1995 OPEN FORUM Abstracts
TRACHEAL GAS INSUFFLATION WITH A NEW DOUBLE LUMEN ENDOTRACHEAL TUBE: A COMPARISON OF CONTINUOUS VS. EXPIRATORY TGI DURING PRESSURE CONTROL VENTILATION
Max Kirmse*. MD, Hideaki Imanaka, MD, Harald Mang*, MD, Dean Hess, PhD, RRT, Robert Kacmarek, PhD, RRT. Anesthesiology and Respiratory Care, Massachusetts General Hospital and Harvard Medical School, Boston, MA. *Dept. of Anaesthesia, University Erlangen-Numberg, Germany
Tracheal Gas Insufflation (TGI) with a small open ended catheter may cause auto-PEEP and mucosal damage. Furthermore, positioning of the catheter close to the carina is difficult and a high pressure source is needed to drive the TGI-flow. We designed a double lumen endotracheal tube with a smaller insufflation lumen ([approx] 3.5 mm I.D.), and a bigger lumen ([approx] 7.5 mm I.D.). Gas flow through the smaller lumen is directed towards the opening of the bigger lumen by a nozzle at the tip of the tube (Reverse Flow Design, RFD). To evaluate the performance of our tube, we compared the effects of continuous flow TGI (C-TGI) and expiratory phase TGI (Ex-TGI) on peak inspiratory pressure (PIP), auto-PEEP (PEEPi) and tidal volume (V_T) during pressure control ventilation (PCV). We employed a single compartment lung model with an artificial trachea into which the TGI-tube was inserted. Ex-TGI, using the same setup as C-TGI, was established by a solenoid valve activated by a Puritan Bennett 7200ae ventilator. The upper pressure level was set at 20 cmH_2O, PEEP at 10 cmH_2O, and respiratory rate at 15/Min. in all settings. Four TGI flows (0, 4, 8, 12 L/Min.) and inspiratory times (Ti: 1.0,1.5,2.0 and 2.5 s) were applied. Three different combinations of lung mechanics (compliance [ml/cmH_2O]/resistance [cmH_2O/L/s]) were used: 20/20,20/5 and 50/20. Statistical analysis was done with a one-way ANOVA followed by a Scheffe test.
Results: As TGI flow and T_i increased, C-TGI caused a significant (p < 0.01) increase of PIP and V_T, whereas no PEEPi was created. During Ex-TGI, no changes in PIP or V_T occurred. Again, no clinically relevant changes of PEEPi were observed.
Mean values across 3 Jung mechanics and 4 inspiratory times
Continuous flow TGI with PCVExpiratory phase TGI with PCV
TGI PIP [cmH_2O] PEEPi [cmH_2O] V_T [mL]PIP PEEPi V_T
028.8 ± 0.81.1 ± 1.6 422 ± 1028.8 ± 0.81.1 ± 1.6 422 ± 80
430.5 ± 2.31.0 ± 1.8 445 ± 7628.9 ± 0.81.0 ± 1.8 418 ± 78
833.3 ± 4.30.6 ±2.0481 ± 8028.9 ± 0.80.5 ± 1.9 424 ± 74
12 36.9 ±6.44 -0.34 ± 2.4 521 ± 100 28.8 ± 0.8 -0.5 ±2.2412 ± 101
Conclusions: 1.Compared to straight catheter TGI, the RFD reliably prevents auto-PEEP at all clinically occurring TGI flows and lung mechanics. 2.During C-TGI adjustment of inspiratory V_T is necessary in order to avoid excessive inspiratory pressures and volumes. 3.Regarding barotrauma, only Ex-TGI seems to be a safe way of applying TGI.