Abstract 228: High Incidence of Hyperventilation Associated with Defibrillation Shock Delivery During Out-of-Hospital Cardiac Arrest Patient Resuscitation
Background Previous studies have highlighted the importance of avoiding hyperventilation during resuscitation of patients with out-of-hospital cardiac arrest (OHCA). Despite this, hyperventilation is often detectable on recorded capnograms, and the causative factors remain undefined. We studied the relationship between hyperventilation and defibrillation shocks. We hypothesized that immediately before and after shock delivery, a link to hyperventilation may exist due to the extreme high stress levels of the rescuers.
Objective To evaluate quantitatively the time difference between hyperventilation events and shock delivery.
Methods CO2 and shock data were collected from 270 OHCA patients from two EMS agencies based in Oregon and Texas between 2008 and 2010. We applied an automated hyperventilation detection algorithm with thresholds of respiratory rate > 12 bpm and EtCO2 < 20 mmHg, and manually reviewed results to obtain a total of 209 hyperventilation events from 83 patients who also had a shock (n=476) delivered within 20 minutes. Each hyperventilation event time was subtracted from the nearest shock time to generate the distribution of this difference. To investigate that this distribution actually shows a relation between hyperventilation and shock time that is not random, we generated a similar distribution of the difference between equally spaced points at 10 second intervals to shock times. The variances of the distributions were compared using a two-sample F-test.
Results The figure shows the distribution of hyperventilation events in relationship to the closest defibrillation shock, and the distribution of all 10 second intervals to shock times. The variances of the distributions were significantly different (p < 0.0001). A total of 48 (23%) hyperventilation events occurred within 1 minute of a defibrillation shock.
Conclusion Hyperventilation is particularly common immediately before and after shock delivery during OHCA resuscitation.
- © 2011 by American Heart Association, Inc.