BACKGROUND: True arterial blood samples are essential in making clinical decisions for respiratory patients. Previous studies using only the Portex Pro-Vent arterial sampler have shown a significant difference between arterial and venous filling times. The goal of this study was to determine whether there is a statistically significant difference between sampler filling times measured at a normal mean arterial pressure among multiple arterial samplers with plungers and to determine whether there is a statistically significant difference in filling times between venous and normal mean arterial pressures for a sampler without a plunger. METHODS: We assembled an extracorporeal laboratory model to circulate a synthetic compound composed of 0.9% sodium chloride solution and Life/form artificial blood, and we used hemostats to create pressures within the circuit. We randomly selected samplers and measured the filling times of 4 arterial samplers with plungers at a normal mean arterial pressure (93 ؎ 1 mm Hg). We also measured the filling time of one arterial sampler without a plunger at a normal mean arterial pressure and at a simulated venous pressure (9 ؎ 2 mm Hg). We used the Kruskal-Wallis one-way analysis of variance to compare arterial filling times in samplers, and we used a t test for independent samples to compare venous and arterial filling times in the sampler without a plunger. RESULTS: There was a statistically significant difference between sampler filling times among the 4 arterial samplers with a plunger (P < .001). There was a statistically significant difference between arterial and venous pressure filling times for the sampler without a plunger (P < .001). CONCLUSIONS: Although there was a statistically significant difference between arterial filling times among various samplers with plungers, the difference was < 1 s and was not deemed clinically important. Regardless of the sampler brand being used, respiratory therapists and other clinicians performing arterial punctures can use sampler filling time to identify a successful arterial puncture while drawing blood.