Test injection rates were determined for each needle based on ISO 7864:2016 Section C3.2.4 Briefly, the standard indicates that when possible, needles should be tested at an injection pressure of 825 mmHg, which simulates the upper pressure of the average user. Using a Nexus 6000 syringe pump (Chemyx Inc., Stafford, TX), pressure versus injection rates were determined for each needle. For the 25-gauge ProFusion and 25-gauge spinal needles, the target pressure was reached at 11.5 and 13.0 mL/min respectively. However, even under the fastest injection rates possible (>60 mL/min), the large bore needles did not approach the target injection pressure. As such, 30 mL/min (or 0.5 mL/sec) was utilized as an injection rate for these needles, as that rate would be considered the upper limit for speed for an operator injecting cells at this injection volume in the clinical setting.
