Comparisons of Metabolic Load between Adaptive Support Ventilation and Pressure Support Ventilation in Mechanically Ventilated ICU Patients

Purpose. The aim of this study was to compare the metabolic load between adaptive support ventilation (ASV) and pressure support ventilation (PSV) modes in critically ill patients. Methods. Sequential 20 min ventilation by PSV followed by 20 min ASV in critically ill patients was assessed. ASV was set for full support, i.e., with the minute volume control set at the same level as the minute volume observed during PSV. The trial started from PSV 8 cmH₂O and continued with high (PSV 12 cmH₂O) to low (PSV 0) conditions or low to high conditions, in random order. The oxygen consumption (VO2), production of carbon dioxide (VCO2), and energy expenditure (EE) were measured by indirect calorimetry (IC). Results. Twenty-four patients with critical illness participated in the study. Comparing with the PSV mode, the EE in the ASV mode was lower in the level of PSV 0 cmH₂O (1069 ± 73 vs. 1425 ± 76 kcal), PS 8 cmH₂O (1116 ± 70 vs. 1284 ± 61 kcal), and PS 12 cmH₂O (1017 ± 70 vs. 1169 ± 58 kcal) (p<0.05). The VO2, VCO2, and P0.1 in PSV were significantly higher than those in ASV (p<0.05). Conclusion. In patients with critical illness, the application of ASV set for full support was associated with a lower metabolic load and respiratory drive than in any of the studied PSV conditions.