 L/min decrease Paco2 (Figure 44-2).
E The greater the Paco2 at the time of initiating TGI, the greater the decrease in Paco2.
F The greater the TGI flow, the greater the effect on Paco2.
G The greater the volume of deadspace washed of CO2, the greater the effect on arterial Pco2.
A Figure 44-3 illustrates a typical TGI system.
B A small-gauge catheter is placed into or along side the ETT with its tip setting just past the tip of the ETT in the trachea.
C In most settings the tube is directed toward the carina (direct TGI).
D However, the flow through the catheter may also be directed up toward the ETT (e.g., indirect or reverse TGI).
E TGI can also be applied continuously or intermittently (during exhalation only).
F By simply attaching the TGI catheter to a flowmeter, continuous flow TGI can be performed.
G To accomplish expiratory phase-only TGI, the flow delivery must be coordinated with the ventilator (i.e., activation of TGI flow must begin and end during the expiratory phase).
