Do we hyperventilate cardiac arrest patients?

INTRODUCTION: Hyperventilation during cardiopulmonary resuscitation is detrimental to survival. Several clinical studies of ventilation during hospital and out-of-hospital cardiac arrest have demonstrated respiratory rates far in excess of the 10 min(-1) recommended by the ERC. We observed detailed ventilation variables prospectively during manual ventilation of 12 cardiac arrest patients treated in the emergency department of a UK Hospital.
METHODS: Adult cardiac arrest patients were treated according to ERC guidelines. Ventilation was provided using a self-inflating bag. A COSMOplus monitor (Respironics Inc.) was inserted into the ventilation circuit at the beginning of the resuscitation from which ventilation data were downloaded to a laptop.
RESULTS: Data were collected from 12 patients (7 male; age 47-82 years). The maximum respiratory rate was 9-41 breaths per minute (median 26). The median tidal volume was 619 ml (374-923 ml) and the median respiratory rate was 21 min(-1) (7-37 min(-1)). The corresponding median minute volume was 13.0 l/min (4.6-21.3 min(-1)). Median peak inspiratory pressures were 60.6 cmH(2)O (range 46-106). Airway pressure was positive for 95.3% of the respiratory cycle (range 87.9-100%).
CONCLUSIONS: Hyperventilation was common, mostly through high respiratory rates rather than excessive tidal volumes. This is the first study to document tidal volumes and airway pressures during resuscitation. The persistently high airway pressures are likely to have a detrimental effect on blood flow during CPR. Guidelines on respiratory rates are well known, but it would appear that in practice they are not being observed.