Comparisons of PCO2 between groups are shown in
Table 2. No significant differences were noted in arterial
PCO2 values between the two ventilated groups (room airand 100% oxygen). However, both of these groups showed
a significant decrease in arterial PCO2 when compared
with the unventilated (compression-alone) group. Mixed
venous PCO2 was significantly decreased in the two ventilated
groups, compared with the compression-only group,
only at the 10- and 20-minute samples.
Defibrillation was attempted in all animals after 20 minutes
of resuscitation. Return of spontaneous circulation was
achieved in three of eight animals ventilated with 100%
oxygen, on the first, first, and third attempts at 300 J, respectively.
Twenty minutes after defibrillation, these three animals
had a normal sinus rhythm, an average blood pressure
of 110/58 mm Hg, and a cardiac output of 3.2 L/minute.
No defibrillations were successful on the other groups. The
37% defibrillation success rate in the 100% oxygen group
was not significantly different from the 0% success rate in
the other treatment groups by Fisher’s exact test.