Background: Epinephrine is the first-line therapy for patients with anaphylaxis, and intramuscular (IM) delivery is shownto be superior to subcutaneous (SC) delivery. There currently is no consensus on the ideal body position for epinephrine autoinjector (EAI) administration.Objective: We designed this study to investigate whether SC tissue depth (SCTD) is affected by body position (e.g., standing, sitting, supine), which can potentially impact delivery of EAI into the IM space.Methods: Volunteer adults (ages >/= 18 years) from a military medical treatment facility in the United States were recruitedto participate in this study. SCTD of the vastus lateralis was measured via ultrasound at standing, sitting, and supine bodypositions. Subjects’ age, sex, and body mass index (BMI) were collected. Statistical analysis was performed to compare averageSCTD between body positions, sex, and BMI.Results: An analysis of variance of 51 participants (33 men and 18 women) did not reveal statistically significant differencein SCTD among standing, sitting, and supine body positions. It did show a significantly greater SCTD in women than in men (2.72 +/- 1.36 cm versus 1.10 +/- 0.38 cm; p < 0.001). There was no significant association observed between BMI and SCTD in this study.Conclusion: Body position did not seem to significantly change the distance between skin and thigh muscle in adults. Thiswould suggest that there might not be an ideal body position for EAI administration. Therefore, in case of anaphylaxis, promptadministration of epinephrine is recommended at any position.
