1995 OPEN FORUM Abstracts
CONTINUOUS VS. EXPIRATORY PHASE TRACHEAL GAS INSUFFLATION DURING PRESSURE CONTROL VENTILATION: A LUNG MODEL STUDY
Hideaki Imanaka, MD, Vincent Riggi, RRT, CBET, Dean Hess, PhD, RRT, Ray Ritz, RRT, Robert Kacmarek, PhD, RRT. Anesthesia and Respiratory Care, Massachusetts General Hospital and Harvard Medical School, Boston MA.
We evaluated the effects of expiratory phase tracheal gas insufflation (Ex-TGI) and continuous flow TGI (C-TGI) on ventilatory parameters during pressure control ventilation (PCV).
Methods: A single compartment lung model was configured with an artificial trachea into which an 8 mm endotracheal tube was positioned. C-TGI was established with a 16 G catheter inserted through the endotracheal tube and positioned 2 cm beyond the distal tip. Ex-TGI was established with a solenoid valve activated by a Puritan Bennett 7200ae ventilator such that flow occurred only during the expiratory phase. Ventilation was provided with PC 20 cm H_2O, respiratory rate of 15 /min, and PEEP 10 cm H_2O. Inspiratory times (T_I) of 1.0, 1.5, 2.0 and 2.5 s were used with TGI flows of 0, 4, 8, and 12 L/min. Lung model compliance (mL/cm H_2O) and resistance (cm H_2O/L/s) combinations of 20/20, 20/5, and 50/20 were used. Statistical analysis was done with a one-way ANOVA followed by Scheffe test.
Results: With C-TGI, peak inspiratory pressure (PIP), auto-PEEP (PEEPi), and tidal volume (V_T) increased significantly (Pɘ.01) as TGI flow and T_I increased. With Ex-TGI, peak inspiratory pressure remained constant, V_T decreased (Pɘ.01), and PEEPi increased significantly (Pɘ.01) as TGI flow increased. Mean ± SD among 3 lung mechanics and 4 T_I are shown below.
Continuous flow TGI with PCV Expiratory phase TGI with PCV
TGI PIP(cmH_2O)PEEPi(cmH_2O) V_T (mL) PIP(cmH_2O)PEEPi(cmH_2O) V_T (mL)
0 28.7±0.81.1±1.7432±78 28.7±0.81.1±1.7432±78
4 30.5±2.21.6±1.9456±76 28.8±0.81.5±1.8418±74
8 33.1±4.22.6±2.0492±83 28.8±0.72.2±1.8399±67
Conclusions: As TGI flow or T_I increased, PIP and V_T increased when continuous flow TGI was applied in PCV. However, PIP did not change and V_T decreased during expiratory phase TGI. The decrease in V_T is likely due to the development of auto-PEEP during Ex-TGI. Auto-PEEP increased with both TGI methods as TGI flow and T_I increased. (Supported in part by Puritan Bennett Corp.)