Applied nutritional investigation Inﬂuence of different ventilator modes on VO 2 and VCO 2 measurements using a compact metabolic monitor George Briassoulis, M.D., Ph.D. a, *, Evi Michaeloudi, M.D. a , Diana-Michaela Fitrolaki, M.D. a , Anna-Maria Spanaki, M.D. a , and Efrossini Briassouli, M.D. b a Paediatric Intensive Care Unit, University Hospital of Heraklion, Heraklion, Crete, Greece b 1st Department of Internal Medicine–Propaedeutic, University of Athens, Athens, Greece Manuscript received October 21, 2008; accepted January 31, 2009 Abstract Objective: We assessed the inﬂuence of different ventilator modes on carbon dioxide elimination (VCO 2 ) and oxygen uptake (VO 2 ) using a new compact modular metabolic monitor (E-COVX) and its impact on calculated respiratory quotient (RQ) and resting energy expenditure (REE) in critically ill children. Methods: Sequential 30-min ventilation by pressure-regulated volume controlled ventilation (PRVC), synchronized intermittent mandatory ventilation (SIMV), and biphasic intermittent positive airway pressure/airway pressure release ventilation (BiVent) in mechanically ventilated critically-ill children was assessed. To determine within- or between-day variations, 30-min VO 2 and VCO 2 measurements were repeated at four separate occasions. Results: A total of 3960 pulmonary 1-min gas exchange measurements were recorded in the 44 sessions for the three ventilator modes. VO 2 ,VCO 2 , and REE did not differ signiﬁcantly among the PRVC, SIMV, and BiVent sequence of measurements. RQ (0.86 6 0.1) in the SIMV and VCO 2 (113 6 55 mL/min) in the BiVent mode had a higher trend compared with PRVC (0.82 6 0.01, P < 0.05, and 103 6 49 mL/min, P < 0.2, respectively). All three modes displayed good agreement and there were no signiﬁcant differences between the ﬁrst and second same-day or between the ﬁrst- and second-day measurements or sequentially changed ventilator modes. Bland-Altman plots compar- ing the means of sequential REE, VO 2 ,VCO 2 , and RQ during the PRVC, SIMV, and BiVent modes of ventilation indicated that the average paired differences were <  5.5%. Conclusion: The inﬂuence of different ventilator modes on VO 2 and VCO 2 measurements in adequately sedated critically ill children is not signiﬁcant. The E-COVX metabolic module is suitable for repeated measurements in well-sedated mechanically ventilated children with stable respiratory patterns using the PRVC, SIMV, or BiVent modes of ventilation. Ó 2009 Elsevier Inc. All rights reserved. Keywords: Critically ill; Resting energy expenditure; Ventilator modes; Oxygen consumption; Carbon dioxide production; Metabolic monitor Introduction The E-COVX (GE Healthcare/Datex-Ohmeda, Helsinki, Finland) is a simple metabolic non-invasive monitor incorpo- rated into existing anaesthetic and critical care monitoring systems. It uses the practical method of breath-by-breath monitoring of metabolic gas exchange by relating ﬂow mea- surements made at the mouth by pneumotachography to measurements of inspired and expired gas compositions. Compared with the Deltatrac II (Datex Ohmeda 2000, Hel- sinki, Finland) [1,2,3] or metabolic monitors integrated into ventilators using different methodologies [4,5], this compact modular monitor has shown variable results. Pressure regulated controlled ventilation (PRVC), syn- chronized intermittent mandatory ventilation (SIMV), and biphasic intermittent positive airway pressure/airway pres- sure release ventilation (BiPAP or BiVent/APRV) are usually used for fully supporting or weaning patients gradually from a ventilator. BiPAP or BiVent is an effective mode of mechanical ventilation similar to APRV, but it also applies *Corresponding author. Tel.: þ2810-375024. (G. Briassoulis). E-mail address: ggbriass@otenet.gr (G. Briassoulis). 0899-9007/09/$ – see front matter Ó 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.nut.2009.01.018 Nutrition 25 (2009) 1106–1114 www.nutritionjrnl.com