2009 OPEN FORUM Abstracts
BENCH STUDY OF THE DRAGER APOLLO ANESTHESIA MACHINES FLOW DELIVERY
Joel M. Brown, John Emberger; Christiana Care Health System, Newark, DE
Background: Inhaled isoflurane therapy is often used in the management of patients with severe status asthmaticus (SA). At our facility we have recently began to use the Draeger Apollo® Inhalation Anesthesia Machine (Apollo), a bellows driven anesthesia ventilator, to deliver inhaled isoflurane to SA patients. In addition to lung sounds, changes in PIP and Raw are often used to assess the effectiveness of inhaled isoflurane therapy. The Apollo does not consistantly use a sqaure flow pattern during volume ventilation. This inconsistancy makes it difficult to calculate Raw and forces the clinician to rely on PIP and lung sounds to assess the effectiveness of therapy. The purpose of this study is to assess the flow characteristics of the Apollo and observe its effects on PIP. Methods: This bench study was performed using a test lung (Michigan Instruments Inc.) with the lung compliance set at 50 mL/cm H20. The Novametrix NICO® Cardiopulmonary Management System was used to obtain PIP and peak inspiratory flow at the test lung. The Draeger Evita® 4 was used as our control (square flow ICU ventilator). Each trial was performed using Volume SIMV, RR=12 and PEEP=5 with the following variables: set Vt’s of 300 and 500, inspiratory times (It) of 0.5 and 1.0 seconds, and fixed airway resistors of 5, 20, 50 cm H20/L/sec. Results: A total of 3 trials were completed. The peak flow and PIP produced by the Apollo were consistently higher than those delivered by the control. The peak flow produced by the Apollo increased when the resistance on the test lung was increased. The resulting PIP from the Apollo had a direct correlation with the control’s PIP as the resistance on the test lung changed (R2=0.973 at 0.5 sec It, and R2=0.998 at 1.0 sec It). The flow time graphic from the Apollo changed from a square waveform to an accelerating waveform as the resistance on the test lung increased (see attached graphic) Conclusion: Our data indicates that the Apollo will increase the peak inspiratory flow and change from a square to an accelerating flow pattern if the airway resistance increases. These automated changes resulted in higher PIP’s than those of the square flow control ventilator. When changing a patient from a fixed flow ventilator to the Apollo it is important to recognize these tendencies in order to properly assess the effect of the ordered therapy. Sponsored Research - None
Graph#1. This graph depicts 2 single breath flow vs. time (seconds) waveforms delivered by the Apollo (SIMV Volume Control Vt=300, It=0.5sec, and PEEP=5).