There is reason to believe that CO monitoring values (carboxyhemoglobin, COHb) obtained while your ambulance is running or driving may be inaccurate. It appears that this tends to result in variable, but generally high COHb numbers. Several units have now reported this experience. We are working with Masimo to identify potential causes and solutions. In the interim, please note COHb values beforeentering a running vehicle with patients in whom CO exposure is a suspicion. If you notice elevated COHb values while in a running vehicle with a patient in whom exposure is unlikely (and/or symptoms do not line up with readings) you may consider finding a safe place to stop the unit to verify readings if the patient is otherwise stable and the values are high enough to be concerning. If the patient is unstable, they are likely already on oxygen and it is likely best to continue transport and re-evaluate COHb once stopped. We have no reason to question the COHb values obtained when not in a running vehicle on patients with adequate perfusion.
Based on errant values obtained while in motion, there have been at least 2 instances in which we have summoned fire department units to respond for CO evaluation at the locations from which the patients were transported in order to assure the safety of others at those locations. In both instances, hospital verification of zero percent COHb were obtained and no CO was detected at the original patient locations. Where safe to do so, and no clinical evidence to support CO poisoning exists, please validate the patient's COHb without a running vehicle before dispatching resources to place themselves in harms way responding to such an event. Where significantly elevated COHb is also found in non-motion assessment, or when clinical symptoms support the obtained elevated COHb values, sending such resources to investigate should be considered.
