Prolonged two-man basic life support may result in hypocarbia in the ventilating rescuer

To determine whether the quality of expired air given during mouth-to-mouth ventilation differs between one- and two-person basic life support.

15 young fit volunteers performed 15-min simulated resuscitation on a manikin. The oxygen and carbon dioxide concentration of their expired breath and the total ventilation was continuously monitored. Compression:ventilation ratios of 15:2 for one-person and 5:1 for two-person resuscitation were used.

In two-man resuscitation, where the rescuer who is ventilating the patient is not performing chest compressions, the oxygen content of the expired breath rises (P<0.01), and the carbon dioxide content falls (P<0.01). The carbon dioxide concentration declined gradually throughout the 15-min session. Most participants complained of light-headedness on completion of the two-man session. Total ventilation did not differ between the two methods (P=0.757, 95% CI=-0.329, 0.242).

Trainees in basic life support should be informed that symptoms of hypocarbia may occur in prolonged mouth-to-mouth ventilation, when acting in a two-man team. We would advise rescuers using these protocols to change places every 5 min to avoid these symptoms. These findings add further weight to the recommendations that all resuscitation should be carried out using 15:2 compression:ventilation ratio.