2002 OPEN FORUM Abstracts
Transmission of Vibrations from the Acapella Airway Clearance Device During the Expiratory Phase of Mechanical Ventilation
Kathleen Deakins RRT, Julie DiFiore BSEE, Timothy Myers BS, RRT and Robert Chatburn, RRT, FAARC. Rainbow Babies and Children?s Hospital, Cleveland, OH
Introduction: Positive expiratory pressure (PEP) is used to facilitate mobilization of retained secretions and re-expand areas of atelectasis. The Acapella (DHD HealthCare Corp.) is a flow operated oscillating PEP device designed to enhance secretion removal using a counterweighted plug and magnet that interrupts expiratory flow through a pivoting cone at frequencies (f) 0-30 Hz. Vibration sensations during exhalation reportedly have been felt when the Acapella is applied to the expiratory valve of ventilators. The purpose of this study is to determine if the Acapella oscillations produced are transmitted to the patient wye during the expiratory phase of mechanical ventilation.
Methods: In this bench study, a Bird VIP ventilator with infant ventilator circuit was connected to a 4.0 mm endotracheal tube and an Infant Star Test Lung to simulate infant ventilation. Settings of Volume-Control SIMV, f = 25/min, PEEP +5 cmH20, VT 50cc, sensitivity -2 cm H20 and a flow 6 L/min. Baseline measures of Flow, PIP, and PEEP were obtained via a Fleisch pneumotach and Borded Cell National Instruments PC-LBM-16 Data Acquisition System with Labview Version 12 software (sampling speed of 500Hz). A low flow Acapella (<15L/min) was placed on the expiratory valve of the ventilator. Oscillation frequency, amplitude, and auto PEEP were measured at the wye on exhalation at two Acapella settings: minimum (-) and maximum (+). We repeated the procedure using an adult ventilator circuit connected to a 7.0 mm endotracheal tube, and Adult/Pediatric Test Lung Model (Ingmar Medical Inc.) set at normal resistance and compliance with a high flow Acapella (>15L/min) attached to the ventilator expiratory valve. Settings of Volume-Control SIMV, f = 12/min, PEEP +5 cmH20, VT 500cc, sensitivity -2 cmH20 and flow 30 L/min were used.
Results: During the infant simulation at (-) and (+) Acapella settings, oscillation f = 26 Hz with amplitude of 21 cm H20 and no auto PEEP. Using the adult simulation at (-) setting, f = 11 Hz, amplitude 30 cmH20. At (+) setting,
f = 33 Hz, amplitude = 17 cmH20 with auto PEEP = 12 cmH20. Oscillations caused the ventilator to auto trigger continuously, requiring the sensitivity to be reduced. The graphs below show representative waveforms.
Conclusion: An Acapella placed at the expiratory valve of a ventilator transmits oscillations to the patient wye on expiration during infant and adult mechanical ventilation, but caused auto PEEP and sensitivity problems. These issues should be addressed before considering use of the Acapella during mechanical ventilation.