The prevalence of pressure injuries in the intensive care unit (ICU) setting is high with rates ranging from 13.1% to 45.5%. Evaluation of interventions to prevent pressure injuries should be informed by preliminary research to identify factors that should be considered during the design of future trials. The study objectives were to evaluate the process of participant recruitment and monitoring in the ICU; measure the maintenance of body angle (in the side‐lying lateral tilt position) and head and neck alignment angle (in the supine position) among immobile critically ill patients when using a purpose‐designed positioning device and usual care equipment, and; ascertain the time required to position patients with the purpose‐designed positioning device and the usual care equipment. A prospective, observational, feasibility study was conducted in an ICU in Victoria, Australia. The sample was immobile critically ill adults at high‐risk of developing pressure injuries. The usual care interventions were pillows, foam wedges, and rolled towels, and the intervention device was the Z‐Flo Fluidized Positioner. The body angle and head and neck alignment were measured on six occasions (at baseline, 1 hour, and 2 hours). The time required for positioning was also measured. The sample was predominately male (n = 5, 62%) with a mean age of 59 years. The majority of patients (n = 106, 92.2%) were not immobile and therefore were ineligible to participate. A total of 48 turning and positioning interventions were observed. For the side‐lying lateral tilt position, the degree of difference from baseline to 2 hours was no more than three degrees for all the devices (the Fluidized Positioner 25°‐26°, the foam wedge 29°‐27°, and the pillow 23°‐21°). For the head and neck position, the degree of difference from baseline to 2 hours was the greatest for the pillow and rolled towel (78°‐71°, a difference of 7°) and the pillow alone (79°‐74°, a difference of 5°). The degree of difference was the lowest for the Fluidized Positioner (84°‐86°, a difference of 2°). Future research to evaluate positioning equipment in the ICU should consider patient eligibility characteristics, particularly immobility. The conduct of preliminary studies to inform the design of larger pressure injury prevention trials is recommended.