Resuscitation: AEDs are safe in helicopters, with caveats

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Three commercially available automated external defibrillators (AEDs) correctly analyzed heart rhythms in an in-motion helicopter on a manikin and a human volunteer. While researchers call for further studies, they were encouraged by the results, according to a study in published online Jan. 25 in Resuscitation.

"Due to high ambient noise levels, space limitations and motion of the aircraft, the effectiveness of certain life-saving ACLS interventions (e.g. defibrillation) is decreased among in-motion helicopters," the authors wrote.

In addition, current European resuscitation guidelines recommend that AEDs should never be placed in the analysis mode during a transport in a moving ambulance because artifact rhythms arising from movement of the ambulance can interfere with rhythm analysis of the AED and can simulate ventricular fibrillation (VF).

While ambulances can stop to deliver shock therapy, thereby minimizing the risk of bumps in the road interfering with rhythm analysis, helicopters cannot turn off their engines in mid flight to minimize noise and vibrations while applying AED shock therapy.

To study this matter further, Sang Mo Je, MD, and colleagues from Yonsei University College of Medicine in Seoul, South Korea, tested three commercial AEDs for analyzing the heart rhythm in a helicopter using an ALS simulator manikin (Laerdal) and a human volunteer.

The AEDs tested were Lifegain HD1, CU Medical Systems; Heartstart MRx, Philips Healthcare; and Lifepak 12, Physio-Control.

The researchers simulated VF, sinus rhythm and asystole by using an arrhythmia simulator of the manikin. The intervals from analysis to shock recommendation were collected on a stationary and in-motion helicopter. Sensitivity and specificity of three AEDs were also calculated. Vibration intensities were measured with a digital vibration meter placed on the chest of the manikin and human volunteer both on the stretcher and on the floor of the helicopter.

The investigators found that all AEDs correctly recommended shock delivery for the cardiac rhythms of the manikin. Sensitivity for VF was 100 percent and specificity for sinus rhythm and asystole were 100 percent.

Although the recorded ECG rhythms of the volunteer in an in-motion helicopter showed baseline artifacts, all AEDs analyzed the cardiac rhythm of the volunteer correctly and did not recommend shock delivery.

Significantly less vibrations were transmitted to the manikin/human volunteer chest than were measured on the floor of the helicopter.

"This study suggested that current AEDs could analyze the heart rhythm correctly during simulated helicopter transport," the authors concluded.

However, they said these results "cannot guarantee the safety of AEDs for use in an in-motion helicopter" because of the VF-like baseline artifacts of ECG from downloaded ECG data of the volunteer in an in-motion helicopter.

"These artifacts can condition the shock/no-shock decision of AEDs. Misinterpreting a motion artifact as a VF can cause harm to patients with an underlying sinus rhythm because an inappropriate defibrillation could induce a lethal arrhythmia. Moreover VF-like rhythm of underlying asystole can cause harm because an inappropriate defibrillation could discontinue during AED rhythm analysis, thereby decreasing the likelihood of resuscitation success."