Continuous and repeat metabolic measurements compared between post-cardiothoracic surgery and critical care patients

OBJECTIVE: Using a system, which accuracy is equivalent to the gold standard Douglas Bag (DB) technique for measuring oxygen consumption (VO(2)), carbon dioxide generation (VCO(2)), and respiratory quotient (RQ), we aimed to continuously measure these metabolic indicators and compare the values between post-cardiothoracic surgery and critical care patients. METHODS: This was a prospective, observational study conducted at a suburban, quaternary care teaching hospital. Age 18 years or older patients who underwent mechanical ventilation were enrolled. RESULTS: We included 4 post-surgery and 6 critical care patients. Of those, 3 critical care patients died. The longest measurement reached to 12 h and 15 min and 50 cycles of repeat measurements were performed. VO(2) of the post-surgery patients were 234 ± 14, 262 ± 27, 212 ± 16, and 192 ± 20 mL/min, and those of critical care patients were 122 ± 20, 189 ± 9, 191 ± 7, 191 ± 24, 212 ± 12, and 135 ± 21 mL/min, respectively. The value of VO(2) was more variable in the post-surgery patients and the range of each patient was 44, 126, 71, and 67, respectively. SOFA scores were higher in non-survivors and there were negative correlations of RQ with SOFA. CONCLUSIONS: We developed an accurate system that enables continuous and repeat measurements of VO(2), VCO(2), and RQ. Critical care patients may have less activity in metabolism represented by less variable values of VO(2) and VCO(2) over time as compared to those of post-cardiothoracic surgery patients. Additionally, an alteration of these values may mean a systemic distinction of the metabolism of critically ill patients. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12890-023-02657-4.