• A Stallinger, V Wenzel, S Oroszy, V D Mayr, A H Idris, K H Lindner, and C Hörmann.
• Department of Anesthesiology and Critical Care Medicine, Leopold-Franzens-University, Innsbruck, Austria. Angelika.Stallinger@uibk.ac.at
• Anesth. Analg. 2001 Nov 1; 93 (5): 1265-9.

UnlabelledThe American Heart Association recommends tidal volumes of 700 to 1000 mL during mouth-to-mouth ventilation, but smaller tidal volumes of 500 mL may be of advantage to decrease the likelihood of stomach inflation. Because mouth-to-mouth ventilation gas contains only 17% oxygen, but 4% carbon dioxide, it is unknown whether 500-mL tidal volumes given during rescue breathing may result in insufficient oxygenation and inadequate carbon dioxide elimination. In a university hospital research laboratory, 20 fully conscious volunteer health care professionals were randomly assigned to breathe tidal volumes of 500 or 1000 mL of mouth-to-mouth ventilation gas (17% oxygen, 4% carbon dioxide, 79% nitrogen), or room air control (21% oxygen, 79% nitrogen) for 5 min. Arterial blood gases were taken immediately before, and after breathing 5 min of the experimental gas composition. When comparing 500 versus 1000 mL of mouth-to-mouth ventilation tidal volumes with 500 mL of room air, 500 mL of mouth-to-mouth ventilation tidal volume resulted in significantly (P < 0.05) lower mean +/- SEM arterial oxygen partial pressure (70 +/- 1 versus 85 +/- 2 versus 92 +/- 3 mm Hg, respectively), and lower oxygen saturation (94 +/- 0.4 versus 97 +/- 0.2 versus 98 +/- 0.2%), but increased arterial carbon dioxide partial pressure (46 +/- 1 versus 40 +/- 1 versus 39 +/- 1 mm Hg, respectively). Sixteen of 20 volunteers had to be excluded from the experiment with 500 mL of mouth-to-mouth ventilation gas after about 3 min instead of after 5 minutes as planned because of severe nervousness, sweating, and air hunger. We conclude that during simulated mouth-to-mouth ventilation, only large (approximately 1000 mL), but not small (approximately 500 mL) tidal volumes were able to maintain both sufficient oxygenation and adequate carbon dioxide elimination.ImplicationsTo provide efficient mouth-to-mouth ventilation, it is important to administer tidal volumes of 1000 mL; tidal volumes of 500 mL were not adequate.

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