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Carboxyhemoglobin half-life during hyperbaric oxygen in a patient with lung dysfunction: a case report

Introduction: The carboxyhemoglobin half-life (COHb t1/2) during hyperbaric oxygen (HBO2) is often quoted as 23 minutes, derived from the average of two adult male volunteers breathing HBO2 at 3 atmospheres absolute (ATA). However, the mean COHb t1/2 of 12 male volunteer smokers was 26.3 minutes at 1.58 ATA and in 12 non-intubated carbon monoxide (CO)-poisoned patients treated at 3 ATA, was 43 minutes.

Case report: An 81-year old male, poisoned by an improperly ventilated natural gas heater, was intubated for coma, then treated with HBO2. His PaO2/FiO2 = 283 from aspiration. His initial COHb was 34.4%, and 18 minutes before HBO2, 5.9%. After a compression interval of 17 minutes, the COHb measured after 22 minutes at 3 ATA was 3.3%.

Results: By exponential decay, his COHb t1/2 before HBO2 was 95 minutes. We estimate the range for COHb t1/2 during compression as 62-81 minutes and for the 3 ATA interval, 58 to 49 minutes, respectively. The mid-point estimate of COHb t1/2 at 3 ATA was 53 minutes.

Conclusions: The COHb t1/2 we calculated is greater than previously reported, but longer in our patient possibly because of concomitant respiratory failure, lung dysfunction, and mechanical ventilation. The often-cited COHb t1/2 of 23 minutes, likely underestimates the actual COHb t1/2 in CO-poisoned patients, especially those with cardiopulmonary dysfunction.

DOI: 10.22462/3.4.2017.12