Influence of different ventilator modes on Vo2 and Vco2 measurements using a compact metabolic monitor

ObjectiveWe assessed the influence of different ventilator modes on carbon dioxide elimination (Vco2) and oxygen uptake (Vo2) 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.MethodsSequential 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 Vo2 and Vco2 measurements were repeated at four separate occasions.ResultsA total of 3960 pulmonary 1-min gas exchange measurements were recorded in the 44 sessions for the three ventilator modes. Vo2, Vco2, and REE did not differ significantly among the PRVC, SIMV, and BiVent sequence of measurements. RQ (0.86 ± 0.1) in the SIMV and Vco2 (113 ± 55 mL/min) in the BiVent mode had a higher trend compared with PRVC (0.82 ± 0.01, P < 0.05, and 103 ± 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 comparing the means of sequential REE, Vo2, Vco2, and RQ during the PRVC, SIMV, and BiVent modes of ventilation indicated that the average paired differences were < − 5.5%.ConclusionThe influence of different ventilator modes on Vo2 and Vco2 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.