Analysis of factors that influence rates of carbon monoxide uptake, distribution, and washout from blood and extravascular tissues using a multicompartment model

Margaret C. Bruce, Eugene N. Bruce
2006 Journal of applied physiology  
Bruce, Margaret C, and Eugene N. Bruce. Analysis of factors that influence rates of carbon monoxide uptake, distribution, and washout from blood and extravascular tissues using a multicompartment model. To better understand factors that influence carbon monoxide (CO) washout rates, we utilized a multicompartment mathematical model to predict rates of CO uptake, distribution in vascular and extravascular (muscle vs. other soft tissue) compartments, and washout over a range of exposure and
more » ... exposure and washout conditions with varied subject-specific parameters. We fitted this model to experimental data from 15 human subjects, for whom subject-specific parameters were known, multiple washout carboxyhemoglobin (COHb) levels were available, and CO exposure conditions were identical, to investigate the contributions of exposure conditions and individual variability to CO washout from blood. We found that CO washout from venous blood was biphasic and that postexposure times at which COHb samples were obtained significantly influenced the calculated CO half times (P Ͻ 0.0001). The first, more rapid, phase of CO washout from the blood reflected the loss of CO to the expired air and to a slow uptake by the muscle compartment, whereas the second, slower washout phase was attributable to CO flow from the muscle compartment back to the blood and removal from blood via the expired air. When the model was used to predict the effects of varying exposure conditions for these subjects, the CO exposure duration, concentration, peak COHb levels, and subject-specific parameters each influenced washout half times. Blood volume divided by ventilation correlated better with half-time predictions than did cardiac output, muscle mass, or ventilation, but it explained only ϳ50% of half-time variability. Thus exposure conditions, COHb sampling times, and individual parameters should be considered when estimating CO washout rates for poisoning victims. mathematical model; Coburn-Forster-Kane equation; carboxyhemoglobin; carboxymyoglobin CARBON MONOXIDE (CO) exposure continues to be the leading cause of poisoning in the United States. Sources of exposure include both the workplace, where CO is the leading cause of work-related inhalation fatalities (21), and the home, where faulty gas-and propane-driven appliances send thousands to the emergency rooms each year. Although the mortality due to CO poisoning (ϳ500 deaths/year) is on the decline, there is increasing concern regarding the incidence of delayed neurological sequelae and ischemic ECG changes, estimated to occur in 25-50 and 30%, respectively, of moderately to severely poisoned patients (18, 24) .
doi:10.1152/japplphysiol.00512.2005 pmid:16339350 fatcat:544rk6tvr5bptlmxr5oovh7tza