Abstract 94: Closed Loop Compression Depth Optimization in a Pig Model
Introduction: CPR success depends on blood flow generated by it, affected among others by compression depth. AHA guidelines advise the same small range of depths for all patients, while their individual optimum may vary widely. Therefore, an individual patient may have an increased chance of survival if CPR is performed at this optimum depth. We investigated the feasibility of an automated compression depth tuning algorithm.
Methods: In five Yorkshire pigs (about 31 kg) aortic and right atrial pressure were measured with Millar catheters. CPP and aortic diastolic blood pressure (DBP) were calculated in real-time. DBP was used as CPR quality indicator (QI), i.e. as a surrogate for myocardial blood flow. After VF induction, CPR was performed at 100 cpm for 10 min with a proprietary automated CPR device. Compression depth was tuned automatically every 2 min by first decreasing depth by 0.5 cm, followed by increasing depth by 1 cm, both for 20 seconds. The depth at the highest QI was used as new depth in the next cycle (Fig. 1). It was determined whether the QI reflected CPP. Tuning step size (cm) and duration (s) were studied to see if these resulted in clinical relevant QI changes.
Results: The mean correlation coefficient between the QI and the CPP was 0.7. The mean QI change per depth change was 2.3 mmHg (about 10% change). The algorithm had a bias towards lower depths as the depth increase first had to overcome the QI change of the preceding decrease which did not result in a steady state QI within 20 seconds. The algorithm tuned to a compression depth between 2.5 and 4.5 cm for these animals.
Conclusion: DBP can be used as a CPR quality indicator as its correlation with CPP is high. A step size of 0.5 cm is a viable choice for a tuning algorithm as it resulted in clinical relevant changes of QI within 20 seconds. A bias to a certain compression depth should be prevented by either lengthening the duration of the depth change or by performing the increase and decrease at non-consecutive time intervals.
Author Disclosures: P. Aelen: Employment; Significant; Philips. S. Ordelman: Employment; Significant; Philips. P. Woerlee: Employment; Significant; Philips. G. Noordergraaf: Consultant/Advisory Board; Significant; Philips.
- © 2014 by American Heart Association, Inc.