 Breath CO monitoring offers a viable alternative to pulse CO @-@ oximetry . Carboxyhemoglobin levels have been shown to have a strong correlation with breath CO concentration . However , many of these devices require the user to inhale deeply and hold their breath to allow the CO in the blood to escape into the lung before the measurement can be made . As this is not possible in a <unk> patient , these devices are not appropriate for use in on @-@ scene emergency care detection of CO poisoning . 
