Figure 1.

Tumor necrosis factor-alpha (TNF-α) and carboxyhemoglobin levels in arterial blood during experimental human endotoxemia. At t = 0 hours, 38 healthy male subjects were infused with 2 ng/kg Escherichia coli endotoxin. Arterial blood was sampled serially to determine concentrations of carboxyhemoglobin (Siemens Rapidlab 348 blood gas analyzer; Siemens Medical Solutions, Munich, Germany) and plasma TNF-α (Bio-plexcytokine assay; Bio-Rad Laboratories, Inc., Hercules, CA, USA, at a Luminex 100; Luminex Corporation, Oosterhout, The Netherlands). Carboxyhemoglobin levels are presented by boxplots, and whiskers indicate 5th to 95th percentiles. TNF-α is presented as median (black line); for clarity, interquartile range is omitted. Statistical analysis was performed by using the Friedman test (carboxyhemoglobin: P = 0.0057; TNF-α: P <0.001). LPS, lipopolysaccharide.