Noninvasive measurement of carbon monoxide levels in patients with headaches

Abstract

Study objectives: Carbon monoxide (CO) exposure is common in emergency department (ED) practice. The clinical diagnosis of CO poisoning is difficult because the medical history and physical examination are often unrevealing, especially at low levels of exposure. In recent years, CO breath analyzers have become readily available, inexpensive, and accurate in determining carboxyhemoglobin (COHb) in exhaled breath. The purpose of this study is to determine whether a CO breath analyzer is a useful tool to identify headache patients presenting to the ED with elevated CO levels. Methods: This controlled, prospective study used a convenience sample of patients presenting to 2 community hospitals in Pennsylvania during October 2003 to April 2004. Inclusion criteria included patients older than 18 years, who presented with the complaint of atraumatic headaches, and who were afebrile. Patients who were hemodynamically unstable and could not hold their breath for 20 seconds or with known CO exposure were excluded. Seventy-nine matched control patients who presented to the ED during the same period without headache were similarly recruited. Patients were matched for age, sex, and smoking status. All patients filled out a brief questionnaire addressing smoking status, age, type of vehicle, and home heating sources. After informed consent, a breath sample was obtained using the Micro CO Breath Analyzer, (Micro Medical Ltd., Rochester, AZ). The CO levels were displayed in COHb percentage. Individuals with elevated breath COHb levels (nonsmokers >2%, smokers >5%) underwent confirmatory blood serum levels analysis. In patients with a normal breath CO level, no further testing was done. Results: One hundred fourteen patients were enrolled. Seven (6.1%) of 114 patients of our study group had elevated CO levels compared with only 1 (1.2%) of 79 in the control group ( P =.09). In those 7 patients who had elevated breath COHb levels, the 6 consenting to blood analysis all had elevated serum COHb levels confirmed. Conclusion: Breath analysis of CO levels in ED patients presenting with headache appears to be an accurate, rapid, and inexpensive screening tool to identify patients with elevated COHb levels.