1995 OPEN FORUM Abstracts
CONTINUOUS VS. EXPIRATORY PHASE TRACHEAL GAS INSUFFLATION DURING VOLUME 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 volume control ventilation (VCV).
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 VCV, decelerating flow pattern, respiratory rate of 15 /min, and PEEP 10 cm H_2O. The tidal volume was set at zero TGI flow at each of four inspiratory times (T_I = 1.0, 1.5, 2.0 and 2.5 s) and maintained at the set level as TGI flows of 4, 8, and 12 L/min were applied. 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 and Ex-TGI, there were significant increases in peak inspiratory pressure (d-PIP), auto-PEEP (d-PEEPi), and tidal volume (d-V_T) (Pɘ.01) as TGI flow increased. However, changes in PIP and V_T were markedly greater with C-TGI than with Ex-TGI (Pɘ.01). Mean ± SD among 3 lung mechanics and 4 T_I are shown below.
Continuous flow TGI with VCV Expiratory phase TGI with VCV
TGI d-PIP(cmH_2O)d-PEEPid-V_T(mL) d-PIP(cmH_2O)d-PEEPi d-V_T(mL)
4 6.9 ± 2.61.0 ± 0.8 132 ± 391.4 ± 0.10.5 ± 0.2 11 ± 3
8 13.1 ± 5.02.5 ± 1.7 247 ± 762.9 ± 0.21.4 ± 0.3 22 ± 4
1219.8 ± 7.54.4 ± 2.6 358 ± 113 5.4 ± 0.32.8 ± 0.4 41 ± 7
Conclusions: As TGI flow increased, increases in peak inspiratory pressure, auto-PEEP and V_T occurred with both C-TGI and Ex-TGI during VCV. However, Ex-TGI resulted in much smaller increases than C-TGI. (Supported in part by Puritan Bennett Corp.)