2003 OPEN FORUM Abstracts
Effects of decreasing inspiratory flow rate and use of a smaller adult self-inflating bag during simulated basic life support ventilation of a cardiac arrest patient on lung and stomach tidal volumes.
Thomas A. Barnes, EdD, RRT, FAARC, Melissa E. Catino, Erin C. Burns, Wing Kei Chan, Garo Ghazarian, Sunly Hem, Werner R. Henneberg, Kendra E. Ruel, Craig T. Tucker, Scott Stanley, MS, RRT
Department of Cardiopulmonary and Exercise Sciences, School of Health Professions, Bouve College of Health Sciences, Northeastern University, Boston, Massachusetts
When ventilating a cardiac arrest patient with an unprotected airway, smaller tidal volumes and low inspiratory flow rate may be beneficial to decrease stomach inflation. The purpose of this study was to determine if there was a significant difference in tidal volumes of air delivered to the lungs and stomach during resuscitation while using a bag valve device with a small self-inflating bag as compared to a limited flow device. Institutional review board approval and written informed consent was obtained from 11 American Heart Association Basic Life Support trained respiratory therapy and nursing student volunteers who ventilated a bench model simulating cardiac arrest patient with an unprotected airway consisting of a face mask, manikin intubation training head (Laerdal Medical Corporation Wappingers Falls, NY), lung analog (Biotek VT-1 Bio-Tek Instruments Inc. Winooski, VT) using both a small adult bag valve device (1000 mL bag, CPR Bag® Mercury Medical, Clearwater, Florida) and a limited flow device (Oxylator EMX® CPR Medical devices Inc., Toronto, Canada) [with lung compliance, 50 mL/0.098 kPa (50 mL/cmH2O); airway resistance, 0.78 kPa/L/s (8 cmH2O/L/s)] esophagus [lower esophageal sphincter pressure, 1.96 kPa (20 cmH2O)] and simulated stomach. Lower esophageal sphincter pressure was set using a water column PEEP valve (Emerson Company, Cambridge, MA) at the distal end of the esophageal outlet. The esophagus was simulated with an 18 cm section of penrose surgical drain. Tidal volume to mask was determined with a respiratory mechanics monitor (VENT, Novametrix Medical Systems Inc. Wallingford, CT). A Wright Panel-Mount Respirometer was placed at the distal end of PEEP valve to measure stomach inflation. The lung analog was used to detect volume of air that entered lung during ventilation. All subjects were given 30 minutes of pre-trial practice with both devices using a Laerdal Recording Anne with computer interface. Five 2-minute ventilation trials with each device were recorded for each subject. Ventilation trials were conducted with two persons, one applying the mask to the manikin face and the second operating the resuscitator. A ventilation rate of 12 breaths/min was accomplished with a prompt every 5 seconds. Inspiratory time was not controlled or measured. Results are listed in the table below:
|Device||Mask Volume*mL (SD)||Lung VolumemL (SD)||Stomach VolumemL (SD)||Mask Leak*mL (SD)|
|CPRBag||651 (111)||283 (122)||211 (197)||157 (116)|
|Oxylator EMX||554 (141)||298 (94)||177 (90)||78 (70)|
In conclusion, volume delivered to lungs and stomach by CPR Bag and Oxylator EMX were similar when ventilating a simulated cardiac arrest patient with an unprotected airway. Differences in tidal volumes delivered to mask and mask leak were not considered clinically important. Inability to assess chest rise and variable inspiratory times may have affected study results.