Decreasing the number of positive-pressure ventilations
delivered during CPR from 12 to 6 per minute significantly
decreased ITP and improved hemodynamics. With
C/V ratio increased from 15:2 to 15:1, mean ITP values
during positive-pressure ventilations (4 compression-decompression
cycles) decreased from 23.7 2.7 mm Hg to
11.1 1.4 mm Hg, p 0.001. Mean ITP values over 1
min were also decreased significantly, from 0.93 0.3
mm Hg to 0.3 0.28 mm Hg, p 0.001 (Table 1). The
changes were echoed with the calculations of the ITP area
over 1 min, which decreased from 55 17 mm Hg s with
15:2 to 22.3 10 mm Hg s with 15:1, p 0.001.
Arterial pressures were significantly improved by increasing
the ratio from 15:2 to 15:1, as seen by the increase
in the arterial systolic and diastolic pressure (see
Table 1). The impact on diastolic pressure was notable;
diastolic blood pressures were 15.5 3.5 mm Hg with the
15:2 ratio and 24.2 2.4 mm Hg with 15:1, p 0.001.
Thus, the impact of the extra breath resulted in a downstream
decrease in diastolic pressure throughout the entire
duration of CPR.
Mean coronary perfusion pressure over 1 min increased
from 10.1 4.5 mm Hg to 19.3 3.2 mm Hg, p 0.007.
The same effect was also observed during the delivery of
positive-pressure breaths (see Table 1). Mean diastolic right
atrial pressure over 1 min with the 15:2 ratio was significantly
higher, when compared to the 15:1 ratio: 5.8 0.8
mm Hg versus 4.8 1 mm Hg, p 0.05. Similarly, the
right atrial diastolic pressures were 8.6 1 mm Hg and
7.2 0.9 mm Hg with the 15:2 and 15:1 ratios, respectively,
p 0.03 (see Table 1).
