Am. J. Respir. Crit. Care Med., Vol 153, No. 3, 03 1996, 1019-1024.
Tracheal gas insufflation-pressure control versus volume control ventilation. A lung model study
H Imanaka, RM Kacmarek, R Ritz and D Hess
Respiratory Care Department, Massachusetts General Hospital, Boston, 02114, USA.
Tracheal gas insufflation (TGI) has been recommended as an adjunct to
mechanical ventilation in the presence of elevated Pa CO2. Based on our
initial clinical experience with continuous flow TGI and pressure control
ventilation (PCV), we were concerned about elevation in peak airway
pressure as TGI was applied. In a lung model, we evaluated the effects of
continuous flow TGI during both PCV and volume control ventilation (VCV). A
single compartment lung model was configured with an artificial trachea
into which an 8-mm endotracheal tube was positioned. TGI was established
with a 16-G catheter positioned 2 cm beyond the tip of the endotracheal
tube. Ventilation was provided by a Puritan-Bennett 7200ae ventilator with
PCV 20 cm H2O or VCV with a tidal volume (VTt) similar to that with PCV. A
rate of 15 breaths/min and PEEP of 10 cm H2O were used throughout.
Inspiratory times (TI) of 1.0, 1.5, 2.0, and 2.5 s were used with TGI of 0,
4, 8, and 12 L/min. Lung model compliance (ml/cm H2O) and resistance (cm
H2O/L/s) combinations of 20/20, 20/5, and 50/20 were used. Auto-PEEP, VT,
and peak alveolar and airway opening pressures increased as TGI and Ti
increased, regardless of lung mechanics settings (p<0.01). All increases
were greater with VCV than PCV (p<0.05). Continuous flow TGI with both
PCV and VT-uncorrected VCV may result in marked increases in Vt and system
pressures, especially at long TI.
