difference in CO kinetics between the mother and the fetus and to call attention to the current recommendations for treating this medical emergency when a pregnant female is involved.

A 20-year-old white female arrived by ambulance at the hospital approximately 60 min after being found unconscious at her mobile home. She had been intubated by the Emergency Medical Services and had received 100% supplemental oxygen en route to the hospital. The patient’s 21-year-old husband was also found at the scene and brought to the hospital. Although initially disoriented, restless, and combative, he was lucid at the time of arrival in the emergency department. From his history, it was determined that the couple’s usual heater was in disrepair, and a portable propane heater was the sole source of heat in their unventilated mobile home. He also disclosed that his wife was 28 weeks into her first pregnancy, that her past medical history was unremarkable, and that she was not currently taking medications or using cigarettes.

During the initial physical examination, the patient was noted to be combative and confused. Her blood pressure was palpable by cuff measurement at 80 torr systolic. She was being ventilated by a volume-cycled ventilator which she triggered 26 times a minute. Carbonaceous material was found in the nares, oropharynx, and adherent to the endotracheal tube. No burns of the skin, nasal hair, face, or eyebrows were present. Abdominal examination results were consistent with a 28-week intrauterine pregnancy.

No fetal movement could be detected by ultrasound, and fetal heart sounds were absent. Peripheral cyanosis was noted in her nail beds. The measured carboxyhemoglobin concentration at the time of admission was 7%. A plasma and urine toxicology screen was negative. The initial chest radiograph was interpreted as showing bilateral alveolar infiltrates consistent with the adult respiratory distress syndrome.

On the second hospital day, the patient went into labor spontaneously and delivered a 1050-g stillborn female fetus of approximately 7 months gestation, with a crown-heel length of 39 cm and crown-rump length of 27 cm. The gross autopsy findings were remarkable only for bright red discoloration of the skin and visceral organs. The corrected fetal COHb saturation at the time of the autopsy was 61% by IL 282-CO-Oximeter³ [4]. On microscopic examination of the tissues, the expected autolytic changes were seen but no other diagnostic abnormalities were found.

The mother began a slow convalescence after delivery of the fetus and subsequently recovered normal pulmonary function. She was discharged on the ninth hospital day.

Approximately 3500 to 4000 deaths each year in the United States are caused from carbon monoxide (CO), the nonirritating, odorless, tasteless, and colorless inert gas that is produced by the incomplete combustion of carbon-containing materials [1].

CO has an affinity for reversibly binding with adult hemoglobin that is 250 times greater than that of oxygen [5]. Measurement of the carboxyhemoglobin (COHb) level provides the clinician with an objective parameter to correlate with clinical symptoms and prognosis. Because CO is endogenously produced in humans during metabolism of protoporphyrin to bilirubin during hemoglobin metabolism, a nonsmoking individual may have a normal resting COHb saturation of 1 to 3% [6]. Cigarette smokers will commonly have