Relationship between end-tidal carbon dioxide and arterial carbon dioxide in critically ill patients on mechanical ventilation: A cross-sectional study

So far, only a few studies have examined and confirmed the correlation between end-expiratory carbon dioxide partial pressure (PETCO(2)) and arterial carbon dioxide tension (PaCO(2)) during invasive mechanical ventilation in critically ill patients. This study aimed to observe the correlation between PaCO(2) and PETCO(2) in patients on invasive mechanical ventilation. This was a cross-sectional study of adult patients on invasive mechanical ventilation enrolled between June 2018 and March 2019. Patients requiring invasive mechanical ventilation underwent one of the following mechanical ventilation modes: assisted/controlled ventilation, synchronized intermittent mandatory ventilation, and spontaneous breathing. Subsequently, the difference and correlation between PETCO(2) and PaCO(2) were analyzed. A total of 184 patients with 298 pairs of PETCO(2)-PaCO(2) data were included in the analysis. Without distinguishing the ventilator mode, there was significant positive correlation between PETCO(2) and PaCO(2). In different ventilator modes, the correlation coefficient was 0.81 for synchronized intermittent mandatory ventilation, 0.47 for assisted/controlled ventilation, and 0.55 for spontaneous breathing, respectively. In patients with chronic obstructive pulmonary disease (r = 0.80), multiple trauma (r = 0.64), severe pneumonia (r = 0.60), gastrointestinal surgery (r = 0.57), and cerebrovascular diseases (r = 0.53), PETCO(2) and PaCO(2) were positively correlated. For oxygenation index <200 mm Hg, correlation coefficient r = 0.69, P < .001; oxygenation index ≥200, r = 0.73, P < .001. Under different oxygenation indexes, there was no statistically significant difference between the 2 correlation coefficients. Among 116 pairs of data with oxygenation index <200 mm Hg, the difference of PaCO(2)-PETCO(2) ≥10 mm Hg was found in 25 pairs (21.55%); in 182 pairs of data with oxygenation index ≥200 mm Hg, the difference of PaCO(2)-PETCO(2) ≥10 mm Hg was found in 26 pairs In patients on invasive mechanical ventilation, there was a good correlation between PETCO(2) and PaCO(2) in different ventilator modes, different disease types, and different oxygenation indexes, especially in synchronized intermittent mandatory ventilation mode and chronic obstructive pulmonary disease patients.