Evaluating nutrient regulation in ICU survivors: A prospective cohort study

This study will observe the energy intake from a weighed, soft diet, energy buffet in adult survivors of critical illness, when compared to general hospitalised patients and healthy controls. Following an overnight fast, participants will have their energy expenditure measured via indirect calorimetry using a metabolic cart (Quark CPET, Cosmed) over a 30-minute period, via a canopy hood. Objective measures of taste thresholds will be assessed using edible taste strips. Appetite will be assessed using a set of Visual Analogue Scales (VAS) at three timepoints (-30min (fasting), 180 mins (prior to buffet), 210 mins (post buffet)). Each VAS will consist of a 100 mm horizontal line, where 0 mm represents ‘sensation not felt at all’ and 100 mm ‘sensation felt the greatest’. The participant will be required to place a vertical mark along the line to indicate the strength of each sensation. Participants will be asked to consume 200 ml of a liquid test meal (Ensure Original (Abbott, 237 ml, 920 kJ, 9 g protein, 33 g carbohydrate, 6 g fat)) over a 5-minute interval, t= 0 mins when the liquid test meal has been consumed. Blood samples will be taken from a venous catheter every 15 minutes for the first hour and every 30 minutes thereafter for the study period. The resulting plasma/serum will be stored at -70º C for subsequent analysis. Hormones associated with appetite control will be analysed at each time-point over the study period, including ghrelin, leptin, insulin, peptide YY (PYY) and cholecystokinin (CCK). Antral area will be assessed using ultrasonography every 15 minutes for the first hour and at 30 minute intervals thereafter until 180 mins. At t=180 minutes, participants will be provided with a standard energy buffet (2666kcal, 123g protein, 81g fat, and 342g carbohydrate) modified to allow for soft diet, which has been validated to assess nutrient intake. Participants will be instructed to consume this buffet until they are comfortably full, within a 30 minute period. The amount of calories and macronutrients consumed will be quantified using Foodworks dietary analysis software (Xyris, Brisbane, Australia). The time taken to reach the point of satisfaction with this meal will also be recorded. The total duration for completion of all study specific procedures will be approximately 5 hours. During the study day, a 24-hour recall of intake from the previous day will be conducted by a trained dietitian. Additionally, a Gastrointestinal Symptoms Questionnaire and a Patient-Generated Subjective Global Assessment (PG-SGA) will be used to assess the presence of gastrointestinal symptoms relating to barriers effecting nutritional intake, for example nausea, loss of appetite, bloating, problems swallowing, requirement for feeding assistance and dry mouth . Quality of life questionnaires will also be used: EQ-5D-5L and SF-36.