Half-life of blood carboxyhemoglobin after short-term and long-term exposure to carbon monoxide.
BACKGROUND
In models of smoke inhalation injury and carbon monoxide poisoning blood carboxy-hemoglobin (COHb) levels decrease faster than predicted by the generally recognized half-life of COHb. We studied the effects of duration of exposure to carbon monoxide (CO) on the subsequent CO elimination.


METHODS
Each of four sheep were insufflated with CO gas mixtures either for a few minutes (short-term exposure) or for several hours (long-term exposure), then ventilated with air for 3 hours. Serial COHb concentrations were analyzed by using a two-compartment, single central outlet mathematical model.


RESULTS
Short-term exposures exhibited biphasic decreases of COHb concentration compatible with a two-compartment model; an initial rapid decrease (half-life 5.7 +/- 1.4 minutes) was followed by a slower phase (103 +/- 20.5 minutes). Long-term exposures exhibited almost monophasic decreases, which were nevertheless compatible with the model (half-life, 21.5 +/- 2.1 and 118 +/- 11.2 minutes).


CONCLUSIONS
This study demonstrated different patterns of CO elimination curve, which suggests distribution of CO to two compartments having different rates of equilibration.
Shimazu
T
T
Department of Traumatology, Osaka University, Medical School, Japan.
Ikeuchi
H
H
Sugimoto
H
H
Goodwin
C W
CW
Mason
A D
AD
Pruitt
B A
BA
D000280:Administration, Inhalation; D000818:Animals; D002248:Carbon Monoxide / Q000008:administration & dosage / Q000493:pharmacokinetics*; D002263:Carboxyhemoglobin / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D006207:Half-Life; D006439:Hemodynamics; D012129:Respiratory Function Tests; D012756:Sheep; D015208:Smoke Inhalation Injury / Q000503:physiopathology*; D013997:Time Factors
D002248:Carbon Monoxide; D002263:Carboxyhemoglobin