2004 OPEN FORUM Abstracts
AUTOMATIC TUBE COMPENSATION DURING EXPIRATION: WHAT EFFECT DOES IT HAVE ON PEAK EXPIRATORY FLOWRATE?
Armstrong, Nikolas Sirs, Lonny Ashworth MEd RRT. Boise State
University, Boise, ID.
Background: Automatic Tube Compensation (ATC) is used with pressure-targeted ventilation to deliver the set pressure to the distal end of the artificial airway, compensating for the resistance of the ETT or tracheostomy tube. When ATC is active during expiration (ATCexp), the PEEP level at the ventilator is reduced at the beginning of expiration in an attempt to deliver the desired PEEP level at the carina. This results in an increased pressure gradient for exhalation, which may increase the peak expiratory flowrate. The purpose of this study is to evaluate the effect of ATCexp on peak expiratory flowrates in a lung model.
Methods: The Drager Evita 2 was connected via an 8.5 mm ETT to one lung of a dual-lung laboratory model (compliance (Cst) 0.05 – 0.09 L/cm H2O). Ventilator settings: Volume-targeted, Assist-control; respiratory rate 12/minute; inspiratory time 0.8 seconds; VT 500 mL; Peak Flowrate 60 LPM; Autoflow off; PEEP 0 – 20 cm H2O. Peak expiratory flowrates were measured immediately before the exhalation valve with ATC off after the ventilator stabilized and with ATC on after the ventilator stabilized.
Results: When ATC was turned on, peak expiratory flowrates increased up to 12% with Cst 0.09 L/cm H2O at 10 cm H2O PEEP, 15% with Cst 0.07 L/cmH2O at 15 cm H2O PEEP and 14% with Cst 0.05 L/cm H2O at 20 cm H2O PEEP.
Conclusion: ATCexp increases the peak expiratory flowrate. Patients with ARDS/ALI may benefit from ATCexp by decreasing the auto-PEEP. However, patients with emphysema/dynamic airway collapse may have a reduction in airway splinting resulting in an increased auto-PEEP and an increased work-of-breathing. Additional studies are needed to evaluate the clinical effects of ATC.