Does the Human Dynamic Influence the Compressive Forces Required to Activate Retractable Intramuscular Syringes?

Background: Previous studies on retractable intramuscular syringes have shown compressive activation forces to vary in magnitude. These studies have all utilized a manual force gauge, to measure the retraction mechanism activation forces, and thus introduced a human factor variable. These forces, devoid of the human factor variable required to activate these devices, have not been explored.

Objective: The objectives of this study were to: 1) measure the compressive forces required to activate 3 specific brands of retractable intramuscular syringes both manually and with a completely automated force testing system, and 2) compare forces between manual vs. automated systems, researchers, and devices.

Methods: A laboratory-based experiment was conducted on three brands of 3 cc retractable intramuscular syringes from Becton Dickinson, Retractable Technologies and Safety 1^st Medical Incorporated, designated as Devices A, B, & C, respectively. Two researchers used a manually operated digital force gauge to activate the retraction mechanism of 100 devices of each brand. A computer-controlled universal testing machine was then used to test 100 each of the same three brands of devices. For each trial, 2 cc of saline was used as the injection solution. Data were analyzed using descriptive statistics and t-tests.

Results: Comparing the two researchers, there was statistically significant difference (p<0.01) between the manual forces required to activate the retraction mechanisms in only 1/3 of the devices. However, there was a statistically significant difference (p<0.01) between the researchers and the automated testing system with regards to the activation force in 2/3 (4 out of 6) of the trials. Finally, the mean activation force between all 3 device brands differed significantly (p<0.01) when tested on the automated system. Descriptive statistics showed considerable variability in mean, standard deviation, and range of forces between the researchers, testing systems (manual vs. automated), and devices.

Conclusions: This study demonstrated a significant difference in activation forces between manual vs. automated activation systems, as well as between devices. This study has implications for those interested in healthcare worker safety, as well as device design manufacturers. The ergonomic impact of these data may have adverse implications for healthcare workers who utilize these devices on a high volume basis. Future studies on the additional forces involved in use of such devices, including the tensile forces to draw up solutions and the contribution of solutions of varying viscosity, should be conducted. Commercially available products should be tested using manual and automated systems to determine the impact of the human dynamic vs. device design on all of the forces required to use such devices. This is an important occupational safety issue which warrants further investigation.