Abstract P111: Applying the Principles of Functional Stimulation to Electrical CPR
Background: We have previously reported on a specialized electrical stimulus that produces coronary and carotid blood flow during VF. The values selected for the Current (C), Pulse Width (PW), Pulse Period (PP), Train Width (TW) and Train Rate (TR) are critical to obtaining effective blood flow. An initial experiment in which these parameters were systematically studied in order to identify the optimal parameters has been previously reported. In this study we utilized some of the principles established in the field of NeuroMuscular Electrical Stimulation (NMES) of the extremities to further optimize ECPR. A primary principle of interest is that the force produced is proportional to charge delivered (Coulombs or amp-seconds.) Consequently, higher C, longer PW, shorter PP and longer TW would be predicted to produce greater force.
Hypothsis: We hypothesized that for ECPR as in NMES that: CPP over time would be proportional to the total charge delivered per constriction.
Methods: We applied 118 episodes of ECPR in 7 porcine subjects as previously described. VF was electrically induced and untreated for 10 seconds. ECPR was then applied for 60 seconds or until CPP dropped below 15 mm Hg. The specific ECPR intervention applied was determined according to a factorial design of experiment in which two levels each of C, PW, PP and TW were evaluated. The CPP was recorded at 10-second intervals during ECPR until it was terminated.
Results: PP and PW showed significant differences in their ability to maintain CPP > 15 mm Hg (T15) for prolonged periods of time (PP=25 ms: 49±15 s to T15 vs PP=50 ms: 41±17 s to T15, p=0.004) (PW=0.2 ms: 42±17 s to T15 vs PW=0.8 ms: 48±16 s to T15, p=0.05). Regression analysis further showed that an increase in PW and a decrease in PP worked independently and without interaction to increase T15 for CPP. These two parameters relate directly to total charge delivered with the result that, for each additional unit of total charge delivered, there was an almost 8 times increase in the T15 time period (coefficient = 7.7, 95% CI=(6.5,8.9))
Conclusions: The increases in charge provided by longer PP and shorter PW produced significantly longer time of CPP > 15 mm Hg within the limits of this test. Further study is required in order to further extend the duration of action ECPR.