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Excerpt
Introduction: Mouth-to-mouth ventilation during CPR results in the administration of a hypoxic ([nearly =] 15% O2) and hypercarbic ([nearly =] 5-6% CO2) gas mixture to the patient, which could adversely affect resuscitation during cardiac arrest. The purpose of this study was to compare the effects of reacuer lung volume and exhaled tidal volume (VT) on the concentrations of O2 and CO2 received by the patient during simulated mouth-to-mouth ventilation.
Methods: Three reacuers (physicians) inhaled to two diacrete lung volumes: (1) total lung capacity (TLC) and (2) a normal VT at functional residual capacity (FRC + VT). At each lung volume the reacuers exhaled into a test lung via a month piece at 10 breaths/min at a VT of 250, 500, and 1000 mL. Real time measurements of VT from a flow sensor attached to the mouth piece, and O2 and CO2 concentrations from inside the test lung, were obtained with a respiratory monitor (Datex). Data were compared with a Friedman two-factor ANOVA of ranks; alpha was set at .05 for statistical significance.
Results: Rescuer breathing pattern during mouth-to-mouth ventilation significantly affects the amount of O2 and CO2 received by the patient. A significant interaction effect was observed, ie, patient lung O2 was highest and CO2 lowest when the rescuer exhaled from TLC at a VT of 250 mL (Figure 1).
P < .05 compared to same delivered VT at the lower rescuer lung volume (FRC + VT) (*), compared to 500 mL (X), and 1000 mL (+) at FRC + VT.
Conclusion: Rescuer breathing strategies, which increase O2 and decrease CO2 administered during mouth-to-mouth ventilation may improve the survivability of patients who suffer cardiac arrest, and thus, further research is warranted.
