The effect of air fluidised bed therapy on hypermetabolism in intensive care unit patients

Major trauma is associated with a hypermetabolic (increased resting energy expenditure) and hypercatabolic (negative nitrogen balance) response. Studies have suggested that nursing injured patients at higher temperatures reduces the metabolic response ( Ryan & Clague 1990 ). In this study the energy expenditure and urinary nitrogen excretion of major trauma patients was examined when nursing them on an air-fluidised bed at 32°C using a crossover study design. Patients were randomised into two groups. Group A patients ( n = 8) remained on a standard intensive care unit bed at an environmental temperature of 22°C while Group B patients ( n = 6) were placed on an air-fluidised bed operating at 32°C. On days 4 and 5 after injury, energy expenditure and urinary nitrogen excretion were measured. On day 6, Group A patients transferred to an air-fluidised bed and Group B patients to a standard bed. On days 7 and 8, energy expenditure and urinary nitrogen excretion were again measured. Within group comparisons of energy expenditure and urinary nitrogen excretion were made for days 3 and 4 (period 1) and days 7 and 8 (period 2). In both groups, mean energy expenditure was significantly increased in the second period irrespective of whether air-fluidised bed therapy preceded or followed a period on a standard bed. We concluded that nursing intensive care patients on an air-fluidised bed at 32°C did not influence energy expenditure or urinary nitrogen.