The Effect on Delivered Oxygen Concentration of the Rescuer's Breathing Supplemental Oxygen during Exhaled-Gas Ventilation

Exhaled-gas ventilation of a victim by a rescuer using mouth-to-mouth technique or mouth-to-mask technique delivers tidal volumes greater than those delivered by the bag-valve-mask technique. However, a disadvantage of exhaled-gas ventilation is its low oxygen concentration. We conducted this study to evaluate whether the rescuer's breathing supplemental oxygen by nasal cannula had an effect on the oxygen concentration delivered during mouth-to-mouth ventilation. Methods: We recruited 15 volunteers to ventilate an adult resuscitation manikin while they breathed room air, 6 L/min oxygen by nasal cannula, and 10 L/min oxygen by nasal cannula. The gas 'exhaled' by the manikin was collected and analyzed for oxygen concentration and PCO ₂ ; this gas represented the exhaled gas of the rescuer, inasmuch as no gas exchange occurred in the manikin. Results: The oxygen concentration of the exhaled gas was 16±1% with the rescuers on room air, 27±3% with the rescuers on 6 L/min oxygen, and 31±5% with the rescuers on 10 L/min oxygen (P<0.001). The differences among PCO ₂ values resulting from the rescuers' breathing room air and breathing 6 L/min and 10 L/min supplemental oxygen were statistically significant; however, the magnitude of the differences was too small to have had any effect on the concentration of oxygen in the rescuers' exhaled gas. Conclusion: We conclude that the oxygen concentration delivered to a victim during exhaled-gas or mouth-to-mouth ventilation can be increased significantly if the rescuer breathes oxygen by nasal cannula at 10 L/min. (Respir Care 1985;30:691-694.)