The Science Journal of the American Association for Respiratory Care

2000 OPEN FORUM Abstracts

BAG-VALVE-MASK VENTILATION DURING CPR: SMALLER TIDAL VOLUMES EVALUATED

Thomas A. Barnes, Ed.D., RRT, Liana M. Katsaros, B.S. Department of Cardiopulmonary Sciences, Northeastern University, Boston, MA 02115

The European Resuscitation Council has recommended smaller tidal volumes of 0.5 L during basic life support ventilation in order to minimize gastric inflation. The purpose of this study was to evaluate the amount of gastric inflation when tidal volumes (VTs) of 1.0 and 0.6 L are delivered during CPR. Methods: A mechanical model of the airway and lower esophageal sphincter (LES) was designed to study gastric inflation. A ventilator delivering volume-controlled breaths was used to simulate manual ventilation. The breaths were delivered to a wye connector, with one leg connected to a Bio-Tek Instruments VT-1 test lung and the other leg connected to a water column pressure valve to mimic LES. The volume of gas passing through LES was measured with a Timeter RT-200 calibration analyzer. VTs of 1.0 L and 0.6 L were delivered with inspiratory time (TI) of 1.0, 1.5, and 2.0 s at lung compliance (CL) of 0.100, 0.040, 0.020 L cm H2O-1. The effect of esophageal opening pressures (EOP) of 20, 15, 10, and 5 cm H2O were also evaluated. Results: Decreasing VT from 1.0 L to 0.6 L significantly (P<0.0001) reduced gastric inflation at TI of 1.0 and 1.5 s at all three CLs. Lengthening TI to 1.5 or 2.0 s improved lung inflation and decreased gastric inflation, but minimal improvement was observed when CL was 0.040 and 0.020 L × cm H2O-1. Gastric inflation was significantly (P<0.0001) higher at CLs of 0.040, 0.020 L × cm H2O-1. When EOP was £10 cm H2O with a VT of 0.6 L, gastric inflation was significantly (P<0.0001) higher.
Conclusion: Smaller tidal volumes reduce gastric inflation during bag-valve-mask ventilation. The use of smaller tidal volumes with bag-valve-mask ventilation is more critical when the EOP and CL are decreased. (See Original for Figure)

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