Objective:
We recently reported that a global-level metabolic alteration occurs after cardiac arrest (CA) in our high fidelity rodent model. The finding was that dissociation of O
2
consumption (VO
2
) and carbon dioxide generation (VCO
2
) resulted in a respiratory quotient (RQ: calculated by dividing VCO
2 by
VO
2
) that fell well outside the normally cited range of 0.7-1.0. We hypothesized that a lowered RQ is similarly found in human CA patients.
Methods:
The study consisted of three subject groups: 1) healthy volunteer, 2) post-surgical patient (control) and 3) post-CA patient. We measured the VO
2
and VCO
2
of mechanically ventilated subjects using the Douglas bag method. Inspiration and expiration gas samples were collected in two separate bags
.
and RQ was calculated from CO
2
and O
2
gas concentrations in the samples. The patients and healthy volunteers were ventilated using the same model mechanical ventilator. Alert healthy volunteers bit onto a mouthpiece and the samples were collected, while post-surgical and post-CA patients were unconscious during the measurements. We measured the RQ of healthy volunteers at normal and high fractions of inspired oxygen (FIO
2
) in order to test the validity of our methods at various inspired O
2
levels.
Results:
The RQs of the three healthy volunteers were 0.83, 0.92 and 0.85 at an FIO
2
of 0.21 and 0.86, 0.88, and 0.83 at an FIO
2
of 0.90 respectively. The RQs of the two post-surgical patients were 0.92 and 0.88 at an FIO
2
of 0.5. None of the post-surgical patients had any complications following the surgery and all were discharged. The RQ of a post-CA patient measured 2.5 hours after the CA was found to be 0.72 at an FIO
2
of 0.9. The CA patient expired within 24 hours of hospital admission.
Conclusions:
The same trend between the findings of both our rodent study and the CA patient suggest that resuscitation from CA alters cellular metabolism on a global level. This metabolic alteration in turn causes the dissociation of O
2
consumption and CO
2
generation resulting in a lowered RQ. Our findings warrant a larger clinical study to confirm a lowered RQ in post-CA patients and bench work to elucidate the causative mechanism of this relationship.