Abstract 261: Intentional or Inadvertent Hyperventilation of Patients with Out-of-Hospital Cardiac Arrest on Hospital Arrival

Abstract

Background The deleterious effects of intentional or inadvertent hyperventilation of out-of-hospital cardiac arrest (OHCA) patients include decreased venous blood return, increased intracranial pressure and decreased coronary perfusion pressure. Recent AHA guidelines specify ventilation rates between 8-12 breaths per minute (bpm). We previously presented findings that hyperventilation is common immediately following placement of an airway device. We also observed a number of cases in which hyperventilation occurred close to the end of recordings from EMS monitor-defibrillators presumably corresponding to the time of hospital arrival and transfer of care. Objective Determine the prevalence of intentional or inadvertent hyperventilation of OHCA patients upon hospital arrival and transfer of care to hospital staff. Methods Capnogram recordings from a convenience sample of 205 OHCA patients collected between 2006 to 2010 from a single EMS agency using Philips HeartStart MRx defibrillators were examined. An automated breath detection algorithm that relied on capnographic waveforms was used to compute ventilation rates and EtCO2 levels. Clinical charts written by the EMS personnel were examined to determine cardiac rhythm and if spontaneous breathing was observed upon hospital arrival, which was excluded. Results 23 cases (11.2%) were identified which were determined to have an episode of hyperventilation at the end of the recordings, with times corresponding to transfer of care after hospital arrival. Running average hyperventilation rates were 28±8 bpm, with average peak instantaneous rate 36±10 bpm, range 24-46 bpm. Average minimum EtCO2 during hyperventilation was 12±14 mmHg, range 1.8-70 mmHg. Conclusion Intentional or inadvertent hyperventilation of OHCA patients at rates well above AHA guidelines was present in 11% of cases at times corresponding to transfer of care from EMS to hospital staff. It is unclear if this was performed by EMS staff or hospital staff. Better awareness and communication of this potentially harmful behavior to EMS personnel and hospital staff is warranted.