This trial investigates the feasibility and reliability of different ultrasound protocols to determine quadriceps muscle architecture in acutely admitted burn patients. The results of this trial will provide more clarity as to whether ultrasound can be used as a bedside tool to monitor muscle wasting.

BACKGROUND Despite the ubiquity of muscle wasting following burns, practical and accurate tools to measure the degree of muscle wasting are lacking in burn care. Ultrasound has been used for this purpose in the critically-ill population and has shown to be valid and reliable. Whether this can be extrapolated to the burn population, however, remains unclear. Open wounds, fluid status, and uncertainty regarding which protocol to use are amongst factors that complicate the use of ultrasound during the acute phase of burns.

AIM This study examines the reliability and feasibility of ultrasound measures in the acute burn setting comparing different techniques and locations of application.

METHODS Burned adults were assessed at admission in two Belgian burn centers by two trained assessors using B-mode ultrasound with a linear transducer. Ultrasound-derived variables included quadriceps muscle layer thickness (QMLT) and rectus femoris cross-sectional area (RF-CSA) on both thighs. Both maximum and minimum compression techniques were used for QMLT, while RF-CSA was determined by minimum compression only. QMLT was measured at a proximal and distal location on the thigh, and RF-CSA was measured at the most proximal location possible where the entire muscle belly still remained visible.

Burn subjects:

Inclusion Criteria:

• ≥10 - ≤80 %TBSA
• Burn depth: 2nd deep / 3rd degree

Exclusion Criteria:

• Electrical burn (except flash burns)
• Associated injury: fracture lower limb
• Diabetes Mellitus type 1
• Central / peripheral neurological/neuromuscular disorders (interfering with exercise)
• Cognitive / psychological disorders (interfering with cooperation)
• Cardiopulmonary disease (interfering with exercise safety)
• Pregnancy
• Palliative care

Healthy subjects:

• none

Burn subjects will be recruited from two specialised burn services in Belgium on a consecutive sampling basis during recruitment of a larger trial investigating the effects of exercise in the acute phase of burns [NCT04511104].

Healthy subjects will be recruited by convenience sampling at the M2Run Metabolic Research Unit of the Department of Rehabilitation Sciences and Physiotherapy at the University of Antwerp.

Datasets will be made available upon request.