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Carboxyhemoglobin Half-life in Carbon Monoxide-Poisoned Patients Treated With 100% Oxygen at Atmospheric Pressure

2000; Elsevier BV; Volume: 117; Issue: 3 Linguagem: Inglês

10.1378/chest.117.3.801

1931-3543

Lindell K. Weaver, Steve Howe, Ramona O. Hopkins, Karen J. Chan,

Neonatal Health and Biochemistry

Study objectives There are large reported differences for the carboxyhemoglobin (COHb) half-life (COHb t 1/2 ) in humans breathing 100% atmospheric O 2 following CO inhalation in tightly controlled experiments compared to the COHb t 1/2 observed in clinical CO poisoning (range, 36 to 131 min, respectively). Other reports have suggested that the COHb t 1/2 may be affected by gender differences, age, and lung function. We wished to test the hypothesis that the COHb t 1/2 might also be influenced by CO poisoning vs experimental CO exposure, by a history of loss of consciousness (LOC), concurrent tobacco smoking, and by Pao 2 . The purpose of the present study was to measure the COHb t 1/2 in a cohort of CO-poisoned patients and to determine if those listed factors influenced the COHb t 1/2 . Design Retrospective chart review from 1985 to 1995. We calculated the COHb t 1/2 of CO-poisoned patients who were treated with high-flow supplemental atmospheric pressure O 2 delivered by nonrebreather face mask or endotracheal tube. Setting Hyperbaric medicine department of a tertiary-care teaching hospital. Patients Of 240 CO-poisoned patients, 93 had at least two COHb measurements > 2% (upper limit of normal) with recorded times of the measurements, permitting calculation of the COHb t 1/2 . Results The COHb t 1/2 was 74 ± 25 min (mean ± 1 SD) with a range from 26 to 148 min. By stepwise multiple linear regression analysis, the Pao 2 influenced the COHb t 1/2 ( R 2 = 0.19; p < 0.001), whereas the COHb t 1/2 was not influenced by gender, age, smoke inhalation, history of LOC, concurrent tobacco smoking, degree of initial metabolic acidosis (base excess), or initial COHb level. Conclusions The COHb t 1/2 of 93 CO-poisoned patients treated with 100% O 2 at atmospheric pressure was 74 ± 25 min, considerably shorter than the COHb t 1/2 reported in prior clinical reports (approximately 130 ± 130 min) and was influenced only by the patient's Pao 2 .