A steady state should be established when using indirect calorimetry to assess resting energy expenditure, reduce error, and improve the validity of the measurement. Steady-state criteria are often rigorous and difficult to achieve in hospitalized patients, particularly in patients recovering from traumatic brain injury. This study aimed to assess whether reducing the timeframe for steady-state conditions to 2, 3, or 4 minutes when using indirect calorimetry was significantly different from the widely accepted 5-minute steady-state protocol in patients recovering from traumatic brain injury. Indirect calorimetry using an open-circuit calorimeter was used to measure resting energy expenditure in 20 spontaneously breathing patients with traumatic brain injury. Each patient underwent repeated measurements once per day at various stages of his or her recovery. Bland-Altman methods comparison was used for statistical analysis. In total, 124 measurements were recorded, of which 59% met 5-minute, 70% met 4-minute, 76% met 3-minute, and 84% met 2-minute steady-state conditions. Mean within-patient coefficient of variation was 13% (range, 0%-35%). Agreement at the +/-10% level using Bland-Altman plots was 100% for a 4-minute steady-state protocol, 96% for a 3-minute protocol, and 90% using a 2-minute protocol. A 4-minute or 3-minute abbreviated steady-state indirect calorimetry protocol is clinically acceptable to measure resting energy expenditure in spontaneously breathing patients with a traumatic brain injury.