TECHNICAL COMMUNICATION A Pilot Study to Evaluate the SMART BAG ® : A New Pressure- Responsive, Gas-Flow Limiting Bag-Valve-Mask Device Horst G. Wagner-Berger, MD, Volker Wenzel, MD, Wolfgang G. Voelckel, MD, Klaus Rheinberger, MSc, Karl H. Stadlbauer, MD, Tilko Mu ¨ ller, BS, Sven Augenstein, MD, Achim von Goedecke, MD, Karl H. Lindner, MD, and Christian Keller, MD From the Department of Anesthesiology and Critical Care Medicine, Leopold-Franzens-University, Innsbruck, Austria Reducing inspiratory flow rate and peak airway pres- sure may be important to minimize the risk of stomach inflation when ventilating an unprotected airway with positive pressure ventilation. In this study, we assessed the effects of a standard self-inflating bag compared with a new pressure-responsive, inspiratory gas flow-limiting device (SMART BAG ® ) on respiratory mechanics in 60 adult patients undergoing routine induction of anesthe- sia. Respiratory variables were measured using a pulmo- nary monitor. The SMART BAG ® resulted in significantly decreased inspiratory flow rate and peak airway pressure while providing adequate tidal volume delivery. (Anesth Analg 2003;97:1686 –9) T he self-inflating bag was developed in 1955 by Henning Ruben, and it has been the primary method of ventilating a patient in respiratory and/or cardiac arrest for 45 yr (1). Previous studies have shown that bag-valve-mask ventilation with an unprotected airway is often poorly performed with high flow rates and unnecessarily large tidal volumes creating excessive peak airway pressures, leading to rapid rates of stomach inflation (2,3). An approach ensuring both adequate ventilation in an unprotected airway and patient safety may be to design a ventila- tion device with an incorporated feature ensuring a margin of protection for the patient’s airway, espe- cially when used by less experienced rescuers. We have previously shown that decreasing peak airway pressure during bag-valve-mask ventilation by de- creasing tidal volume from 1000 to 500 mL is one strategy in improving bag-valve-mask ventilation (4). Another option may be to limit inspiratory flow rate to reduce peak airway pressure. Based on this concept, a new pressure-responsive, inspiratory gas-flow-limiting bag-valve mask device has been developed (SMART BAG ® ; O-Two-Systems, Mississauga, Canada) that limits peak inspiratory gas flow from up to 120 L/min in a standard self-inflating bag to  40 L/min (Fig. 1). The purpose of this study was to assess the effects of a standard self-inflating bag compared with the new pressure-responsive, inspiratory gas flow-limiting de- vice on respiratory mechanics in adult supine patients undergoing routine induction of anesthesia. Our hy- pothesis was that there would be no differences in study end-points between groups. Methods With ethics committee approval and written informed consent, we studied 60 healthy adult ASA physical status I and II patients with no respiratory disease (age, 18 –76 yr; mean body mass index, 25 kg/m 2 ) who were scheduled for peripheral musculoskeletal sur- gery. Patients were excluded if they had a predicted respiratory disease, oropharyngeal or facial pathol- ogy, a body mass index 30 kg/m 2 , or if they had more than one symptom of gastroesophageal reflux per week. Premedication was with oral midazolam 7.5 mg 1 h preoperatively. Anesthesia was in the supine position with the patient’s head on a standard pillow 5 cm in height. A standard anesthesia protocol was followed and routine monitoring was applied. Fentanyl 1.5 g/kg was administered. Patients were preoxygen- ated for 3 min. Anesthesia was induced with propofol Supported, in part, by the Austrian Science Foundation Grant P14169-MED, Vienna, Austria; O-Two Systems International, Mis- sissauga, Ontario, Canada; and the Department of Anesthesiology and Critical Care Medicine, Leopold-Franzens-University, Inns- bruck, Austria. Accepted for publication June 26, 2003. Address correspondence and reprint requests to Dr. Horst Wagner-Berger, Department of Anesthesiology and Critical Care Medicine, Leopold-Franzens-University, Anichstrasse 35, 6020 Inns- bruck, Austria. Address email to Horst.Wagner-Berger@uibk.ac.at. DOI: 10.1213/01.ANE.0000087064.29929.CE ©2003 by the International Anesthesia Research Society 1686 Anesth Analg 2003;97:1686–9 0003-2999/03